ZHCSOU3C August 2021 – November 2022 LMH32404
PRODUCTION DATA
The LMH32404 can be placed in low-power mode by setting EN high, which helps in saving system power. Enabling low-power mode puts the outputs of the internal amplifiers in the LMH32404, including the differential outputs, in a high-impedance state.
If a system consists of high number of amplifier channels multiplexed to a few ADC channels. Figure 7-4 shows how this device feature can further save board space and cost by eliminating the need for a discrete high-speed multiplexer. The disabled LMH32404 outputs are high-impedance so multiple LMH32404 device outputs can be directly shorted to each other. If one LMH32404 device is enabled and others are disabled, the disabled devices will not load the enabled device. This further makes the LMH32404 easy to use in photodiode array applications.
When the amplifier is in its low-power mode, the clamp circuitry is still active thereby protecting the TIA input. The ambient light cancellation loop is disabled when the amplifier is placed in low-power mode. When the LMH32404 is brought out of low-power operation the ambient light cancellation loop requires several time constants to settle. The time constant is based on the 400-kHz cutoff frequency of the loop.