SLUSEK7 September 2024 BQ25773
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
In high power application, monitoring and controlling external component temperature can enhance reliability by limiting the total converter power under certain scenarios. The CMPIN_TR pin can be configured as temperature regulation feedback sensing pin when CMPIN_TR_SELECT=1b. It is the temperature feedback pin temperature regulation loop. The external voltage divider circuit is shown in Figure 7-5 consisting of RS and NTC resistor RTH. External NTC is placed where temperature is regulated (for example charger power stage) and generates feedback voltage on CMPIN_TR pin based on temperature variation. When temperature is lower than target, the voltage should be above 1.2 V, temperature regulation is not effective and TREG_STAT=0b ; As temperature increases, CMPIN_TR pin voltage drops to VTREG=1.2 V or lower , converter begin to reduce converter current and regulate CMPIN_TR voltage to stay at 1.2 V and set TREG_STAT=1b which is locked until host read or REG_RESET bit action.
To enable temperature regulation feature:
The RS and NTC resistor RTH network generate some quiescent current which may not be negligible under light load. In order to reduce quiescent current under light load, instead of pull down RTH to GND locally at power stage, we can pull down through CMPOUT pin shown in Figure 7-5. Under either TREG is enabled (CMPIN_TR_SELECT=1b & EN_TREG=1b) or thermal PROCHOT channel is enabled (CMPIN_TR_SELECT=1b & PP_THERMAL=1b), then CMPOUT pin is pulled down to GND to generate sensing voltage on CMPIN_TR pin. However under light load both TREG and PP_THERMAL can be both disabled (CMPIN_TR_SELECT=1b & EN_TREG=0b & PP_THERMAL=0b), then device will keep CMPOUT pin high impedance to reduce quiescent current flow through voltage divider network.
The target temperature regulation value can be chosen through configuring RS fixed resistor. A 10k NTC thermistor(ERTJ0EG103FA) is recommended in this application, corresponding RS fixed value can be calculated through equation below. The RS corresponding value at 60ºC/80ºC/100ºC TREG refers to Table 7-4. The corresponding CMPIN_TR pin voltage with swept temperature under 60ºC/80ºC/100ºC TREG configuration can be found in Figure 7-6. Based on this graph, besides temperature regulation function, the NTC temperature can also be measured through CMPIN_TR pin voltage. The device has a dedicated CMPIN_TR pin voltage ADC channel which can be enabled through setting EN_ADC_CMPIN=1b.
There is a dedicated PROCHOT profile in case regulation target gets overheat more than TREG target. The profile can enabled through setting PP_THERMAL=1b referring to Figure 7-10.
RS | TREG TEMPERATURE |
---|---|
9.53kΩ | 60ºC |
5.23kΩ | 80ºC |
3.01kΩ | 100ºC |