TPS23753A: POE Circuit displaying weird resetting behavior when touched

Brad Varnum

Part Number: TPS23753A

Hello,

I am using the TPS23753A for POE and it seems to reset the circuit when touched somewhere in the blue area circled in the images below.

The schematic is basically the same as the development board for this part.

Is there something that I should have been more mindful about in my board layout?

Thanks,

Brad

over 5 years ago

0 Thomas Amlee over 5 years ago

TI__Genius 9230 points

Hi Brad,

The resistor connected to APD (R40) is located in that area. When touched, APD may have momentarily increased above the 1.5V rising threshold, turning off the RTN-VSS hotswap FET.

For layout suggestions, I recommend looking at our guide: www.ti.com/.../slua469.pdf

Regards,
Tom Amlee
PoE PD Apps Engineer

0 Brad Varnum over 5 years ago in reply to Thomas Amlee

Prodigy 20 points

Hi Tom,

Thanks for your reply.

According to the datasheet for for the TPS23753A the APD pin should be tied to RTN when not used. Would it make more sense for me to remove R40 and have it connected directly?

Thanks,

Brad

0 Thomas Amlee over 5 years ago in reply to Brad Varnum

TI__Genius 9230 points

Hi Brad,

Yes, I would agree with that statement. Instead of using a zero ohm (that may be touched), connecting the trace directly to RTN may be a safer route.

Regards,
Tom Amlee
PoE PD Apps Engineer

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TPS23753A: POE Circuit displaying weird resetting behavior when touched