BQ24700 Datasheet, PDF (16/29 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
PERCENT DUTY CYCLE
vs
COMPENSATION VOLTAGE
100
90
80
70
60
50
40
30
20
10
0
1.2
1.7
2.2
2.7
3.2
VCOMP – Compensation Voltage – V
Figure 4
As any one of the three controlling loops approaches the programmed limit, the g_m amplifier begins to shunt
current away from the COMP pin. The rate of voltage rise on the COMP pin slows due to the decrease in total
current out of the pin, decreasing the rate of duty cycle increase. When the loop has reached the programmed
limit the g_m amplifier shunts the entire bias current (100 µA) and the duty cycle remains fixed. If any of the control
parameters tries to exceed the programmed limit, the g_m amplifier shunts additional current from the COMP pin,
further reducing the PWM duty cycle until the offending parameter is brought into check.
16
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