TPS24700: PGb Keeps High

Kuan Wei Chen (Kevin Chen)

Part Number: TPS24700

Dear Team,

We are not sure why the PGb keeps high after system power up.

The schematic will be below thread:

Only open frame PSU power on , hotswap PG have strange behavior(always high). We check below signal status on this test condition.

Hotswap enble is 1.5V

MOSFET turn on

Open frame PSU can provide 12V to system

Do you have any comments for the reason?

Kevin

over 4 years ago

0 Rakesh over 4 years ago

TI__Guru* 95881 points

Hi Kevin,

Praveen is out of office and will be back in office on Monday. He will look into this and reply before Tuesday.

Best Regards,

Rakesh

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to Rakesh

TI__Genius 9710 points

Dear Rakesh,

Can you take a look first?

We already go through the check list below.

But didn't find any reason why PGb keep high.

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Genius 9710 points

Dear Rakesh,

Pluggable PSU on==>PGb go high, and then turn on open frame PSU==>PGb go low.(working properly)

If only use open frame PSU, the PGb will keep high. But it should go low. Do you have any ideas?

Why PGb keep high but Gate pin have signal?

I think if gate pin have signal, PGb should go low, right?

Kevin

0 Praveen GD over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru 57737 points

Hi Kevin,

You are right! If gate has signal, PGb should go low.

Can you share the waveform of Gate voltage and PGb together along with Vin and Vout.
What is the voltage across the Mosfet ?
As per the resistor divider calculation and 12V at Vin, the PGb has to be pulled high to 3.36V but I see PGb is pulled to only 2.98 V. Can you check if there are any parallel paths in the system ?
Did you try replacing the IC ? Is the same behaviour observed ?

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to Praveen GD

TI__Genius 9710 points

Dear Praveen,

Since the customer don't have differential probe, so we separate the waveform.

Kevin

0 Praveen GD over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru 57737 points

Hi Kevin,

PGb goes high when VDS exceeds 240 mV. I can see this condition multiple times in your waveform. The waveform with Vds shows that Vds is around 2.5V multiple times but there is no drop in Vout in the above waveform. May be the wave forms are captured at different instances. Can you check if your Vout is dropping by 2.5 V at any instant ?

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to Praveen GD

TI__Genius 9710 points

Dear Praveen,

They are current using AON6290 MOS, is their any concern here?

Kevin

0 Praveen GD over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru 57737 points

Hi Kevin,

Please use the design calculator to check if the selected MOSFET is suitable for this application. You can share the design calculator with us for review as well.

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to Praveen GD

TI__Genius 9710 points

Dear Praveen,

Here Is the Excel File.

TPS24700.xlsx

Please check whether the design of this hotswap controller is suitable for our system application (open frame PSU*1 and pluggable PSU*1, any PSU can be turned on the system when it is powered)

0 Praveen GD over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru 57737 points

Hi Kevin,

After the hot-swap circuit successfully starts up, the PGb pin can return to a high-impedance status whenever the drain-to-source voltage of MOSFET M1 exceeds its upper threshold of 340 mV, which presents the downstream converters a warning flag. This flag may occur as a result of overload fault, output short fault, high die temperature, or the GATE shutdown by UVLO and EN.

The design calculator shows that the design has enough margin with AON6290 FET.

TI reviewed Copy of TPS24700.xlsx

Power management

Power management forum

TPS24700: PGb Keeps High