ADA4255ACPZ-R7 datasheet(34/64 Pages) AD

34 / 64 page

Data Sheet

ADA4255

THEORY OF OPERATION

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Rev. 0 | 34 of 64

WIRE BREAK DETECTION

The ADA4255 contains two programmable current sources that

can be configured to 0.25 μA, 2 μA, 4 μA, or 16 μA via the

WB_CURRENT bits (Register WB_DETECT). Both currents are

conducted from VDDH. These currents, in conjunction with the

on-chip comparators, enable continuity testing on the ADA4255

inputs.

The currents are switched to the amplifier inputs using F1 and F2,

as shown in Figure 95. The voltage to which these currents bias the

amplifier inputs is monitored internally by the ADA4255. When this

voltage is within 4 V of VDDH, the WB_ERR

(Register ANALOG_ERR_DIS) flag trips.

When F1 or F2 are closed, the amplifier gain settings in the

GAIN_MUX register are temporarily overridden to the default values

to avoid saturating the amplifier output in the event of an open-cir-

cuit input. Reads of the GAIN_MUX register during this time do not

reflect this. When F1 and F2 are open, the GAIN_MUX register

values automatically return to their previous values. This override

can be disabled via the WB_G_RST_DIS bit

(Register WB_DETECT).

Figure 95. Wire Break Current Connectivity

ADA4255ACPZ-R7 Datasheet(PDF) 34 Page - Analog Devices