SLUAAJ8 January   2023 BQ25180

 

  1.   Abstract
  2.   Trademarks
  3. 1Temperature Sensing
    1. 1.1 Temperature Sensing and JEITA Standard
    2. 1.2 Current Driven TS Function
    3. 1.3 Calculating RS and RP
  4. 2BQ25180 and NTC Monitoring Calculator
  5. 3Example of TS Circuit Design
  6. 4References

3 Example of TS Circuit Design

If a BQ25180 used with a battery pack that includes an NTC with a calibrated resistance of 10 k Ω and a beta value of 4250, the TS circuit will need to be compensated with additional resistors. Without additional resistors, using this NTC would cause the charger to enter the cold threshold at 5°C and enter the hot threshold at 52°C, thus significantly reducing the battery temperature range within which the charger can operate normally.

Figure 3-1 TS Thresholds Without Compensating Resistors

To calculate the necessary additional resistors, the following values are obtained from the BQ25180 data sheet or are calculated using Equation 1 and known thermistor values.

Table 3-1 Equation Constants
VHVCITS_BIASRH( RNTC at 60°C)RC( RNTC at 0°C)
0.115 V1.0075 V38 µA2.2 kΩ36.8 kΩ

Using the values from the table to solve Equation 3 and Equation 4 we arrive at an Rs of 896 Ω and an RP of 89 kΩ. With these resistors placed in the appropriate configuration, we achieve the following thresholds at the following temperature:

Table 3-2 Expected JEITA Threshold Temperatures
VCOLDVCOOLVWARMVHOT
0°C10°C44°C60°C
Figure 3-2 TS Threshold with Compensating Resistors