MAX1645AEEI+ [MAXIM]
Battery Charge Controller, PDSO28, QSOP-28;
| 型号： | MAX1645AEEI+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Battery Charge Controller, PDSO28, QSOP-28 电池 光电二极管 |
| 文件： | 总32页 (文件大小：329K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1566; Rev 2; 1/01
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
General Description
Features
The MAX1645 are high-efficiency battery chargers capa-
ble of charging batteries of any chemistry type. It uses the
Intel System Management Bus (SMBus) to control volt-
age and current charge outputs.
ꢀ Input Current Limiting
ꢀ 175s Charge Safety Timeout
ꢀ 128mA Wake-Up Charge
When charging lithium-ion (Li+) batteries, the MAX1645
automatically transition from regulating current to regu-
lating voltage. The MAX1645 can also limit line input
current so as not to exceed a predetermined current
drawn from the DC source. A 175s charge safety timer
prevents “runaway charging” should the MAX1645 stop
receiving charging voltage/ current commands.
ꢀ Charges Any Chemistry Battery: Li+, NiCd,
NiMH, Lead Acid, etc.
ꢀ Intel SMBus 2-Wire Serial Interface
ꢀ Compliant with Level 2 Smart Battery Charger
Spec Rev. 1.0
ꢀ +8V to +28V Input Voltage Range
ꢀ Up to 18.4V Battery Voltage
ꢀ 11-Bit Battery Voltage Setting
The MAX1645 employs a next-generation synchronous
buck control circuity that lowers the minimum input-to-
output voltage drop by allowing the duty cycle to
exceed 99%. The MAX1645 can easily charge one to
four series Li+ cells.
ꢀ
0.8ꢀ ꢁutput Voltage Accuracy with Internal
Reference
Applications
ꢀ 3A max Battery Charge Current
ꢀ 6-Bit Charge Current Setting
Notebook Computers
Point-of-Sale Terminals
Personal Digital Assistants
ꢀ 99.99ꢀ max Duty Cycle for Low-Dropout ꢁperation
ꢀ Load/Source Switchover Drivers
ꢀ >97ꢀ Efficiency
Ordering Information
Pin Configuration
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
TOP VIEW
MAX1645EEI
MAX1645AEEI
DCIN
LDO
CLS
REF
1
2
3
4
5
6
7
8
9
28 CVS
27 PDS
26 CSSP
25 CSSN
24 BST
23 DHI
28 QSOP
CCS
CCI
MAX1645
MAX1645A
CCV
GND
BATT
22 LX
21 DLOV
20 DLO
19 PGND
18 CSIP
17 CSIN
16 PDL
15 INT
DAC 10
11
V
DD
THM 12
SCL 13
SDA 14
Typical Operating Circuit appears at end of data sheet.
SMBus is a trademark of Intel Corp.
QSꢁP
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ABSꢁLUTE MAXIMUM RATINGS
DCIN, CVS, CSSP, CSSN, LX to GND....................-0.3V to +30V
CSSP to CSSN, CSIP to CSIN ...............................-0.3V to +0.3V
V
, SCL, SDA, INT, DLOV to GND.........................-0.3V to +6V
DD
THM to GND...............................................-0.3V to (V
+ 0.3V)
DD
PDS, PDL to GND ...................................-0.3V to (V
BST to LX..................................................................-0.3V to +6V
DHI to LX...................................................-0.3V to (V + 0.3V)
+ 0.3V)
PGND to GND .......................................................-0.3V to +0.3V
LDO Continuous Current.....................................................50mA
CSSP
Continuous Power Dissipation (T = +70°C)
BST
A
CSIP, CSIN, BATT to GND .....................................-0.3V to +22V
28-Pin QSOP (derate 10.8mW/°C above +70°C).........860mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature.........................................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
LDO to GND.....................-0.3V to (lower of 6V or V
+ 0.3V)
+ 0.3V)
+ 0.3V)
DCIN
DLOV
DLO to GND ...........................................-0.3V to (V
REF, DAC, CCV, CCI, CCS, CLS to GND.....-0.3V to (V
LDO
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
= +3.3V, V
= +16.8V, V
= +18V, T = 0°C to +85°C, unless otherwise noted. Typical values are at
A
DCIN
DD
BATT
T
A
= +25°C.)
PARAMETER
SYMBꢁL
CꢁNDITIꢁNS
MIN
TYP
MAX
UNITS
GENERAL SPECIFICATIꢁNS
DCIN Typical Operating Range
DCIN Supply Current
V
8
28
6
V
DCIN
I
8V < V
< 28V
1.7
0.7
mA
DCIN
DCIN
DCIN Supply Current Charging
Inhibited
8V < V
< 28V
2
mA
DCIN
DCIN rising
DCIN falling
7.5
7.4
5.4
7.85
When AC_PRESENT
switches
DCIN Undervoltage Threshold
LDO Output Voltage
V
V
V
7
V
8V < V
< 28V, 0 < I
< 15mA
LDO
5.15
5.65
5.65
2.8
LDO
DCIN
V
Input Voltage Range
DD
8V < V
< 28V
2.8
2.1
DCIN
(Note 1)
V
V
rising
falling
2.55
2.5
DD
When the SMB res-
ponds to commands
V
V
Undervoltage Threshold
Quiescent Current
V
DD
DD
DD
0 < V
< 6V, V
= 5V, V
= 5V,
SCL
DCIN
= 5V
DD
I
80
150
4.126
2.8
µA
V
DD
V
SDA
REF Output Voltage
V
0 < I
< 200µA
4.066
2.4
4.096
REF
REF
BATT Undervoltage Threshold
(Note 2)
When I
drops to 128mA
V
CHARGE
PDS Charging Source Switch
Turn-Off Threshold
V
V
V
V
referred to V
referred to V
= 0
, V
falling
50
100
8
100
200
10
150
300
mV
mV
V
PDS-OFF
PDS-HYS
CVS
CVS
PDS
BATT CVS
PDS Charging Source Switch
Threshold Hysteresis
BATT
PDS Output Low Voltage, PDS
Below CSSP
I
12
PDS Turn-On Current
PDS Turn-Off Current
PDS = CSSP
100
10
150
50
300
µA
V
PDS
= V
- 2V, V = 16V
DCIN
mA
CSSP
PDL Load Switch Turn-Off
Threshold
V
V
CVS
referred to V
, V
CVS
rising
-150
-100
-50
mV
PDL-OFF
BATT
2
_______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
= +3.3V, V
= +16.8V, V
= +18V, T = 0°C to +85°C, unless otherwise noted. Typical values are at
A
DCIN
DD
BATT
T
A
= +25°C.)
PARAMETER
SYMBꢁL
CꢁNDITIꢁNS
referred to V
MIN
TYP
MAX
UNITS
PDL Load Switch Threshold
Hysteresis
V
V
V
100
200
300
mV
PDL-HYS
CVS
BATT
PDL Turn-Off Current
PDL Turn-On Resistance
CVS Input Bias Current
- V
= 1V
PDL
6
12
100
6
mA
kΩ
µA
CSSN
PDL to GND
= 28V
50
150
20
V
CVS
ChargingVoltage() = 0x41A0
ChargingVoltage() = 0x3130
ChargingVoltage() = 0x20D0
ChargingVoltage() = 0x1060
16.666
16.8
16.934
12.492 12.592 12.692
BATT Full-Charge Voltage
V0
I0
V
8.333
4.150
8.4
8.467
4.234
4.192
ChargingCurrent() =
0x0BC0
2.798
61.6
3.008
128
3.218
194.4
A
mA
A
BATT Charge Current (Note 3)
R
R
= 50mΩ
CS
ChargingCurrent() =
0x0080
V
V
V
= 4.096V
= 2.048V
4.714
2.282
5.12
2.56
5.526
2.838
DCIN Source Current Limit
(Note 3)
CLS
CLS
= 40mΩ
CSS
= 1V,
BATT
MAX1645
20
61.6
0
128
128
200
194.4
20
R
= 50mΩ
CSI
BATT Undervoltage Charge
Current
mA
V
= 1V,
BATT
MAX1645A
R
= 50mΩ
CSI
BATT/CSIP/CSIN Input Voltage
Range
V
Total of I
, I
and I
and I
;
;
BATT CSIP,
CSIN
Total BATT Input Bias Current
Total BATT Quiescent Current
Total BATT Standby Current
-700
-100
-5
700
100
5
µA
µA
µA
V
= 0 to 20V
BATT
Total of I
, I
BATT CSIP,
CSIN
V
= 0 to 20V, charge inhibited
BATT
Total of I
, I
and I
;
BATT CSIP,
CSIN
V
V
V
V
= 0 to 20V, V
= 0
BATT
CSSP
CSSP
CSSP
DCIN
CSSP Input Bias Current
CSSN Input Bias Current
CSSP/CSSN Quiescent Current
= V
= V
= 0 to 28V
= 0 to 28V
-100
-100
-1
540
35
1000
100
1
µA
mA
µA
CSSN
DCIN
= C
= V
DCIN
CSSN
CSSN
= V
= 28V, V
= 0
DCIN
Battery Voltage-Error Amp DC
Gain
From BATT to CCV
= V /2 to V
REF
200
-1
500
0.05
V/V
µA
CLS Input Bias Current
V
1
CLS
REF
Battery Voltage-Error Amp
Transconductance
From BATT to CCV, ChargingVoltage() =
0x41A0, V = 16.8V
0.111
0.222
0.444 µA/mV
BATT
Battery Current-Error Amp
Transconductance
From CSIP/SCIN to CCI, ChargingCurrent() =
0x0BC0, V - V = 150.4mV
0.5
0.5
1
1
2
2
µA/mV
µA/mV
mV
CSIP
CSIN
Input Current-Error Amp
Transconductance
From CSSP/CSSN to CCS, V
= 2.048V,
CLS
V
- V
= 102.4mV
CSSP
CSSN
CCV/CCI/CCS Clamp Voltage
(Note 4)
V
= V
= V = 0.25V to 2V
CCS
150
300
600
CCV
CCI
_______________________________________________________________________________________
3
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
= +3.3V, V
= +16.8V, V
= +18V, T = 0°C to +85°C, unless otherwise noted. Typical values are at
A
DCIN
DD
BATT
T
A
= +25°C.)
