LTC4079IDD#PBF [Linear]
LTC4079 - 60V, 250mA Linear Charger with Low Quiescent Current; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C;
| 型号： | LTC4079IDD#PBF |
| 厂家： | 
Linear |
| 描述： | LTC4079 - 60V, 250mA Linear Charger with Low Quiescent Current; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C |
| 文件： | 总20页 (文件大小：262K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4079
60V, 250mA Linear Charger
with Low Quiescent Current
FeaTures
DescripTion
The LTC®4079 is a low quiescent current, high voltage
linear charger for most battery chemistry types including
Li-Ion/Polymer, Lead-Acid or NiMH battery stacks up to
60V. The maximum charge current is adjustable from
10mA to 250mA with an external resistor. The battery
charge voltage is set using an external resistor divider.
n
Wide Input Voltage Range: 2.7V to 60V
n
Adjustable Battery Voltage: 1.2V to 60V
n
Adjustable Charge Current: 10mA to 250mA
n
Low Quiescent Current While Charging: I = 4µA
IN
n
Ultralow Battery Drain When Shutdown or Charged:
I
< 0.01µA
BAT
n
n
n
Auto Recharge
With an integrated power device, current sensing and
reverse current protection, a complete charging solution
usingtheLTC4079requiresveryfewexternalcomponents.
Thermalregulationensuresmaximumchargecurrentupto
thespecifiedlimitwithouttheriskofoverheating.Charging
can be terminated by either C/10 or adjustable timer.
Input Voltage Regulation for High Impedance Sources
Thermal Regulation Maximizes Output Current
without Overheating
Constant Voltage Feedback with 0.5ꢀ Accuracy
NTC Thermistor Input for Temperature Qualified
Charging
Adjustable Safety Timer
Charging Status Indication
Thermally Enhanced 10-Lead (3mm × 3mm)
DFN Package
n
n
n
n
n
Input voltage regulation reduces charge current when
the input voltage falls to an adjustable level or the battery
voltage, making it well suited for energy harvesting
applications. Other features include temperature qualified
charging, bad battery detection, automatic recharge with
sampled feedback in standby for negligible battery drain,
and an open-drain CHRG status output. The device is
offered in a compact, thermally enhanced 10-lead (3mm
× 3mm) DFN package.
applicaTions
n
Embedded Automotive and Industrial
n
Backup Battery Charging from Another Battery
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
n
Energy Harvesting Charger
Thin Film Battery Products
n
Typical applicaTion
Li-Ion Battery Charge Cycle
140
120
8.6
8.4
Charging a Backup Battery
500mAh 2-CELL LI-ION
V
BAT
9V TO 60V
IN
BAT
FB
8.4V
1µF
I
BAT
1.54M
249k
LTC4079
100
8.2
EN
80
60
40
20
8.0
7.8
7.6
7.4
CHRG
FBG
PROG NTCBIAS
C/10
TERMINATION
3.01k
10k
TIMER
GND
NTC
+
10k
Li-Ion
T
0
7.2
1
2
8
0
3
4
5
6
7
TIME (HOURS)
4079 TA01a
4079 TA01b
4079f
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For more information www.linear.com/LTC4079
LTC4079
absoluTe MaxiMuM raTings
pin conFiguraTion
(Notes 1, 2)
TOP VIEW
IN, BAT, EN, CHRG, FB, FBG Voltage.......... –0.3V to 62V
PROG TIMER Voltage..................................................3V
BAT Current....................................................... –400mA
PROG Current .....................................................–1.6mA
FBG Current .............................................................2mA
CHRG Current ..........................................................2mA
Operating Junction Temperature Range
IN
EN
1
2
3
4
5
10 BAT
9
8
7
6
FB
11
GND
PROG
NTCBIAS
NTC
FBG
CHRG
TIMER
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
(Notes 3, 5)................................................–40 to 125°C
Storage Temperature Range ......................–65 to 150°C
T
= 125°C, θ = 43°C/W
JA
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
JMAX
orDer inForMaTion
LEAD FREE FINISH
LTC4079EDD#PBF
LTC4079IDD#PBF
TAPE AND REEL
PART MARKING*
LGNQ
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4079EDD#TRPBF
LTC4079IDD#TRPBF
–40°C to 125°C
–40°C to 125°C
10-Lead (3mm × 3mm) Plastic DFN
10-Lead (3mm × 3mm) Plastic DFN
LGNQ
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
4079f
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For more information www.linear.com/LTC4079
LTC4079
elecTrical characTerisTics
The ldenotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at
TA = 25°C (Notes 2, 3). VIN = 12V, VBAT = 7.4V, VFB = 1.057V, VEN = 12V, RPROG = 3k (100mA charge current) unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
60
UNITS
l
l
l
V
Operating Supply Voltage
Battery Voltage Range
2.7
V
V
IN
VBAT
60
V
V
V
V
Undervoltage Lockout
V Rising
IN
Hysteresis
2.55
140
2.7
V
mV
UVLO
IN
l
Differential Undervoltage Lockout
V -V Rising
–20
120
15
80
50
mV
mV
DUVLO
IN BAT
Hysteresis
l
Differential Voltage Regulation
Input Supply Quiescent Current
Minimum V -V for Charge Current
160
200
mV
DVREG
Q(IN)
IN BAT
l
l
I
Charging (Note 4)
4
2
0.2
9
4
0.6
µA
µA
µA
Charging Terminated (V = 1.210V)
FB
Shutdown (EN = 0)
I
Battery Drain Current
Charging Terminated (V =1.210V)
0.01
0.00
0.05
0.2
0.2
0.2
µA
µA
µA
Q(BAT)
FB
Shutdown (EN = 0)
V
= 0 or IN open
IN
