EUP8086 [EUTECH]
Battery Charger and Step-Down Converter for Portable Applications; 电池充电器和降压型转换器，用于便携式应用
| 型号： | EUP8086 |
| 厂家： | 
EUTECH MICROELECTRONICS INC |
| 描述： | Battery Charger and Step-Down Converter for Portable Applications |
| 文件： | 总19页 (文件大小：563K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
芯美 子
Preliminary
EUP8086
Battery Charger and Step-Down
Converter for Portable Applications
DESCRIPTION
FEATURES
The EUP8086 is
a
complete constant-current/
ꢀ
Battery Charger:
constant-voltage linear battery charger for a single-cell
4.2V lithium-ion battery with a 600mA step-down
converter. The input voltage range is 3.75V to 5.5V for the
battery charger and 2.6V to 5.5V for the step-down
converter, making it ideal for applications operating with
single-cell lithium-ion/polymer batteries.
- Input Voltage Range : 3.75 V to 5.5V
- Constant-Current/Constant-Voltage Operation
with Thermal Feedback to Maximize Charge
Rate Without Risk of Overheating
- Internal 4.5 Hour Safety Timer for Termination
- Charge Current Programmable Up to 500mA
with 5% Accuracy
The battery charger offers an integrated pass device,
reverse blocking protection, high accuracy current and
voltage regulation, charge status, and charge termination.
The charging current is programmable via external resistor
from 15mA to 500mA. In addition to these standard
features, the device offers current limit, thermal protection,
and soft-start.
- C/10 Charge Current Detection Output
- 5ꢀA Supply Current in Shutdown Mode
ꢀ
ꢀ
Synchronous Buck Converter:
- Input Voltage Range: 2.6V to 5.5V
- Output Voltage Range: 0.6V to VIN
- 600mA Output Current
- Up to 90% Efficiency
- 36ꢀA Quiescent Current
The step-down converter is a highly integrated converter
operating at a 1.5MHz switching frequency, minimizing
the size of external components while keeping switching
losses low. It has independent input and enable pins. The
output voltage ranges from 0.6V to the input voltage.
- 1.5MHz Switching Frequency
- 120ꢀs Start-Up Time
Short-Circuit, Over-Temperature, and Current
Limit Protection
×
The EUP8086 is available in a 12-lead 3mm 3mm TDFN
package and is rated over the -40°C to 85°C temperature
range.
ꢀ
ꢀ
3mm
×3mm TDFN-12 Package
RoHS Compliant and 100% Lead (Pb)-Free
APPLICATIONS
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Bluetooth Headsets
Cellular Phones
Handheld Instruments
MP3 and Handheld Computers
Portable Media Players
Typical Application Circuit
Figure 1.
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Block Diagram
Preliminary
EUP8086
Figure 2.
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Pin Configurations
Preliminary
EUP8086
Package Type
Pin Configurations
TDFN-12
Pin Description
Pin
1
PIN
DESCRIPTION
Feedback input. This pin must be connected directly to an external resistor divider.
Nominal voltage is 0.6V.
FB
2,8,10
GND
Ground.
Enable pin for the step-down converter. When connected to logic low, the step-down
3
EN_BUCK converter is disabled and consumes less than 1µA of current. When connected to
logic high, it resumes normal operation.
Enable pin for the battery charger. When internally pulled down, the battery charger
4
5
EN_BAT
ISET
is disabled and it consumes less than 1µA of current. When connected to logic high, it
resumes normal operation.
Charge current set point. Connect a resistor from this pin to ground. Refer to typical
curves for resistor selection.
6
7
9
BAT
STAT
ADP
Battery charging and sensing.
Charge status input. Open drain status output.
Input for USB/adapter charger.
Output of the step-down converter. Connect the inductor to this pin. Internally, it is
connected to the drain of both high- and low-side MOSFETs.
11
12
LX
VIN
Input voltage for the step-down converter.