PARAMETER
SYMBꢁL
CꢁNDITIꢁNS
MIN
TYP
MAX
UNITS
DC-Tꢁ-DC CꢁNVERTER SPECIFICATIꢁNS
Minimum Off-Time
t
1
5
1.25
10
1.5
15
µs
ms
%
OFF
Maximum On-Time
t
ON
Maximum Duty Cycle
LX Input Bias Current
LX Input Quiescent Current
BST Supply Current
99
99.99
200
V
V
= 28V, V
= V = 20V
500
1
µA
µA
µA
µA
A
DCIN
DCIN
BATT
LX
= 0, V
= V = 20V
LX
BATT
DHI high
= V
6
5
15
10
7.0
14
14
DLOV Supply Current
Inductor Peak Current Limit
DHI Output Resistance
DLO Output Resistance
V
, DLO low
LDO
DLOV
R
= 50mΩ
5.0
-1
6.0
6
CSI
DHI high or low, V
- V = 4.5V
Ω
BST
LX
DLO high or low, V
= 4.5V
6
Ω
DLOV
THERMISTꢁR CꢁMPARATꢁR SPECIFICATIꢁNS
V
V
= 4% of V
= 2.8V to 5.65V
to 96% of V
,
THM
DD
DD
DD
THM Input Bias Current
1
µA
Thermistor Overrange Threshold
Thermistor Cold Threshold
Thermistor Hot Threshold
V
V
V
= 2.8V to 5.65V, V
= 2.8V to 5.65V, V
= 2.8V to 5.65V, V
falling
falling
falling
89.5
74
91
92.5 % of V
DD
DD
DD
THM
THM
THM
DD
DD
DD
75.5
23.5
77
25
% of V
% of V
22
Thermistor Underrange
Threshold
V
= 2.8V to 5.65V, V
falling
6
7.5
1
9
% of V
DD
THM
DD
DD
Thermistor Comparator
Threshold Hysteresis
All 4 comparators, V
= 2.8V to 5.65V
% of V
DD
SMB INTERFACE LEVEL SPECIFICATIꢁNS (V
SDA/SCL Input Low Voltage
= 2.8V to 5.65V)
DD
0.6
1
V
SDA/SCL Input High Voltage
1.4
V
SDA/SCL Input Hysteresis
220
25
mV
µA
mA
µA
mV
SDA/SCL Input Bias Current
-1
6
SDA Output Low Sink Current
INT Output High Leakage
INT Output Low Voltage
V
V
I
= 0.4V
SDA
= 5.65V
= 1mA
1
INT
200
INT
SMB INTERFACE TIMING SPECIFICATIꢁNS (V
= 2.8V to 5.65V, Figures 4 and 5)
DD
SCL High Period
SCL Low Period
t
4
µs
µs
HIGH
t
4.7
LOW
Start Condition Setup Time
from SCL
t
4.7
4
µs
µs
SU:STA
Start Condition Hold Time
from SCL
t
t
HD:STA
SDA Setup Time from SCL
SDA Hold Time from SCL
250
0
ns
ns
SU:DAT
HD:DAT
t
4
_______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
= +3.3V, V
= +16.8V, V
= +18V, T = 0°C to +85°C, unless otherwise noted. Typical values are at
A
DCIN
DD
BATT
T
A
= +25°C.)
PARAMETER
SYMBꢁL
CꢁNDITIꢁNS
MIN
TYP
MAX
UNITS
SDA Output Data Valid from SCL
t
1
µs
DV
Maximum Charge Period
Without a ChargingVoltage() or
Charging Current() Loaded
t
140
175
210
s
WDT
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V = +3.3V, V
DD
= +16.8V, V
= +18V, T = -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
BATT
DCIN A
PARAMETER
SYMBꢁL
CꢁNDITIꢁNS
MIN
MAX
UNITS
GENERAL SPECIFICATIꢁNS
DCIN Typical Operating Range
DCIN Supply Current
V
8
28
6
V
DCIN
I
8V < V
< 28V
mA
DCIN
DCIN
DCIN Supply Current Charging
Inhibited
8V < V
< 28V
2
mA
DCIN
DCIN rising
DCIN falling
7.85
When AC_PRESENT
switches
DCIN Undervoltage Threshold
LDO Output Voltage
V
V
V
7
V
8V < V
< 28V, 0 < I
< 15mA
LDO
5.15
5.65
5.65
2.8
LDO
DCIN
V
DD
Input Voltage Range
8V < V
< 28V
2.8
2.1
DCIN
(Note 1)
V
V
rising
falling
DD
DD
When the SMB res-
ponds to commands
V
Undervoltage Threshold
Quiescent Current
V
DD
DD
0 < V
< 6V, V
= 5V, V
= 5V,
SCL
DCIN
= 5V
DD
V
I
150
4.157
2.8
µA
V
DD
V
SDA
REF Output Voltage
V
0 < I
< 200µA
4.035
2.4
REF
REF
BATT Undervoltage Threshold
(Note 2)
When I
drops to 128mA
V
CHARGE
PDS Charging Source Switch
Turn-Off Threshold
V
V
V
V
referred to V
referred to V
= 0
, V
falling
50
100
8
150
300
mV
mV
V
PDS-OFF
CVS
CVS
PDS
BATT CVS
PDS Charging Source Switch
Threshold Hysteresis
PDS-HYS
BATT
PDS Output Low Voltage, PDS
Below CSSP
I
12
PDS Turn-On Current
PDS Turn-Off Current
PDS = CSSP
100
10
300
µA
V
PDS
= V
- 2V, V = 16V
DCIN
mA
CSSP
PDL Load Switch Turn-Off
Threshold
V
V
V
referred to V
referred to V
, V
rising
-150
-50
mV
PDL-OFF
CVS
BATT CVS
PDL Load Switch Threshold
Hysteresis
V
V
100
6
300
mV
mA
PDL-HYS
CVS
BATT
PDL Turn-Off Current
- V
= 1V
PDL
CSSN
_______________________________________________________________________________________
5
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V = +3.3V, V
DD
= +16.8V, V = +18V, T = -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
DCIN A
BATT
PARAMETER
PDL Turn-On Resistance
CVS Input Bias Current
SYMBꢁL
CꢁNDITIꢁNS
MIN
MAX
150
20
UNITS
kΩ
PDL to GND
50
V
CVS
= 28V
µA
ERRꢁR AMPLIFIER SPECIFICATIꢁNS
ChargingVoltage() = 0x41A0
ChargingVoltage() = 0x3130
ChargingVoltage() = 0x20D0
ChargingVoltage() = 0x1060
16.532
12.391
8.266
17.068
12.793
8.534
BATT Full-Charge Voltage
V0
I0
V
4.124
4.260
ChargingCurrent() =
2.608
15.2
3.408
240.8
A
mA
A
0x0BC0
BATT Charge Current (Note 3)
R
R
= 50mΩ
= 40mΩ
CSI
ChargingCurrent() =
0x0080
V
V
= 4.096V
= 2.048V
4.358
2.054
5.882
3.006
CLS
CLS
DCIN Source Current Limit
(Note 3)
CSS
BATT Undervoltage Charge
Current
V
BATT
= 1V, R
= 50mΩ
20
0
200
20
mA
V
CSI
BATT/CSIP/CSIN Input Voltage
Range
Total of I
, I
and I
and I
;
;
BATT CSIP,
CSIN
Total BATT Input Bias Current
Total BATT Quiescent Current
Total BATT Standby Current
-700
-100
-5
700
100
5
µA
µA
µA
V
BATT
= 0 to 20V
Total of I
, I
BATT CSIP,
CSIN
V
BATT
= 0 to 20V, charge inhibited
Total of I
, I
and I
;
BATT CSIP,
CSIN
V
V
V
V
= 0 to 20V, V
= 0
BATT
DCIN
CSSP/Input Bias Current
CSSN Input Bias Current
CSSP/CSSN Quiescent Current
= V
= V
= V
= V
= V
= 28V
= 28V
-100
-100
-1
1000
100
1
µA
µA
µA
CSSP
CSSP
CSSP
CSSN
CSSN
CSSN
DCIN
DCIN
= 28V, V
= 0
DCIN
Battery Voltage-Error Amp DC
Gain
From BATT to CCV
= V /2 to V
REF
200
-1
V/V
µA
CLS Input Bias Current
V
1
CLS
REF
Battery Voltage-Error Amp
Transconductance
From BATT to CCV, ChargingVoltage() =
0x41A0, V = 16.8V
0.111
0.444 µA/mV
BATT
Battery Current-Error Amp
Transconductance
From CSIP/CSIN to CCI, ChargingCurrent() =
0x0BC0, V -V = 150.4mV
0.5
0.5
150
2
2
µA/mV
µA/mV
mV
CSIP CSIN
Input Current-Error Amp
Transconductance
From CSSP/CSSN to CCS, V
= 2.048V,
CLS
V
CSSP
- V
= 102.4mV
CSSN
CCV/CCI/CCS Clamp Voltage
(Note 4)
V
CCV
= V
= V = 0.25V to 2V
CCS
600
CCI
DC-Tꢁ-DC CꢁNVERTER SPECIFICATIꢁNS
Minimum Off-Time
Maximum On-Time
Maximum Duty Cycle
t
1
5
1.5
15
µs
ms
%
OFF
t
ON
99
6
_______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V = +3.3V, V
DD
= +16.8V, V = +18V, T = -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
DCIN A
BATT
PARAMETER
LX Input Bias Current
LX Input Quiescent Current
BST Supply Current
SYMBꢁL
CꢁNDITIꢁNS
= 28V, V = V = 20V
BATT
MIN
MAX
500
