Monitor battery temperature

nPM1300 Product Specification

CHARGER supports three types of NTC thermistors for battery temperature (TBAT) monitoring. Only one can be enabled at a time.

The host software must select the corresponding setting that matches the battery thermistor before enabling charging in register ADCNTCRSEL. The following thermistor resistors are supported.

Table 2. Supported thermistor resistors
Nominal resistance Resistance accuracy B25/50 Beta accuracy B25/85
10 kΩ 1% 3380 K 1% 3434/3435 K
47 kΩ 1% 4050 K 1% 4108 K
100 kΩ 1% 4250 K 1% 4311 K
Note: If a capacitor is placed in parallel with the thermistor, the max capacitance is 100 pF.

If a thermistor is not used, the NTC pin must be tied directly to ground or through a resistor. The functionality must be disabled in register BCHGDISABLESET. This does not impact Charger thermal regulation.

The following battery temperature thresholds can be set: TCOLD ≤ TCOOL ≤ TWARM ≤ THOT.

These limits can be set between −20°C and +60°C, and setting adjacent thresholds to identical values is allowed. For example, setting TWARM = THOT means that there is no warm region. Charging does not happen below TCOLD or above THOT. Charging can be paused at TWARM instead of THOT by setting register BCHGCONFIG.

The thresholds are written into corresponding registers. The battery temperature variable, KNTCTEMP, is calculated using the following equation:

Equation for battery temperature

Here, RT is the thermistor resistance at a desired temperature and RB (internal bias resistor) equals the thermistor resistance at 25°C. See NTCCOLD, NTCCOOL, NTCWARM, and NTCHOT for more information. Default values in the registers match the JEITA guideline and are intended for the 10 kΩ thermistor defined in Supported thermistor resistors.

Table 3. Battery temperature default values
Temp. 10 kΩ 47 kΩ 100 kΩ Register
0°C 749 787 799 NTCCOLD
10°C 658 684 693 NTCCOOL
45°C 337 306 297 NTCWARM
60°C 237 197 186 NTCHOT

The charging current can be reduced by 50% between NTCCOLD and NTCCOOL. The termination voltage can be configured independently between NTCWARM and NTCHOT. Default is ICOOL (50% of ICHG), but this can be disabled.

Table 4. Battery temperature regions
Temperature region Temperature limits, default setting Charge current Termination voltage
Cold

TBAT < TCOLD

TCOLD = 0°C

 0 (OFF) N/A
Cool

TCOLD < TBAT < TCOOL

TCOOL = 10°C

 ICOOL / ICHG VTERM
Nominal

TCOOL < TBAT < TWARM

TWARM = 45°C

 ICHG VTERM
Warm

TWARM < TBAT < THOT

THOT = 60°C

 ICHG VTERMR
Hot TBAT > THOT 0 (OFF) N/A

Battery temperature is measured by the on-chip System Monitor at regular intervals during charging. The latest result is available in registers ADCNTCRESULTMSB and ADCGP0RESULTLSBS.

When the battery temperature rises over TWARM or THOT, or falls below TCOOL or TCOLD, an interrupt is sent.