Preliminary User's Manual l TQMa8Xx UM 0002 l © 2018, TQ-Systems GmbH
Page 16
3.2.6.4
ADC input voltage V_ADC_IN
The voltage input V_ADC_IN at TQMa8Xx connector X3-34 serves as voltage reference for the ADC of the i.MX 8X.
This voltage is filtered and connected to pin V_ADC_VREFH of the i.MX 8X.
V_ADC_IN must typically be supplied with 1.8 V in order to use the ADC function of the i.MX 8X.
Depending on the accuracy requirements, V_1V8_OUT can be used for this.
Further information about the ADC can be found in the data sheet of the i.MX 8X (1).
3.2.6.5
USB_OTG[2:1]_VBUS
The voltage inputs USB_OTG1_VBUS and USB_OTG2_VBUS are used to detect the voltage USB-VBUS.
They are usually connected to the VBUS voltage switched by the USB host.
Due to the different implementations of the OTG PHYs in the i.MX 8X, different voltages must be used for this.
Table 13:
USB_OTG[2:1]_VBUS
Signal
TQMa8Xx
Voltage
Usage
USB_OTG1_VBUS
X1-73
5 V
Input for VBUS comparator OTG1
USB_OTG2_VBUS
X1-74
3.3 V
Input for VBUS comparator OTG2
3.2.6.6
Provided TQMa8Xx voltages
In addition to the TQMa8Xx supply input, some TQMa8Xx-internal voltages are available on the TQMa8Xx connectors.
The following table shows these voltages:
Table 14:
Provided TQMa8Xx voltages
Voltage
TQMa8Xx
Max. current
Usage
V_1V8
X2-11, X2-12
1 A
Internal supply for periphery and I/O, should be used on carrier board
V_1V8_ANA
X2-21
25 mA
Pull-Up voltage for pins BOOT_MODE[3:0]
Voltage V_1V8 has to be used to switch the supply on the carrier board.
Note: Voltages V_1V8 and V_1V8_ANA
Up to 1 A can be drawn from V_1V8, which increases the PMIC's power consumption and thus the
TQMa8Xx’s self-heating.
The BOOT_MODE pins should be pulled-up to V_1V8_ANA, or a voltage switched by V_1V8_ANA.
This ensures that the boot mode pins are read-in correctly and that no cross-supply occurs.
The voltages mentioned are outputs and must not be supplied externally under any circumstances.
3.2.6.7
Voltage monitoring
The 3.3 V input voltage is monitored on the TQMa8Xx.
If the input voltage is too low, a reset is triggered until the input voltage is within the defined range again.
Attention: Malfunction or destruction
The voltage monitoring does not detect an exceedance of the maximum permitted input voltage.
An excessively high supply voltage can lead to malfunctions, untimely aging or destruction of the
TQMa8Xx.
