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BQ24702PW View Datasheet(PDF) - Texas Instruments

Part NameBQ24702PW TI
Texas Instruments TI
DescriptionMULTICHEMISTRY BATTERY CHARGER CONTROLLER AND SYSTEM POWER SELECTOR


BQ24702PW Datasheet PDF : 32 Pages
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bq24702, bq24703
SLUS553D − MAY 2003 − REVISED JULY 2005
Zero Volt Operating
The zero volt operation is intended to provide a low current path to close open packs and protect the system
in the event of a pack cell short-circuit condition or if a short is applied to the pack terminal. It is not designed
to precharge depleted packs, as it is disabled at voltages that are not within normal pack operating range for
precharge.
If the voltage at BATDEP pin is below the zero volt operation threshold , charge is enabled (EN=HI), and ac is
selected (ACSEL=HI) the bq24702/3 enters the zero volt operation mode. When the zero volt operation mode
is on, the internal PWM is disabled, and an internal power MOSFET connects SRP to VCC. The battery charge
current is limited by the filter resistor connected to SRP pin (R19). R19 must be dimensioned to withstand the
worst case power dissipation when in zero volt operation mode.
The zero volt operation mode is disabled when BATDEP is above the zero volt operation threshold, and the main
PWM loop is turned on if charge is enabled, regulating the current to the value set by SRSET voltage. To avoid
errors on the charge current both resistors on the SRP, SRN filter must have the same value. Note, however,
that R21 (connected to SRN) does not dissipate any power when in zero volt operation and can be of minimum
size.
PWM Operation
The three open collector gm amplifiers are tied to the COMP pin (refer to Figure 2), which is internally biased
up by a 100-µA constant current source. The voltage on the COMP pin is the control voltage (VC) for the PWM
comparator. The PWM comparator compares VC to the sawtooth ramp of the internally fixed 300-kHz oscillator
to provide duty cycle information for the PWM drive. The PWM drive is level-shifted to provide adequate gate
voltage levels for the external P-channel MOSFET. Refer to PWM selector switch gate drive section for gate
drive voltage levels.
Q1
+
ISW
SW
VADPT
D1
VBAT
COMP
10
ZCOMP
CLK
OSC
RAMP
5V
100 µA
ENABLE
LATCH OUT
SQ
RQ
PWM COMPARATOR
FROM ENABLE LOGIC
LEVEL
SHIFT
VCC
PWM
DRIVE
VHSP
21
PWM
ENABLE
+
BATTERY
VOLTAGE
BATTERY CHARGE
CURRENT
ADP CURRENT
gm
AMPLIFIERS
+
1.25 V
13
BATP
Figure 2. PWM Controller Block Diagram
UDG−00114
www.ti.com
17
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DESCRIPTION
The bq24702/bq24703 is a highly integrated battery charge controller and selector tailored for notebook and sub-notebook PC applications.
The bq24702/bq24703 uses dynamic power management (DPM) to minimize battery charge time by maximizing use of available wall-adapter power. This is achieved by dynamically adjusting the battery charge current based on the total system (adapter) current.
The bq24702/bq24703 uses a fixed frequency, pulse width modulator (PWM) to accurately control battery charge current and voltage. Charge current limits can be programmed from a keyboard controller DAC or by external resistor dividers from the precision 5-V, ±0.6%, externally bypassed voltage reference (VREF), supplied by the bq24702/bq24703.

FEATURES
● Dynamic Power Management, DPM
   Minimizes Battery Charge Time
● Integrated Selector Supports Battery
   Conditioning and Smart Battery Learn Cycle
● Zero Volt Operation
● Selector Feedback Circuit Ensures
   Break-Before-Make Transition
● ±0.4% Charge Voltage Accuracy, Suitable for
   Charging Li-Ion Cells
● ±4% Charge Current Accuracy
● 300-kHz Integrated PWM Controller for
   High-Efficiency Buck Regulation
● Depleted Battery Detection and Indication to
   Protect Battery From Over Discharge
● 20-µA Sleep Mode Current for Low Battery
   Drain
● 24-Pin TSSOP Package and 5 mm × 5 mm
   QFN package (bq24703 only)

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