AXP221

The AXP221 is the PMIC (Power Management IC) used by A31 SoCs and developed by X-Powers, a sister company of Allwinner.

Overview

AXP221 is a highly integrated PMIC targeted at single cell Li-battery (Li-ion or Li-polymer) applications that require multi-channel power conversion outputs. It provides an easy and flexible power management solution for multi-core processors to meet the increasingly complex and accurate requirements of power control.

AXP221 comes with an adaptive USB3.0-compatible Flash Charger that supports up to 94% efficiency and 2.2A charge current. It also provides 21 power output channels (including 5-CH DC-DC, with efficiency up to 95%). To ensure the security and stability of the power system, AXP221 provides multiple-channel 12-bit ADC for voltage/current/temperature monitoring and integrates protection circuits such as OVP, UVP, OTP, and OCP. Moreover, AXP221 integrates a unique E-Gauge™ system which simplifies battery power measurement.

Importantly, AXP221 also Featuress an IPS™ (Intelligent Power Select) circuit that transparently selects power path among USB, external adaptor, Li-battery, and system load, allowing the system to function normally when only running on external input power and not the battery.

AXP221 is available in 8mm x 8mm x 0.75mm 68-pin QFN package.

Features

• IPS™

• Input voltage range: 2.9V~6.3V (AMR: -0.3V~11V)
• Configurable IPS™ system
• Adaptive USB/AC adaptor voltage/current limit (4.4V/900mA/500mA)

• Buck DC-DC Converters (5-CH)

• DC-DC1: 1.6V~3.4V adjustable, 100mV/step, load current up to 1.4A
• DC-DC2: 0.6V~1.54V adjustable, 20mV/step, load current up to 2.5A, supports VRC (Voltage Ramp Control)
• DC-DC3: 0.6V-1.86V adjustable, 20mV/step, load current up to 2.5A
• DC-DC4: 0.6V-1.54V adjustable, 20mV/step, load current up to 0.6A
• DC-DC5: 1.0V-2.55V adjustable, 50mV/step, load current up to 2A

• System Management

• Support soft reset and hard reset
• Support soft shutdown and hard shutdown
• Support external wakeup triggers
• Support PWROK for system rest or shutdown indication
• External power detection (insert/remove/drive strength deficiency)
• All output voltage support software boot
• Over/Under-voltage protection (OVP/UVP)
• Over-current protection (OCP)
• Over-temperature protection (OTP)

• E-Gauge™ System

• Highly accurate gauge system with dual modes
• Easy Mode: highly adaptive to different powers
• Exact Mode: highly accurate data is provided for specific power
• Provide rich power information, such as instantaneous power consumption (mA or mW), remaining power (% or mA), charge status (%), remaining power life, charge time, etc
• Low power warning and low power protection
• Provide die temperature

• High Integration

• Highly accurate (0.5%) reference voltage
• Integrates MOSFET

• Flash Charger

• Integrated MOSFET charge current up to 2.2A
• Battery temperature monitor
• Fully supports USB charge
• High charge accuracy, ±0.5% accuracy
• Supports 4.1V/4.2V/4.22V/4.24V battery
• Automatic charge control
• Supports LED to indicate charge status
• Automatic charge current adjustment based on system load

• LDOs (14-CH)

• RTC_VCC: 30mA, always valid
• ALDO1/2: low noise LDO, 0.7V~3.3V adjustable, 100mV/step, load current up to 300mA
• ALDO3: low noise LDO, 0.7V~3.3V adjustable, 100mV/step, load current up to 200mA
• LDOIO0/LDOIO1: low noise LDO, 0.7V~3.3V adjustable, 100mV/step, load current up to 100mA
• DLDO1/ ELDO1: 0.7~3.3V adjustable, 100mV/step, load current up to 400mA
• DLDO2/ DLDO3/ ELDO2/ ELDO3: 0.7~3.3V adjustable, 100mV/step, load current up to 200mA
• DLDO4: 0.7V~3.3V adjustable, 100mV/step, load current up to 100mA
• DC5LDO: 0.7V~1.4V adjustable, 100mV/step, load current up to 200mA

