AXP209 datasheet(17/45 Pages) ETC2

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AXP209

Enhanced single Cell Li-Battery and Power System Management IC

System reset function and output monitoring (PWROK)

The PWROK in AXP209 can be used as the reset signal for the application system. During AXP209

startup, PWROK outputs low level, which will then be pulled high to startup and reset the system after

all output voltage reaches the regulated value.

Under normal operation, the AXP209 will be always monitoring the voltage and load status. If overload

or under-voltage occurs, the PWROK will instantly be driven low to reset the system and prevent data

losses.

9.2 Power path management (IPS)

The AXP209 power input can come from lithium battery (BAT),USB VBUS Input, external power

supply (ACIN). The IPS will select an appropriate power source depending on the battery and external

power conditions.

O When only the battery is available, no external power input, the battery powers the system;

O When there is a valid external power source(VBUS Or ACIN), is is the preferred power supply.

O When the external power is removed, the IPS will seamlessly switch over to battery power.

O When both VBUS and ACIN are available, ACIN will be used to power the system and recharge

the lithium battery;

O If the ACIN cannot provide sufficient current, VBUS is also connected to source more

current;

O If the drive capacity is still insufficient, then the charge current is reduced to zero, the

battery is used to power the system.

Therefore, compatibility of the system with external powers of different drive ability can be

dramatically improved, and no special customized adapters are required to be provided on the part

of manufacturers.

Please refer to the following diagram.

As shown above, when ACIN provides insufficient load ability, IPSOUT voltage will fall, and BAT

will change from charge to discharge to supply load current together with ACIN.

Confidential

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