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Ordering Information
Preliminary
EUP8086
Order Number
Package Type
Marking
Operating Temperature range
xxxxx
P8086
EUP8086JIR1
TDFN-12
-40 °C to 85°C
EUP8086-□ □ □ □
Lead Free Code
1: Lead Free
Packing
R: Tape & Reel
Operating temperature range
I: Industry Standard
Package Type
J: TDFN
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Absolute Maximum Ratings
Preliminary
EUP8086
ꢁ
ꢁ
Input Voltage to GND (VIN) ------------------------------------------------------------------------------------ 6V
Adapter Voltage to GND (VADP -------------------------------------------------------------------- -0.3V to 6V
)
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
LX to GND (VLX) ----------------------------------------------------------------------- -0.3V to VIN +0.3V
FB to GND (VFB) ---------------------------------------------------------------------------- -0.3V to VIN +0.3V
EN_BUCK, EN_BAT to GND (VEN) -------------------------------------------------------------- -0.3V to 6V
BAT, ISET, STAT (VX) --------------------------------------------------------------------- -0.3V to VADP+0.3V
Operating Junction Temperature Range (TJ) ------------------------------------------------- -40℃ to 150℃
ꢁ
Maximum Soldering Temperature (at leads, 10sec) ---------------------------------------------------- 260℃
Thermal Information
ꢁ
ꢁ
Maximum Power Dissipation (PD) --------------------------------------------------------------------------- 2W
Thermal Resistance (θJA) --------------------------------------------------------------------------------- 50℃/W
Electrical Characteristics (VIN=3.6V; TA = -40℃ to 85℃, unless otherwise noted. Typical values are TA=25℃)
EUP8086
Min. Typ. Max.
Symbol
Parameter
Conditions
Unit
Step-Down Converter
VIN
Input Voltage
2.6
5.5
2.6
V
V
VIN Rising
Hysteresis
VIN Falling
200
36
mV
V
VUVLO
UVLO Threshold
2.4
-3
IOUT = 0 to 250mA,
IN = 2.6V to 5.5V
VOUT
Output Voltage Tolerance
3
%
V
VOUT
IQ
Output Voltage Range
Quiescent Current
0.6
VIN
V
µA
µA
A
No Load
ISHDN
Shutdown Current
EN_BUCK = GND
1
ILIM
P-Channel Current Limit
High-Side Switch On Resistance
Low-Side Switch On Resistance
LX Leakage Current
1
RDS(ON)H
RDS(ON)L
ILXLEAK
△VLinereg/△VIN
0.26
0.28
ꢁ
ꢁ
VIN = 5.5V, VLX = 0 to VIN
VIN = 2.8V to 5.5V
1
µA
%/V
Line Regulation
0.2
0.6
0.4
Feedback Threshold Voltage
Accuracy
VFB
V
IN = 3.6V
0.588
1.2
0.612
V
IFB
FOSC
TS
FB Leakage Current
Oscillator Frequency
Startup Time
VOUT = 1.0V
0.2
1.8
µA
MHz
µs
1.5
From Enable to Output Regulation
120
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
℃
TSD
150
20
℃
THYS
VEN(L)
Enable Threshold Low
0.4
V
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Preliminary
EUP8086
Electrical Characteristics (VIN=3.6V; TA = -40℃ to 85℃, unless otherwise noted. Typical values are TA=25℃)
EUP8086
Symbol
Parameter
Conditions
Unit
Min. Typ. Max.
Step-Down Converter
VEN(H)
IEN
Enable Threshold High
Input Low Current
1.4
V
VIN = VEN_BUCK = 5.5V
-1
1
µA
Electrical Characteristics (VADP=5V; TA = -40℃ to 85℃, unless otherwise noted. Typical values are TA=25℃)
EUP8086
Symbol
Parameter
Conditions
Unit
Min. Typ. Max.
Battery Charger
Operation
VADP
Adapter Voltage Range
3.75
85
5
5.5
135
70
V
110
45
(VCC-VBAT),VCC Low to High
(VCC-VBAT),VCC High to Low
Automatic Shutdown Threshold
Voltage
mV
VASD
tSS_CHRG
VUVLO
15
Battery Charger Soft-Start Time
Under-Voltage Lockout (UVLO)
120
3.6
3
µs
V
ADP Rising Edge
3.4
2.8
3.8
3.2
300
5
ADP Falling Edge
V
Operating Current
Shutdown Current
115
0.2
0.7
IOP
VBAT=4.5V(Forces IBAT and IISET=0)
VBAT = 4V, EN_BAT = GND
µA
µA
µA
ISHUTDOWN
ILEAKAGE
Reverse Leakage Current from
BAT Pin
2
VBAT = 4V, VADP=3.5V
Voltage Regulation
End of Charge Accuracy
4.158
2.80
4.200
1
4.242
3.10
V
VBAT_EOC
ΔVBAT_EOC
VBAT_EOC
/
Output Charge Voltage Tolerance
%
Preconditioning Voltage Threshold
2.95
-0.15
300
V
V
VMIN
VRCH
Battery Recharge Voltage
Threshold
Measured from VBAT_EOC
IBAT = 0.9 ICH
△VUVCL1
△VUVCL2
180
90
mV
mV
(ADP - VBAT) Undervoltage
Current Limit Threshold Voltage
IBAT = 0.1 ICH
130
Current Regulation
Charge Current Programmable
Range
Charge Current Regulation
Tolerance
15
500
mA
%
ICHG
ΔICHG/ICHG
10
1
ISET Pin Voltage
V
VISET
KI_A
400
Current Set Factor: ICHG/IISET
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Preliminary
EUP8086
Electrical Characteristics (VADP=5V; TA = -40℃ to 85℃, unless otherwise noted. Typical values are TA=25℃)
EUP8086
Symbol
Parameter
Conditions
Unit
Min. Typ. Max.