• Switch (2-CH)

• DC1SW: internal resistance 100mOhm, power sourced from DCDC1
• CHGLED:100mA sink strength, can be used to drive the motor and charging LED

• Host Interface

• P2WI (Push-Pull Two Wire Interface) for host communication
• Configurable interrupt management
• Flexible pin function configuration: 2 GPIOs can be set as IO or LDO, etc
• Integrated timer
• 12 groups of registers for system shutdown data storage

Pinout Diagram

Pinout List

Number	Pin Name	Type	Control Criteria	Description
1	ELDOIN	PI		ELDO Input Source
2	ELDO2	O		ELDO2 Output
3	ELDO3	O		ELDO3 Output
4	DC5LDO	O		DC5LDO Output
5	DCDC5	I		DC-DC5 Feedback
6	PGND5	G		DC-DC5 NMOS ground
7,8	LX5	IO		DC-DC5 Inductor
9	VIN5	PI		DC-DC5 Input Source
10	DC5SET	I		Set DC-DC5 output voltage
11	N_VBUSEN	IO	Input	VBUS-IPSOUT channel control Connected to GND: IPSOUT uses VBUS Connected to IPSOUT: IPSOUT does not use VBUS
11	N_VBUSEN	IO	Output	VBUS-IPSOUT channel control GND: IPSOUT uses VBUS: High: IPSOUT does not use VBUS
12	PWRON	I		Power On-Off key (PEK) input, Internal 100kΩ pull-up resistor to APS
13	VIN1	PI		DC-DC1 Input Source
14	LX1	IO		DC-DC1 Inductor
15	PGND1	G		DC-DC1 NMOS ground
16	DLDO3	O		DLDO3 Output
17	DLDO2	O		DLDO2 Output
18	DLDOIN	PI		DLDO Input Source
19	DLDO1	O		DLDO1 Output
20	DLDO4	O		DLDO4 Output
21	DCDC1	I		DC-DC1 Feedback
22	DC1SW	O		DC-DC1 Switch output
23	VIN2	PI		DC-DC2 Input Source
24,25	LX2	IO		DC-DC2 Inductor
26,27	PGND2	G		DC-DC2 NMOS ground
28	DCDC2	I		DC-DC2 Feedback
29	IRQ/WAKEUP	IO		IRQ output or wakeup
30	TS	I		Battery temperature sensor or external ADC input
31	GPIO1	IO	Reg 92h [2:0]	GPIO1 / LDOIO0 output
32	ALDO1	O		ALDO1 Output
33	ALDOIN	PI		ALDO Input Source
34	ALDO2	O		ALDO2 Output
35	VREF	I		Internal reference voltage
36	ALDO3	O		ALDO3 Output
37	GPIO0	IO	Reg 90h [2:0]	GPIO0 / LDOIO0 output
38	DCDC3	I		DC-DC3 Feedback
39	VIN3	PI		DC-DC3 Input Source
40,41	LX3	IO		DC-DC3 Inductor
42	PGND3	G		DC-DC3 NMOS ground
43	PWROK	O		Power good indicator
44	SCK	I		Serial interface clock pin. Normally pulled-up to 3.3V by 2.2k resistor
45	SDA	IO		Serial interface data pin. Normally pulled-up to 3.3V by 2.2k resistor
46	VCC_RTC	O		VCC_RTC output
47	VINT	PO		Internal logic power, 1.8V
48	VBUS	PI		VBUS input
49	BATSENSE	I		PWM Charger current sense resistance positive input
50	LOADSENSE	I		PWM Charger current sense resistance negative input
51	N_BATDRV	O		BAT to PS external PMOS driver
52	CHGLED	O		Charger status indicator
53,54	IPSOUT	PO		System power source
55,56	ACIN	PI		Power adapter input
57	CHSENSEP	I		PWM Charger current limit sense resistance positive input
58	CHSENSEN	I		PWM Charger current limit sense resistance negative input
59	PGND_CHG	G		PWM Charger NMOS ground
60,61	LX_CHG	IO		PWM Charger Inductor
62,63	VIN_CHG	PI		PWM Charger Input Source
64	VIN4	PI		DC-DC4 Input Source
65	LX4	IO		DC-DC4 Inductor
66	PGND4	G		DC-DC4 NMOS ground
67	DCDC4	I		DC-DC4 Feedback
68	ELDO1	O		ELDO1 Output
69	EP	G		Exposed Pad, need to connect to ground