1
UNITS
µA
µA
µA
µA
A
V
V
DCIN
LX
= 0, V
= V = 20V
LX
DCIN
BATT
DHI high
= V
15
DLOV Supply Current
Inductor Peak Current Limit
DHI Output Resistance
DLO Output Resistance
V
DLOV
, DLO low
LDO
10
R
= 50mΩ
5.0
-1
7.0
14
CSI
DHI high or low, V
- V = 4.5V
Ω
BST
LX
DLO high or low, V
= 4.5V
14
Ω
DLOV
THERMISTꢁR CꢁMPARATꢁR SPECIFICATIꢁNS
V
V
= 4% of V
to 96% of V
,
THM
DD
DD
DD
THM Input Bias Current
1
µA
= 2.8V to 5.65V
Thermistor Overrange Threshold
Thermistor Cold Threshold
Thermistor Hot Threshold
V
DD
V
DD
V
DD
= 2.8V to 5.65V, V
= 2.8V to 5.65V, V
= 2.8V to 5.65V, V
falling
falling
falling
89.5
74
92.5 % of V
THM
THM
THM
DD
DD
DD
77
25
% of V
% of V
22
Thermistor Underrange
Threshold
V
DD
= 2.8V to 5.65V, V
falling
6
9
% of V
THM
DD
SMB INTERFACE LEVEL SPECIFICATIꢁNS (V
SDA/SCL Input Low Voltage
= 2.8V to 5.65V)
DD
0.6
1
V
SDA/SCL Input High Voltage
1.4
-1
6
V
SDA/SCL Input Bias Current
µA
mA
µA
mV
SDA Output Low Sink Current
INT Output High Leakage
INT Output Low Voltage
V
V
I
= 0.4V
SDA
= 5.65V
= 1mA
1
INT
200
INT
SMB INTERFACE TIMING SPECIFICATIꢁNS (V
= 2.8V to 5.65V, Figures 4 and 5)
DD
SCL High Period
SCL Low Period
t
4
µs
µs
HIGH
t
4.7
LOW
Start Condition Setup Time
from SCL
t
4.7
4
µs
µs
SU:STA
Start Condition Hold Time
from SCL
t
t
HD:STA
SDA Setup Time from SCL
SDA Hold Time from SCL
250
0
ns
ns
SU:DAT
HD:DAT
t
_______________________________________________________________________________________
7
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V = +3.3V, V
DD
= +16.8V, V = +18V, T = -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
DCIN A
BATT
PARAMETER
SYMBꢁL
CꢁNDITIꢁNS
MIN
MAX
UNITS
SDA Output Data Valid
from SCL
t
1
µs
DV
Maximum Charge Period
Without a ChargingVoltage() or
Charging Current() loaded
t
140
210
s
WDT
Note 1: Guaranteed by meeting the SMB timing specs.
Note 2: The charger reverts to a trickle-charge mode of I
= 128mA below this threshold.
CHARGE
Note 3: Does not include current-sense resistor tolerance.
Note 4: Voltage difference between CCV, and CCI or CCS when one of these three pins is held low and the others try to pull high.
Typical Operating Characteristics
(Circuit of Figure 1, V
= 20V, T = +25°C, unless otherwise noted.)
A
DCIN
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
(STEP IN LOAD CURRENT)
(BATTERY REMOVAL AND REINSERTION)
LDO LINE REGULATION
MAX1645 toc01
MAX1645 toc02
16V
14V
12V
1A
4A
2A
0
5.60
5.55
5.50
5.45
5.40
5.35
5.30
5.25
5.20
I
= 0
LOAD
CCS
0
2A
1V
0
CCI
CCI
CCI
1.5V
1V
CCV
CCI
CCV
CCI
CCI
CCS
CCS
CCV
0.5V
2ms/div
1ms/div
ChargingCurrent() = 3008mA
= 16V
BATTERY REMOVED
BATTERY INSERTED
5
10
15
20
(V)
25
30
ChargingVoltage() = 15000mV
ChargingCurrent() = 1000mA
V
DCIN
V
BATT
LOAD STEP: 0A TO 2A
LIMIT = 2.5A
I
SOURCE
REFERENCE VOLTAGE
vs. TEMPERATURE
LDO LOAD REGULATION
REFERENCE VOLTAGE LOAD REGULATION
4.110
4.105
4.100
4.095
4.090
4.085
4.080
5.60
5.55
5.50
5.45
5.40
5.35
5.30
5.25
5.20
4.100
4.098
4.096
4.094
4.092
4.090
-40 -20
0
20
40
60
80 100
0
2
4
6
8
10 12 14 16 18 20
0
50
100
150
200
250
300
TEMPERATURE (°C)
LOAD CURRENT (mA)
LOAD CURRENT (µA)
8
_______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
= 20V, T = +25°C, unless otherwise noted.)
A
DCIN
EFFICIENCY vs. BATTERY CURRENT
(VOLTAGE-CONTROL LOOP)
EFFICIENCY vs. BATTERY CURRENT
(CURRENT-CONTROL LOOP)
OUTPUT VI CHARACTERISTICS
100
95
90
85
80
75
70
65
60
55
50
100
95
90
85
80
75
70
65
60
55
50
0.001
0.01
0.1
A
B
A
B
1.0
ChargingVoltage() = 16,800mV
ChargingCurrent() = 3008mA
A: V
B: V
= 20V, ChargingVoltage() = 16.8V
= 16V, ChargingVoltage() = 8.4V
A: V
B: V
= 20V, V
= 16V, V
= 16.8V
= 8.4V
DCIN
DCIN
DCIN
DCIN
BATT
BATT
10
0
500 1000 1500 2000 2500 3000
BATTERY CURRENT (mA)
0
500 1000 1500 2000 2500 3000
ChargingCurrent() (CODE)
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
BATT VOLTAGE ERROR
vs. ChargingVoltage() CODE
CURRENT-SETTING ERROR
vs. ChargingCurrent() CODE
5
4
0.3
0.2
0.1
0
3
2
1
0
-1
-2
-3
-4
-5
-0.1
-0.2
-0.3
V
= 12.6V
I
= 0
BATT
BATT
MEASURED AT AVAILABLE CODES
MEASURED AT AVAILABLE CODES
0000
4000
8000
12000 16000 20000
0
500 1000 1500 2000 2500 3000
ChargingCurrent() (CODE)
ChargingVoltage() (CODE)
SOURCE/BATT CURRENT vs. V
BATT
WITH SOURCE CURRENT LIMIT
SOURCE/BATT CURRENT vs. LOAD CURRENT
WITH SOURCE CURRENT LIMIT
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
I
IN
I
IN
I = 2A
LOAD
V
CLS
R
CSS
V
BATT
= 2V
V
R
= 2V
= 40mΩ
CLS
CSS
I
BATT
I
BATT
= 40mΩ
= 16.8V
ChargingVoltage() = 18,432mV
ChargingCurrent() = 3008mA
SOURCE CURRENT LIMIT = 2.5A
SOURCE CURRENT LIMIT = 2.5A
ChargingCurrent() = 3008mA
ChargingVoltage() = 18,432mV
0
2
4
6
8
10 12 14 16 18 20
(V)
0
0.5
1.0
1.5
2.0
2.5
V
LOAD CURRENT (A)
BATT
_______________________________________________________________________________________
9
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Pin Description
PIN
1
NAME
DCIN
LDO
CLS
FUNCTIꢁN
DC Supply Voltage Input
2
5.4V Linear-Regulator Voltage Output. Bypass with a 1µF capacitor to GND.
Source Current Limit Input
3
4
REF
4.096V Reference Voltage Output
5
CCS
CCI
Charging Source Compensation Capacitor Connection. Connect a 0.01µF capacitor from CCS to GND.
Battery Current-Loop Compensation Capacitor Connection. Connect a 0.01µF capacitor from CCI to GND.
6
Battery Voltage-Loop Compensation Capacitor Connection. Connect a 10kΩ resistor in series with a 0.01µF
capacitor to GND.
7
CCV
8
GND
BATT
DAC
Ground
9
Battery Voltage Output
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
DAC Voltage Output
V
Logic Circuitry Supply Voltage Input (2.8V to 5.65V)
Thermistor Voltage Input
DD
THM
SCL
SMB Clock Input
SDA
INT
SMB Data Input/Output. Open-drain output. Needs external pull-up.
Interrupt Output. Open-drain output. Needs external pull-up.
PMOS Load Switch Driver Output
PDL
CSIN
CSIP
PGND
DLO
DLOV
LX
Battery Current-Sense Negative Input
Battery Current-Sense Positive Input
Power Ground
Low-Side NMOS Driver Output
Low-Side NMOS Driver Supply Voltage. Bypass with 0.1µF capacitor to GND.
Inductor Voltage Sense Input
DHI
High-Side NMOS Driver Output
BST
High-Side Driver Bootstrap Voltage Input. Bypass with 0.1µF capacitor to LX.