tTIMER
Termination Timer
3
4.5
2.25
1.125
2
6
hrs
hrs
hrs
Hz
Recharge Time
1.5
3
Low-Battery Charge Time
VBAT = 2.5V
0.75
1.5
Defective Battery Detection STAT
Pulse Frequency
Defective Battery Detection STAT
Pulse Frequency Duty Ratio
Junction Temperature in Constant-
Temperature Mode
fBADBAT
DBADBAT
TLIM
75
%
℃
115
Charging Devices
Charging Transistor On Resistance
1
RDS(ON)
VADP = 4.2V
ꢁ
Battery Charger
Logic Control / Protection
Enable Threshold High
1.6
V
V
VEN(H)
VEN(L)
Enable Threshold Low
Output Low Voltage
0.4
0.4
8
STAT Pin Sinks 4mA
IBAT = 100mA
V
VSTAT
STAT Pin Current Sink Capability
Pre-Charge Current
mA
%
ISTAT
10
10
ITK/ICHG
ITERM/ICHG
Charge Termination Threshold
Current
%
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Preliminary
EUP8086
Typical Operating Characteristics-Battery Charge
Battery Regulation(Float) Voltage vs Temperature
Battery Regulation (Float) Voltage vs Charge Current
4.210
4.205
4.200
4.195
4.190
4.185
4.180
4.175
4.170
4.165
4.160
4.21
RISET = 2k
4.20
4.19
4.18
4.17
4.16
4.15
4.14
4.13
0
50
100
150
200
-40
-20
0
20
40
60
80
TEMPERATURE (oC)
CHARGE CURRENT (mA)
Charge Current vs Battery Current
ISET = 2k
VBAT RISING
Battery Regulation (Float) Voltage vs Supply Voltage
250
200
150
100
50
4.25
4.20
4.15
4.10
4.05
4.00
3.95
3.90
R
PRECONDITIONING CHARGE
0
-50
0.5
4.0
4.5
5.0
5.5
6.0
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE(V)
BATTERY VOLTAGE (V)
Charge Current vs Temperature
with Thermal Regulation(Constant-Current Mode)
ISET Pin Voltages vs Charge Current
RISET = 2k
250
200
150
100
50
1.0
0.8
0.6
0.4
0.2
0.0
ADP= 6V
VBAT = 3V
RISET =2k
THERMAL CONTROL
LOOP IN OPERATION
0
0
25
50
75
100
125
150
175
200
-25
0
25
50
75
100
125
TEMPERATURE (oC)
CHARGE CURRENT (mA)
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Preliminary
EUP8086
Typical Operating Characteristics-Battery Charge
EN_BAT vs Temperature
EN_BAT Pin Threshold Voltage vs Temperature
10
9
0.80
0.75
RISING
8
0.70
0.65
7
6
0.60
FALLING
5
0.55
0.50
4
3
-40
-40
-20
0
20
40
60
80
-20
0
20
40
60
80
TEMPERATURE (oC)
TEMPERATURE (oC)
Normalized Charger Timer Period vs Temperature
STAT Pin Output LowVoltage vs Temperature
ISTAT=5mA
1.05
1.00
0.95
0.90
0.85
0.80
0.32
0.30
0.28
0.26
0.24
0.22
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
STAT
-40 -30 -20 -10
0
10
20
30
40
50
60
70
80
-40
-20
0
20
40
60
80
TEMPERATURE (oC)
TEMPERATURE (oC)
Charger FET On-Resistance vs Temperature
ADP = 4.2V
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
ICH = 350mA
-40
-20
0
20
40
60
80
TEMPERATURE (oC)
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Preliminary
EUP8086
Typical Operating Characteristics-Step-Down Converter
BUCK Efficiency vs Load Current (Vout=1.5V)
BUCK Efficiency vs Load Current (Vout=1.8V)
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
VIN=2.7V
VIN=3.8V
VIN=4.2V
VIN=2.7V
VIN=3.6V
VIN=4.2V
L=2.2uH
C=10uF
L=2.2uH
C=10uF
0.1
1
10
100
1000
0.1
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
BUCK Efficiency vs Load Current (VOUT=1.2V)
Reference Voltage vs Temperature (VIN=3.6V)
100
90
80
70
60
50
40
30
20
10
0
0.610
0.605
0.600
0.595
0.590
0.585
VIN=2.7V
VIN=3.6V
VIN=4.2V
L=2.2uH
C=10uF
L=2.2uH
C=10uF
0.1
1
10
100
1000
-40
-20
0
20
40
60
80
TEMPERATURE (oC)
LOAD CURRENT (mA)
Output Voltage vs Temperature (VIN=3.6V,ILoad=1mA)
Output Voltage vs Input Voltage (VIN=3.6V,ILoad=1mA)
1.92
1.90
1.88
1.86
1.84
1.82
1.80
1.78
1.76
1.74
1.96
1.92
1.88
1.84
1.80
1.76
1.72