Functional Diagram

Typical Usage

Regulators

The AXP221 features 5 DC-DC step-down (buck) converters, 14 linear regulators (5 of which are low-noise), and 2 switches. The DC-DC converters operate in automatic (PFM + PWM) or PWM mode, controllable via reg 80h, at a default frequency of 3 MHz. The frequency is controlled via reg 37h. It also supports spread spectrum.

Output	Type	Voltage Range	Default Voltage	Enable steps	Example Usage	Maximum Output	Note
DCDC1	Buck	1.6 - 3.4 V	3.3 V	1	3.3V I/O	1400 mA
DCDC2	Buck	0.6 - 1.53 V	1.1 V	1	1.1V CPU	2500 mA
DCDC3	Buck	0.6 - 1.86 V	1.1 V	1	1.1V GPU	2500 mA
DCDC4	Buck	0.6 - 1.53 V	1.1 V	1	1.1V Core	600 mA
DCDC5	Buck	1.0 - 2.55 V	1.5 V	1	1.5V DDR3	2000 mA	DC5SET pin configurable default
RTC-LDO	LDO	Fixed	3.0 V	1	RTC	30 mA	Always on
ALDO1	LDO	0.7 - 3.3 V	Off	Off	N/A	300 mA	Low noise
ALDO2	LDO	0.7 - 3.3 V	1.8 V	1	N/A	300 mA	Low noise
ALDO3	LDO	0.7 - 3.3 V	3.0 V	1	N/A	200 mA	Low noise
LDOIO0	LDO	0.7 - 3.3 V	Off	Off	N/A	100 mA	Low noise, output on GPIO0
LDOIO1	LDO	0.7 - 3.3 V	Off	Off	N/A	100 mA	Low noise, output on GPIO1
DLDO1	LDO	0.7 - 3.3 V	Off	Off	N/A	400 mA
DLDO2	LDO	0.7 - 3.3 V	Off	Off	N/A	200 mA
DLDO3	LDO	0.7 - 3.3 V	Off	Off	N/A	200 mA
DLDO4	LDO	0.7 - 3.3 V	Off	Off	N/A	200 mA
ELDO1	LDO	0.7 - 3.3 V	Off	Off	N/A	400 mA
ELDO2	LDO	0.7 - 3.3 V	Off	Off	N/A	200 mA
ELDO3	LDO	0.7 - 3.3 V	Off	Off	N/A	200 mA
DC5LDO	LDO	0.7 - 1.4 V	1.1 V	1	N/A	200 mA	Powered from DCDC5
DC1SW	Switch	Fixed to DCDC1	Off	Off	N/A	400 mA	Powered from DCDC1, equivalent resistance is 160 mΩ

Interrupts

This section corresponds to section 9.8 in the datasheet.

The AXP221 pulls the IRQ pin low to signal an interrupt to the host, and stores the interrupt status in the interrupt status registers (48h ~ 4Ch). Writing 1 to the corresponding bit clears the interrupt. When there are no interrupts, the IRQ pin is pulled up (by an external 51KΩ resistor). Each interrupt can be masked via the interrupt control registers (40h ~ 44h).

