BQ24700 Datasheet, PDF (19/29 Pages) Texas Instruments – NOTEBOOK PC BATTERY CHARGE CONTROLLER AND SELECTOR WITH DPM

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bq24700, bq24701
NOTEBOOK PC BATTERY CHARGE CONTROLLER
AND SELECTOR WITH DPM
SLUS452B – APRIL 2001 – REVISED NOVEMBER 2002
APPLICATION INFORMATION
RS
COMP 10
VREF
+
SRSET
5
+
2 kΩ
SRP
16
SRN
15
50 kΩ
UDG–00117
Figure 7. Battery Charge Current Input Threshold Function
The battery charge current can be defined as:
IBAT
+
VSRSET
25 RS
(2)
where V_SRSET is the programming voltage on the SRSET pin. V_SRSET maximum is 2.5 V.
programming the adapter current
Like the battery charge current described previously, the adapter current is programmed via a voltage on the
ACSET pin. That voltage can either be from an external resistor divider from the 5-V VREF or from an external
DAC. The adapter current is defined as:
IADPT
+
VACSET
25 RS2
(3)
component selection
MOSFET selection
MOSFET selection depends on several factors, namely, gate-source voltage, input voltage and input current.
The MOSFET must be a P-channel device capable of handling at least 20-V gate-to-source with a drain-source
breakdown of VBV~ VIN+1V. The average input current can be approximated by:
ǒ _{IIN(avg) ^ VO}
IO^Ǔ
VIN
1.2
A
(4)
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