1.68
1.64
1.60
L=2.2uH
C=10uF
RFB1=620Kohm
RFB2=300Kohm
L=2.2uH
C=10uF
RFB1=620Kohm
RFB2=300Kohm
2.5
3.0
3.5
4.0
4.5
5.0
-40
-20
0
20
40
60
80
100
TEMPERATURE (oC)
INPUT VOLTAGE (V)
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Preliminary
EUP8086
Typical Operating Characteristics-Step-Down Converter
Quiescent Current vs Input Voltage (No Load)
Quiescent Current vs Temperature (No Load)
44
40
36
32
28
24
20
16
12
8
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
L=2.2uH
C=10uF
L=2.2uH
C=10uF
4
0
2.5
3.0
3.5
4.0
4.5
5.0
-40
-20
0
20
40
60
80
100
INPUT VOLTAGE (V)
TEMPERATURE (oC)
Switching Frequency vs Input Voltage
Switching Frequency vs Temperature
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.70
1.68
1.66
1.64
1.62
1.60
1.58
1.56
1.54
1.52
1.50
1.48
1.46
1.44
1.42
1.40
L=2.2uH
C=10uF
L=2.2uH
C=10uF
-40
-20
0
20
40
60
80
100
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
TEMPERATURE (oC)
Ron(PMOS) vs Input Voltage
Ron(PMOS) vs Temperature
0.30
0.25
0.20
0.15
0.10
0.05
0.32
0.30
0.28
0.26
0.24
0.22
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
L=2.2uH
C=10uF
L=2.2uH
C=10uF
-40
-20
0
20
40
60
80
100
2.5
3.0
3.5
4.0
4.5
5.0
5.5
TEMPERATURE (oC)
INPUT VOLTAGE (V)
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Preliminary
EUP8086
Typical Operating Characteristics-Step-Down Converter
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OPERATION
Preliminary
EUP8086
impedance state even if C/10 has not yet been reached.
To restart the charge cycle, remove the input-voltage and
reapply it or momentarily force the EN_BAT pin below
VIL. A new charge cycle will automatically restart if the
BAT pin voltage falls below VBAT_EOC (typically 4.05V).
The EUP8086 is a full-featured linear battery charger
with an integrated synchronous buck converter designed
primarily for handheld applications. The battery charger
is capable of charging single-cell 4.2V Li-Ion batteries.
The buck converter is powered from the VIN pin and has
a programmable output voltage providing a maximum
load current of 600mA. The converter and the battery
charger can run simultaneously or independently of each
other.
Constant-Current / Constant-Voltage /
Constant- Temperature
The EUP8086 battery charger uses a unique architecture
to charge a battery in a constant-current, constant-voltage
and constant-temperature fashion. Figure 2 shows a
Simplified Block Diagram of the EUP8086. Three of the
amplifier feedback loops shown control the constant-
current, CA, constant-voltage, VA, and constant-
temperature, TA modes. A fourth amplifier feedback loop,
MA, is used to increase the output impedance of the
current source pair, MP1 and MP3 (note that MP1 is the
internal P-channel power MOSFET). It ensures that the
drain current of MP1 is exactly 400 times the drain
current of MP3.
BATTERY CHARGER OPERATION
Featuring an internal P-channel power MOSFET, MP1,
the battery charger uses a constant-current/constant-
voltage charge algorithm with programmable current.
Charge current can be programmed up to 500mA with a
final float voltage of 4.2V ± 1%. The STAT open-drain
status output indicates when C/10 has been reached. No
blocking diode or external sense resistor is required; thus,
the basic charger circuit requires only two external
components. An internal termination timer adheres to
battery manufacturer safety guidelines. Furthermore, the
EUP8086 battery charger is capable of operating form a
USB power source.
