TDA4VM: PORZ OUT connected to PORZ

David Dominguez Moises

Part Number: TDA4VM

HI,

I'm working on a custom design based on TDA4 EVM. Looking at the reset signals, PORz is generated from some power goods and also PCIEx_PORz.

Looking deeper into how the PCIEx_PORz generates, it seems there is a case in which SOC_PORz_OUT drives low PCIEx_PORz which would drive low PORz when configured as root complex.

What is the reason behind this? From TRM PORz is the input and then PORz_OUT propagates that input to other devices, so if PORz_OUT drive PORz it seems that would hold the device in reset forever.

The relevant schematic portion:

Thanks,

David

over 4 years ago

+1 Robert Eschler over 4 years ago

TI__Guru 51665 points

The green path you show cannot exist as either buffer U117 or buffer U118 is disabled, both are not enabled at same time. The circuit allows either the EVM to generate PORz to the PCIe card (RC mode) or the card generate PORz to the processor (EP mode).

0 David Dominguez Moises over 4 years ago in reply to Robert Eschler

Intellectual 570 points

Hi Robert,

That makes sense. Also hadnt noticed that U119 is NAND and not an AND gate, so my logic was messed up.

Thanks,

David

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TDA4VM: PORZ OUT connected to PORZ