ZHCS089G February 2011 – September 2017 TPS65185
PRODUCTION DATA.
Figure 23 below shows the block diagram of the NTC bias and measurement circuit. The NTC is biased from an internally generated 2.25-V reference voltage through an integrated 7.307-kΩ bias resistor. A 43-kΩ resistor is connected parallel to the NTC to linearize the temperature response curve. The circuit is designed to work with a nominal 10-kΩ NTC and achieves accuracy of ±1°C from 0°C to 50°C. The voltage drop across the NTC is digitized by a 10-bit SAR ADC and translated into an 8-bit two’s complement by digital per Table 1.
| TEMPERATURE | TMST_VALUE[7:0] |
|---|---|
| < –10°C | 1111 0110 |
| –10°C | 1111 0110 |
| –9°C | 1111 0111 |
| ... | ... |
| –2°C | 1111 1110 |
| –1°C | 1111 1111 |
| 0°C | 0000 0000 |
| 1°C | 0000 0001 |
| 2°C | 0000 0010 |
| ... | ... |
| 25°C | 0001 1001 |
| ... | |
| 85°C | 0101 0101 |
| > 85°C | 0101 0101 |
Figure 23. NTC Bias and Measurement Circuit
A temperature measurement is triggered by setting the READ_THERM bit of the TMST1 register to 1.During the A/D conversion the CONV_END bit of the TMST1 register reads 0, otherwise it reads 1. At the end of the A/D conversion the EOC bit in the INT2 register is set and the temperature value is available in the TMST_VALUE register.