System Monitor

The chip includes a 10-bit ADC which is used for measuring internal parameters. It can be used in the following measurement modes:

Single-shot
Automatic
Timed

Measurement request priority

When multiple measurement requests happen at the same time, the priority is as follows:

VBAT
Battery temperature, T_BAT
Battery current, I_BAT
Die temperature, T_DIE
VSYS
VBUS

If a measurement has been requested but the measurement has not started, a higher priority can be requested.

When a low priority measurement is requested and the system has started the measurement, a higher priority can be requested. The system will complete the lower priority measurement before the higher priority measurement.

Single-shot measurements

Single-shot measurements are triggered by a task specific for each measurement.

Table 1. Tasks for single-shot measurements
Value	Task
Battery temperature	TASKNTCMEASURE
Battery voltage, Single-shot mode and Burst mode	TASKVBATMEASURE ADCCONFIG
VSYS voltage	TASKVSYSMEASURE
Battery current	ADCIBATMEASEN (occurs after VBAT measurement)
VBUS voltage	TASKVBUS7MEASURE
Die temperature	TASKTEMPMEASURE

A VBAT measurement triggered in Burst mode performs four consecutive measurements, with each result available separately. Conversions are run back-to-back and complete in t_CONV.

Note: To repeat a measurement, it must be requested once the previous request is complete. Repeat measurement requests are lost when made while the previous conversion is still ongoing. Alternate measurements can be requested, which are queued. See System Monitor for more information.

Automatic measurements

Automatic measurements for battery voltage are enabled in register ADCCONFIG. The default interval is 1024 ms.

Automatic measurements during charging

Battery temperature and die temperature are measured automatically at regular intervals when the battery is charging. The host software can read this value and returns the latest measurement.

The measurement intervals are as follows:

Battery temperature – once every 64, 128, or 1024 ms.
Die temperature – once every 4 ms, see Charger thermal regulation.

Note: To enable automatic thermistor and die temperature monitoring, set register TASKAUTOTIMUPDATE. This should also be set after changing the automated period.

Timed measurements

Timed measurements for battery voltage in Single-shot mode and Burst mode are initiated in register ADCDELTIMCONF. See Monitor battery state of charge for more information.

Measurement results

Results from the ADC are stored in registers according to the following table. Some registers hold alternate results when that feature is requested. Host software must concatenate the LSB to the MSB of the result register for full accuracy.

Table 2. ADC measurements
Value/alternate result	Register
VBAT	ADCVBATRESULTMSB
Battery temperature	ADCNTCRESULTMSB
Die temperature	ADCTEMPRESULTMSB
VSYS Single-shot mode	ADCVSYSRESULTMSB
LSBs for Single-shot mode VSYS, Die temperature, NTC thermistor, and VBAT	ADCGP0RESULTLSBS
Burst mode VBAT0	ADCVBAT0RESULTMSB
Burst mode VBAT1	ADCVBAT1RESULTMSB
Burst mode VBAT2 Battery current IBAT	ADCVBAT2RESULTMSB
Burst mode VBAT3 Single-shot mode VBUS	ADCVBAT3RESULTMSB
LSBs for Burst mode VBAT0, VBAT1, VBAT2, VBAT3, IBAT and VBUS	ADCGP1RESULTLSBS

The following equations can be used to read the results.

VBAT

The equation for VBAT is given by the following:

Here, V_BATADC is the ADC value from the VBAT register and VFS_VBAT is the full scale voltage for measuring VBAT.

VBUS

The equation for VBUS is given by the following:

Here, V_BUSADC is the ADC value from the VBUS register and VFS_VBUS is the full scale voltage for measuring VBUS.

VSYS

Equation for VSYS is given by the following:

Here, V_SYSADC is the ADC value from the VBUS register and VFS_VSYS is the full scale voltage for measuring VBUS.

Battery temperature (Kelvin)

The battery temperature T_BAT (in Kelvin) is given by the following equation:

Here, T₀ = 298.15 K, T_BATADC is the ADC value from the battery temperature register ADCNTCRESULTMSB and β is the NTC beta parameter.