Register Address
Control	Status	Bit	Interrupt #	Description	Notes
40h	48h	[7]	IRQ 1	ACIN over voltage
40h	48h	[6]	IRQ 2	ACIN connected
40h	48h	[5]	IRQ 3	ACIN removed
40h	48h	[4]	IRQ 4	VBUS over voltage
40h	48h	[3]	IRQ 5	VBUS connected
40h	48h	[2]	IRQ 6	VBUS removed
40h	48h	[1]	IRQ 7	VVBUS < VHOLD	VHOLD defaults to 4.4V, controlled via reg 30h [3:5]
40h	48h	[0]
41h	49h	[7]	IRQ 8	Battery connected
41h	49h	[6]	IRQ 9	Battery removed
41h	49h	[5]	IRQ 10	Battery discharging
41h	49h	[4]	IRQ 11	Battery discharge stopped
41h	49h	[3]	IRQ 12	Battery charging
41h	49h	[2]	IRQ 13	Battery charge complete
41h	49h	[1]	IRQ 14	Battery temperature too high	see reg 39h (charge) and 3Dh (discharge)
41h	49h	[0]	IRQ 15	Battery temperature too low	see reg 38h (charge) and 3Ch (discharge)
42h	4Ah	[7]	IRQ 16	IC overheat
42h	4Ah	[6]	IRQ 17	Insufficient charging current	The PMIC raises this interrupt when charging current is lower than 65% of the default
42h	4Ah	[5]
42h	4Ah	[4]
42h	4Ah	[3]
42h	4Ah	[2]
42h	4Ah	[1]	IRQ 18	PEK short press	See reg e6h
42h	4Ah	[0]	IRQ 19	PEK long press	See reg 36h
43h	4Bh	[7]
43h	4Bh	[6]
43h	4Bh	[5]
43h	4Bh	[4]
43h	4Bh	[3]
43h	4Bh	[2]
43h	4Bh	[1]	IRQ 20	Battery low warning 1	warning, see reg E6h
43h	4Bh	[0]	IRQ 21	Battery low warning 2	power off, see reg E6h
44h	4Ch	[7]	IRQ 22	Timer expired	See reg 8Ah
44h	4Ch	[6]	IRQ 23	PEK rising edge
44h	4Ch	[5]	IRQ 24	PEK falling edge
44h	4Ch	[4]
44h	4Ch	[3]
44h	4Ch	[2]
44h	4Ch	[1]	IRQ 25	GPIO 1 edge trigger	See reg 91h
44h	4Ch	[0]	IRQ 26	GPIO 0 edge trigger	See reg 90h

Registers

Power Control

REG 00h: Power input status

Bit	Description	R/W
7	ACIN presence 0: ACIN not present 1: ACIN present	R
6	Indicates whether ACIN is usable	R
5	VBUS presence 0: VBUS not present; 1: VBUS present	R
4	Indicates whether VBUS is usable	R
3	Indicates whether VBUS was VHOLD before use	R
2	Indicates the battery current direction 0: battery discharging; 1: battery charging	R
1	Indicates whether ACIN and VBUS input are shorted on the PCB	R
0	Indicates starting power is ACIN or VBUS 0: Start power source is not ACIN / VBUS ; 1: Starting power source ACIN / VBUS	R

REG 01h: Power operation mode and charge status

Bit	Description	R/W
7	Indicates whether AXP221 is overheating 0: normal; 1: overheating	R
6	Charging indicator 0: not charging or charging complete; 1: Charging	R
5	Battery existence 0: no battery connected to AXP209; 1: the battery has been connected to the AXP209	R
4	Reserved
3	Battery discharge indicator 0: Battery not discharging; 1: battery discharging	R
2-0	Reserved

Reg 30h: VBUS-IPSOUT control

Bit	Description	R/W	Default Value
7	VBUS-IPSOUT path control when VBUS available 0: N_VBUSEN ​​pin decide whether to enable this path 1: VBUS-IPSOUT enabled regardless of N_VBUSEN ​​pin	RW	0
6	VBUS VHOLD voltage limiting	RW	1
5-3	VHOLD = [4.0 + (Bit5-3) * 0.1] V	RW	100
2	DRIVEVBUS output status 0: low; 1: IPSOUT	RW	0
1-0	VBUS current limit control open time limit stream selection 00:900 mA; 01: 500 mA; 1x: not limit	RW	0

