PT8A2803
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500mA Li-ion/Polymer Battery Charger
Features
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Description
The PT8A2803 is a fully integrated single-cell Li-
ion/Polymer battery charger. The charger operates in a
constant-current-constant-voltage (CC/CV) charging
profile without employing external FETs and blocking
diodes.
The fast charge current and end-of-charge (EOC) current
can be easily programmed by modifying two external
resistors. When the battery is deeply discharged to lower
than 2.8V, the charger firstly pre-charges the battery
with typically 20% of the programmable fast charge
current. When the charge current is reduced to the
programmed EOC current level (almost works
completely in a constant-voltage (CV) mode), an EOC
indication is displayed through the
CHG
pins.
PT8A2803 is protected by thermal regulation
technology to prevent the IC from over-heat during
charging.
Two status indication pins (
PPR
and
CHG
), which are
both implemented as an open-drain outputs, can be used
to drive LEDs or work as logic interface to a
microprocessor. When no adapter is attached or when
the charger is disabled, the leakage current from battery
cell is less than 1µA typically.
A Constant-Current / Constant-Voltage Linear
Charger for Single-Cell Li-ion/Polymer Batteries
Integrated Pass Element and Current Sensor
Highly-Integrated, Requiring No External FETs or
Blocking Diode
±0.5%
4.2V Voltage Accuracy at Room
Temperature.
±1%
All Temperatures. (Available
with 4.1V and 4.36V options upon request)
Programmable Charge Current 50mA to 500mA
Programmable End-Of-Charge Current by Current
Recharge Algorithm
Pre-Charge for Fully Discharged Batteries
Less Than 1µA Leakage Current Of the Battery
when No Input Power Attached or Charger Disabled
Power Present and Charge Status Indications
Thermal Regulation on Charging Current to Prevent
Over-Heat
Available with 8-pin 2x3 TDFN Package
Cell-phones, PDA, MP3, MP4, PMP
Standalone Chargers
Bluetooth Applications
Applications
Pin Assignment
VIN
PPR
CHG
EN
1
2
3
4
TDFN 2x3
8
7
6
5
BAT
IREF
IMIN
GND
Pin Description
Pin
1
2
3
4
5
6
7
8
I/O
I/O
O
O
I
I/O
I
I
O
Name
VIN
PPR
CHG
EN
GND
IMIN
IREF
BAT
Descriptions
Supply Input.
Power Present Active-Low Open Drain Power Status Indicator
Charge Active-Low Open Drain Charge Status Indicator
Enable Active-Low Input
Ground
End-Of-Charge Current Setting Input
Charge Current Setting Input
Battery Terminal
PT0324S-1
1
12/21/10
PT8A2803
500mA Li-ion/Polymer Battery Charger
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Maximum Ratings
Storage Temperature………………………………………………………..-65oC to +150oC
Supply Voltage to Ground Potential (V
IN
PT8A2803)……………………………-0.3V to+7.0V
Supply Voltage to Ground Potential (IMIN/IREF/BAT/
CHG
/
EN
/
PPR
)………0.3V to+7.0V
Thermal Resistance (Typical for TDFN Package)………………….θJA (°C/W)=59
………………………………………………………………….…..θJC (°C/W)=4.5
Note:
Stresses greater than those listed under
MAXIMUM RATINGS may cause
permanent damage to the device. This is a
stress rating only and functional operation
of the device at these or any other
conditions above those indicated in the
operational sections of this specification
is not implied. Exposure to absolute
maximum rating conditions for extended
periods may affect reliability.
Max
5.5
500
+85
Unit
V
mA
°C
Recommended Operating Conditions
Sym
VIN
Programmable Current
T
A
Parameter
Operating Voltage
-
Operating temperature
Min
4.3
50
-30
Typ
-
-
-
Electrical Specifications
Typical values are at V
IN
=5V and T
A
=25°C. All maximum and minimum values are at T
A
= -30°C to +85°C, unless otherwise
noted.