Die temperature in °C

The die temperature, T_D (in °C), is given by the following equation:

Here, K_DIETEMP is the ADC value for the die temperature.

Events and interrupts

An event register and interrupt are available for each measurement and are issued once the measurement has been completed.

See registers EVENTSADCSET, EVENTSADCCLR, INTENEVENTSADCSET, and INTENEVENTSADCCLR.

Battery temperature measurement

Before using a battery temperature measurement, the appropriate NTC thermistor must be configured. See Monitor battery temperature for information about suitable thermistors and how to configure.

Monitor battery state of charge

The host runs the fuel gauge algorithm and periodically requests measurements from the ADC. These measurements update the algorithm parameters and allow the state of charge to be determined.

The algorithm must be provided with the battery model parameters for accurate fuel gauge readings. The battery model parameters can be created from the nPM PowerUP application.

Once the battery is modeled over the operating temperature range, the fuel gauge algorithm is optimized to operate over the full range of battery voltages, temperatures, and application currents.

Battery current measurement

Host software can request a IBAT measurement by setting bit IBAT.MEAS.ENABLE to 1 in register ADCIBATMEASEN. This allows consecutive VBAT and IBAT measurements. When both measurements are available in the ADC registers, the ADCIBATRDY event is generated. See register ADCIBATMEASSTATUS for more information about the IBAT measurement.

Measurements are invalid and a new measurement is needed when bit IBAT.MEASE.INVALID is set.

Direction of current flow is shown in bit BCHARGER.MODE.

A value of 01 means the battery is discharging. During a discharge, the full scale current (in Amps) is the battery discharge current limit (as configured in registers BCHGISETDISCHARGEMSB and BCHGISETDISCHARGELSB) multiplied by 1.12.

A value of 10 means the system is supplied by VBUS.

A value of 11 means the battery is charging. When charging, the full scale current (in Amps) is the charge current setting (as configured in registers BCHGISETMSB and BCHGISETLSB) multiplied by 1.25.

Electrical specification

Table 3. System Monitor electrical specification
Symbol	Description	Min.	Typ.	Max.	Unit
VFS_VBAT	Full scale voltage for VBAT measurement		5.0		V
V_BATACCUR	Accuracy of the VBAT measurement (3 V < VBAT < 4.5 V and -10°C < T_J < +125°C)	-1		+1	%
VFS_VBUS	Full scale voltage for VBUS measurement		7.5		V
V_BUSACCUR	Accuracy of the VBUS measurement		±1.5		%
VFS_VSYS	Full scale voltage for VSYS measurement		6.375		V
V_SYSACCUR	Accuracy of the VSYS measurement		±1.5		%
C_BATNTC	Capacitance in parallel with the thermistor	0		100	pF
VFS_TEMP	Full scale for battery and die temperature measurements		1.5		V
t_CONV	Conversion time		250		μs
DNL	Differential non-linearity		< 0.5		LSB

Registers

Instances


Instance	Base address	Description
ADC	0x00000500	SAADC registers ADC register map

Register overview


Register	Offset	Description
TASKVBATMEASURE	0x0	Battery voltage measurement
TASKNTCMEASURE	0x1	Battery temperature measurement
TASKTEMPMEASURE	0x2	Die temperature measurement
TASKVSYSMEASURE	0x3	VSYS measurement
TASKIBATMEASURE	0x6	Battery current measurement
TASKVBUS7MEASURE	0x7	VBUS measurement
TASKDELAYEDVBATMEASURE	0x8	Delayed battery voltage measurement
ADCCONFIG	0x9	ADC configuration
ADCNTCRSEL	0xA	Select battery NTC thermistor
ADCAUTOTIMCONF	0xB	Auto measurement intervals
TASKAUTOTIMUPDATE	0xC	Strobe for AUTOTIMCONF
ADCDELTIMCONF	0xD	Configure delay for battery voltage measurement
ADCIBATMEASSTATUS	0x10	Battery current measurement status
ADCVBATRESULTMSB	0x11	Battery voltage measurement result MSB
ADCNTCRESULTMSB	0x12	Battery temperature measurement result MSB
ADCTEMPRESULTMSB	0x13	Die temperature measurement result MSB
ADCVSYSRESULTMSB	0x14	VSYS measurement result MSB
ADCGP0RESULTLSBS	0x15	Result LSBs (VBAT, battery temperature, die temperature and VSYS)
ADCVBAT0RESULTMSB	0x16	VBAT0 burst measurement result MSB
ADCVBAT1RESULTMSB	0x17	VBAT1 burst measurement result MSB
ADCVBAT2RESULTMSB	0x18	VBAT2 burst measurement result MSB
ADCVBAT3RESULTMSB	0x19	VBAT3 burst or VBUS measurement result MSB
ADCGP1RESULTLSBS	0x1A	VBAT burst measurement result LSBs (VBAT0, VBAT1, VBAT2 and VBAT3)
ADCIBATMEASEN	0x24	Enable automatic battery current measurement