REG 31h: Wake-up control and V_OFF Shutdown voltage setting

Default value: 03H

Bit	Description	Value	R/W	Default Value
7	PWROK pulled down during wakeup	0: no; 1: yes	RW	0
6	soft-reset	write 1 to reset PMU; auto-cleared	RW	0
5	soft-wakeup	write 1 to restore outputs; auto-cleared	RW	0
4	IRQs trigger wake-up	0: IRQs trigger wake-up, IRQs masked after wake-up 1: IRQs normal operation, will not trigger wake-up	RW	0
3	Enable wake-up during sleep mode; auto-cleared	0: off 1: on	RW	0
2-0	VOFF setting	VOFF = [2.6 + (Bit2-0) * 0.1] V; Default: 2.9V	RW	011

REG 32h: Shutdown control, battery detection and CHGLED pin control

Default value: 43h

Bit	Description	R/W	Default Value
7	Shutdown; Writing 1 turns off AXP221, except RTC and charger	RW	0
6	Enable battery monitoring	RW	1
5-4	CHGLED pin function 00: Hi-Z 01: 25% 1Hz blinking 10: 25% 4Hz blinking 11: output low	RW	00
3	CHGLED pin control 0: controlled by REG 32h [5:4] 1: control by charging function	RW	0
2	Output power off sequence 0: Turn off all outputs at the same time 1: Reverse of power on sequence	RW	0
1-0	Delay of PWROK from last enabled output 00: 8 mS; 01: 16 mS; 10: 32 mS; 11: 64 mS	RW	10

REG 33h: Charge control 1

Default value: C6H

Bit	Description	R/W	Default Value
7	Enable charging function	RW	1
6-5	Charging target voltage 00:4.1 V; 01:4.15 V; 10:4.2 V; 11:4.36 V	RW	10
4	End of charge current threshold 0: end of charge when charge current is less than 10% of the set value 1: end of charge when charge current is less than 15% of the set value	RW	0
3-0	Charging current Icharge = [300 + (Bit3-0) * 150] mA	RW	X

REG 34h: Charge control 2

Default value: 45h

Bit	Description	R/W	Default Value
7-6	Pre-charge timeout settings 00: 40 min; 01: 50min; 10: 60min; 11: 70min	RW	01
5	Enable charge retention (trickle-charge)	RW	0
4	CHGLED mode selection 0: Mode A 1: Mode B	RW	0
3	Reserved
2	Should charging voltage change with current	RW	0
2	Enable external circuit when charging (duplicate bit here?)	RW	0
1-0	constant current mode timeout settings 00: 6Hours; 01: 8Hours; 10: 10Hours; 11: 12Hours	RW	01

REG 35h: Charge control 3

Default value: 0Eh

Bit	Description	R/W	Default Value
7-4	Reserved
3-0	Charging circuit current limit = [300 + (Bit3-0) * 150] mA ; Default: 2400 mA	RW	1110

REG 36h: PEK button parameters

Default value: 5Dh

Bit	Description	R/W	Default Value
7-6	Power on timing 00: 128mS; 01: 1S; 10: 2S; 11: 3S	RW	01
5-4	Long press timing T = [ 1 + (bit 1-0) * 0.5 ] S; default: 1.5S	RW	01
3	Automatic shutdown when pressed longer than Tshutdown	RW	1
2	Auto power on after automatic shutdown due to long press	RW	1
1-0	Tshutdown = [ 4 + (bit 1-0) * 2 ] S; default: 6S	RW	01

REG 38h: V_LTF-charge Battery charging low temperature threshold

Default value: A5h

Bit	Description	Value	R/W	Default Value
7-0	Battery charging low temperature threshold	VLTF-charge = (val << 4) * 0.0008 V; 0 ~ 3.264V	RW	A5h (2.112V)

REG 39H: V_HTF-charge Battery charging high temperature threshold

Default value: 1Fh

Bit	Description	Value	R/W	Default Value
7-0	Battery charging low temperature threshold	VLTF-charge = (val << 4) * 0.0008 V; 0 ~ 3.264V	RW	1Fh (0.397V)