Charging Source Current-Sense Negative Input
Charging Source Current-Sense Positive Input
Charging Source PMOS Switch Driver Output
Charging Source Voltage Input
CSSN
CSSP
PDS
CVS
10 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Input Current Limiting
Detailed Description
The MAX1645/MAX1645A limit the current drawn by the
The MAX1645/MAX1645A consist of current-sense
charger when the load current becomes high. The
amplifiers, an SMBus interface, transconductance
devices limit the charging current so the AC adapter
amplifiers, reference circuitry, and a DC–DC converter
voltage is not loaded down. An internal amplifier, CSS,
(Figure 2). The DC–DC converter generates the control
compares the voltage between CSSP and CSSN to the
signals for the external MOSFETs to maintain the volt-
voltage at CLS/20. V
is set by a resistor-divider
CLS
age and the current set by the SMBus interface. The
MAX1645/MAX1645A feature a voltage-regulation loop
and two current-regulation loops. The loops operate
independently of each other. The voltage-regulation
loop monitors BATT to ensure that its voltage never
exceeds the voltage set point (V0). The battery current-
regulation loop monitors current delivered to BATT to
ensure that it never exceeds the current-limit set point
(I0). The battery current-regulation loop is in control as
long as BATT voltage is below V0. When BATT voltage
reaches V0, the current loop no longer regulates. A
third loop reduces the battery-charging current when
the sum of the system (the main load) and the battery
charger input current exceeds the charging source cur-
rent limit.
between REF and GND.
The input source current is the sum of the device cur-
rent, the charge input current, and the load current. The
device current is minimal (6mA max) in comparison to
the charge and load currents. The charger input cur-
rent is generated by the DC-DC converter; therefore, the
actual source current required is determined as follows:
I
= I
+ [(I
· V
/ (V · η)]
BATT) IN
SOURCE
LOAD
CHARGE
where η is the efficiency of the DC-DC converter (typi-
cally 85% to 95%).
V
determines the threshold voltage of the CSS com-
CLS
parator. R3 and R4 (Figure 1) set the voltage at CLS.
Sense resistor R1 sets the maximum allowable source
current. Calculate the maximum current as follows:
Setting Output Voltage
The MAX1645/MAX1645A voltage DACs have a 16mV
LSB and an 18.432V full scale. The SMBus specifica-
tion allows for a 16-bit ChargingVoltage() command
that translates to a 1mV LSB and a 65.535V full-scale
voltage; therefore, the ChargingVoltage() value corre-
sponds to the output voltage in millivolts. The
MAX1645/MAX1645A ignore the first four LSBs and use
the next 11 LSBs to control the voltage DAC. All codes
greater than or equal to 0b0100 1000 0000 0000
(18432mV) result in a voltage overrange, limiting the
charger voltage to 18.432V. All codes below 0b0000
0100 0000 0000 (1024mV) terminate charging.
I
= V
/ (20 · R )
1
CLS
MAX
(Limit V
- V
to between 102.4mV and
CSSN
CSSP
204.8mV.)
The configuration in Figure 1 provides an input current
limit of:
I
= (2.048V / 20) / 0.04Ω = 2.56A
MAX
LDO Regulator
An integrated LDO regulator provides a +5.4V supply
derived from DCIN, which can deliver up to 15mA of
current. The LDO sets the gate-drive level of the NMOS
switches in the DC-DC converter. The drivers are actu-
ally powered by DLOV and BST, which must be con-
nected to LDO through a lowpass filter and a diode as
shown in Figure 1. See also the MOSFET Drivers sec-
tion. The LDO also supplies the 4.096V reference and
most of the control circuitry. Bypass LDO with a 1µF
capacitor.
Setting Output Current
The MAX1645/MAX1645A current DACs have a 64mA
LSB and a 3.008A full scale. The SMBus specification
allows for a 16-bit ChargingCurrent() command that
translates to a 1mA LSB and a 65.535A full-scale cur-
rent; the ChargingCurrent() value corresponds to the
charging voltage in milliamps. The MAX1645/
MAX1645A drop the first six LSBs and use the next
six LSBs to control the current DAC. All codes above
0b00 1011 1100 0000 (3008mA) result in a current
overrange, limiting the charger current to 3.008A. All
codes below 0b0000 0000 1000 0000 (128mA) turn the
charging current off. A 50mΩ sense resistor (R2 in
Figure 1) is required to achieve the correct CODE/cur-
rent scaling.
V
Supply
DD
This input provides power to the SMBus interface and
the thermistor comparators. Typically connect V to
DD
LDO or, to keep the SMBus interface of the
MAX1645/MAX1645A active while the supply to DCIN is
removed, connect an external supply to V
.
DD
______________________________________________________________________________________ 11
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ADAPTER IN
R13
D4
P1
FDS6675
1k
1N4148
D1
1N5821
PDS
CVS
R14
DCIN
4.7Ω
C5
1µF
C23
0.1µF
CSSP
C2
22µF
C1
22µF
C20, 1µF
C19, 1µF
R1
0.04Ω
MAX1645A
REF
CSSN
LDO
R15
4.7Ω
C7
1µF
R3
100k
LOAD
C6
1µF
CLS
R12
33Ω
D3
1N4148
R4
100k
BST
GND
DLOV
DAC
CCV
C16
0.1µF
C8
0.1µF
C14
0.1µF
R5
10k
DHI
LX
N1
FDS6680
CCI
C9
0.01µF
C10
0.01µF
CCS
DLO
C11
0.01µF
L1
22µH
N2
FDS6612A
D2
1N5821
PGND
R11
1Ω
CSIP
C18
0.1µF
R2
0.05Ω
C24
0.1µF
R16
1Ω
CSIN
PDL
P2
FDS6675
C3
22µF
C4
22µF
BATT
R7
BATTERY
HOST
R6
10k
10k
THM
C13
1.5nF
V
DD
C12
1µF
R8
10k
R10
10k
R9
10k
SCL
SDA
INT
Figure 1. Typical Application Circuit
12 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
BST
MAX1645/MAX1645A
DHI
LX
CSSP
CSSN
CLS
DHI
CSS
GMS
DC-DC
LVC
DLOV
DLO
DLO
CSIP
CSIN
CSI
PGND
GMI
BATT
CCS
CCI
CCV
GMV
CVS
BATT
PDL
PDS
PDS
PDL
DCIN
LDO
V
DD
VL
SCL
SDA
INT
DACI
SMB
REF
REF
DACV
GND
DAC
TEMP
THM
Figure 2. Functional Diagram
______________________________________________________________________________________ 13
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
that monitors the battery-to-charger communications as
a Level 2 SMBus charger. The MAX1645/MAX1645A
are SMBus slave devices and do not initiate communi-
cation on the bus. They receive commands and
respond to queries for status information. Figure 3
shows examples of the SMBus Write-Word and Read-
Word protocols, and Figures 4 and 5 show the SMBus
serial-interface timing.
Operating Conditions
The MAX1645/MAX1645A change their operation
depending on the voltages at DCIN, BATT, V
THM. Several important operating states follow:
and
DD,
• AC Present. When DCIN is > 7.5V, the battery is
considered to be in an AC Present state. In this con-
dition, both the LDO and REF will function properly
and battery charging is allowed. When AC is pre-
sent, the AC_PRESENT bit (bit 15) in the
ChargerStatus() register is set to “1.”
Each communication with these parts begins with the
MASTER issuing a START condition that is defined as a
falling edge on SDA with SCL high and ends with a
STOP condition defined as a rising edge on SDA with
SCL high. Between the START and STOP conditions,
the device address, the command byte, and the data
bytes are sent. The MAX1645/MAX1645As’ device
address is 0x12 and supports the charger commands
as described in Tables 1–6.
• Power Fail. When DCIN is < BATT + 0.3V, the part is
in the Power Fail state, since the charger doesn’t
have enough input voltage to charge the battery. In
Power Fail, the PDS input PMOS switch is turned off
and the POWER_FAIL bit (bit 13) in the
ChargerStatus() register is set to “1.”
• Battery Present. When THM is < 91% of V , the
DD
battery is considered to be present. The MAX1645/
MAX1645A use the THM pin to detect when a battery
is connected to the charger. When the battery is pre-
sent, the BATTERY_PRESENT bit (bit 14) in the
ChargerStatus() register is set to “1” and charging
can proceed. When the battery is not present, all of
the registers are reset. With no battery present, the
charger will perform a "Float" charge to minimize
contact arcing on battery connection. "Float" charge
will still try to regulate the BATT pin voltage at 18.32V
with 128mA of current compliance.
Battery Charger Commands
ChargerSpecInfo()
The ChargerSpecInfo() command uses the Read-Word
protocol (Figure 3b). The command code for
ChargerSpecInfo() is 0x11 (0b00010001). Table 1 lists
the functions of the data bits (D0–D15). Bit 0 refers to
the D0 bit in the Read-Word protocol. The
MAX1645/MAX1645A comply with level 2 Smart Battery
Charger Specification Revision 1.0; therefore, the
ChargerSpecInfo() command returns 0x01.
ChargerMode()
The ChargerMode() command uses the Write-Word
protocol (Figure 3a). The command code for
ChargerMode() is 0x12 (0b00010010). Table 2 lists the
functions of the data bits (D0–D15). Bit 0 refers to the
D0 bit in the Write-Word protocol.
• Battery Undervoltage. When BATT < 2.5V, the bat-
tery is in an undervoltage state. This causes the
charger to reduce its current compliance to 128mA.
The content of the ChargingCurrent() register is unaf-
fected and, when the BATT voltage exceeds 2.7V,
normal charging resumes. ChargingVoltage() is unaf-
fected and can be set as low as 1.024V.
