SN75LVC600S Power Off Input Impedance

Tom Roe1

Other Parts Discussed in Thread: SN75LVCP600S

I have a new application where I want to shut off power to the SN75LVCP600S device and it will still be driven by the SATA input lines. I would like to know the behavior with respect to the input pins of the device with Vcc down. Will the input feed through to the power rail while power is off? If it feeds through and I have a lot of capacitance on the VCC line what will the input signal see? Will it see a diode and the capacitance I have on the Vcc line?

Thanks, Tom

over 11 years ago

0 Diego Cortes over 11 years ago

TI__Mastermind 36085 points

Hello Tom,

We are reviewing your question and we will reply within the next 48 hours.

Regards,

Diego.

0 Diego Cortes over 11 years ago

TI__Mastermind 36085 points

Hello Tom,

When the device is off, the common mode voltage is at ground but connected through a high impedance. So the input impedance is 100Ohm differential, but the single ended impedance from the pin to ground is very large (high impedance).

Best regards,

Diego

0 Tom Roe1 over 11 years ago in reply to Diego Cortes

Prodigy 90 points

Diego

I would guess its also a very high single ended impedance to the Vcc rail.

We will only basically have parasitic impedance to the Vcc rail and the ground rail from the differential inputs. We will see Mosfet inputs that are off except the 100 Ohm impedance which is differential and always on. Is this correct?

I guess I always think there is some type of protection circuit at the input that may bleed into the Vcc rail when powered off.

Thanks

Tom

0 Diego Cortes over 11 years ago in reply to Tom Roe1

TI__Mastermind 36085 points

Tom,

Your assumptions are correct.

Best regards,

Diego.

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SN75LVC600S Power Off Input Impedance