Vault 7: Projects
This publication series is about specific projects related to the Vault 7 main publication.
PIC24F Family Reference Manual
DS39724B-page 11-26 © 2010 Microchip Technology Inc.
11.9 MEASURING ON-CHIP TEMPERATURE WITH THE CTMU
The CTMU module can be used to measure the internal temperature of the device through an
internal diode that is available for such purposes. When EDGE1 is not equal to EDGE2 and
TGEN = 0, the current is steered into the temperature sensing diode. The voltage across the
diode is available as an input to the ADC module (AN13).
Figure 11-4 shows how this module can be used for temperature measurement. As the temper-
ature rises, the voltage across the diode will drop by about 300 mV over a 150ºC range. Selecting
a higher current drive strength will raise the voltage value by a few 100 mV.
Figure 11-4: CTMU Temperature Measurement Circuit
At 25ºC, the forward voltage of the temperature diode is 0.83V. The rate of change between the
forward voltage of the diode and its temperature is 1.87 mV per degree Celsius. The formula
shown in Equation 11-7 can be used to calculate the forward voltage.
Equation 11-7: Voltage versus Temperature
Note: This feature is available only on devices with CTMUCON1 and CTMUCON2 registers.
Please refer to the specific data sheet to ensure this feature is available.
PIC24F Device
A/D Converter
CTMU
Current Source
A/D
Trigger
A/D
MUX
Diode
AN13
Vf (in mV) 783.24mV 1.87mV T+=
Where,
Vf = Forward voltage of temperature diode
T = Temperature in degrees Celsius
Protego_Release_01_05-Related-OEM-Documentation-PIC24FJ32MC10X-Reference_Manual-Section11-Charge_Time_Measurement_Unit.pdf