Charging Functions
V
Feedback Pin Regulation Voltage in Constant-
Voltage Charge Mode
1.165 1.170 1.175
1.156 1.170 1.184
V
V
FB(CHG)
l
PROG Pin Regulated Voltage
Constant-Current Mode
1.190
250
V
Ratio of BAT Current to PROG Pin Current
mA/mA
l
l
l
I
I
Battery Charge Current in Constant-Current
Mode (Note 5)
R
R
R
= 1.2k
= 3k
236
93
248
99
260
105
11.5
mA
mA
mA
CHG
PROG
PROG
PROG
= 30k
8.5
10
l
l
l
Charging Termination Threshold
R
R
R
= 1.2k
= 3k
= 30k
22
8.2
0.7
25
10
1
28
11.8
1.3
mA
mA
mA
TERMINATE
PROG
PROG
PROG
t
t
Deglitch Filter on C/10 Charge Termination
Safety Timer Accuracy
I
Drops Below Termination Threshold
CHG
5
9
13
10
ms
ꢀ
ꢀ
V
TERMINATE
TIMER
–10
96.9
V
V
Recharge Threshold Voltage of FB Pin
Low Battery Threshold
Relative to V
with V Falling
97.6
98.3
RECHRG
FB(CHG)
FB
l
V
for Low Battery Detection
FB
0.780 0.800 0.820
18
FB(LOWBAT)
Low Battery Time Out (Percentage of Safety
Timer)
Charging with V < V
ꢀ
FB
FB(LOWBAT)
R
Resistance of the Charge Path
Feedback Pin Leakage
5
Ω
ON
l
l
I
V
V
= 1.170V (in Regulation)
= 8.4V (in Shutdown)
0.1
0.1
20
100
nA
nA
FB
FB
FB
l
I
Feedback Ground Pin Leakage
V
= 8.4V, EN = 0
0.1
160
118
100
nA
Ω
FBG
FBG
R
Switch Resistance from FBG Pin to GND
FBG
Die Temperature (T ) at Thermal Regulation
°C
J
4079f
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For more information www.linear.com/LTC4079
LTC4079
elecTrical characTerisTics
The ldenotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at
TA = 25°C (Notes 2, 3). VIN = 12V, VBAT = 7.4V, VFB = 1.057V, VEN = 12V, RPROG = 3k (100mA charge current) unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
NTC Temp Monitor
l
l
l
V
V
V
Low Temp. Fault NTC Threshold Voltage
High Temp. Fault NTC Threshold Voltage
NTC Disable Voltage Threshold
Pulsed NTCBIAS Voltage
V
V
V
/V
NTC NTCBIAS
72.3
35.6
60
73.8
36.6
80
75.3
37.6
100
ꢀ
ꢀ
COLD
/V
HOT
NTC NTCBIAS
mV
V
NTC(DIS)
NTC
20k from NTCBIAS to Ground
4
NTCBIAS Period
3
Sec
µs
NTCBIAS Pulse Width
210
0.1
l
l
NTC Input Leakage Current
V
V
= V
100
nA
NTC
NTCBIAS
Enable Input (EN)
V
Shutdown Threshold
Falling
EN
Hysteresis
0.400 0.750 1.100
55
V
mV
EN(SD)
l
l
V
Enable Pin Regulation Voltage
Minimum V for Charge Current
1.170 1.190 1.210
V
EN(REG)
EN
Enable Pin Leakage Current When Pulled High
V
= 60V
0
20
nA
EN
Status Outputs (CHRG)
Output Low Voltage
Output Leakage Current
l
l
1mA Into the Open-Drain Output
= 60V, V = 0V
0.16
0.1
0.4
V
V
100
nA
CHRG
EN
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 4: BAT pin charge current, PROG pin and feedback divider currents
are excluded from supply quiescent current.
Note 5: Charge current is reduced by thermal regulation as the junction
temperature rises above T (118°C).
LIM
Note 2: Unless otherwise specified, current into a pin is positive and
current out of a pin is negative.
Note 3: The LTC4079 is tested under pulsed load conditions such that
T ≈ T . The LTC4079E is guaranteed to meet performance specifications
J
A
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC4079I is guaranteed over the full –40°C to 125°C operating junction
temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance and other environmental factors.
4079f
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For more information www.linear.com/LTC4079
LTC4079
Typical perForMance characTerisTics VIN = 12V, TA = 25°C unless otherwise noted.
Regulated Feedback Voltage
vs Temperature
Regulated Feedback Voltage
vs VIN
Load Regulation of Regulated
Feedback Voltage
1.182
1.178
1.174
1.170
1.166
1.162
1.158
1.182
1.178
1.174
1.170
1.166
1.162
1.158
1.182
1.178
1.174
1.170
1.166
1.162
1.158
R
I
= 1.2k
PROG
CHG
= 248mA
INTERNAL REFERENCE
ONSET OF
THERMAL REGULATION
75 100
–50 –25
0
25 50
125 150
50
0
10
20
30
(V)
40
60
0
50
100
I
150
(mA)
200
250
TEMPERATURE (°C)
V
IN
BAT
4079 G01
4079 G02
4079 G03
Input Supply Quiescent Current
vs Temperature
Input Supply Quiescent Current
vs Supply Voltage
Battery Quiescent Current
vs Temperature
5
4
3
2
6
5
4
3
2
1
0
0.20
0.15
0.10
0.05
V
= 1.2V
BAT
CHARGING
FB
V
= 8.4V
BAT
(I
= 0)
CHARGING TERMINATED
OR SHUTDOWN
CHARGING
V
= 1.2V
BAT
FB
(I
= 0)
STANDBY
(CHARGING TERMINATED)
STANDBY
(CHARGING TERMINATED)
1
0
SHUTDOWN (EN = 0)
SHUTDOWN (EN = 0)
0
75 100
–50 –25
0
25 50
125 150
0
20
30
(V)
40
50
60
10
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
V
IN
4079 G04
4079 G05
4079 G06
Battery Quiescent Current
vs Battery Voltage
Battery Charge Current
vs Battery Voltage
Battery Charge Current
vs Temperature
60
50
40
30
20
10
0
120
100
80
60
40
20
0
300
250
200
150
100
50
ONSET OF THERMAL
REGULATION
V
V
= 12V
BAT
IN
V
= 8.4V
FB(CHG)
= 8.4V
R
PROG
= 3k
R
PROG
= 1.2k
STANDBY
(CHARGING TERMINATED)
R
PROG
= 3k
R
PROG
= 30k
R
0
= 30k
PROG
SHUTDOWN (EN = 0)
50
0
75 100
0
10
20
30
(V)
40
60
0
2
4
6
8
10
–50 –25
25 50
125 150
V
V
BAT
(V)
TEMPERATURE (°C)
BAT
4079 G07
4079 G08
4079 G09
4079f
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For more information www.linear.com/LTC4079
LTC4079
Typical perForMance characTerisTics VIN = 12V, TA = 25°C unless otherwise noted.