REG 3Ch: V_LTF-charge Battery discharging low temperature threshold

Default value: FCh

Bit	Description	Value	R/W	Default Value
7-0	Battery discharging low temperature threshold	VLTF-charge = (val << 4) * 0.0008 V; 0 ~ 3.264V	RW	FCh (3.226V)

REG 3DH: V_HTF-charge Battery discharging high temperature threshold

Default value: 16h

Bit	Description	Value	R/W	Default Value
7-0	Battery charging low temperature threshold	VLTF-charge = (val << 4) * 0.0008 V; 0 ~ 3.264V	RW	16h (0.282V)

REG 8Ah: Timer control

Default value: 00h

Bit	Description	Value	R/W	Default Value
7	Timer expired	write 1 to clear	RW	0
6-0	Timer duration	Bit(6-0) min. ; write 0 to clear	RW	0

REG 8Ch: PWREN control 1

Default value: 00h

Bit	Description	Value	R/W	Default Value
7	PWREN controls DC-DC1	0: yes ; 1: no	RW	0
6	PWREN controls DC-DC2		RW	0
5	PWREN controls DC-DC3		RW	0
4	PWREN controls DC-DC4		RW	0
3	PWREN controls DC-DC5		RW	0
2	PWREN controls ALDO1		RW	0
1	PWREN controls ALDO2		RW	0
0	PWREN controls ALDO3		RW	0

REG 8Dh: PWREN control 2

Default value: 00h

Bit	Description	Value	R/W	Default Value
7	PWREN controls DLDO1	0: yes ; 1: no	RW	0
6	PWREN controls DLDO2		RW	0
5	PWREN controls DLDO3		RW	0
4	PWREN controls DLDO4		RW	0
3	PWREN controls ELDO1		RW	0
2	PWREN controls ELDO2		RW	0
1	PWREN controls ELDO3		RW	0
0	PWREN controls DC5LDO		RW	0

REG 8Fh: Thermal protection and misc. control

Default value: 01h

Bit	Description	Value	R/W	Default Value
7	IRQ pin triggers power on or wake-up	0: no; 1: yes	RW	0
6	ACIN / VBUS In-short function	0: auto; 1: controlled by REG 8Fh [5]	RW	0
5	ACIN / VBUS In-short status	0: normal; 1: short	RW	0
4	N_VBUSEN pin function	0: output, as DRIVEBUS (control USB OTG VBUS regulator) 1: input, as N_VBUSEN (sense USB OTG VBUS regulator enabled)	RW	x
3	reserved
2	AXP221 thermal protection power off	0: ignore 1: power off when overheating	RW	0
1-0	reserved		RW	01

Storage

REG 04-0Fh: Data storage

As long as power exists, this data will be kept, not affected by system power off.

Regulators

REG 10h: Regulator output control

Default value: XXH

Bit	Description	R/W	Default Value
7	ALDO2 on/off	RW	X
6	ALDO1 on/off	RW	X
5	DC-DC5 on/off	RW	X
4	DC-DC4 on/off	RW	X
3	DC-DC3 on/off	RW	X
2	DC-DC2 on/off	RW	X
1	DC-DC1 on/off	RW	X
0	DC5LDO on/off	RW	X

REG 12h: Regulator output control

Default value: XXH

Bit	Description	R/W	Default Value
7	DC1SW on/off	RW	0
6	DLDO4 on/off	RW	0
5	DLDO3 on/off	RW	0
4	DLDO2 on/off	RW	0
3	DLDO1 on/off	RW	X
2	ELDO3 on/off	RW	0
1	ELDO2 on/off	RW	0
0	ELDO1 on/off	RW	X

REG 13h: Regulator output control

Default value: 01H

Bit	Description	R/W	Default Value
7	ALDO3 on/off	RW	0
6-0	Reserved

Reg 15h: DLDO1 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 16h: DLDO2 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 17h: DLDO3 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 18h: DLDO4 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 19h: ELDO1 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 1Ah: ELDO2 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 1Bh: ELDO3 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 1Ch: DC5LDO output voltage