To charge a battery that has a thermistor impedance in
the HOT range (i.e., THERMISTOR_HOT = 1 and THER-
MISTOR_UR = 0), the host must use the Charger
Mode() command to clear HOT_STOP after the battery
is inserted. The HOT_STOP bit returns to its default
power-up condition (“1”) whenever the battery is
removed.
• V
Undervoltage. When V
< 2.5V, the V
sup-
DD
DD
DD
ply is in an undervoltage state, and the SMBus inter-
face will not respond to commands. Coming out of
the undervoltage condition, the part will be in its
Power-On Reset state. No charging will occur when
V
is under voltage.
DD
ChargerStatus()
The ChargerStatus() command uses the Read-Word
protocol (Figure 3b). The command code for Charger
Status() is 0x13 (0b00010011). Table 3 describes the
functions of the data bits (D0–D15). Bit 0 refers to the
D0 bit in the Read-Word protocol.
SMBus Interface
The MAX1645/MAX1645A receive control inputs from
the SMBus interface. The serial interface complies with
the SMBus specification (refer to the System
Management Bus Specification from Intel Corporation).
Charger functionality complies with the Intel/Duracell
Smart Charger Specification for a Level 2 charger.
The ChargerStatus() command returns information
about thermistor impedance and the MAX1645/
MAX1645A’s internal state. The latched bits, THERMIS-
TOR_HOT and ALARM_INHIBITED, are cleared when-
The MAX1645/MAX1645A use the SMBus Read-Word
and Write-Word protocols to communicate with the bat-
tery being charged, as well as with any host system
14 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ever BATTERY_PRESENT = 0 or ChargerMode() is writ-
ten with POR_RESET = 1. The ALARM_INHIBITED sta-
tus bit can also be cleared by writing a new charging
current OR charging voltage.
a) Write-Word Format
LꢁW
DATA
BYTE
HIGH
DATA
BYTE
SLAVE
ADDRESS
CꢁMMAND
BYTE
S
W
ACK
ACK
ACK
ACK
P
7 bits
1b
0
1b
0
8 bits
1b
0
8 bits
1b
0
8 bits
1b
0
MSB LSB
MSB LSB
MSB LSB
MSB LSB
ChargerMode() = 0x12
ChargingCurrent() = 0x14
ChargerVoltage() = 0x15
AlarmWarning() = 0x16
Preset to
0b0001001
D7
D0
D15
D8
b) Read-Word Format
SLAVE
LꢁW
DATA
BYTE
HIGH
DATA
BYTE
CꢁMMAND
ACK
SLAVE
ADDRESS
S
W
ACK
S
R
ACK
ACK
NACK P
ADDRESS
BYTE
7 bits
1b 1b
8 bits
1b
0
7 bits
1b 1b
8 bits
1b
0
8 bits
1b
1
MSB LSB
0
0
MSB LSB
MSB LSB
1
0
MSB LSB
MSB LSB
Preset to
0b0001001
Preset to
0b0001001
D7
D0
D15
D8
ChargerSpecInfo() =
0x11
ChargerStatus() =
0x13
Legend:
S = Start Condition or Repeated Start Condition
ACK = Acknowledge (logic low)
W = Write Bit (logic low)
P = Stop Condition
NACK = NOT Acknowledge (logic high)
R = Read Bit (logic high)
MASTER TO SLAVE
SLAVE TO MASTER
Figure 3. SMBus a) Write-Word and b) Read-Word Protocols
______________________________________________________________________________________ 15
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
MOST SIGNIFICANT
ADDRESS BIT (A6)
CLOCKED INTO SLAVE
A5 CLOCKED
INTO SLAVE
A4 CLOCKED
INTO SLAVE
A3 CLOCKED
INTO SLAVE
START
CONDITION
SCL
SDA
t
t
t
HIGH
LOW
HD:STA
t
t
t
HD:DAT
t
t
SU:DAT
SU:STA
HD:DAT
SU:DAT
Figure 4. SMBus Serial Interface Timing—Address
MOST SIGNIFICANT BIT
OF DATA CLOCKED
INTO MASTER
ACKNOWLEDGE
BIT CLOCKED
INTO MASTER
R/W BIT
CLOCKED
INTO SLAVE
SCL
SDA
SLAVE PULLING
SDA LOW
t
t
DV
DV
Figure 5. SMBus Serial Interface Timing—Acknowledgment
16 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Table 1. ChargerSpecInfo()
BIT
0
NAME
DESCRIPTIꢁN
CHARGER_SPEC
CHARGER_SPEC
CHARGER_SPEC
CHARGER_SPEC
SELECTOR_SUPPORT
Reserved
Returns a “1” for Version 1.0
Returns a “0” for Version 1.0
Returns a “0” for Version 1.0
Returns a “0” for Version 1.0
1
2
3
4
Returns a “0,” indicating no smart battery selector functionality
Returns a “0”
5
6
Reserved
Returns a “0”
7
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Returns a “0”
Returns a “0”
Returns a “0”
Returns a “0”
Returns a “0”
Returns a “0”
Returns a “0”
Returns a “0”
Returns a “0”
8
9
10
11
12
13
14
15
Command: 0x11
______________________________________________________________________________________ 17
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Table 2. ChargerMode()
BIT
NAME
DESCRIPTIꢁN
0* = Allow normal operation; clear the CHG_INHIBITED flip-flop.
1 = Turn off the charger; set the CHG_INHIBITED flip-flop.
The CHG_INHIBITED flip-flop is not affected by any other commands.
0
INHIBIT_CHARGE
ENABLE_POLLING
1
Not implemented
0 = No change.
1 = Change the ChargingVoltage() to 0xFFFF and the ChargingCurrent()
to 0x00C0; clear the THERMISTOR_HOT and ALARM_INHIBITED flip-
flops.
2
POR_RESET
3
4
RESET_TO_ZERO
Not implemented
0* = Interrupt on either edge of the AC_PRESENT status bit.
1 = Do not interrupt because of an AC_PRESENT bit change.
AC_PRESENT_MASK
0* = Interrupt on either edge of the BATTERY_PRESENT status bit.
1 = Do not interrupt because of a BATTERY_PRESENT bit change.
5
6
BATTERY_PRESENT_ MASK
POWER_FAIL_MASK
0* = Interrupt on either edge of the POWER_FAIL status bit.
1 = Do not interrupt because of a POWER_FAIL bit change.
7
8
9
Not implemented
Not implemented
Not implemented
0 = The THERMISTOR_HOT status bit does not turn off the charger.
1* = The THERMISTOR_HOT status bit does turn off the charger.
THERMISTOR_HOT is reset by either POR_RESET or
BATTERY_PRESENT = 0 status bit.
10
HOT_STOP
11
Not implemented
Not implemented
Not implemented
Not implemented
Not implemented
12
13
14
15
Command: 0x12
*State at chip initial power-on (i.e., V
from 0 to +3.3V)
DD
18 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Table 3. ChargerStatus()
BIT
NAME
FUNCTIꢁN
0* = Ready to charge Smart Battery.
0
CHARGE_INHIBITED
1 = Charger is inhibited, I(chg) = 0mA.
This status bit returns the value of the CHG_INHIBITED flip-flop.
1
2
MASTER_MODE
Always returns “0”
0 = Battery voltage is limited at the set point.
1 = Battery voltage is less than the set point.
VOLTAGE_NOT_REG
0 = Battery current is limited at the set point.
1 = Battery current is less than the set point.
3
CURRENT_NOT_REG
4
5
LEVEL_2
LEVEL_3
Always returns a “1”
Always returns a “0”
0* = The ChargingCurrent() value is valid for the MAX1645.
1 = The ChargingCurrent() value exceeds the MAX1645 output range, i.e.,
programmed ChargingCurrent() exceeds 3008mA.
6
7
CURRENT_OR
VOLTAGE_OR
0 = The ChargingVoltage() value is valid for the MAX1645.
1* = The ChargingVoltage() value exceeds the MAX1645 output range, i.e.,
programmed ChargingVoltage() exceeds 1843mV.
0 = THM is < 91% of the reference voltage.
1 = THM is > 91% of the reference voltage.
8
9
THERMISTOR_OR
0 = THM is < 75.5% of the reference voltage.
1 = THM is > 75.5% of the reference voltage.
THERMISTOR_COLD
0 = THM has not dropped to < 23.5% of the reference voltage.
1 = THM has dropped to < 23.5% of the reference voltage.
THERMISTOR_HOT flip-flop cleared by BATTERY_PRESENT = 0 or writing a “1” into
the POR_RESET bit in the ChargerMode() command.
10
11
THERMISTOR_HOT
THERMISTOR_UR
0 = THM is > 7.5% of the reference voltage.
1 = THM is < 7.5% of the reference voltage.
Returns the state of the ALARM_INHIBITED flip-flop. This flip-flop is set by either a
watchdog timeout or by writing an AlarmWarning() command with bits 11, 12, 13, 14,
or 15 set. This flip-flop is cleared by BATTERY_PRESENT = 0, writing a “1” into the
POR_RESET bit in the ChargerMode() command, or by receiving successive
ChargingVoltage() and ChargingCurrent() commands. POR: 0.
12
ALARM_INHIBITED
0 = The charging source voltage CVS is above the BATT voltage.
1 = The charging source voltage CVS is below the BATT voltage.
13
POWER_FAIL
BATTERY_PRESENT
AC_PRESENT
0 = No battery is present (based on THM input).
1 = Battery is present (based on THM input).
14
0 = DCIN is below the 7.5V undervoltage threshold.
1 = DCIN is above the 7.5V undervoltage threshold.
15
Command: 0x13
*State at chip initial power-on.
