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Vimicro |
VA7205_100-1.3_En
ADVANCED LINEAR CHARGER IC
For LITHIUM-ION AND LITHIUM-POLYMER Battery
FEATURES
• Ideal for Single (4.2V) Li-ion or Li-Polymer
Packs
• Better Than ±1% Voltage Regulation Accuracy
With Preset Voltage
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• Adjustable precharge current with an external
resistor
• Adjustable Charging Current During Constant
Current Charging Stage
• Constant Voltage Charging
• Automatic Battery-Recharge Feature
• Cell-Temperature Monitoring Before and During
Charge
• Dynamic compensation of Battery Pack’s
Internal Impedance to Reduce Charge Time
• Charge Status Output for Dual Led
• Cell Condition Monitoring
• Automatic Low-Power Sleep Mode When Vcc is
Removed or When Voltage Supply is Lower
than battery voltage
• Requires Small Number of External
Components
• Packaging: 8-Pin SOP or MSOP
DESCRIPTION
The VA7205 series advanced Lithium-Ion (Li-Ion)
and Lithium-Polymer (Li-Pol) Linear Charger ICs
are designed for cost-sensitive and compact
portable electronics.
They combine
high-accuracy current and voltage regulation,
battery condition monitoring, temperature
monitoring, charge termination, charge-status
indication, and internal impedance compensation
in a single 8-pin IC. It is the best suitable device
to be used in the PDA, mobile phones, and other
portable devices.
The VA7205 monitors the battery charging status
by detecting the battery voltage level. The
VA7205 charges the battery in three phases:
conditioning, constant current, and constant
voltage.If the battery voltage is below the
low-voltage threshold, Vmin (normally at 3V), the
VA7205 precharges using a low current to
FUNCTION BLOCK DIAGRAM
condition the battery. The conditioning charge
rate can be adjusted with an external resistor.
After the battery is precharged to Vmin, the
VA7205 applies a constant current to the battery.
An external sense-resistor sets the current.
The constant-current phase continues until the
battery reaches the charge-regulation voltage
(normally at 4.2V) and then the VA7205 begins
the constant-voltage phase. The accuracy of the
voltage regulation is better than ±1% over the
operating-temperature and supply-voltage
ranges. Under this stage the charging current
will gradually decrease. Charge stops when the
current tapers to the charge termination
threshold, ITERM. The VA7205 will continue
monitoring the battery voltage level and entering
a new cycle of charging if the battery’s voltage
level has fell below VRECHG (normally at VREG -
125mV).
During the charging process, for the safety
concern, the VA7205 continuously measures
battery temperature using the battery’s internal
heat sensitive resistor and an external resistors.
If the temperature of the battery exceeds the
pre-set temperature range, the charging process
will come to a halt after 0.5 seconds; After the
temperature fell back into the pre-set
temperature range, the charging will continue
again after 0.5 seconds. The VA7205 can also
dynamically compensate the battery pack’s
internal impedance to reduce the charge time.
LED
S
T
S
VSS
1
2
3
BAT 4
VA7205CF
Top
View
(Not to
Scale)
8 VCC
7 CS2/LEDT
6 CS1
5
DRIV
E
Figure 1 VA7205CF 8-Pin SOP
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1
BAT 4
Voltage
Regulator
CS2/LEDT
7
VA7205_100-1.3_En
Driver
5D
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VCC 8
Internal
Reference
Current
Regulator
Control
Block
Timer
61
Figure 2 VA7205 Function Block Diagram
3
2 TS
Ordering Information
MODEL
VA7205CF
VA7205DF
OUTPUT VOLTAGE
4.2V
4.2V
RECHARGING VOLTAGE
4.075V
4.075V
PACKAGING
SOP
MSOP
PIN COUNT
8
8
PIN DESCRIPTION
PIN
NAME
PIN
NO.
I/O
PIN DESCRIPTION
LEDS
1
Charge Status Output
During the charging, this pin is pulled low to VSS. After the charging completed, this pin will
O be appear as high-impedance state. Under the case of abnormal battery operation or
abnormal high temperature, a 50% duty-cycle 2Hz pulse will be generated. This pin can be
connected to the LED diode via a 330 ohm resistor.
Temperature Sense Input
TS 2 I Input for an external battery-temperature monitoring circuit. The input voltage level for this
pin has to be between VTS1 and VTS2, otherwise, VA7205 will treat as abnormal temperature
range.
VSS 3 PWR Ground
BAT 4
Battery Voltage Sense Input
I This pin should be tied directly to the positive side of the battery via a 300~680Ω resistor. A
10uF capacitor should be connected between battery’s positive and negative terminals.
DRIVE
5
External Pass Transistor Drive Output
O This output drives an external pass-transistor (PNP or P-Channel MOSFET) for current and
voltage regulation.
CS1 6
Current-Sense Input
I Battery current is sensed via the voltage developed on this pin by an external sense resistor.
The external resistor can be placed between positive terminal of the power supply and the
emitter (PNP transistor) or source (PMOS transistor).
2
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