CAT874 Datasheet, PDF (6/7 Pages) ON Semiconductor – Smart Phone Battery Switch Controller

CAT874
APPLICATION INFORMATION
Output Operation
System with Two Different Power Supply Voltages
When both V_CHG and VBAT are present, the following
application can be adapted. Schottky diodes D1 and D2 can
be used to isolate the two sources. The higher source will
supply the VDD power.
If V_CHG is not present then drop across D2 should be low
enough to turn off Q1. If both V_CHG and VBAT are present,
the timing waveforms should be used as shown in Figure 4.
An external resistor 1M should be used OUT, to discharge
the output when both sources turn off.
Operation with Low VDD Voltage and Brownout
Condition
The CAT874 requires a minimum supply voltage VDD of
1.8 V to guarantee the normal operation within the
specification. To prevent small VDD supply glitch, a small
ceramic capacitor can be added between the VDD pin and
GND.
V_CHG
D1
D2
V_BAT
Battery
PWR_ON
V_DD
PWR_ON
V_CHG
CAT874
GND
0.1 mF
OUT
1 MW
NTLUS3A18P2
Q1
P−MOS
D3
NTLUS3A18P2
Q2
P−MOS
DRV
PWR_ON
V_SYS
PMU
Figure 5. Application Schematic in Dual Supply System
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