Battery Charge Current
vs VIN – VBAT
Battery Charge Current vs VEN
IBAT/IPROG Ratio vs IBAT
120
100
80
60
40
20
0
120
100
80
60
40
20
0
290
280
270
260
250
240
230
220
210
4 DEVICES TESTED
PROG
R
= 3k
R
= 3k
PROG
PROG
R
= 1.2k
OHMIC REGION
(DROPOUT)
R
= 30k
1.21
R
= 30k
PROG
PROG
1.18
1.19
1.12
(V)
1.22
0.0
0.1
0.2
V
0.3
– V
0.4
(V)
0.5
0.6
0
50
100
150
(mA)
200
250
V
EN
I
IN
BAT
BAT
4079 G10
4079 G11
4079 G12
Charge Path Dropout Resistance
vs Temperature
Charge Path Dropout Resistance
vs VIN
EN and FB Pin Leakages
vs Temperature
25
20
15
10
5
10
8
20
15
10
5
PULSED LOAD (T ≈T )
PULSED LOAD (T ≈T )
J A
J
A
V
– V
PROG
= 0.6V
V
– V
= 0.6V
BAT
IN
BAT
IN
R
= 1.2k
R
= 1.2k
PROG
PIN AT 60V
PIN AT 1.2V
THERMAL REGULATION
6
V
IN
= 2.7V
4
2
V
IN
= 5.0V
0
0
0
75 100
TEMPERATURE (°C)
50
75 100
125 150
TEMPERATURE (°C)
–50 –25
0
25 50
125 150
0
10
20
30
(V)
40
60
–50 –25
0
25 50
V
IN
4079 G13
4079 G14
4079 G15
Switch Resistance from
FBG to GND vs Temperature
Normalized Timer Duration
vs Temperature
NTCBIAS Period and Pulse Width
vs Temperature
350
300
250
200
150
100
50
1.2
1.1
1.0
0.9
0.8
3.2
3.1
3.0
2.9
2.8
2.7
2.6
260
250
240
230
220
210
200
PERIOD
PULSE WIDTH
0
75 100
75 100
75 100
125 150
–50 –25
0
25 50
125 150
–50 –25
0
25 50
125 150
–50 –25
0
25 50
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4079 G16
4079 G17
4079 G18
4079f
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For more information www.linear.com/LTC4079
LTC4079
pin FuncTions
IN (Pin 1): Input Supply Pin. This input provides power
to the battery charger. Bypass this pin with a ceramic
capacitor of at least 1µF.
For maximum charge duration of t
(in Hours), the
TIMER
required capacitance value can be determined as follows:
C
TIMER
= (t • 18.2nF/Hr)
TIMER
EN (Pin 2): Enable Input. Charge current starts flowing
whenthisinputrisesabove1.190V,itsregulationthreshold.
When using a current limited power source, connect this
inputtoanexternalresistordividerfromINtoGNDtoavoid
UVLO oscillations. This configuration can also be used
to maintain the source voltage (IN pin) at the maximum
power threshold (e.g., for solar panel). Pulling this pin
below 0.750V shuts down the device. This pin should
not be left floating.
A typical value of C
charge cycle after 5½ hours. Minimize leakage on this pin
to maintain timer accuracy.
is 100nF which terminates the
TIMER
The timer is disabled when this pin is tied to GND. In this
case charging terminates when the charge current falls
below 1/10th of the programmed charge current I
.
CHG
CHRG(Pin7):Open-DrainChargeStatusOutput.Typically
pulled up to a voltage source through a resistor or a low
power LED and a resistor. This pin is pulled low by an
internal NMOS when LTC4079 is charging the battery.
The pin goes to high impedance when the charge current
drops below 1/10th of the programmed current, or the
charge cycle is timer terminated.
PROG (Pin 3): Charge Current Program Pin. The current
out of this pin is 1/250th of the current out of the BAT
pin. A resistor connected from PROG to ground sets the
charge current in constant-current mode. This pin servos
to 1.190V during constant-current charging. Do not leave
this pin open. Limit parasitic capacitance on this node to
less than 50pF.
FBG(Pin8):GroundReferenceforBatteryVoltageDivider.
ThispinisconnectedtogroundinternallythroughanNMOS
switch when the battery is charging and disconnects the
battery voltage divider from GND when it is not needed.
When sensing the battery voltage the NMOS switch
NTCBIAS (Pin 4): NTC Thermistor Bias Output. Connect
a low drift bias resistor from NTCBIAS to NTC pin, and
a thermistor from NTC pin to GND. The value of the bias
resistor is typically equal to the nominal resistance of
the thermistor at 25°C. Minimize parasitic capacitance
on this pin.
presents a low resistance (R
=160Ω) to GND.
FBG
FB (Pin 9): Sense Pin for Divided Battery Voltage. This pin
servos to 1.170V (V ) during the constant-voltage
FB(CHG)
phase of the battery charge algorithm. The battery charge
voltage is set by using an appropriate resistor divider
from BAT to FB to FBG. Minimize leakage and parasitic
capacitance on this pin.
NTC (Pin 5): Input to the Battery Temperature Sense
Circuit. Connect the NTC pin to a negative temperature
coefficient(NTC)thermistor,whichistypicallyco-packaged
with the battery, to signal the charger if the battery is too
hot or too cold to charge. The room temperature value
of the thermistor should be at least 2kΩ. If the battery’s
temperature is out of range, charging is paused until the
battery temperature re-enters the valid range. Connect a
1ꢀ, low drift bias resistor from NTCBIAS to NTC and a
thermistor from NTC to ground. Minimize parasitic ca-
pacitance on this pin. Tie the NTC pin to GND to disable
battery temperature sensing.
BAT (Pin 10): Battery Charger Output. This pin provides
charge current to the battery.
GND (Exposed Pad Pin 11): Ground. The exposed pad
must be soldered to a continuous ground plane of the
printedcircuitboardforelectricalconnectionandtherated
thermal performance.
TIMER (Pin 6): Timer Capacitor Input. A capacitor on this
pin sets the maximum duration for battery charging from
charger enable or from the beginning of a recharge cycle.
