Dear Team,
We are facing some issue regarding Over Current Fault at startup of the TPS.
Our setup:
- TPS536C7B1
- 12V input
- Phase used:
- APWM1
- APWM2
- APWM3
- APWM4
- Only 1 Channel used (CHA)
- OCF set to 10A
- OCF / Phase is set to 26 A
- Power staged used: TDA21490AUMA1
We are using a custom PMBus driver through an FPGA to control the TPS.
The Power Up sequence is the folowing:
- Drive high AVR_EN
- Send write command to VOUT_COMMAND (21h) to set a specific voltage.
Here are some measurement:
CH1: ACSP4
CH2: VIN_CSNIN (input 12V)
CH3: output voltage
CH4: VREF
The VOUT_COMMAND (21h) was set to 1.1 V.
This fault trigger with a light load (~ 1A), but also without any load.
If we follow the formula for the Iout ((ACSP4– VREF)/0.005), the second peak reach 98.6 A, which justifies the OCF.
We were wondering why this is happening and how to prevent it.
This is not happening every time, it is hard to reproduce, but we have seen it 1 every 100 startup (approximately).
When the startup succeeds:
Here the peak is at 53.6A, and no OCF occurs, although there is no charge.
We have tried to play with the MFR_PROTECTION_CONFIG (BBh) register, by allowing more Cycle counter for Phase OCL, but with no success.
Thanks for your help.
Regards,
Eliot
