When the PD pin is asserted high, close to the positive supply, the device will be in normal active mode of operation. To disable the device for reduced power consumption, PD pin must be asserted low, close to the negative supply. Figure 7-22 shows the PD pin voltage and the corresponding quiescent current drawn. For applications that require the device to only be powered on when the supplies are present, tie the PD pin to the positive supply voltage.

The disable operation is referenced from the negative supply (normally, ground). For split-supply operation, with the negative supply below ground, a disable control voltage below ground is required to turn the LMH5485-SP off when the negative supply exceeds –0.7 V.

For single-supply operation, a minimum of 1.7 V above the negative supply (ground, in this case) is required to assure operation. This minimum logic-high level allows for direct operation from 1.8 V supply logic.