______________________________________________________________________________________ 19
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Table 4. ChargerCurrent()
BIT
0
NAME
FUNCTIꢁN
Not used. Normally a 1mA weight.
Not used. Normally a 2mA weight.
Not used. Normally a 4mA weight.
Not used. Normally an 8mA weight.
Not used. Normally a 16mA weight.
Not used. Normally a 32mA weight.
1
2
3
4
5
0 = Adds 0mA of charger-current compliance.
1 = Adds 64mA of charger-current compliance, 128mA min.
6
7
Charge Current, DACI 0
Charge Current, DACI 1
Charge Current, DACI 2
Charge Current, DACI 3
Charge Current, DACI 4
Charge Current, DACI 5
0 = Adds 0mA of charger-current compliance.
1 = Adds 128mA of charger-current compliance.
0 = Adds 0mA of charger-current compliance.
1 = Adds 256mA of charger-current compliance.
8
0 = Adds 0mA of charger-current compliance.
1 = Adds 512mA of charger-current compliance.
9
0 = Adds 0mA of charger-current compliance.
1 = Adds 1024mA of charger-current compliance.
10
11
12–15
0 = Adds 0mA of charger-current compliance.
1 = Adds 2048mA of charger-current compliance, 3008mA max.
0 = Adds 0mA of charger current compliance.
1 = Sets charger compliance into overrange, 3008mA.
Command: 0x14
20 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Table 5. ChargingVoltage()
PIN
0
BIT NAME
FUNCTIꢁN
Not used. Normally a 1mV weight.
Not used. Normally a 2mV weight.
Not used. Normally a 4mV weight.
Not used. Normally an 8mV weight.
1
2
3
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 16mV of charger-voltage compliance, 1.024V min.
4
5
Charge Voltage, DACV 0
Charge Voltage, DACV 1
Charge Voltage, DACV 2
Charge Voltage, DACV 3
Charge Voltage, DACV 4
Charge Voltage, DACV 5
Charge Voltage, DACV 6
Charge Voltage, DACV 7
Charge Voltage, DACV 8
Charge Voltage, DACV 9
Charge Voltage, DACV 10
Charge Voltage, Overrange
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 32mV of charger-voltage compliance, 1.024V min.
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 64mV of charger-voltage compliance, 1.024V min.
6
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 128mV of charger-voltage compliance, 1.024V min.
7
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 256mV of charger-voltage compliance, 1.024V min.
8
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 512mV of charger-voltage compliance, 1.024V min.
9
0 = Adds 0mA of charger-voltage compliance.
1 = Adds 1024mV of charger-voltage compliance.
10
11
12
13
14
15
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 2048mV of charger-voltage compliance.
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 4096mV of charger-voltage compliance.
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 8192mV of charger-voltage compliance.
0 = Adds 0mV of charger-voltage compliance.
1 = Adds 16384mV of charger-voltage compliance, 18432mV max.
0 = Adds 0mV of charger-voltage compliance.
1 = Sets charger compliance into overrange, 18432mV.
Command: 0x15
______________________________________________________________________________________ 21
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Table 6. AlarmWarning()
BIT
0
BIT NAME
Error Code
DESCRIPTIꢁN
Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used
1
Error Code
2
Error Code
3
Error Code
4
FULLY_DISCHARGED
FULLY_CHARGED
DISCHARGING
5
6
7
INITIALIZING
8
REMAINING_TIME_ ALARM
REMAINING_CAPACITY_ ALARM
Reserved
9
10
0 = Charge normally
1 = Terminate charging
11
12
13
14
TERMINATE_ DISCHARGE_ALARM
OVER_TEMP_ALARM
0 = Charge normally
1 = Terminate charging
0 = Charge normally
1 = Terminate charging
OTHER_ALARM
0 = Charge normally
1 = Terminate charging
TERMINATE_CHARGE_ ALARM
OVER_CHARGE_ALARM
0 = Charge normally
1 = Terminate charging
15
Command: 0x16
22 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
ChargingCurrent() (POR: 0x0080)
The ChargingCurrent() command uses the Write-Word
protocol (Figure 3a). The command code for Charging-
Current() is 0x14 (0b00010100). The 16-bit binary num-
ber formed by D15–D0 represents the current-limit set
point (I0) in milliamps. However, since the
MAX1645/MAX1645A have 64mA resolution in setting
I0, the D0–D5 bits are ignored as shown in Table 4.
Figure 6 shows the mapping between I0 (the current-
regulation-loop set point) and the ChargingCurrent()
code. All codes above 0b00 1011 1100 0000 (3008mA)
result in a current overrange, limiting the charger current
to 3.008A. All codes below 0b0000 0000 1000 0000
(128mA) turn the charging current off. A 50mΩ sense
resistor (R2 in Figure 1) is required to achieve the cor-
rect CODE/current scaling.
sets the ALARM_INHIBITED status bit in the
MAX1645/MAX1645A if D15, D14, D13, D12, or D11 of
the Write-Word protocol data equals 1. Table 6 summa-
rizes the Alarm-Warning() command’s function. The
ALARM_INHIBITED status bit remains set until the bat-
tery is removed, a ChargerMode() command is written
with the POR_RESET bit set, or new ChargingCurrent()
AND ChargingVoltage() values are written. As long as
ALARM_INHIBITED = 1, the MAX1645/MAX1645A
switching regulators remain off.
Interrupts and Alert Response Address
The MAX1645/MAX1645A request an interrupt by
pulling the INT pin low. An interrupt is normally request-
ed when there is a change in the state of the
ChargerStatus() bits POWER_FAIL (bit 13),
BATTERY_PRESENT (bit 14), or AC_PRESENT (bit 15).
Therefore, the INT pin will pull low whenever the AC
adapter is connected or disconnected, the battery is
inserted or removed, or the charger goes in or out of
dropout. The interrupts from each of the ChargerStatus()
bits can be masked by an associated ChargerMode()
bit POWER_FAIL_MASK (bit 6), BATTERY_PRE-
SENT_MASK (bit 5), or AC_PRESENT_MASK (bit 4).
The power-on reset value for the ChargingCurrent() reg-
ister is 0x0080; thus, the first time a MAX1645/
MAX1645A is powered on, the BATT current regulates
to 128mA. Any time the battery is removed, the
ChargingCurrent() register returns to its power-on reset
state.
ChargingVoltage() (POR: 0x4800)
The ChargingVoltage() command uses the Write-Word
protocol (Figure 3a). The command code for
ChargingVoltage() is 0x15 (0b00010101). The 16-bit
binary number formed by D15–D0 represents the volt-
age set point (V0) in millivolts; however, since the
MAX1645/MAX1645A have 16mV resolution in setting
V0, the D0, D1, D2, and D3 bits are ignored as shown in
Table 5.
All interrupts are cleared by sending any command to
the MAX1645/MAX1645A, or by sending a command to
the AlertResponse() address, 0x19, using a modified
Receive Byte protocol. In this protocol, all devices that
set an interrupt will try to respond by transmitting their
address, and the device with the highest priority, or
most leading 0’s, will be recognized and cleared. The
process will be repeated until all devices requesting
interrupts are addressed and cleared. The MAX1645/
The ChargingVoltage command is used to set the bat-
tery charging voltage compliance from 1.024V to
18.432V. All codes greater than or equal to 0b0100
1000 0000 0000 (18432mV) result in a voltage over-
range, limiting the charger voltage to 18.432V. All codes
below 0b0000 0100 0000 0000 (1024mV) terminate
charge. Figure 7 shows the mapping between V0
(the voltage-regulation-loop set point) and the
ChargingVoltage() code.
150.4
102.4
The power-on reset value for the ChargingVoltage() reg-
ister is 0x4880; thus, the first time a MAX1645/
MAX1645A are powered on, the BATT voltage regulates
to 18.432V. Any time the battery is removed, the
ChargingVoltage() register returns to its power-on reset
state. The voltage at DAC corresponds to the set com-
pliance voltage divided by 4.5.
51.2
6.4
AlarmWarning() (POR: Not Alarm)
The AlarmWarning() command uses the Write-Word
protocol (Figure 3a). The command code for
AlarmWarning() is 0x16 (0b00010110). AlarmWarning()
0x0400
1024
0XFFFF
65535
0x0080
128
0x0800
2048
0x0BC0
3008
Figure 6. Average Voltage Between CSIP and CSIN vs. Charging
Current() Code
______________________________________________________________________________________ 23
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
18.432V
16.800V
V
= 4.096V
REF
VDCIN > 20V
12.592V
8.400V
4.192V
1.024V
0
0
0x0400
0xFFFF
0x106x
0x20Dx
0x313x
0x41A0 0x4800
ChargingVoltage() D15–D0 DATA
Figure 7. ChargingVoltage() Code to Voltage Mapping
MAX1645A respond to the AlertResponse() address
with 0x13, which is their address and a trailing “1.”
DC-to-DC Converter
The MAX1645/MAX1645A employ a buck regulator with
a boot-strapped NMOS high-side switch and a low-side
NMOS synchronous rectifier.
Charger Timeout
The MAX1645/MAX1645A include a timer that termi-
nates charge if the charger has not received a
ChargingVoltage() or ChargingCurrent() command in
175sec. During charging, the timer is reset each time a
ChargingVoltage() or ChargingCurrent() command is
received; this ensures that the charging cycle is not ter-
minated.
DC-DC Controller
The control scheme is a constant off-time, variable fre-
quency, cycle-by-cycle current mode. The off-time is
constant for a given BATT voltage; it varies with V
BATT
to keep the ripple current constant. During low-dropout
operation, a maximum on-time of 10ms allows the con-
troller to achieve >99% duty cycle with continuous con-
duction. Figure 8 shows the controller functional
diagram.