TASKVBATMEASURE

Address offset: 0x0

Battery voltage measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKVBATMEASURE			Start VBAT measurement
			NOEFFECT	0	No effect
			TRIGGER	1	Trigger task

TASKNTCMEASURE

Address offset: 0x1

Battery temperature measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKNTCMEASURE			Start battery NTC thermistor measurement
			NOEFFECT	0	No effect
			TRIGGER	1	Trigger task

TASKTEMPMEASURE

Address offset: 0x2

Die temperature measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKTEMPMEASURE			Start die temperature measurement
			NOEFFECT	0	No effect
			TRIGGER	1	Trigger task

TASKVSYSMEASURE

Address offset: 0x3

VSYS measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKVSYSMEASURE			Start VSYS measurement
			NOEFFECT	0	No effect
			TRIGGER	1	Trigger task

TASKIBATMEASURE

Address offset: 0x6

Battery current measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKIBATMEASURE			Start IBAT measurement
			NOEFFECT	0	No effect
			TRIGGER	1	Trigger task

TASKVBUS7MEASURE

Address offset: 0x7

VBUS measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKVBUS7MEASURE			Start VBUS measurement
			NOEFFECT	0	No effect
			TRIGGER	1	Trigger task

TASKDELAYEDVBATMEASURE

Address offset: 0x8

Delayed battery voltage measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKDLYDVBATMEASURE			Start delayed VBAT measurement
			NOEFFECT	0	No effect
			TRIGGER	1	Trigger task

ADCCONFIG

Address offset: 0x9

ADC configuration


Bit number						7	6	5	4	3	2	1	0
ID												B	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	RW	VBATAUTOENABLE			Enable VBAT Auto measurement every 1 s
			NOAUTO	0	No automatic measurements
			AUTOENABLE	1	Trigger measurement every 1 s
B	RW	VBATBURSTENABLE			Enable VBAT burst mode VBAT0, VBAT1, VBAT2, VBAT3
			SINGLEMODE	0	Trigger a single measurement
			BURSTMODE	1	Trigger 4 consecutive measurements

ADCNTCRSEL

Address offset: 0xA

Select battery NTC thermistor


Bit number						7	6	5	4	3	2	1	0
ID												A	A
Reset 0x01						0	0	0	0	0	0	0	1
ID	R/W	Field	Value ID	Value	Description
A	RW	ADCNTCRSEL			Select thermistor value
			Hi_Z	0	No thermistor
			10K	1	NTC 10 kOhm
			47K	2	NTC 47 kOhm
			100K	3	NTC 100 kOhm

ADCAUTOTIMCONF

Address offset: 0xB

Auto measurement intervals


Bit number						7	6	5	4	3	2	1	0
ID										B	B	A	A
Reset 0x03						0	0	0	0	0	0	1	1
ID	R/W	Field	Value ID	Value	Description
A	RW	NTCAUTOTIM			Battery thermistor measurement interval when charging
			4MS	0	4 ms
			64MS	1	64 ms
			128MS	2	128 ms
			1024MS	3	1024 ms
B	RW	TEMPAUTOTIM			Die temperature measurement interval when charging
			4MS	0	4 ms
			8MS	1	8 ms
			16MS	2	16 ms
			32MS	3	32 ms

