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AXP209 View Datasheet(PDF) - Unspecified

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AXP209 Datasheet PDF : 45 Pages
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AXP209
Enhanced single Cell Li-Battery and Power System Management IC
The Host can set IPS parameters and read the feedback by using internal registers in AXP209 via
TWSI.
Voltage Limiting/Current Limiting mode and Direct Mode
In order not to affect the USB communication, VBUS is always working under Voltage-Limit mode by
default. In this mode, AXP209 ensures that VBUS voltage remains above a configurable reference
voltage VHOLD which can meet the USB specification. The default VHOLD is 4.4V, adjustable in
Reg30H [5:3] register.
If the system has limit on current obtained from USB VBUS, a current-limit mode is provided (See
REG30H[1] register), with 900mA/500mA/100mA (Reg30H [0]) selectable.
If the system just utilizes the USB for power supply rather than communication, or the USB power
adapter is utilized, AXP209 can be set to “VBUS Direct Mode” by modifying register REG30H[6], and
then AXP202 will give priority to the application power demand. When the drive ability of USB Host is
insufficient or system power consumption is large then the VBUS voltage is lower than VHOLD,
AXP202 will release IRQ to indicate the weak power supply ability of Host VBUS, which may affect
USB communication, and then Host software will follow up.
AXP209’s Reaction to External Power Supply Connection
AXP209 can automatically detect the connection of external power and judge whether the power is
usable or not. The result will be set in corresponding registers, and IRQ will be asserted to inform the
Host at the same time.
The following table has listed the status bits and meanings of external power registers:
Status register bits
Description
Register REG00H [7] Indicates the presence of external ACIN
Register REG00H [6] Indicates whether the external ACIN is usable or not
Register REG00H [5] Indicates the presence of external VBUS
Register REG00H [4] Indicates whether the external VBUS is usable or not
Register REG00H [3] Indicates whether the VBUS voltage is above VHOLD when used
Register REG00H [1] Indicates whether ACIN/VBUS short circuits on PCB or not
Register REG00H [0] Indicates whether the system is triggered to startup by ACIN/VBUS
The status bit indicating “whether the VBUS voltage is above VHOLD or not when used” allows the Host
to judge when it receives IRQ7 (indicating weak supply ability) whether VBUS is pulled low by system
load input or the external power itself is below VHOLD, which may facilitate Host software to decide
either to keep on working in Voltage-Limit mode or switch to Direct Mode.
When to Select VBUS as Input Power
N_VBUSEN and register REG30H[7]: is used to determined when shall VBUS be used as the power
supply
N_VBUSEN
Low
Low
REG30H [7] Input Power
Description
Select if VBUS is valid and no ACIN is
0
VBUS available
1
VBUS Select if VBUS is valid
Confidential
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