Amplifiers CA and VA are used in separate feedback
loops to force the charger into constant-current or
constant voltage mode, respectively. Diodes D1 and D2
provide priority to either the constant-current or
constant-voltage loop, whichever is trying to reduce the
charge current the most. The output of the other amplifier
saturates low which effectively removes its loop from the
system. When in constant-current mode, CA servos the
voltage at the ISET pin to be precisely 1V. VA servos its
non-inverting input to 1.22V when in constant-voltage
mode and the internal resistor divider made up of R1 and
R2 ensures that the battery voltage is maintained at 4.2V.
The ISET pin voltage gives an indication of the charge
current anytime in the charge cycle, as discussed in
“Programming Charge Current” in the Applications
Information section.
A charge cycle begins when the voltage at the ADP pin
rises above 3.6V and approximately 110mV above the
BAT pin voltage, a 1% program resistor is connected
form the ISET pin to ground, and the EN_BAT pin is
pulled above the enable threshold (VIH). If the battery
voltage is less than 2.95V, the battery charger begins
trickle charging at 10% of the programmed charge
current.
When the BAT pin approaches the final float voltage of
4.2V, the battery charger enters constant-voltage mode
and the charge current begins to decrease. When the
current drops to 10% of the full-scale charge current, an
internal comparator turns off the N-channel MOSFET
driving the STAT pin, and the pin becomes high
impedance.
If the die temperature starts to creep up above 115°C due
to internal power dissipation, the transconductance
amplifier, TA, limits the die temperature to
approximately 115°C by reducing the charge current.
Diode D3 ensures that TA does not affect the charge
current when the die temperature is below 115°C. In
thermal regulation, the ISET pin voltage continues to
give an indication of the charge current.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
preset value of approximately 115℃. This feature
protects the EUP8086 from excessive temperature and
allows the user to push the limits of the power handling
capability of a given circuit board without the risk of
damaging the EUP8086 or external components. Another
benefit of the thermal limit is that charge current can be
set according to typical, rather than worst-case, ambient
temperatures for a given application with the assurance
that the battery charger will automatically reduce the
current in worst-case conditions.
In typical operation, the charge cycle begins in constant-
current mode with the current delivered to the battery
equal to 400V/RISET. If the power dissipation of the
EUP8086 results in the junction temperature approaching
115°C, the amplifier (TA) will begin decreasing the
charge current to limit the die temperature to
approximately 115°C. As the battery voltage rises, the
EUP8086 either returns to constant-current mode or
enters constant-voltage mode straight from constant-
temperature mode.
An internal timer sets the total charge time, tTIMER
(typically 4.5 hours). When this time elapses, the charge
cycle terminates and the STAT pin assumes a high
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Preliminary
EUP8086
Battery Charger Undervoltage Lockout (UVLO)
forced to the high impedance state. If the battery charger
is not in constant-voltage mode when the charge current
is forced to drop below 10% of the full-scale current by
UVCL, STAT will stay in the strong pulldown state.
An internal undervoltage lockout circuit monitors the
input voltage and keeps the battery charger off until ADP
rises above 3.6V and approximately 110mV above the
BAT pin voltage. The 3.6V UVLO circuit has a built-in
hysteresis of approximately 0.6V, and the 110mV
automatic shutdown threshold has a built-in hysteresis of
approximately 65mV. During undervoltage lockout
conditions, maximum battery drain current is 5ꢀA and
maximum supply current is 10ꢀA.
Charge Current Soft-Start and Soft-Stop
The EUP8086’s battery charger includes a soft-start
circuit to minimize the inrush current at the start of a
charge cycle. When a charge cycle is initiated, the charge
current ramps from zero to full-scale current over a
period of approximately 120ꢀs. Likewise, internal
circuitry slowly ramps the charge current from full-scale
to zero when the battery charger is turned off or self
terminates. This has the effect of minimizing the transient
current load on the power supply during start-up and
charge termination.
Undervoltage Charge Current Limiting (UVCL)
The battery charger in the EUP8086 includes
undervoltage charge current limiting that prevents full
charge current until the input supply voltage reaches
approximately 300mV above the battery voltage
(ꢂVUVCL1). This feature is particularly useful if the
EUP8086 is powered from a supply with long leads (or
any relatively high output impedance). See Applications
Information section for further details.
Timer and Recharge
The EUP8086’s battery charger has an internal
termination timer that starts when the input voltage is
greater than the undervoltage lockout threshold and at
least 110mV above BAT, and the battery charger is
leaving shutdown.
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage
is below 2.95V, the battery charger goes into trickle
charge mode, reducing the charge current to 10% of the
programmed current. If the low battery voltage persists
for one quarter of the total time (1.125 hr), the battery is
assumed to be defective, the charge cycle terminates and
the STAT pin output pulses at a frequency of 2Hz with a
75% duty cycle. If, for any reason, the battery voltage
rises above 2.95V, the charge cycle will be restarted. To
restart the charge cycle (i.e., when the dead battery is
replaced with a discharged battery less than 2.95V), the
charger must be reset by removing the input voltage and
reapplying it or temporarily pulling the EN_BAT pin
below the enable threshold.