If timeout occurs, charging will terminate and both
ChargingVoltage() and ChargingCurrent() commands
are required to restart charging. A power-on reset will
also restart charging at 128mA.
24 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
10ms
S
CSSP
ADAPTER IN
LDO
RESET
4.0V
BST
R1
CSS
IMAX
CCMP
IMIN
MAX1645/MAX1645A
CSSN
BST
R
Q
DHI
LX
R
S
Q
C
BST
DHI
CHG
Q
L1
R2
0.25V
0.1V
DLO
DLO
1µs
CSIP
ZCMP
CSI
CSIN
BATT
GMS
GMI
LVC
C
OUT
BATTERY
R
FC
70k
GMV
R
FI
20k
DACV
DACI
CLS
CONTROL
ON
CCS
CCI
CCV
Figure 8. DC-to-DC Converter Functional Diagram
______________________________________________________________________________________ 25
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
MOSFET Drivers
1000
The low-side driver output DLO swings from 0V to DLOV.
DLOV is usually connected through a filter to LDO. The
high-side driver output DHI is bootstrapped off LX and
100
swings from V to V
. When the low-side driver turns
LX
BST
on, BST rises to one diode voltage below DLOV.
10
1
Filter DLOV with an RC circuit whose cutoff frequency
is about 50kHz. The configuration in Figure 1 intro-
duces a cutoff frequency of around 48kHz.
f = 1 / 2πRC = 1 / (2 · π · 33Ω · 0.1µF) = 48kHz
0.1
Thermistor Comparators
Four thermistor comparators evaluate the voltage at the
THM input to determine the battery temperature. This
input is meant to be used with the internal thermistor
connected to ground inside the battery pack. Connect
the output of the battery thermistor to THM. Connect a
-40
-50
-30 -20 -10
0
10 20 30 40 50 60 70 80 90 100 110
TEMPERATURE (°C)
Figure 9. Typical Thermistor Characteristics
• THERMISTOR_HOT bit is set when the thermistor
value is <3kΩ. This is a latched bit and is cleared by
removing the battery or sending a POR with the
ChargerMode() command. The MAX1645 charger is
stopped unless the HOT_STOP bit is cleared in the
ChargerMode() command. The MAX1645A charger
is stopped unless the HOT_STOP bit is cleared in the
ChargerMode() command or the RES_UR bit is set.
See Table 7.
resistor from THM to V . The resistor-divider sets the
DD
voltage at THM. When the charger is not powered up,
the battery temperature can still be determined if V
powered from an external voltage source.
is
DD
Thermistor Bits
Figure 9 shows the expected electrical behavior of a
103ETB-type thermistor (nominally 10kΩ at +25°C 5%
or better) to be used with the MAX1645/MAX1645A:
• THERMISTOR_UR bit is set when the thermistor
• THERMISTOR_OR bit is set when the thermistor
value is >100kΩ. This indicates that the thermistor is
open or a battery is not present. The charger is set to
POR, and the BATTERY_PRESENT bit is cleared.
value is <500Ω (i.e., THM is grounded).
Multiple bits may be set depending on the value of the
thermistor (e.g., a thermistor that is 450Ω will cause both
the THERMISTOR_HOT and the THERMISTOR_UR bits
to be set). The thermistor may be replaced by fixed-
value resistors in battery packs that do not require the
thermistor as a secondary fail-safe indicator. In this
• THERMISTOR_COLD bit is set when the thermistor
value is >30kΩ. The thermistor indicates a cold bat-
tery. This bit does not affect the charge.
Table 7. Thermistor Bit Settings
THERMISTꢁR
DESCRIPTIꢁN
STATUS BIT
CꢁNTRꢁLLED
WAKE-UP CHARGE
CHARGE
REG_UR and RES_HOT
RES_UR and RES_HOT
RES_HOT
Under Range
Under Range
Hot
Not allowed by MAX1645
Not allowed by MAX1645
Allowed by MAX1645A
Not Allowed
Allowed for Timeout
Period by MAX1645A
Not Allowed
Allowed for Timeout
Period
(None)
Normal
Allowed
Allowed for Timeout
Period
RES_COLD
Cold
Allowed
RES_OR and RES_COLD
Over Range
Float Charge*
Not Allowed
*See Battery Present item under Operating Conditions for more information.
26 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
V
CC
SYSTEM
POWER
CONTROL
SYSTEM
POWER
SUPPLY
DC (UNREGULATED) / V
+12V, -12V
BATTERY
AC
AC-DC
V
DC (UNREGULATED)
BATTERY
CONVERTER
(UNREGULATED)
SAFETY
SIGNAL
SMART
BATTERY
MAX1645A
SYSTEM HOST
(SMBus HOST)
SMART BATTERY
CHARGER
CRITICAL EVENTS
CHARGING VOLTAGE/CURRENT
REQUESTS
SMBus
BATTERY DATA/STATUS REQUESTS
CRITICAL EVENTS
Figure 10. Typical Single Smart Battery System
case, it is the responsibility of the battery pack to manip-
ulate the resistance to obtain correct charger behavior.
time. This allows the charger to achieve dropout perfor-
mance limited only by resistive losses in the DC-DC
converter components (P1, R1, N1, R2; see Figure 1).
The actual dropout voltage is limited to 300mV between
CVS and BATT by the power-fail comparator (see
Operating Conditions).
Load and Source Switch Drivers
The MAX1645/MAX1645A can drive two P-channel
MOSFETs to eliminate voltage drops across the
Schottky diodes, which are normally used to switch the
load current from the battery to the main DC source:
Applications Information
Smart Battery Charging
System/Background Information
• The source switch P1 is controlled by PDS. This P-
channel MOSFET is turned on when CVS rises to
300mV above BATT and turns off when CVS falls to
100mV above BATT. The same signal that controls
the PDS also sets the POWER_FAIL bit in the
Charger Status() register. See Operating Conditions.
A smart battery charging system, at a minimum, con-
sists of a smart battery and smart battery charger com-
patible with the Smart Battery System Specifications
using the SMBus.
• The load switch P2 is controlled by PDL. This P-
channel MOSFET is turned off when the CVS rises to
100mV below BATT and turns on when CVS falls to
300mV below BATT.
A system may use one or more smart batteries. Figure 10
shows a single-battery system. This configuration is
typically found in notebook computers, video cameras,
cellular phones, or other portable electronic equipment.
Dropout Operation
The MAX1645/MAX1645A have a 99.99% duty-cycle
capability with a 10ms maximum on-time and 1µs off-
Another configuration uses two or more smart batteries
(Figure 11). The smart battery selector is used either to
______________________________________________________________________________________ 27
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
AC
V
CC
SYSTEM
POWER
SUPPLY
+12V, -12V
DC (UNREGULATED) / V
BATTERY
NOTE: SB 1 POWERING SYSTEM
SB 2 CHARGING
AC-DC
CONVERTER
(UNREGULATED)
SMART BATTERY 1
SMART BATTERY 2
SMBus
MAX1645A
SYSTEM HOST
(SMBus HOST)
SAFETY SIGNAL
SMART BATTERY
SELECTOR
SMART
BATTERY
CHARGER
V
CHARGE
CRITICAL EVENTS
SMBus
BATTERY DATA/STATUS REQUESTS
Figure 11. Typical System Using Multiple Smart Batteries
connect batteries to the smart battery charger or the
system, or to disconnect them, as appropriate. For
each battery, three connections must be made: power
(the battery’s positive and negative terminals), the
SMBus (clock and data), and the safety signal (resis-
tance, typically temperature dependent). Additionally,
the system host must be able to query any battery so it
can display the state of all batteries present in the system.
Table 8. Smart Battery Charger Type
by SMBus Mode and Charge Algorithm
Source
CHARGE ALGꢁRITHM SꢁURCE
SMBus MꢁDE
MꢁDIFIED FRꢁM
BATTERY
BATTERY
Figure 11 shows a two-battery system where battery 2
is being charged while battery 1 is powering the sys-
tem. This configuration may be used to “condition” bat-
tery 1, allowing it to be fully discharged prior to
recharge.
Slave only
Level 2
Level 3
Level 3
Level 3
Slave/Master
Note: Level 1 smart battery chargers were defined in the ver-
sion 0.95a specification. While they can correctly interpret
smart battery end-of-charge messages, minimizing over-
charge, they do not provide truly chemistry-independent
charging. They are no longer defined by the Smart Battery
Charger Specification and are explicitly not compliant with this
and subsequent Smart Battery Charger Specifications.
Smart Battery Charger Types
Two types of smart battery chargers are defined: Level 2
and Level 3. All smart battery chargers communicate
with the smart battery using the SMBus; the two types
differ in their SMBus communication mode and whether
they modify the charging algorithm of the smart battery
28 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
(Table 8). Level 3 smart battery chargers are supersets
of Level 2 chargers and, as such, support all Level 2
charger commands.
ers’ contacts. The following sections describe how to
select these components.
MOSFETs and Schottky Diodes
Schottky diode D1 provides power to the load when the
AC adapter is inserted. Choose a 3A Schottky diode or
higher. This diode may not be necessary if P1 is used.
Level 2 Smart Battery Charger
The Level 2 or smart battery-controlled smart battery
charger interprets the smart battery’s critical warning
messages and operates as an SMBus slave device to
respond to the smart battery’s ChargingVoltage() and
ChargingCurrent() messages. The charger is obliged to
adjust its output characteristics in direct response to
the ChargingVoltage() and ChargingCurrent() mes-
sages it receives from the battery. In Level 2 charging,
the smart battery is completely responsible for initiating
the communication and providing the charging algo-
rithm to the charger.
