DS90LV004: Open input failsafe recommendations in addition to high Z power down

Peter Campellone

Part Number: DS90LV004

Hi,

Is open input failsafe circuitry recommended in addition to a DS90LV004 when in a situation where Vcc = 0V and the inputs are actively being driven by another device, likely an FPGA in this case?

Thanks, Peter

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 264040 points

When the device is not powered, it does not care about the voltages.

But there are three devices involved. Which ones of them are powered down?

0 Peter Campellone over 1 year ago in reply to Clemens Ladisch

Prodigy 10 points

In this case, the LVDS repeater/buffer (DS90LV0004) would be powered down and the LVDS driver would still be active and possibly driving.

0 Clemens Ladisch over 1 year ago in reply to Peter Campellone

Guru 264040 points

When the repeater is powered down, the receiving device (connected to the DS90LV004's outputs) sees an invalid state on the bus. If that device does not have fail-safe inputs, then you need to add fail-safe resistors to that bus. (Whether the inputs of the DS90LV004 are driven by the transmitter does not matter.)

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DS90LV004: Open input failsafe recommendations in addition to high Z power down