Parameter
Sym
Conditions
Min
Typ Max Units
POWER-ON RESET
Rising POR Threshold
V
POR
3.3
3.9
4.3
V
V
BAT
=3.0V, use
PPR
to indicate the
3.1
3.6
4.15
V
Falling POR Threshold
V
POR
output
VIN-VBAT OFFSET VOLTAGE
Rising Edge
V
OS
-
90
150
mV
V
BAT
=4.0V, use
CHG
pin to indicate the
Falling Edge
V
OS
10
50
-
mV
comparator output
STANDBY CURRENT
BAT pin sink current
I
STBY
Charger disabled or the input is floating
-
1
-
µA
DC Supply Current
I
DC
Charger disabled
-
300
400
µA
DC Supply Current
I
DC
Charger enabled
-
500
700
µA
VOLTAGE REGULATION
Output voltage
V
CH
4.3V < V
IN
<5.5V Charge current=20mA 4.158 4.20 4.242
V
V
BAT
=3.8V, charge current=0.5A, R
IREF
-
0.6
-
Ω
Power FET “ON” Resistance
R
DS(ON)
=8kΩ
CHARGE CURRENT
135
150
165
Constant Charge Current
I
CHG
R
IREF
=29.4kΩ, V
BAT
= 2.8–4.0V
mA
18
25
32
Precharge Charge Current
I
PRE
R
IREF
=29.4kΩ, V
BAT
= 2.4V
mA
20
30
40
End of Charge Current
I
MIN
R
IMIN
=137kΩ
mA
90
100
130
EOC Rising Threshold
I
RECHG
R
IREF
=29.4kΩ
mA
PRECHARGE CHARGE THRESHOLD
Precharge Threshold Voltage
V
PRE
-
2.45 2.55 2.65
V
Precharge Voltage Hysteresis
V
PREHYS
-
40
100
150
mV
INTERNAL TEMPERATURE MONITORING
Thermal regulation threshold (Note)
T
FOLD
-
-
115
-
°C
LOGIC INPUT AND OUTPUTS
V
ENH
-
1.3
-
-
V
EN
Pin Logic Input High
-
-
-
0.5
V
V
ENL
EN
Pin Logic Input Low
R
EN
-
100
200
400
kΩ
EN
Pin Internal Pull Down Resistance
V
CHG
=1V
10
20
-
mA
I
CHGOL
CHG
Pin Sink Current When LOW
V
CHG
=5.5V
-
-
1
µA
CHG
Pin Leakage Current When HIGH I
CHGOH
V
PPR
=1V
10
20
-
mA
I
PPROL
PPR
Pin Sink Current When LOW
V
PPR
=5.5V
-
-
1
µA
PPR
Pin Leakage Current When HIGH I
PPROH
Note: This parameter is guaranteed by design, not tested.
PT0324S-1
2
12/21/10
PT8A2803
500mA Li-ion/Polymer Battery Charger
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Application Circuits
DC IN
VIN
C1
1
8
7
6
5
VIN
PPR
CHG
EN
VBAT
BATTERY
PT8A2803
R2
R1
D2
D1
OFF
ON
2
3
4
IREF
IMIN
GND
RIRE
F
RIMIN
C2
Figure 1 PT8A2803 Typical Application Circuit to Indication LEDs
Part
C1
C2
RIREF
RIMIN
R1, R2
D1, D2
Component Description for Figure 1
Description
1µF X5R ceramic cap
1µF X5R ceramic cap
29.4kΩ, 1% for 150mA charge current
294kΩ, 1% for 15mA EOC current
300Ω, 5%
LEDs for indication
DC IN
VIN
C1
1
2
3
4
OFF
ON
8
BAT
MCU
BAT
VIN
PPR
CHG
EN
VBAT
BATTERY
PT8A2803
R2
R1
MCU
IREF
IMIN
GND
F
7
RIRE
6
5
C2
RIMIN
MCU
Figure 2 PT8A2803 Typical Application Circuit Interfacing to a MCU
Part
C1
C2
RIREF
RIMIN
R1, R2
Component Description for Figure 2
Description
1µF X5R ceramic cap
1µF X5R ceramic cap
29.4kΩ, 1% for 150mA charge current
294kΩ, 1% for 15mA EOC current
100kΩ, 5%
PT0324S-1
3
12/21/10
PT8A2803
500mA Li-ion/Polymer Battery Charger
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Function block diagram
VIN
VREF
POR
VBAT
VOS
BAT
PPR
VREF
Charge Control
EN
CHG
200K
DIE
TEMP
GND
115°C
EN
IREF
IMIN
Figure 3 Block diagram of PT8A2803
Functional Description
(Refer to Function Block Diagram)
The PT8A2803 charges a single-cell Li-ion/Polymer battery with a programmable constant current (CC) or a constant voltage (CV)
algorithm. The fast charge current (ICHG) can be programmed by setting an external resistor RIREF (see
Figure 1/2)
while
constant voltage is factory-trimmed at 4.2V (4.1V or 4.36V) options area available upon request). If the battery voltage was
deeply discharged to lower than 2.55V, PT8A2803 firstly pre-charges the battery with 20% of the programmed fast charge current.
Normally, the battery voltage rises gradually during CC charge phase. When the battery voltage reaches almost 4.2V, the charger
enters the constant-voltage (CV) charging mode and begins to regulate the battery voltage at 4.2V while diminishing the charging
current gradually. When charging current is reduced to an amount smaller than the programmed End-Of-Charge (EOC) current
level, the charger gives out a “full-charge” indication through the
CHG
pin, but the charger still continues to regulate the battery
voltage at 4.2V with safe & small current.
Figure 4
shows the typical charge profile with the EOC/reset event.