TASKAUTOTIMUPDATE

Address offset: 0xC

Strobe for AUTOTIMCONF


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	W	TASKAUTOTIMUPDATE			Update NTCAUTOTIM and TEMPAUTOTIM measurement intervals
			NOEFFECT	0	No effect
			UPDATEAUTOTIM	1	Update

ADCDELTIMCONF

Address offset: 0xD

Configure delay for battery voltage measurement


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	RW	VBATDELTIM			Delay from 4 ms (value 0) to 514 ms (value 255) in 2 ms steps

ADCIBATMEASSTATUS

Address offset: 0x10

Battery current measurement status


Bit number						7	6	5	4	3	2	1	0
ID									C	B	B	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	BCHARGERICHARGE			Scaling factor for charging current (00=10%, 01=50%, 11=100%)
B	R	BCHARGERMODE			Battery charger mode (01=discharging, 10=idle, no battery current, 11=charging)
C	R	IBATMEASEINVALID			IBAT measurement invalid

ADCVBATRESULTMSB

Address offset: 0x11

Battery voltage measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VBATRESULTMSB			Battery voltage measurement result MSB

ADCNTCRESULTMSB

Address offset: 0x12

Battery temperature measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	NTCRESULTMSB			Battery temperature measurement result MSB

ADCTEMPRESULTMSB

Address offset: 0x13

Die temperature measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	TEMPRESULTMSB			Die temperature measurement result MSB

ADCVSYSRESULTMSB

Address offset: 0x14

VSYS measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VSYSRESULTMSB			VSYS measurement result MSB

ADCGP0RESULTLSBS

Address offset: 0x15

Result LSBs (VBAT, battery temperature, die temperature and VSYS)


Bit number						7	6	5	4	3	2	1	0
ID						D	D	C	C	B	B	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VBATRESULTLSB			Battery voltage measurement result LSBs
B	R	NTCRESULTLSB			Battery temperature measurement result LSBs
C	R	TEMPRESULTLSB			Die temperature measurement result LSBs
D	R	VSYSRESULTLSB			VSYS measurement result LSBs

ADCVBAT0RESULTMSB

Address offset: 0x16

VBAT0 burst measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VBAT0RESULTMSB			VBAT0 burst measurement result MSB

ADCVBAT1RESULTMSB

Address offset: 0x17

VBAT1 burst measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VBAT1RESULTMSB			VBAT1 burst measurement result MSB

ADCVBAT2RESULTMSB

Address offset: 0x18

VBAT2 burst measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VBAT2RESULTMSB			ADC VBAT2 burst measurement result MSB

ADCVBAT3RESULTMSB

Address offset: 0x19

VBAT3 burst or VBUS measurement result MSB


Bit number						7	6	5	4	3	2	1	0
ID						A	A	A	A	A	A	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VBAT3RESULTMSB			If TASKVBATMEASURE is triggered in burst mode, this register will contain ADC VBAT3 burst measurement result MSB If TASKVBUS7MEASURE is triggered, this register will contain VBUS measurement result MSB

ADCGP1RESULTLSBS

Address offset: 0x1A

VBAT burst measurement result LSBs (VBAT0, VBAT1, VBAT2 and VBAT3)


Bit number						7	6	5	4	3	2	1	0
ID						D	D	C	C	B	B	A	A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	R	VBAT0RESULTLSB			Burst VBAT0 measurement result LSBs
B	R	VBAT1RESULTLSB			Burst VBAT1 measurement result LSBs
C	R	VBAT2RESULTLSB			Burst VBAT2 measurement result LSBs
D	R	VBAT3RESULTLSB			Burst VBAT3 measurement result LSBs

ADCIBATMEASEN

Address offset: 0x24

Enable automatic battery current measurement


Bit number						7	6	5	4	3	2	1	0
ID													A
Reset 0x00						0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value	Description
A	RW	IBATMEASENABLE			Enable IBAT measurement after VBAT measurement