AXP209 datasheet(22/45 Pages) ETC2

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AXP209

Enhanced single Cell Li-Battery and Power System Management IC

BAT

10uF

NTC

GND

In the diagram above, VTH/VTL refers to the high temperature threshold and low temperature

threshold, which is programmable via registers REG38H/39H/3CH/3DH respectively. VTE=0.2V. The

temperature sensitive resistor suggested is a NTC temperature-sensitive resistor, which is 10Kohm and

1% accuracy at 25℃. The AXP209 will send a constant current via TS pin, and the current can be set

as 20uA, 40uA, 60uA, and 80uA (See registerREG84H) to adapt to different NTC resistors. When the

current goes through the temperature-sensitive resistor, a

voltage is generated, which will be

measured by ADC, and compared with regulated value to release corresponding IRQ or suspend the

charge.

If the resistance value of temperature-sensitive resistor is too high or too low, extra resistors can be

placed in series or parallel to expand the detect extent. If the battery does not incorporate a themistor,

the TS pin can be linked to the ground, and in that case, AXP209 will automatically disable the battery

temperature monitoring function.

Battery Detection

AXP209 will automatically detect the battery presence, record the result in registers (refer to REG01H)

and send IRQ13, IRQ14.

Battery detection can be enabled and disabled by the Host. (Refer to register REG32H.)

9.4 Backup battery

The AXP209 supports backup battery charging and discharge. When no main power(BAT/ACIN/VBUS)

is available, LDO1 will choose the backup battery to support the operation of some circuits, such as the

system real-time clock, etc.

When there is a main power, REG35H[7] can be set to charge the backup battery, whose target voltage

is 3.0V by default (adjustable via REG35H[6:5]) and charge current is 200uA by default ( adjustable via

REG35H[1:0]).

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