The P-channel MOSFET P1 turns on when V
BATT
>
CVS
V
. This eliminates the voltage drop and power con-
sumption of the Schottky diode. To minimize power loss,
select a MOSFET with an R
of 50mΩ or less. This
DS(ON)
MOSFET must be able to deliver the maximum current
as set by R1. D1 and P1 provide protection from
reversed voltage at the adapter input.
The N-channel MOSFETs N1 and N2 are the switching
devices for the buck controller. High-side switch N1
should have a current rating of at least 6A and have an
The smart battery is in the best position to tell the smart
battery charger how it needs to be charged. The charg-
ing algorithm in the battery may request a static charge
condition or may choose to periodically adjust the
smart battery charger’s output to meet its present
needs. A Level 2 smart battery charger is truly chem-
istry independent and, since it is defined as an SMBus
slave device only, the smart battery charger is relatively
inexpensive and easy to implement.
R
of 50mΩ or less. The driver for N1 is powered
DS(ON)
by BST; its current should be less than 10mA. Select a
MOSFET with a low total gate charge and determine
the required drive current by I
= Q
· f (where f
GATE
GATE
is the DC-DC converter maximum switching frequency
of 400kHz).
The low-side switch N2 should also have a current rat-
ing of at least 3A, have an R
of 100mΩ or less,
DS(ON)
and a total gate charge less than 10nC. N2 is used to
provide the starting charge to the BST capacitor C14.
During normal operation, the current is carried by
Schottky diode D2. Choose a 3A or higher Schottky
diode.
Selecting External Components
Table 10 lists the recommended components and
refers to the circuit of Figure 1; Table 9 lists the suppli-
D3 is a signal-level diode, such as the 1N4148. This
diode provides the supply current to the high-side
MOSFET driver.
Table 9. Component Suppliers
CꢁMPꢁNENT
MANUFACTURER
PART
The P-channel MOSFET P2 delivers the current to the
load when the AC adapter is removed. Select a MOS-
Sumida
CDRH127 series
D03316P series
UP2 series
FET with an R
of 50mΩ or less to minimize power
DS(ON)
loss and voltage drop.
Inductor
Coilcraft
Coiltronics
Internal Rectifier
Fairchild
Vishay-Siliconix
Dale
Inductor Selection
IRF7309
Inductor L1 provides power to the battery while it is
MOSFET
FDS series
being charged. It must have a saturation current of at
Si4435/6
1
least 3A plus /2 of the current ripple (∆I ).
L
WSL series
Sense Resistor
Capacitor
1
I
= 3A + /2 ∆I
SAT
L
IRC
LR2010-01 series
The controller determines the constant off-time period,
which is dependent on BATT voltage. This makes the
ripple current independent of input and battery voltage
TPS series,
TAJ series
AVX
Sprague
Motorola
Nihon
595D series
and should be kept to less than 1A. Calculate the ∆I
L
1N5817–1N5822
NSQ03A04
with the following equation:
Diode
∆I = 21Vµs / L
L
Central
Semiconductor
CMSH series
Higher inductor values decrease the ripple current.
Smaller inductor values require higher saturation cur-
______________________________________________________________________________________ 29
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Table 10. Component Selection
DESIGNATIꢁN
C1, C2 Input Capacitors
DESCRIPTIꢁN
22µF, 35V low-ESR tantalum capacitors
AVX TPSE226M035R0300
22µF, 25V low-ESR tantalum capacitors
AVX TPSD226M025R0200
C3, C4 Output Capacitors
C5, C19, C20
1µF, >30V ceramic capacitors
1µF ceramic capacitors
C6, C7, C12
C8, C14, C16
0.1µF ceramic capacitors
0.01µF ceramic capacitors
1500pF ceramic capacitor
0.1µF, >20V ceramic capacitors
0.1µF, >30V ceramic capacitor
C9, C10, C11 Compensation Capacitors
C13
C18, C24
C23
40V, 2A schottky diodes
Central Semiconductor CMSH2-40
D1, D2
Small-signal diodes
Central Semiconductor CMPSH-3
D3, D4
22µH, 3.6A buck inductor
Sumida CDRH127-220
L1
30V, 11.5A, high-side N-channel MOSFET (SO-8)
Fairchild FDS6680
N1 High-Side MOSFET
30V, 8.4A, low-side N-channel MOSFET
Fairchild FDS6612A or
30V, signal level N-channel MOSFET
2N7002
N2 Low-Side MOSFET
30V, 11A P-Channel MOSFET load and source switches
Fairchild FDS6675
P1, P2
R1
40mΩ 1%, 0.5W battery current-sense resistor
Dale WSL-2010/40mΩ/1%
50mΩ 1%, 0.5W source current-sense resistor
Dale WSL-2010/50mΩ/1%
R2
R3, R4
R3 + R4 >100kΩ input current-limit setting resistors
10kΩ 5% resistors
R5, R7, R8, R9, R10
R6
10kΩ 1% temperature sensor network resistor
1Ω 5% resistors
R11, R16
R12
33Ω 5% resistor
R13
1kΩ 5% resistor
R14, R15
4.7Ω 5% resistors
30 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
rent capabilities and degrade efficiency. Typically, a
22µH inductor is ideal for all operating conditions.
• Minimize current-sense resistor trace lengths and
ensure accurate current sensing with Kelvin con-
nections.
Other Components
CCV, CCI, and CCS are the compensation points for the
three regulation loops. Bypass CCV with a 10kΩ resistor
in series with a 0.01µF capacitor to GND. Bypass CCI
and CCS with 0.01µF capacitors to GND. R7 and R13
serve as protection resistors to THM and CVS, respec-
tively. To achieve acceptable accuracy, R6 should be
10kΩ and 1% to match the internal battery thermistor.
• Minimize ground trace lengths in the high-current
paths.
• Minimize other trace lengths in the high-current
paths:
• Use > 5mm-wide traces
• Connect C1 and C2 to high-side MOSFET
(10mm max length)
Current-Sense Input Filtering
In normal circuit operation with typical components, the
current-sense signals can have high-frequency tran-
sients that exceed 0.5V due to large current changes
and parasitic component inductance. To achieve prop-
er battery and input current compliance, the current-
sense input signals should be filtered to remove large
common-mode transients. The input current limit sens-
ing circuitry is the most sensitive case due to large cur-
rent steps in the input filter capacitors (C1 and C2) in
Figure 1. Use 1µF ceramic capacitors from CSSP and
CSSN to GND. Smaller 0.1µF ceramic capacitors can
be used on the CSIP and CSIN inputs to GND since the
current into the battery is continuous. Place these
capacitors next to the single-point ground directly
under the MAX1645/MAX1645A.
• Connect rectifier diode cathode to low-side.
MOSFET (5mm max length)
• LX node (MOSFETs, rectifier cathode, inductor:
15mm max length). Ideally, surface-mount
power components are flush against one another
with their ground terminals almost touching.
These high-current grounds are then connected
to each other with a wide, filled zone of top-
layer copper so they do not go through vias.
The resulting top-layer subground plane is con-
nected to the normal inner-layer ground plane
at the output ground terminals, which ensures
that the IC’s analog ground is sensing at the
supply’s output terminals without interference
from IR drops and ground noise. Other high-
current paths should also be minimized, but
focusing primarily on short ground and current-
sense connections eliminates about 90% of all
PC board layout problems.
Layout and Bypassing
Bypass DCIN with a 1µF to GND (Figure 1). D4 protects
the device when the DC power source input is
reversed. A signal diode for D4 is adequate as DCIN
only powers the LDO and the internal reference.
Bypass LDO, BST, DLOV, and other pins as shown in
Figure 1.
2) Place the IC and signal components. Keep the main
switching nodes (LX nodes) away from sensitive ana-
log components (current-sense traces and REF
capacitor). Important: The IC must be no further
than 10mm from the current-sense resistors.
Good PC board layout is required to achieve specified
noise, efficiency, and stable performance. The PC
board layout artist must be given explicit instructions,
preferably a pencil sketch showing the placement of
power-switching components and high-current routing.
Refer to the PC board layout in the MAX1645/
MAX1645A evaluation kit manual for examples. A
ground plane is essential for optimum performance. In
most applications, the circuit will be located on a multi-
layer board, and full use of the four or more copper lay-
ers is recommended. Use the top layer for high-current
connections, the bottom layer for quiet connections
Keep the gate drive traces (DHI, DLO, and BST)
shorter than 20mm and route them away from the
current-sense lines and REF. Place ceramic bypass
capacitors close to the IC. The bulk capacitors can
be placed further away. Place the current-sense
input filter capacitors under the part, connected
directly to the GND pin.
3) Use a single-point star ground placed directly below
the part. Connect the input ground trace, power
ground (subground plane), and normal ground to
this node.
(REF, CCV, CCI, CCS, DAC, DCIN, V , and GND),
DD
and the inner layers for an uninterrupted ground plane.
Chip Information
Use the following step-by-step guide:
TRANSISTOR COUNT: 6996
1) Place the high-power connections first, with their
grounds adjacent:
______________________________________________________________________________________ 31
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Typical Operating Circuit
ADAPTER IN
DDS
CVS
DCIN
CSSP
MAX1645A
REF
CSSN
LDO
LOAD
CLS
BST
AGND
DLOV
DAC
CCV
DHI
LX
CCI
CCS
DLO
PGND
CSIP
CSIN
PDL
BATT
BATTERY
HOST
THM
V
DD
SCL
SDA
INT
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
32 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
相关型号：
MAX1645BEEI
Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
MAXIM
MAX1645EEI
Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
MAXIM
©2020 ICPDF网 联系我们和版权申明