PT8A2803 employs current recharge algorithm. The end-of charge (EOC) current level can be easily programmed with an
external resistor RIMIN (see Figure 3/4). The
CHG
signal turns to LOW when pre-charge starts and rises to HIGH when EOC is
reached. After reaching EOC, the charge current has to rise to typically 76% ICHG before the
CHG
signal will turn on again, as
shown in
Figure 4.
The current surge after EOC can be caused by a load connected to the battery.
When the die temperature reaches 115°C (typically) during charging, a thermal regulation function is employed to reduce the
charge current accordingly to maintain the temperature from increasing furthermore. This is an important function to achieve safe
operation especially when the printed circuit board (PCB) is not effective in leaking out heat generated by the linear charger.
PPR
Indication
The
PPR
pin is implemented as an open-drain output to provide a power-good indication of the input power source such as an AC
adapter. When the input voltage is higher than the POR (Power-On Reset) threshold, the
PPR
pin turns on the internal open-drain
MOSFET to indicate a logic LOW signal. The
PPR
indication is designed to be independent on the chip enable (
EN
-pin) input.
When the internal open-drain FET is turned off, the
PPR
pin should leak less than 1µA current. When turned on, the
PPR
pin
should be able to sink at least 10mA current under all operating conditions. The
PPR
pin can be used to drive an LED (see
Figure
1)
or worked as logic interface to a microprocessor (see
Figure 2).
PT0324S-1
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12/21/10
PT8A2803
500mA Li-ion/Polymer Battery Charger
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Power-Good Range
The input voltage is considered as power good when it meets the following three conditions:
1. VIN > VPOR
2. VIN - VBAT > VOS
The VOS is the offset voltage to determine if the battery voltage is even higher than the input voltage. All VPOR and VOS are
realized with sufficient hysteresis, as given in the Electrical Specification table. All charging activities are disabled when the input
voltage falls out of the power-good range.
Input and Output Comparator
Obviously, when the input source voltage is lower than the battery voltage, no charging activity could be started and the charger
will disable the internal pass element to prevent battery leakage. Charge begins when the input voltage is higher than the battery
voltage by a defined offset voltage (VOS). This scheme also ensures that the charger is completely turned off when the input
power is removed from the charger.
CHG
Indication
The
CHG
pin is implemented as an open-drain output to give a logic LOW when a charge cycle begins and turn HIGH when an
end-of-charge (EOC) condition is reached. This pin is designed with a sinking ability of more than 10mA so as to drive an LED.
When the charger is disabled through
EN
-pin, the
CHG
outputs a high impedance. The
CHG
pin can also be used to interface with
a microprocessor.
EN
Input
The chip is enabled by a logic LOW signal applied to the
EN
pin. This pin is realized with a 200kΩ internal pull-down resistor
such that even the
EN
pin is left floating, the input is equivalent to logic LOW and the chip is enabled by default. Similarly, the
chip is disabled when the
EN
pin receives a logic HIGH signal. The threshold for HIGH is given in the ES (Electrical
Specifications).
IMIN Indication
The IMIN pin can be used to program the End-of-Charge (EOC) current by connecting a resistor between this pin and the GND
pin. The programming is defined by the following equation:
IMIN (mA) = 4180/ R
IMIN
Where R
IMIN
is usually in kΩ.
IREF Pin
The IREF pin is for fast charge-current programming. By connecting a resistor between this pin and the GND pin, the fast charge
current limit is determined by the following equation:
I
CHG
(mA) = 4400/R
IREF
Where R
IREF
is in kΩ. The actual charge current is guaranteed to have 10% accuracy of I
CHG
with the charge current set at 150mA.
BAT pin
Always connect the BAT pin to a single-cell Li-ion/Polymer battery in parallel with a 1µF (or larger) X5R ceramic capacitor for
decoupling and guaranteeing system stability. When the
EN
pin is pulled to logic HIGH, the BAT output is disabled. The
PT8A2803 relies on a battery for stability and is not guaranteed to be stable if the battery is not connected.
Dropout Voltage
When the input voltage is low while the battery voltage is high, the charging current may not be maintained according to the
equation I
MIN
(mA) = 4180/R
IMIN
due to a limited internal on-resistance (R
DS(ON)
) of the internal pass element. The worst resistance
of the pass FET is about 1.2Ω at the maximum operating temperature, thus if tested with 500mA current and 4.2V battery voltage,
constant current could still be maintained when the input voltage is below 4.62V.
Thermal Foldback
The bottom big exposed pad in DFN package is used for thermal foldback. For reducing the chip ambient temperature as much as
possible, it is recommended to connect as much copper as possible to this pad either on the component layer or other layers
through thermal vias. The thermal regulation function starts to reduce the charge current when the internal temperature reaches a
typical value of 115°C.
PT0324S-1
5
12/21/10
FPGA/CPLD
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