4079f
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For more information www.linear.com/LTC4079
LTC4079
block DiagraM
IN
1
BAT
FB
10
9
P1
I
BAT
250
CC/CV REGULATION,
EN REGULATION,
REGULATION
THERMAL REGULATION
R
FB1
V
-V
IN BAT
+
T
BG REF
–
+
BATTERY PACK
RECHARGE
REFERENCE
R
FB2
FBG
8
EN
UVLO,
DIFF UVLO
2
7
CHRG
NTCBIAS
NTC
CONTROL
4
5
R
BIAS
OSC
TIMER
6
PROG
4079 F01
3
C
TIMER
R
PROG
Figure 1. Block Diagram of LTC4079
4079f
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For more information www.linear.com/LTC4079
LTC4079
operaTion
TheLTC4079isafullfeaturedconstant-current, constant-
voltage charger designed to charge multiple chemistry
types of batteries from voltage sources up to 60V. The low
quiescent current of the device minimizes power drain on
the source and the battery, making it suitable for a variety
of applications including backup and energy harvesting
from an intermittent power source. The battery charge
voltage is set using an external resistor divider. Charge
duration can be set using a capacitor on the TIMER pin.
Forsafetyandimprovedbatterylife, theLTC4079includes
a thermistor input for temperature qualified charging.
A 6ms filter (t
) is used on the C/10 detector to
prevent premature termination due to transient loads on
the battery during charging.
TERMINATE
4. Automatic Recharge: When V drops below the
BAT
recharge threshold (97.6ꢀ of the charge voltage),
whether by battery drainage or replacement of the
battery, the charger automatically re-engages and starts
charging.
Setting The Battery Charge Voltage
The battery charge voltage is set by connecting a resistor
divider from the battery to the FB and FBG pins as shown
in Figure 3. The charge voltage is determined as follows:
Charge current starts when the EN pin is brought above
1.190V. Figure 2 shows a flow chart of the primary states
and state transitions of the LTC4079. A typical charge
cycle includes:
RFB1
RFB2 + R
VCHG = 1.170V • 1+
1. Constant-Current (CC) Charging: The programmed
charge current is used to charge the battery until the
battery voltage reaches the charge voltage set using
the feedback divider. For a low ESR battery, this mode
provides the bulk of the charge. The charge timer should
generally be set long enough to charge the battery above
the recharge threshold, otherwise another charge cycle
would immediately follow.
FBG
where R
is the resistor from BAT to FB, R
is the
FB1
FB2
resistor from FB to FBG and R
is the resistance of the
FBG
internal switch of the FBG pin (160Ω typical).
BAT
R
R
+
LTC4079
FB1
BATTERY
2. Constant-Voltage (CV) Charging: Once the battery
reaches the set charge voltage, constant voltage is
maintained across the battery by controlling the charge
current.Thechargecurrentreduceswithtimeinthismode
as the battery nears its full charge capacity.
FB
FB2
FBG
4079 F03
ENABLE
3.ChargingTermination:TheLTC4079canbeconfigured
to terminate charging automatically based on time or
current. The CHRG status pin goes to high impedance
when the charge current reduces below 1/10th of the
programmed current, indicating that the battery is almost
fully charged. The charge current continues to top-off the
batteryuntilthetimerterminatesthechargecurrent.Timer
termination can be disabled by connecting the TIMER
pin to ground. In this case, charging terminates when
the charge current falls below 1/10th of the programmed
charge current.
Figure 3. Setting the Battery Charge Voltage
Setting and Monitoring the Charge Current
The charge current delivered to the battery in constant-
current mode, I
is set using a resistor from the PROG
CHG
pintoground.Thevalueofthisresistoriscalculatedusing:
297.5V
ICHG
RPROG
=
4079f
9
For more information www.linear.com/LTC4079
LTC4079
operaTion
SHUTDOWN*
V
IN
– V
> 0.805V
> 2.57V
BAT
EN
NO
V
V
IN
> 15mV?
YES
ASSERT CHRG STATUS
START SAFELY TIMER IF
TIMER NOT GROUNDED
NO
PAUSE CHARGE CURRENT
PAUSE TIMER
BATTERY TEMP
IN RANGE?
YES
EN REG, DIFF REG
OR THERMAL REG
NO CV REG?
YES
NO
RUN TIMER
PAUSE TIMER
CC-CV CHARGING
CHARGING IN EN REG,
DIFF REG OR THERMAL REG
YES
LATCH-OFF*
CHRG REMAINS
ASSERTED
V
< 0.8V?
FB
BAD BATTERY*
CHRG REMAINS
ASSERTED
NO
YES
INCREMENT
RETRY
COUNTER
YES
NO
SAFETY TIMER
EXPIRED?
1/4 SAFETY TIMER
EXPIRED?
V
< V ?
RECHG
RETRY COUNT = 5?
FB
YES
YES
NO
NO
NO
I
< C/10?
CHG
NO
IN CV REG, NO EN REG,
DIFF REG OR
STANDBY
CHARGING TERMINATED
RESET SAFETY TIMER
RESET RETRY COUNTER
DEASSERT CHRG STATUS
V
FB
< V
RECHG
THERM REG
4079 F02
YES
SAMPLE FB PIN EVERY 3 SEC
DEASSERT CHRG SATUS
YES
TIMER
GROUNDED?
NO
* V < 0.75V OR ULVO TAKES THE DEVICE
EN
TO SHUTDOWN FROM ANY STATE
Figure 2. Battery Charger Operations Flow Chart
4079f
10
For more information www.linear.com/LTC4079
LTC4079
operaTion
The PROG pin also provides a voltage signal proportional
tothebatterychargecurrent.Therefore,theinstantaneous
batterycurrentcanbedeterminedasfollowsbymonitoring
the PROG pin voltage:
LTC4079
NTC SAMPLE
BAT
PULSE
NTCBIAS
INTERNAL SUPPLY
R
250•VPROG
BIAS
NTC
IBAT
=
+
–
RPROG
TOO COLD
TOO HOT
73.8% V
36.6% V
NTCBIAS
NTCBIAS
+
–
Minimize the parasitic capacitance while monitoring the
PROG pin voltage as any capacitance on this pin forms a
pole that may cause instability in the charge control loop.