Bit	Description	R/W	Default Value
7-3	Reserved
2-0	0.7 - 1.4 V, 100 mV/step	RW	100

Reg 21h: DC-DC1 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	1.6 - 3.4 V, 100 mV/step	RW	10001

Reg 22h: DC-DC2 output voltage

Bit	Description	R/W	Default Value
7-6	Reserved
5-0	0.6 - 1.54 V, 20 mV/step	RW	011001

Reg 23h: DC-DC3 output voltage

Bit	Description	R/W	Default Value
7-6	Reserved
5-0	0.6 - 1.86 V, 20 mV/step	RW	011001

Reg 24h: DC-DC4 output voltage

Bit	Description	R/W	Default Value
7-6	Reserved
5-0	0.6 - 1.54 V, 20 mV/step	RW	011001

Reg 25h: DC-DC5 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	1.0 - 2.55 V, 50 mV/step	RW	01010

Reg 27h: DC-DC 2/3 Voltage Ramp Control

Bit	Description	R/W	Default Value
7-4	Reserved
3	DC-DC3 VRC enable	RW	0
2	DC-DC2 VRC enable	RW	0
1	DC-DC3 VRC rate 0: 20mV/15.625μs = 1.6mV/μs ; 1: 20mV/31.250μs = 0.8mV/μs	RW	0
1	DC-DC2 VRC rate 0: 20mV/15.625μs = 1.6mV/μs ; 1: 20mV/31.250μs = 0.8mV/μs	RW	0

Reg 28h: ALDO1 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	00000

Reg 29h: ALDO2 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	01011

Reg 2Ah: ALDO3 output voltage

Bit	Description	R/W	Default Value
7-5	Reserved
4-0	0.7 - 3.3 V, 100 mV/step	RW	01011

Reg 37h: DC-DC operating frequency

Default value: 08h

Bit	Description	R/W	Default Value
7	Enable spread spectrum for DC-DC and PWM charger	RW	0
6	DC-DC and PWM charger spread spectrum bandwidth 0: 50 KHz; 1: 100KHz	RW	0
5	reserved
4	Enable DC-DC 2/3 poly-phase function	RW	0
3-0	DC-DC switching frequency F = [1 + / - (Bit3-0) * 5%)] * 1.5MHz	RW	1000

REG 80h: DC-DC operation mode

Default value: 80H

Bit	Description	Value	R/W	Default Value
7-5	Reserved
4	DC-DC5 operation mode	0: PFM+PWM 1: PWM	RW	0
3	DC-DC4 operation mode		RW	0
2	DC-DC3 operation mode		RW	0
1	DC-DC2 operation mode		RW	0
0	DC-DC1 operation mode		RW	0

Interrupts

See Interrupts section.

GPIO controls

REG 90H: GPIO0 function control

Default value: 07h

Bit	Description	Values	R/W	Default Value
7	Enable GPIO0 rising edge IRQ/wakeup	1 to enable	RW	0
6	Enable GPIO0 falling edge IRQ/wakeup	1 to enable	RW	0
5-3	Reserved
2	GPIO0 pin function	000: output low 001: output high (3.3V) 010: input 011: LDOIO0 off 100: LDOIO0 on 1XX: floating	RW	111
1
0

REG 91h: LDO_IO0 voltage control

Default value: 1Fh

Bit	Description	Values	R/W	Default Value
7-5	Reserved
4-0	LDOIO0 output voltage	Vout = 0.7 + 0.1 * (Bit 4-0) V	RW	00000

REG 92H: GPIO1 function control

Default value: 07h

Bit	Description	Values	R/W	Default Value
7	Enable GPIO1 rising edge IRQ/wakeup	1 to enable	RW	0
6	Enable GPIO1 falling edge IRQ/wakeup	1 to enable	RW	0
5-3	Reserved
2	GPIO1 pin function	000: output low 001: output high (3.3V) 010: input 011: LDOIO1 off 100: LDOIO1 on 1XX: floating	RW	111
1
0

