To test this feature, simply switch GPIO3 from ‘Output High’ to ‘Output Low’ every 5-10 seconds. This will
connect/disconnect the high voltage supply through the Q9 photoMOS. Measurements are then taken at GPIO1
under both conditions to ensure that the device is properly insulated. The CB1 pin may also be used in place of
the GPIO1 pin if the user wishes to utilize this GPIO pin for another purpose.
If additional accuracy is required, the user may utilize the Q7 switch by populating pins 1-2 on J23 shown below.
This switch will be controlled by an inverted GPIO3 signal so that the Q7 FET switches opposite to the Q9
photoMOS. This introduces no delay in the system and is simply an option available to the user to implement in
their design.
Figure 4-7. Additional FET Option
4.4 Current Sense
4.4.1 SRP/SRN
Current sense in the BQ79631-Q1 device is handled through the SRP and SRN pins that feed into a dedicated
current sense ADC. This measurement occurs through a 50-μΩ shunt resistor that can be measured directly on
the EVM through the shunt(+) and shunt(-) connectors.
4.4.2 VCSamp_Out
For bidirectional over current detection, it is recommended to utilize the VCSamp_Out circuit on the EVM. This
circuit connects to VC1 and utilizes dedicated analog UV/OV comparators found within the BQ79631-Q1 device.
While this method may not be used to give precise readings on the voltage from Shunt(+) to Shunt(-), it provides
a quick response to any over current fault and can be instrumental in preventing catastrophic failures from
arising within the system. Additional to over current detection, the VC1 measurement ADC can also be used as
an alternate, less accurate, current measurement path. To enable the VCSamp_Out measurements to be made
on the EVM via VC1, simply place a shunt across pins 1 and 2 (top-middle) of J37.
The VCSamp_Out connection may be used simultaneously with the measurements being taken through SRP
and SRN.
4.5 GPIO Connections
On the BQ79631EVM there are 8 GPIO pins that can be used for a variety of purposes and may be configured
in the following manners:
• ADC and OTUT inputs
• ADC only input
• Digital input
Connectors
SLUUCC3 – FEBRUARY 2021
BQ79631EVM Evaluation Module
17
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