+
R
T
NTC
+
–
0.1V
IGNORE NTC
Undervoltage Detection
4079 F04
An internal undervoltage lockout circuit monitors the V
voltage and disables the battery charging circuit until V
IN
IN
Figure 4. Battery Temperature Sensing Using NTC Thermistor
rises above the undervoltage lockout threshold, 2.55V
(typically). The UVLO threshold has built-in hysteresis
of 140mV. Furthermore, the differential UVLO circuit
also keeps the charger in a low quiescent current mode
Chargingresumeswhenthebatterytemperaturereturnsto
the normal range and the timer continues from the point
where it was paused.
by disabling the battery charging circuits when V falls
IN
Input Voltage Regulation
below V
by more than 65mV. The differential UVLO
has hysteresis of 80mV, with turn-on at V -V = 15mV
BAT
The LTC4079 can regulate a constant voltage on the IN pin
when charging from a current-limited power source such
as a weak battery or a solar panel. This feature can be used
to prevent the input voltage from collapsing below UVLO,
or to maintain the input source voltage at peak power.
The charge current is reduced as the input voltage falls to
the threshold set by an external resistor divider from the
input power source to the EN pin and GND, as shown in
IN BAT
(typical).
Battery Temperature Qualified Charging
Duringbatterycharging,thebatterytemperatureissensed
by sampling the voltage on the NTC pin every 3 seconds.
Connect a low drift bias resistor from the NTCBIAS output
to the NTC input and a negative temperature coefficient
(NTC) thermistor, close to the battery pack, from the NTC
pintoground,asshowninFigure4.Thebiasresistorshould
be equal to the value of the chosen thermistor at 25°C.
Figure 5. The input voltage regulation threshold, V
is calculated as follows:
IN(REG)
REN1
R
V
IN(REG) = 1.190V • 1+
EN2
The LTC4079 pauses charging and the charge timer when
theNTCpinvoltageindicatesthatthethermistorresistance
has dropped to 0.576 times its room temperature value.
ForaVishaycurve2thermistor, thiscorrespondsto40°C.
Charging is also paused when the thermistor resistance
increases to 2.816 times the room temperature value. For
a Vishay curve 2 thermistor, this increase corresponds
to 0°C.
Thisregulationmechanismallowsthechargecurrenttobe
selected based on battery requirement and the maximum
power available from the charging source. The LTC4079
automatically reduces the charge current when the input
source cannot provide the programmed charge current.
When input voltage regulation is not needed, connect the
EN pin to the input power source or a digital enable signal.
The hot and cold trip points can be adjusted using a
different type of thermistor, or a different R
resistor,
BIAS
or by adding a desensitizing resistor in series with the
thermistor, or by a combination of these measures.
4079f
11
For more information www.linear.com/LTC4079
LTC4079
operaTion
When C/10 termination is used, the LTC4079 provides
battery charge current as long as the current remains
above the C/10 threshold. As the battery terminal voltage
reaches the target charge voltage, the charge current falls
until the C/10 threshold is reached, at which time the
chargerterminatesandtheLTC4079entersstandbymode.
Premature termination is prevented when input voltage,
differential or thermal regulation is active.
INPUT POWER
SOURCE
IN
R
R
LTC4079
EN
EN1
EN2
4079 F05
Figure 5. Setting Input Voltage Regulation
Differential Voltage (V -V ) Regulation
IN BAT
To preventtermination-rechargeoscillations,itisimportant
to set the termination charge current low enough for bat-
terieswithhighinternalresistance.Foranominalrecharge
threshold of 2.4ꢀ below the charge voltage, the charge
current should be set as follows with sufficient margin:
The LTC4079 provides an additional method to keep the
inputvoltagefromcollapsingwhentheinputpowercomes
from a weak power source. If the input voltage falls close
to the battery voltage, the differential voltage regulation
loop in LTC4079 keeps the input voltage above the battery
voltage by 160mV (typical value) by reducing the charge
current as the input to battery differential voltage falls.
VCHG
ICHG < 0.24•
R
BAT
Inbothoftheaboveregulationconditions,theinputsource
must provideatleastthequiescent currentofthedevice to
prevent UVLO. The charge timer is paused whenever the
charge current is reduced due to input voltage regulation
or differential voltage regulation.
where R is the battery's internal series resistance. The
BAT
CHRG status pin is high impedance when the charger is
not actively charging.
Timer Termination
The LTC4079 also supports a timer-based termination
scheme, wherethebatterychargecycleisterminatedafter
a specific amount of time elapses. Connect a capacitor
from the TIMER pin to ground to engage timer based
charge termination. Calculate the capacitance required
Thermal Regulation
An internal thermal feedback loop reduces the charge
currentbelowtheprogrammedvalueifthedietemperature
approaches 118°C. This feature protects the LTC4079
from excessive temperature and allows the user to set
the charge current to typical (not worst case) ambient
temperature with the assurance that the charger will
automatically reduce the current to prevent overheating
in worst-case conditions.
for the desired charge cycle duration, t
as follows:
TIMER
C
TIMER
= t
• 18.2nF/Hr
TIMER
A 200nA current source is used to source/sink current
to/from C to generate a sawtooth periodic signal
TIMER
(nominally 0.8V to 1.2V) for use by the timer. Since the
TIMER pin current is small, minimize leakage on this pin
to maintain timer accuracy.
The charge timer is paused during thermal limiting to
prevent under-charging the battery and to allow the full
charge current to flow for the set timer duration.
The timer starts on charger enable or the beginning of a
C/10 Termination
recharge cycle, and is reset on disable or when V falls
IN
below UVLO or DUVLO.
TheLTC4079supportsacurrentbasedterminationscheme,
where a battery charge cycle terminates when the current
output from the charger falls below one-tenth of the
programmed charge current. The C/10 threshold current
corresponds to 119mV on the PROG pin. This termination
mode is engaged by shorting the TIMER pin to ground.
Thetimerispausedwheneverthechargecurrentislimited
by EN pin or differential voltage or thermal regulation,
unless the charger is also in constant-voltage regulation
mode. It is also paused with the charge current during an
NTC fault. The timer is not paused if the charge current is
4079f
12
For more information www.linear.com/LTC4079
LTC4079
operaTion
limitedbydropout.Forexample,foraprogrammedcharge
In order to avoid wasting power in recharging a defective
battery indefinitely, LTC4079 contains a recharge latch-
off feature. Charging is latched off and the CHRG pin
remains asserted after 5 recharge attempts if the battery
voltage remains below the recharge threshold at the end
of all five recharge cycles. The latch-off counter is reset
if a charge cycle terminates normally during any recharge
current of 100mA, this occurs when V -V falls below
IN BAT
about 0.5V due to the voltage drop across the charge path
(5Ω typically). If V -V
falls below 160mV to trigger
IN BAT
differential voltage regulation, the timer will be paused.