At power-up or when exiting shutdown, the charge time
is set to 4.5 hours. Once the charge cycle terminates, the
battery charger continuously monitors the BAT pin
voltage using a comparator with a 2ms filter time. When
the average battery voltage falls below 4.05V (which
corresponds to 80%-90% battery capacity), a new charge
cycle is initiated and a 2.25 hour timer begins. This
ensures that the battery is kept at, or near, a fully charged
condition and eliminates the need for periodic charge
cycle initiations. The STAT output assumes a strong
pulldown state during recharge cycles until C/10 is
reached or the recharge cycle terminates.
SWITCHING REGULATOR OPERATION:
The switching regulator in the EUP8086 can be turned on
by pulling the ENB pin above VIH.
Battery Charger Shutdown Mode
Main Control Loop
The EUP8086’s battery charger can be disabled by
pulling the EN_BAT pin below the shutdown threshold
(VIL). In shutdown mode, the battery drain current is
reduced to less than 2ꢀA and the ADP supply current to
about 5ꢀA provided the regulator is off. When the input
voltage is not present, the battery charger is in shutdown
and the battery drain current is less than 5ꢀA.
The switching uses
a slop-compensated constant
frequency, current mode PWM architecture. Both the
main (P-Channel MOSFET) and synchronous
(N-channel MOSFET) switches are internal. During
normal operation, the buck converter regulates output
voltage by switching at a constant frequency and then
modulating the power transferred to the load each cycle
using PWM comparator. It sums three weighted
differential signals: the output feedback voltage from an
external resistor divider, the main switch current sense,
and the slope-compensation ramp. It modulates output
power by adjusting the inductor-peak current during the
first half of each cycle. An N-channel, synchronous
switch turns on during the second half of each cycle (off
time). When the inductor current starts to reverse or
STAT Status Output Pin
The charge status indicator pin has three states: pulldown,
pulse at 2Hz (see Defective Battery Detection) and high
impedance. The pulldown state indicates that the battery
charger is in a charge cycle. A high impedance state
indicates that the charge current has dropped below 10%
of the full-scale current or the battery charger is disabled.
When the timer runs out (4.5 hrs), the STAT pin is also
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when the PWM reaches the end of the oscillator period,
the synchronous switch turns off. This keep excess
current from flowing backward through the inductor,
from the output capacitor to GND, or through the main
and synchronous switch to GND.
APPLICATIONS INFORMATION
BATTERY CHARGER
Programming Charge Current
The battery charge current is programmed using a single
resistor from the ISET pin to ground. The charge current
is 400 times the current out of the ISET pin. The program
resistor and the charge current are calculated using the
following equations:
Switching Regulator Undervoltage Lockout
Whenever VIN is less than 2.6V, an undervoltage lockout
circuit keeps the regulator off, preventing unreliable
operation. However, if the regulator is already running
and the battery voltage is dropping, the undervoltage
comparator does not shut down the regulator until VIN
drops below 2.4V.
1V
1V
R
= 400 ×
, I
= 400 ×
ISET
CHG
I
R
CHG
ISET
The charge current out of the BAT pin can be determined
at any time by monitoring the ISET pin voltage and using
the following equation:
Thermal Consideration
To avoid the switching regulator from exceeding the
maximum junction temperature, the user will need to do
a thermal analysis. The goal of the thermal analysis is to
determine whether the operating conditions exceed the
maximum junction temperature of the part. The
temperature rise is given by:
V
ISET
I
=
× 400
CHG
R
ISET
Stability Considerations
The EUP8086 battery charger contains two control loops:
constant-voltage and constant-current. The constant-
voltage loop is stable without any compensation when a
battery is connected with low impedance leads.
Excessive lead length, however, may add enough series
inductance to require a bypass capacitor of at least 1ꢀF
from BAT to GND.
TR=(PD)(θJA)
2
Where PD=ILOAD × RDS(ON) is the power dissipated by
the regulator ; θJA is the thermal resistance from the
junction of the die to the ambient temperature.
The junction temperature, TJ, is given by:
TJ=TA+TR
In constant-current mode, the ISET pin voltage is in the
feedback loop, not the battery voltage. Because of the
additional pole created by ISET pin capacitance,
capacitance on this pin must be kept to a minimum. With
no additional capacitance on the ISET pin, the battery
charger is stable with ISET resistor values as high as 25k.
