ADA4099-1BUJZ-R5 datasheet(23/34 Pages) AD

23 / 34 page

Data Sheet

ADA4099-1/ADA4099-2

THEORY OF OPERATION

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Rev. A | 23 of 34

Figure 59. Supply Current vs. VSHDN with Respect to −VS

SHDN or SHDNx can be driven beyond the +VS supply up to the

absolute maximum voltage (60 V with respect to −VS) and draws

little current (<1.5 μA). For normal active amplifier operation, SHDN

or SHDNx can be floated or driven by an external voltage source

low (within 0.5 V of −VS). If SHDN or SHDNx are left floating, an

internal current source (~600 nA) pulls SHDN or SHDNx to –VS,

which places the amplifiers into a default, active amplifying state.

Because of the close proximity of the −IN pin (ADA4099-1) or

−INx pins (ADA4099-2 10-lead LFCSP) and SHDN or SHDNx, fast

edges on the −IN pin or −INx pins may ac-couple to the adjacent

high impedance SHDN or SHDNx, inadvertently placing the devices

in shutdown. If this scenario is a concern, add a 1 nF capacitor

between SHDN or SHDNx and the −VS pin.

Alternatively, the amplifiers can be effectively placed in a low power

state by removing +VS. In this low power state, the inputs typically

leak <1 nA with either ±IN pin or either ±INx biased between −VS

and 70 V above −VS. If the ±IN pins or ±INx pins are taken below

−VS, they appear as a diode connected to the −VS supply in series

with a resistance of 250 Ω. In this condition, limit the current to <30

mA.

Using an external source to drive the output beyond either ±VS

supply under shutdown conditions may produce unlimited current

and may damage the device.

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