TPS54331: 5 V Backwards when IC is off

Sebastian Summer

Part Number: TPS54331

Hello,

we are currently using the IC above to convert 9V into 5V. To reduce safety precautions in production, we would like to power the circuit by an external connector.

Therefore the 5V is provided somewhere else, but will the IC get damaged if we supply 5V to PH/BOOT or VSENSE Pin ?

The schematic is confidential, but can be provided to engineers from TI.

Best regards,

over 8 years ago

0 Ryan Hu (BSR-MV) over 8 years ago

TI__Expert 4035 points

Hi Sebastian,

It should be ok when supplying a addtion 5VDC to PH/BOOT, but not ok to VSENSE pin, 5V is higher than its ABS Max voltage. It might do a damage to the internal ESD circuit.

BRs,

Ryan

0 Sebastian Summer over 8 years ago in reply to Ryan Hu (BSR-MV)

Prodigy 30 points

Hello Ryan,

the VSense Pin is not supplied with 5V. There is a voltage divider as shown in the reference circuit.

The VSense Pin should be supplied with max. 1V, but I am more concerned about the current that flows through the IC back to VIN as there are capacitors at around 220uF. on the VIn side.

Best regards,

Sebastian Summer

0 Ryan Hu (BSR-MV) over 8 years ago in reply to Sebastian Summer

TI__Expert 4035 points

Hi Sebastian,
This is not a FCCM part, when Vout is higher than the expected value or Vin is power off, Highside FET is not working. The reverse current should be ok, since Highside FET has the ability through 5.8A current.
BRs,
Ryan

0 Sebastian Summer over 8 years ago in reply to Ryan Hu (BSR-MV)

Prodigy 30 points

Hello Ryan,

what do you mean by a 'FCCM part' ?

Best regards,
Sebastian Summer

0 Ryan Hu (BSR-MV) over 8 years ago in reply to Sebastian Summer

TI__Expert 4035 points

Hi Sebastian,

FCCM part operates in force continous conduction mode (FCCM) during light load conditions,the switching frequency is intained at an almost constant level over entire load range. Under specific conditions, the device work in Boost mode boost energy from Vout to Vin, making Vin higher than ABS Max. You could refer to the datasheet of TPS54308 to know more about the FCCM function. While TPS54331 has high Efficiency at Light Loads With a Pulse Skipping Eco-mode™, it's not a FCCM part. For non FCCM part, usually we don't need to be worry about the reverse current.

BRs,
Ryan

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TPS54331: 5 V Backwards when IC is off