However, additional capacitance on this node reduces the
maximum allowed program resistor. The pole frequency
at the ISET pin should be kept above 100kHz. Therefore,
if the ISET pin is loaded with a capacitance, CISET, the
following equation should be used to calculate the
Where TA is the ambient temperature.
TJ should be below the maximum junction temperature
of 150°C.
maximum resistance value for RISET
:
1
R
≤
ISET
5
2π ×10 × C
ISET
Average, rather than instantaneous, battery current may
be of interest to the user. For example, when the
switching regulator operating in low-current mode is
connected in parallel with the battery, the average current
being pulled out of the BAT pin is typically of more
interest than the instantaneous current pulses. In such a
case, a simple RC filter can be used on the ISET pin to
measure the average battery current as shown in Figure 3.
A 10k resistor has been added between the ISET pin and
the filter capacitor to ensure stability.
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power dissipated during this phase of charging is
approximately 40mW. That is a ten times improvement
over the non-current limited supply power dissipation.
USB and Wall Adapter Power
Although the EUP8086 allows charging from a USB port,
a wall adapter can also be used to charge Li-Ion batteries.
Figure 4 shows an example of how to combine wall
adapter and USB power inputs. A P-channel MOSFET,
MP1, is used to prevent back conducting into the USB
port when a wall adapter is present and Schottky diode,
D1, is used to prevent USB power loss through the 1k
pulldown resistor.
Figure 3. Isolating Capacitive Load on ISET Pin and Filtering
Undervoltage Charge Current Limiting (UVCL)
USB powered systems tend to have highly variable
source impedances (due primarily to cable quality and
length). A transient load combined with such impedance
can easily trip the UVLO threshold and turn the battery
charger off unless undervoltage charge current limiting is
implemented.
Typically a wall adapter can supply significantly more
current than the current-limited USB port. Therefore, an
N-channel MOSFET, MN1, and an extra program resistor
can be used to increase the charge current when the wall
adapter is present.
Consider a situation where the EUP8086 is operating
under normal conditions and the input supply voltage
begins to sag (e.g. an external load drags the input supply
down). If the input voltage reaches VUVCL (approximately
300mV above the battery voltage, ꢂVUVCL), under-
voltage charge current limiting will begin to reduce the
charge current in an attempt to maintain ꢂVUVCL between
ADP and BAT. The EUP8086 will continue to operate at
the reduced charge current until the input supply voltage
is increased or voltage mode reduces the charge current
further.
Figure 4. Combining Wall Adapter and USB Power
Power Dissipation
Operation from Current Limited Wall Adapter
By using a current limited wall adapter as the input
supply, the EUP8086 can dissipate significantly less
power when programmed for a current higher than the
limit of the supply.
The conditions that cause the EUP8086 battery charger to
reduce charge current through thermal feedback can be
approximated by considering the total power dissipated
in the IC. For high charge currents, the EUP8086 power
dissipation is approximately:
Consider a situation where an application requires a
200mA charge current for a discharged 800mAh Li-Ion
battery. If a typical 5V (non-current limited) input supply
is available then the peak power dissipation inside the
part can exceed 300mW.
P
=
V
− V
BAT
× I
+ P
CHG D _ BUCK
ADP
D
Now consider the same scenario, but with a 5V input
supply with a 200mA current limit. To take advantage of
the supply, it is necessary to program the EUP8086 to
charge at a current greater than 200mA. Assume that the
EUP8086 charger is programmed for 300mA (i.e., RISET
= 1.33kꢁ) to ensure that part tolerances maintain a
programmed current higher than 200mA. Since the
battery charger will demand a charge current higher than
the current limit of the input supply, the supply voltage
will collapse to the battery voltage plus 200mA times the
on-resistance of the internal PMOSFET. The
on-resistance of the battery charger power device is
approximately 1ꢁ with a 5V supply. The actual
on-resistance will be slightly higher due to the fact that
the input supply will have collapsed to less than 5V. The
DS8086 Ver 0.1 Aug. 2007
Where PD is the total power dissipated within the IC,
ADP is the input supply voltage, VBAT is the battery
voltage, IBAT is the charge current and PD_BUCK is the
power dissipation due to the regulator. PD_BUCK can be
calculated as:
1
P
= V
× I
−1
D _ BUCK
OUT OUT
η
Where VOUT is the regulated output of the switching
regulator, IOUT is the regulator load and
regulator efficiency at that particular load.