The CHRG status pin signals charging at a rate of more
than C/10, regardless of which termination scheme is
used. When timer termination is used, the CHRG status
pin pulls low during a charging cycle until the charger
output current falls below the C/10 threshold. The charger
continues to top off the battery until timer termination,
when the LTC4079 enters standby mode.
attempt, or if the charge current falls below I /10 in
CHG
constant-voltage regulation mode during a charge cycle.
Charger disable using the EN pin or UVLO also resets the
latch-off counter..
Bad Battery Scenario
Standby and Automatic Recharge
If the feedback voltage remains below V
for
FB(LOWBAT)
longer than 1/4th of the safety timer set by C
, the
TIMER
If the LTC4079 remains enabled after charge cycle
termination, it monitors the battery voltage in standby
mode by sampling the FB pin connected to the external
resistor divider. In order to minimize the battery drain, the
feedback divider is only turned on (by connecting FBG pin
to ground) for 210µs once every 3 seconds. When this
sampling detects that the battery voltage has dropped
by more than 2.4ꢀ, the feedback divider is kept on for
1.5 seconds (typical). If the FB voltage remains below
the recharge threshold for more than 2.5ms (typical), a
rechargecyclestarts.This2.5msfilterpreventspremature
recharge due to load transients. The recharge cycle also
terminates in constant-voltage charge mode as described
above. Theautomaticrechargefunctionmaintainsthatthe
battery at, or near, a fully charged condition.
battery is considered bad. Charging stops in this case and
the CHRG pin remains asserted. NTC sampling and FB
sampling for recharge is also turned-off. The charge cycle
is restarted by toggling the EN pin below V
(typically
EN(SD)
0.75V)andthenbackhigh.UVLOalsoclearsthebadbattery
lockout.Thereisnobadbatterydetectionwhenthebattery
charge timer is disabled (TIMER pin grounded).
CHRG Status Output
The charge status open-drain output (CHRG) has two
states: pull down and high impedance. The pull-down
state indicates that LTC4079 is in charging mode. A high
impedance state indicates that the charge current has
droppedbelow10ꢀoftheprogrammedchargecurrent.In
mostcases,chargecurrentisreducedduetotheconstant-
voltage loop, meaning that the battery voltage is near the
target charge voltage. But if charge current is reduced due
Ifthebatteryvoltageremainsbelowtherechargethreshold
on timer expiration, another recharge cycle begins as
explained below.
to V regulation (through EN or V -V
regulation) or
IN
IN BAT
thermal regulation, CHRG remains asserted until only the
constant-voltage regulation loop reduces charge current
below 10ꢀ of the programmed charge current.
Timer Retry and Latch-off
Anewchargecycleisstartedifthebatteryvoltageremains
below the recharge threshold at the end of a charge cycle.
This happens in the following situations: 1) the timer is
not set long enough for the battery with the programmed
charge current, 2) the battery is defective, 3) a load drains
the battery during charging, 4) charge current is limited
by dropout.
A high impedance state at the CHRG pin occurs on timer
termination, or UVLO or differential UVLO, or when the
LTC4079 is disabled by pulling EN low. This output can
be used as a logic interface or to light a low power LED.
4079f
13
For more information www.linear.com/LTC4079
LTC4079
applicaTions inForMaTion
Feedback Divider Selection
Table 1. Recommended 1% Resistors for Common Battery
Charge Voltages
Using too low or too high values of resistors for the
feedback divider can cause small charge voltage errors
due to: 1) Finite on-resistance of the internal switch on
the FBG pin and 2) leakage on the FB pin. The impact of
these two factors on the target battery charge voltage is
calculated as follows:
V
R
R
FB2
TYPICAL ERROR
+0.53ꢀ
CHG
FB1
3.6V
4.1V
4.2V
7.2V
8.2V
8.4V
12.3V
12.6V
1070k
422k
511k
169k
412k
267k
178k
249k
187k
261k
–0.27ꢀ
1070k
1370k
1070k
1540k
1780k
2550k
+0.18ꢀ
–0.42ꢀ
-0.04ꢀ
RFB1
RFB2 + R
+0.02ꢀ
VCHG = 1.170V • 1+
+ RFB1 •(IFB +ILEAK)
-0.02ꢀ
FBG
-0.05ꢀ
where R and R are the top and bottom resistors of
FB1
FB2
Stability Considerations
the feedback divider, R is the resistance of the internal
FBG
switch from the FBG pin to GND (160Ω typical) and I
When the charger is in constant-current mode, the PROG
pin impedance forms part of the charger current control
loop. The constant-current mode stability is therefore
affected by the roll-off frequency of the PROG pin
impedance. With minimum capacitance on this pin (less
than about 10pF), the charger is stable with a program
LEAK
is the parasitic leakage on the FB pin as shown in Figure
6. A graph of I vs Temperature is given in the Typical
FB
Performance section.
According to the above equation, high value feedback
resistors minimize the impact of R , while low values
FBG
resistor, R
, as high as 60k (I
PROG
= 5mA); however,
CHG
minimizetheimpactofI andl
.ATheveninequivalent
FB
LEAK
any additional capacitance at this pin limits the maximum
allowed program resistor.
resistance of 100k to 500k on the FB node is generally a
good compromise in most scenarios.
The constant-voltage loop is stable without any
compensation as long as a typical low impedance battery
is connected to the BAT pin. However, a1µF capacitor with
1Ω series resistor is recommended when charging high
ESR batteries, typically more than 1kΩ.
BAT
R
R
+
LTC4079
FB1
BATTERY
FB
I
FB
I
FB2
LEAK
FBG
4079 F06
PARASITIC
LOAD
ENABLE
Charging High Resistance Batteries
When charging a battery with high internal resistance,
the battery voltage can rise quickly, entering constant-
voltage mode. If the charge current falls below 1/10th of
the programmed charge current, charging may terminate
based on C/10 even if a timer capacitor is connected
on the TIMER pin. This is because C/10 termination is
assumed if the timer pin remains below 0.3V. With only
200nA being sourced from the TIMER pin, a large timer
capacitance may limit the TIMER voltage below 0.3V for
a short duration at the beginning of a charge cycle. After
charging terminates, a recharge cycle would begin if the
Figure 6. Feedback Divider Considerations
For example, for R = 1.54M and R = 249k (for bat-
FB1
FB2
tery charge voltage of 8.4V), accounting for R
=160Ω
= 10nA
FBG
lowers the charge voltage by 0.06ꢀ, while I
raises it by 0.18ꢀ.