REG 93h: LDO_IO1 voltage control

Default value: 1Fh

Bit	Description	Values	R/W	Default Value
7-5	Reserved
4-0	LDOIO1 output voltage	Vout = 0.7 + 0.1 * (Bit 4-0) V	RW	00000

REG 94h: GPIO 0/1 input

Bit	Description	Values	R/W
7-2	Reserved
1	GPIO 1 input value	0: low; 1: high	R
0	GPIO 0 input value	0: low; 1: high	R

REG 95h: GPIO 0/1 input pull-down

Bit	Description	Values	R/W
7-2	Reserved
1	GPIO 1 input pull-down	0: disable; 1: enable	R
0	GPIO 0 input pull-down	0: disable; 1: enable	R

ADC

First register is high 8 bits, second is lower 4 (lower 5 for battery current).

Channel	Control Register	Value Registers	000h	Step	FFFh
Internal Temperature	82h [5]	56h, 57h	-267.7 C	0.1 C	165.8 C
TS Pin Voltage	82h [0]	58h, 59h	0 mV	0.8 mV	3.276 V
Battery Voltage	82h [7]	78h, 79h	0 mV	1.1 mV	4.5045 V
Battery Discharge Current	82h [6]	7Ah, 7Bh	0 mA	0.5 mA	4.095 A
Battery Charge Current	82h [6]	7Ch, 7Dh	0 mA	0.5 mA	4.095 A

REG 82H: ADC Enable

Default value: E0h

Bit	Description	R/W	Default Value
7	Enable battery voltage ADC	RW	1
6	Enable battery current ADC	RW	0
5	Enable internal temperature ADC	RW	0
4-1	Reserved
0	Enable TS pin voltage ADC	RW	1

REG 84h: ADC sampling rate, TS pin control

Default value: 32h

Bit	Description	Values	R/W	Default Value
7-6	ADC sampling rate	100 * 2<super>(Bit 7-6)</super> Hz	RW	00
5-4	TS pin output current	I = 20 + 20 * (Bit 5-4) μA; Default: 80 μA	RW	11
3	Reserved
2	TS pin function selection	0: battery temperature monitoring function 1: independent external ADC input path	RW	0
1-0	TS pin current output settings	00: Off 01: On when charging 10: On when ADC enabled 11: Always on	RW	10

Fuel Gauge

REG B8h: Fuel Gauge Control

Default value: C0h

Bit	Description	Values	R/W	Default Value
7	Fuel Gauge enable	0: off; 1: on	RW	1
6	Coulomb Counter enable	0: off; 1: on	RW	1
5	Battery capacity calibration enable	0: off; 1: on	RW	0
4	Battery capacity calibration status	0: no calibration; 1: calibration in progress	RW	0
3-0	Reserved

REG B9h: Battery Charge Reading

Default value: 64h

Bit	Description	Values	R/W	Default Value
7	Is battery charge correctly calculated	0: no; 1: yes	RW	1
6-0	Battery charge percentage	0~64h (0~100) %	RW	64

REG E0h: Battery Capacity Setting 1

Default value: 64h

Bit	Description	Values	R/W	Default Value
7	Is battery capacity set	0: no; 1: yes	RW	0
6-0	Battery capacity bit [14:8]		RW	64

REG E1h: Battery Capacity Setting 1

Default value: 64h

Bit	Description	Values	R/W	Default Value
7-0	Battery capacity bit [7:0]		RW	64

Battery capacity = value * 1.456mAh

REG E6h: Battery Low Warning Threshold Setting 1

Default value: A0h

Bit	Description	Values	R/W	Default Value
7-4	Battery low warning threshold 1 (warning)	Threshold = (value + 5)%	RW	1010
3-0	Battery low warning threshold 2 (power off)	Threshold = value %	RW	0000

Spec Sheets

AXP221 Datasheet v1.2 (PDF, 52 pages, 2013-03-26)