UCD3040: Questions of UCD3040

HAN LEE

Part Number: UCD3040
Other Parts Discussed in Thread: UCD3138,

Hi Experts,

I measured the pin impedance of UCD3138/UCD3040 , but there were 2 results of this measurement ;UCD31xx, the pins of related pmbus(pmbus_clk...) were measured OL by meter, UCD3040 were measured mega level pin impedance by meter ,as far as I know, it should be open-drain circuit of pmbus pin.can you tell me why it has 2 different result,thanks.

over 4 years ago

0 Amiel Hussain over 4 years ago

TI__Expert 4040 points

Hello,

An engineer is looking into this and will respond.

0 HAN LEE over 4 years ago in reply to Amiel Hussain

Expert 1515 points

Hi Experts,

Any update?

0 HAN LEE over 4 years ago in reply to Amiel Hussain

Expert 1515 points

Hi Experts,

Any update?

0 Ian Bower over 4 years ago in reply to HAN LEE

TI__Genius 17090 points

I know on the UCD3138, we removed the upper protection upper ESD protection diode on the PMBus CLK and Data pins. This was so that the UCD could be powered down when other devices were active on the bus. With the diodes in place, the UCD would draw some power through the diode into the rest of the chip, which caused problems when starting up, as well as putting a bit of a drain on the PMBus lines.\

I suspect we did the same thing on the 3040. Do you have the UCD powered up when you are doing this test? If not, you may be powering it up through the other pins, but not through the PMBus pins.

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UCD3040: Questions of UCD3040