LEAK
Table 1 lists possible choices of standard 1ꢀ resistor
values for common battery charge voltages. The Typical
Error column gives systematic error due to the granularity
in the values of 1ꢀ resistors.
4079f
14
For more information www.linear.com/LTC4079
LTC4079
applicaTions inForMaTion
internal battery voltage has not been charged above the
Example: Consider an LTC4079 operating from a 12V
input source programmed to supply 100mA current to
a discharged 2-cell Li-Ion battery with a voltage of 6.6V.
recharge threshold, determined by ∆V
and the
RECHRG
feedbackdivider.AsshowninFigure7,thischarge/recharge
cycle continues until the TIMER pin rises above 0.3V, at
which point timer termination is engaged and the battery
is charged for the duration set by the timer capacitor.
Assumingθ is43°C/Wtheambienttemperatureatwhich
JA
thechargecurrentbeginstofallduetothermalregulationis:
T = 118°C – (12V-6.6V) • 100mA • 43°C/W = 95°C
A
4.2V
V
BAT
The LTC4079 can be used above 95°C ambient but the
chargecurrentwillbereducelinearlyfromtheprogrammed
value of 100mA to 0mA as the ambient temperature
increases from 95°C to 118°C.
0.2V/DIV
TIMER
0.5V/DIV
PROG
0.1V/DIV
Increasing Thermal Regulation Current
CHRG
5V/DIV
In applications with large V to V drop, the charge
BAT
4079 F01
IN
20ms/DIV
currentcanbesignificantlyreducedduringthermalregula-
tion. One way to increase the thermally regulated charge
current is to dissipate some of the power in a resistor in
series with the IN pin. This works well when the resistor
value is designed to be small enough to avoid pushing the
LTC4079 into dropout.
Figure 7. Repeated Charge Terminations on
Startup Due to High Resistance of the Battery,
CTIMER = 82nF, VCHG = 4.2V, ICHG = 10mA and
Battery Resistance = 300Ω
Power Dissipation and Thermal Regulation
Input Capacitor Selection
The LTC4079 automatically reduces charge current
during high power conditions that result in high junction
temperature. Therefore, it is not necessary to design
the charging system for worst-case power dissipation
scenarios. The conditions that cause the LTC4079 to
reduce charge current through thermal regulation can be
approximated by considering the power dissipated in the
IC. Most of the power dissipation is in the charge path.
Thus the power dissipation is approximately:
When an input supply is connected to a portable product,
the inductance of the cable and the high Q ceramic input
capacitorformanL-Cresonantcircuit. WhiletheLTC4079
is capable of withstanding input voltages as high as 62V, if
the input cable does not have adequate mutual inductance
orifthereisnotmuchimpedanceinthecable,itispossible
for the voltage at the input of LTC4079 to reach as high as
2x the cable input voltage before it settles out. To prevent
excessive voltage from damaging the LTC4079 during a
hot insertion, it is best to have a low voltage coefficient
capacitor at the supply input pin of the LTC4079.
P = (V -V ) • I
BAT
D
IN BAT
Theapproximateambienttemperatureatwhichthethermal
regulation begins to lower the charge current is:
Using a tantalum capacitor or an aluminum electrolytic
capacitor for input bypassing, or paralleling with a ce-
ramiccapacitorwillalsoreducevoltageovershootduring
a hot insertion.
T = 118°C – P • θ
JA
A
D
T = 118°C – (V -V ) • I • θ
JA
A
IN BAT
BAT
The reduced charge current at an ambient temperature
above the onset of thermal regulation can be calculated
as follows:
118°C–TA
IBAT
=
V – V
•θ
(
)
IN
BAT
JA
4079f
15
For more information www.linear.com/LTC4079
LTC4079
applicaTions inForMaTion
Board Layout Considerations
3. Minimize the parasitic capacitance and leakage on the
FB node for stability and charge voltage accuracy.
When laying out the printed circuit board, the following
checklist should be followed to ensure proper operation
of the LTC4079:
4. Minimize the parasitic capacitance and leakage on the
TIMER pin for timer accuracy.
1. Connect the exposed pad of the package (Pin 11)
directly to a large PC board ground to minimize thermal
5. Minimize the parasitic capacitance on the PROG pin for
stable operation.
2
impedance. Correctly soldered to a 1500mm double
6. Minimize the parasitic capacitance and leakage on the
EN pin if it is connected to a resistor divider from the
input supply for input voltage regulation.
sided 1oz copper board, the LTC4079 DFN package has
a thermal resistance (θ ) of approximately 43°C/W.
JA
Failure to make good contact between the exposed pad
on the backside of the package and an adequately sized
groundplaneresultsinmuchlargerthermalresistance.
2. The top of the feedback divider resistor should be
connected as close to the positive battery terminal as
possible in order to avoid inaccuracies due to voltage
drop in the charge current path. The negative terminal
of the battery should be connected to the chip ground
plane directly to avoid any ground loop induced charge
voltage inaccuracy.
4079f
16
For more information www.linear.com/LTC4079
LTC4079
Typical applicaTions
Li-Ion Charger with Timer Termination
Li-Ion Charging from a Solar Panel with Differential
Voltage Regulation, C/10 Termination
In the Figure 8 configuration, the input source charges
the battery for 5½ hours and also supplies current to the
load. The maximum current provided by the charger (on
BAT pin) is limited to the charge current of 246mA set by
the 1.21k resistor on the PROG pin. A small resistor is
Figure 10 shows a simple charging solution from a solar
panel.Differentialvoltageregulationreduceschargecurrent
to prevent the panel voltage from drooping below the
battery voltage when charging under low light conditions.
The LTC4079 does not require a Schottky diode in series
with the panel.
used in series with the input supply to reduce V -V
,
IN BAT
and thereby increase the available charge current during
thermal regulation. Once the battery is charged, it sup-
plies power to the load until V falls below the recharge
BAT
TO
threshold, at which point a recharge cycle starts.
