User's Manual l TQMa8MxML UM 0103 l © 2022, TQ-Systems GmbH
Page 45
3.2.9.3
Voltage monitoring
The TQMa8MxML features a supervisor which monitors the input voltage (V
IN
).
If the input voltage drops below 4.38 V, a Reset is triggered and the TQMa8MxML is held in reset until the input voltage is in the
permitted range again.
Attention: Destruction or malfunction, supply voltage exceedance
The voltage monitoring does not detect an exceedance of the permitted input voltage.
An exceedance of the permitted input voltage may cause malfunction, destruction
or accelerated ageing of the TQMa8MxML.
3.2.9.4
Other supply voltages
USBx_VBUS:
The voltage inputs USB1_VBUS and USB2_VBUS are used to detect the USB-VBUS voltage and are usually connected to the VBUS
voltage switched by USB[2:1]_PWR. Protective circuitry on the TQMa8MxML allows up to 5 V to be applied to these LGA pads.
It is recommended to provide one 220 nF capacitor (10 V) each between USBx_VBUS and Ground on the carrier board.
V_LICELL:
A coin cell can be connected to the TQMa8MxML LGA pad D15 (V_LICELL) to supply the optional discrete RTC.
See chapter 3.2.4.2 for information on the LICELL or RTC options.
Note: RTC power supply
If the supply voltage fails, the CPU-internal RTC is reset.
In this case the system time can be maintained if the discrete RTC is supplied by a coin cell.
3.2.9.5
Supply outputs
The TQMa8MxML provides three voltages that can be used on the carrier board.
Table 38:
Voltages provided by TQMa8MxML
Voltage
TQMa8MxML
Usage
Max. load
V_1V8
N1
General usage on carrier board
500 mA
V_3V3
P1
General usage on carrier board
500 mA
V_3V3_SD
F6
SD card supply
400 mA
The voltage V_3V3 can be used as Power-Good signal for the supply of circuitry on the carrier board.
Attention: Destruction or malfunction, current exceedance
A load of up to 500 mA at V_1V8 or V_3V3, as well as up to 400 mA at V_3V3_SD causes
an increased power consumption of the TQMa8MxML and thus a higher self-heating.
These three voltages are outputs and must never be supplied from external sources!
Furthermore the outputs are not short-circuit proof. Overloading the voltage outputs
can damage the TQMa8MxML.
