LP8733: PGOOD is fixed at Low.

user6333457

Part Number: LP8733
Other Parts Discussed in Thread: TIDA-050038

Hi,

We desighed a circuit consist of LP873347RHDT and TPS6521825RSLT for i.MX8M mini.
But PGOOD is fixed at Low.

BUCK0 and BUCK1 output is correct voltage.
So, I think there is a problem with LDO input or output.

Since LDO0 and LDO1 are not used, the connection is as follows.

VIN_LDO0 +5V(=VANA)
VIN_LDO1 +5V(=VANA)
VOUT_LDO0 NC
VOUT_LDO1 NC

Can you give me an idea of what is wrong with the circuit.

In drawing of TIDA-050038, VIN_LDO connected to the +3.3V. Is this a problem?

over 3 years ago

0 Tomi Koskela over 3 years ago

TI__Genius 11020 points

Hello,

You can read back the fault status through I2C to check what is causing the PGOOD fault.

LDO outputs must be bypassed with 1uF capacitor even if not used. Without output capacitors they can start oscillating triggering the PGOOD. Once the PGOOD is triggered it must be cleared through I2C or with power cycling.

Thansk.

Regards,

Tomi Koskela

0 user6333457 over 3 years ago in reply to Tomi Koskela

Prodigy 50 points

Thank you for your answer.

I will check the falut status later because the OS has not booted yet.
BUt I think you're right.

A bypass capacitor was connected to the LDO_OUT in the figure of the data sheet.
I was only looking at the description of Pin Functions . - leave the pin floating.

Best Regards,

+1 Tomi Koskela over 3 years ago in reply to user6333457

TI__Genius 11020 points

Hello,

Yes the LDOs can be left floating if they are not enabled at all. But they will turn on automatically in the LP873347 OTP setup once you set EN high.

Thanks.

Regards,

Tomi Koskela

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LP8733: PGOOD is fixed at Low.