This page provides an overview about the voltage monitoring on Colibri modules.
VDD voltage threshold for Reset generation:
< 2.55V (VDD falling)
> 2.65V (VDD rising)
Internal 1/3 VDD voltage divisor present. Pin can be left floating.
Voltage thresholds for VDD_Fault assertion:
VDD_Fault pin open, using internal 1/3 VDD voltage divisor
< 3.00V (VDD falling)
> 3.15V (VDD rising)
VDD_Fault pin externally driven (Ri=333k)
< 1.00V (pin voltage falling)
> 1.05V (pin voltage rising)
Internal pull-up resistor present. Pin can be left floating to avoid Batt_Fault assertion.
Voltage threshold for Batt_Fault assertion:
Batt_Fault pin externally driven (Ri=1M)
< 1.00V (pin voltage falling)
> 1.05V (pin voltage rising)
VDD voltage threshold for Reset generation:
< 2.35V (VDD falling)
> 2.40V (VDD rising)
Internal pull-up resistor present. Pin can be left floating to avoid Batt_Fault assertion.
Voltage threshold for Batt_Fault assertion:
Batt_Sense pin externally driven (Ri=1M)
< 1.20V (pin voltage falling)
> 1.25V (pin voltage rising)
tbd
2.8V (programmable)
The Colibri T20 do not have this inputs. SODIMM pins 22 and 24 are normal GPIOs. We recommend to use a dedicated circuit to monitor the voltage if this is required. Then any interrupt GPIO can be used to notify the system about the voltage change.
3.0V ±2.5%
The Colibri T20 monitors its own 3.3V power supply. When an undervoltage condition is detected, the behavior depends on the Windows CE image version used:
The system enters a SLEEP mode which can only be left with a power cycle.
The system issues a hardware reset. The boot process only starts after Vcc has rised 0.2V above the threshold.
As an alternative, the system can be configured by registry to ignore the undervoltage condition at all and continue operation out-of-spec. We have seen systems running down to 2.65V.
