31.1 Circuit Operation

Figure 31-1 shows a simplified block diagram of the temperature circuit. The proportional voltage output is achieved by measuring the forward voltage drop across multiple silicon junctions.

The following equation describes the output characteristics of the temperature indicator.

$HighRange:V_{OUT}=V_{DD}-4V_T$

$LowRange:V_{OUT}=V_{DD}-2V_T$

The temperature sense circuit is integrated with the Fixed Voltage Reference (FVR) module. See “Fixed Voltage Reference (FVR)” chapter for more information.

The circuit is enabled by setting the TSEN bit of the FVRCON register. When disabled, the circuit draws no current.

The circuit operates in either high or low range. The high range, selected by setting the TSRNG bit of the FVRCON register, provides a wider output voltage. This provides more resolution over the temperature range, but may be less consistent from part to part. This range requires a higher bias voltage to operate and thus, a higher V_DD is needed.

The low range is selected by clearing the TSRNG bit of the FVRCON register. The low range generates a lower voltage drop and thus, a lower bias voltage is needed to operate the circuit. The low range is provided for low voltage operation.