η is the
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It is not necessary to perform worst-case power
dissipation scenarios because the EUP8086 will
automatically reduce the charge current to maintain the
die temperature at approximately 115°C. However, the
approximate ambient temperature at which the thermal
feedback begins to protect the IC is:
ADP Bypass Capacitor
Many types of capacitors can be used for input bypassing;
however, caution must be exercised when using
multi-layer ceramic capacitors. Because of the self-
resonant and high Q characteristics of some types of
ceramic capacitors, high voltage transients can be
generated under some start-up conditions, such as
connecting the battery charger input to a live power
source.
o
T
= 115 C − P θ
A
D JA
o
= 115 C −
(
V
− V
BAT
)
× I
× θ
T
A
ADP
CHG
JA
SWITCHING REGULATOR
Inductor Selection
if the regulator is off.
Example: Consider the extreme case when an EUP8086
is operating from a 6V supply providing 250mA to a 3V
Li-Ion battery and the switching regulator is off. The
ambient temperature above which the EUP8086 will
begin to reduce the 250mA charge current is
approximately: (Correctly soldered to a 2500mm2
double-sided 1 oz. copper board, the EUP8086 has a
thermal resistance of approximately 43°C/W.)
The output inductor is selected to limit the ripple current
to some predetermined value, typically 20%~40% of the
full load current at the maximum input voltage. Large
value inductors lower ripple currents. Higher VIN or
VOUT also increases the ripple current as shown in
equation. A reasonable starting point for setting ripple
current is ꢂIL=240mA (40% of 600mA).
o
o
V
1
T
= 115 C −
(
6V − 3V
)
×
(
250mA
)
× 43 C / W
OUT
ꢂI
=
V
1−
A
L
OUT
(f)(L)
V
o
o
o
o
IN
T
= 115 C − 0.75W × 43 C / W = 115 C − 32.25 C
A
o
The DC current rating of the inductor should be at least
equal to the maximum load current plus half the ripple
current to prevent core saturation. Thus, a 720mA rated
inductor should be enough for most applications
(600mA+120mA). For better efficiency, choose a low
DC-resistance inductor.
T
= 82.75 C
A
If there is more power dissipation due to the switching
regulator, the thermal regulation will kick in at a
somewhat lower temperature than this. In the above
circumstances, the EUP8086 can be used above 82.75°C,
but the charge current will be reduced from 250mA. The
approximate current at a given ambient temperature can
be calculated:
CIN and COUT Selection
In continuous mode, the source current of the top
MOSFET is a square wave of duty cycle VOUT/VIN. The
primary function of the input capacitor is to provide a
low impedance loop for the edges of pulsed current
drawn by the EUP8086. A low ESR input capacitor sized
for the maximum RMS current must be used. The size
required will vary depending on the load, output voltage
and input voltage source impedance characteristics. A
typical value is around 4.7µF.
115o C −
T
A
)
I
=
CHG
(
−
×
θ
V
V
ADP
BAT
JA
Using the previous example with an ambient temperature
of 85°C, the charge current will be reduced to approxim-
ately:
The input capacitor RMS current varies with the input
voltage and the output voltage. The equation for the
maximum RMS current in the input capacitor is:
115o C − 85o C
30o C
I
=
=
= 232.6mA
V
V
CHG
(
6V − 3V
)
× 43o C / W 129o C / A
O
O
I
= I
×
× 1 −
RMS
O
V
V
IN
IN
Note: 1V = 1J/C = 1W/A
Furthermore, the voltage at the ISET pin will change
proportionally with the charge current as discussed in the
Programming Charge Current section.
The output capacitor COUT has a strong effect on loop
stability.
The selection of COUT is driven by the required effective
series resistance (ESR).
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ESR is a direct function of the volume of the capacitor;
that is, physically larger capacitors have lower ESR.
Once the ESR requirement for COUT has been met, the
RMS current rating generally far exceeds the IRIPPLE(P-P)
requirement. The output ripple ꢂVOUT is determined by:
1
ꢂV
OUT
ꢂI ESR +
L
8fC
OUT
When choosing the input and output ceramic capacitors,
choose the X5R or X7R dielectric formulations. These
dielectrics have the best temperature and voltage
characteristics of all the ceramics for a given value and
size.
Output Voltage Programming
The output voltage is set by a resistive divider according
to the following formula:
R
R
FB1
FB2
V
= 0.6V 1+
OUT
The external resistive divider is connected to the output,
allowing remote voltage sensing as shown in Figure 5.
Figure 5.
Figure 6. EUP8086 Evaluation Circuit
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EUP8086
Packaging Information
TDFN-12
MILLIMETERS
INCHES
SYMBOLS
MIN.
0.70
0.00
0.18
2.90
2.90
MAX.
0.80
0.05
0.30
3.10
3.10
MIN.
0.028
0.000
0.007
0.114
0.114
MAX.
A
A1
b
E
D
0.031
0.002
0.012
0.122
0.122
D1
E1
e
2.40
1.70
0.45
0.094
0.067
0.018
L
0.30
0.50
0.012
0.020
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