BQ24700 Datasheet, PDF (18/29 Pages) Texas Instruments – NOTEBOOK PC BATTERY CHARGE CONTROLLER AND SELECTOR WITH DPM

bq24700, bq24701
ą
NOTEBOOK PC BATTERY CHARGE CONTROLLER
AND SELECTOR WITH DPM
SLUS452B – APRIL 2001 – REVISED NOVEMBER 2002
APPLICATION INFORMATION
VBAT
BATP
13
BATSET
10
1.25 V
gm AMPLIFIER
+
COMP
9
VBAT
0.25 V
1.25 V
(a) VBATSET < 0.25 V
VREF = 5 V
R1
BATP
13
R2
10
BATSET
1.25 V
gm AMPLIFIER
+
COMP
9
0.25 V
1.25 V
(b) VBATSET > 0.25 V
Figure 6. Battery Error Amplifier Input Multiplexing Scheme
UDG–00116
programming the battery charge current
The battery charge current is programmed via a voltage on the SRSET pin. This voltage can be derived from
a resistor divider from the 5-V VREF or by means of an DAC. The voltage is converted to a current source that
is used to develop a voltage drop across an internal offset resistor at one input of the SR g_m amplifier. The charge
current is then a function of this voltage drop and the sense resistor (R_S), refer to Figure 7.
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