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hi,
When Host(MCU) try to control DSG MOS Fet status from OFF to ON through I2C commands or DSGFet pin, the delay varies from 80 ms to 200 ms.
The detailed samples just like the following:
1) Host turns DSG MOS ON through DSG FET Pin:
Data1:80ms
Data2:173ms
Data3:205ms
Data4:94ms
Average:138ms
One of the signal capture is as following:
2) Host turns DSG MOS ON through I2C commands:
Data1:166ms
Data2:72ms
Data3:72ms
Data4:178ms
Data5:186ms
Average:134.8ms
When Host turns DSG MOS ON through TEST MODE, the delay will reduced to 1000- uS level.
The delay time is too high and unacceptable. Please help to improve it.
Thanks!
Hi David,
The BQ76952 checks the FET state every 250 ms to determine whether the FET is on or off. More information on this can be found in Section 6.9 Device Event Timing of the Technical Reference Manual linked here: BQ76952 Technical Reference Manual (Rev. B) (ti.com).
A possible way to turn on the FETs faster is to use the FET Test mode all the time. This is not typically recommended, however, because this option has some additional considerations/challenges.
There should be an FAQ discussing this issue coming soon.
Best,
Andria
Hi Andria,
Thanks for your clarification.
We had tried the FET test mode. When we try to put bq76952 into sleep mode, Bq76952 will turn DSG MOS to off state after the CFG UPDATE command. In some cases it doesn't meet the requirement.
As an AFE, We need Bq76952 takes action immediately when receiving the valid command, such as turn on MOS Fets, Start/Stop cell balancing.
Best,
David
Hi David,
Currently, all our employees will be out of office from 11/24 - 11/27 for Thanksgiving break. Everyone will be back in office Monday, 11/28, and your question will be answered then. Apologies for any inconvenience!
Best,
Andria
Hi David,
Could you please clarify what requirements you need FET TEST mode to meet?
Unfortunately, without FET TEST mode, it will take up to 250 ms for the FETs to turn on. FET TEST mode is your best bet for ensuring fast FET turn on. Here is a previous e2e post that discusses FET TEST mode in more detail: (+) [FAQ] BQ76952: FET Control using FET Test Mode - Power management forum - Power management - TI E2E support forums.
Best,
Andria