IN
BAT
FB
LOAD
1µF
1µF
LTC4079
1.54M
249k
EN
25Ω, 2W
+
SOLAR
TO
24V
SUPPLY
V
= 8.4V
CHG
CHG
IN
BAT
FB
LOAD
I
= 246mA
CHRG
FBG
1µF
LTC4079
1.54M
249k
PANEL
PROG
NTCBIAS
EN
–
10k
1.21k
TIMER
NTC
V
I
= 8.4V
= 246mA
CHG
CHG
CHRG
FBG
+
GND
PROG
NTCBIAS
T
BATTERY
PACK
10k
1.21k
10k
TIMER
NTC
+
100nF
GND
4079 F10
T
BATTERY
PACK
Figure 10. Li-Ion Charger with Differential Voltage Regulation
10k
4079 F08
Figure 8. Li-Ion Charger with Timer Termination
Supercapacitor Charger from 2-Cell Li-ion
Charging terminates when the stacked supercapacitor
voltage reaches the set charge voltage. A recharge cycle
begins automatically when the supercap voltage falls
below the recharge threshold. A resistor divider balancer
can optionally be switched in for balancing a stacked
supercapacitor during charging.
2-Cell NiMH Trickle Charger from Automotive Supply
with Timer Termination
Figure 9 shows a trickle charger for 2-cell, 2500mAh,
AA NiMH battery with timer termination after 31 hours.
Charge current drops when the battery voltage reaches
1.65V per cell.
TO
2-CELL
Li-Ion
TO
12V
CAR BATTERY
IN
BAT
FB
IN
BAT
FB
LOAD
LOAD
+
1µF
LTC4079
324k
178k
LTC4079
1.02M
309k
V
I
= 5.0V
CHG
= 10mA
CHG
EN
EN
V
= 3.3V
= 99mA
CHG
CHG
FDG6308P
I
CHRG
FBG
CHRG
FBG
1k
1k
C
SC
+
2500mAh
2-CELL
NiMH
PROG
NTCBIAS
PROG
NTCBIAS
0.6F
HS206
3.01k
30.1k
TIMER
NTC
4079 F09
TIMER
NTC
560nF
GND
GND
SUPERCAP BALANCER (OPTIONAL)
4079 F11
Figure 9. NiMH Trickle Charger with Timer Termination
Figure 11. Supercap Charger with C/10 Termination
4079f
17
For more information www.linear.com/LTC4079
LTC4079
Typical applicaTions
12V Lead-Acid Charger from Rectified 24V AC
In the following charging circuit example, a lead acid
battery is trickle charged at a C/10 rate for 15 hours. An
NTC thermistor is used to alter the target charge voltage
of the lead-acid battery based on the battery temperature.
I
= 99mA
CHG
TO
IN
BAT
LOAD
100µF
1µF
LTC4079
1M
+
EN
12V
LEAD-ACID
BATTERY
100k
102k
T
CHRG
FB
100k
24V AC
FBG
PROG
NTCBIAS
3.01k
TIMER
NTC
270nF
4079 F12
GND
Figure 12. Lead-Acid Battery Trickle Charger from Rectified 24V AC
4079f
18
For more information www.linear.com/LTC4079
LTC4079
package DescripTion
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
0.70 ±0.05
3.55 ±0.05
2.15 ±0.05 (2 SIDES)
1.65 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.125
0.40 ± 0.10
TYP
6
10
3.00 ±0.10
(4 SIDES)
1.65 ± 0.10
(2 SIDES)
PIN 1 NOTCH
R = 0.20 OR
PIN 1
TOP MARK
(SEE NOTE 6)
0.35 × 45°
CHAMFER
(DD) DFN REV C 0310
5
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.200 REF
2.38 ±0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
4079f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
19
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LTC4079
Typical applicaTion
Energy Harvesting Charger with Buck, Buck-Boost and LDO Supplies
4V TO 19V
AC1
AC2
SW
PIEZO
MIDE
V25W
22µH
22µH
3V TO 19V
+
V
IN
10µF
25V
4.7µF
6.3V
1µF
6.3V
LTC3330
SOLAR
PANEL
SWA
SWB
CAP
–
1.8V TO 5V
50mA
V
V
OUT
IN2
47µF
6.3V
V
= 15V
IN
IN(REG)
LDO_IN
SCAP
BAL
I
= 99mA
1.07M
CHG
10mF
2.7V
BAT
FB
BAT
1.2M
102k
LTC4079
4.7µF
3
3
3
4
OUT[2:0]
LDO[2:0]
IPK[2:0]
UV[3:0]*
LDO_EN
10mF
2.7V
EN
EH_ON
412k
PGVOUT
PGLDO
OPTIONAL
CHRG
FBG
PROG
NTCBIAS
1.2V TO 3.6V
50mA
LDO_OUT
10k
3.01k
22µF
6.3V
V
IN3
TIMER
NTC
1µF
6.3V
GND
+
100nF
GND
4079 TA02
T
Li-Ion
10k
SET V
E.G. V
OF LTC4079 ABOVE THE UVLO THRESHOLDS OF LTC3330.
= 15V FOR UVLO RISING = 14V AND UVLO FALLING = 13V.
*
IN(REG)
IN(REG)
THIS ENSURES THAT THE BATTERY IS CHARGED ONLY WHEN EXCESS
POWER IS AVAILABLE FROM THE INPUT SOURCE.
relaTeD parTs
PART NUMBER
DESCRIPTION
COMMENTS
LTC4078
Dual Input Li-Ion Battery Charger with Overvoltage
Protection
Overvoltage Protection Up to 22V. Charge Current 100mA to 950mA.
LTC4065/LTC4065A 250mA Li-Ion Battery Charger
3.75V to 5.5V Input. Up to 250mA Programmable Charge Current. Internal
4.5Hrs Safety Timer.
LTC4054L-4.2
LTC4070
150mA Linear Li-Ion Battery Charger
Li-Ion/Polymer Shunt Battery Charger
4.25V to 6.5V Input. 10mA to 150mA Programmable Charge Current.
I = 0.5µA, Pin Selectable Battery Charge Voltage: 4.0V, 4.1V or 4.2V
Q
LTC4071
Li-Ion/Polymer Shunt Battery Charger with Low Battery Pack Protection Version of LTC4070
Disconnect
LT®3650
High Voltage 2A Monolithic Li-Ion Battery Charger
4.75V to 32V Input. Buck Architecture.
LTC4121/
LTC4121-4.2
High Voltage 400mA Synchronous Step-Down Battery 4.4V to 40V Input. Low Dropout Buck Architecture with MPPT.
Charger
4079f
LT 0914 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC4079
●
●
LINEAR TECHNOLOGY CORPORATION 2014
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