AD8293G80/AD8293G160

Rev. 0 | Page 12 of 16

he addition of another single pole of 700 Hz on the output

hs

C3 (nF)

T

(from the secondary filter in Figure 18) is required for bandwidt

greater than 10 Hz. These two filters, together, produce an overall

bandwidth of 500 Hz. The internal resistors, R2 and R3, have an

absolute tolerance of 20%. Table 8 lists the standard capacitors

needed to create a filter with an overall bandwidth of 500 Hz.

Table 8. Standard Capacitors Used to Form a Filter with an

Overall Bandwidth of 500 Hz

Model

C2 (pF)

AD8293G80

1300

39

AD8293G160

680

39

For applications with low bandwi ths (<10 Hz), only the primary

H

use two synchronized clocks

ncies can be observed at

d

filter is required. In such an event, the high frequency noise

from the auto-zero amplifier (output amplifier) is not filtered

before the following stage.

CLOCK FEEDTHROUG

The AD8293G80/AD8293G160

to perform the autocorrection. The input voltage-to-current

amplifiers are corrected at 60 kHz.

Trace amounts of these clock freque

the OUT pin. The amount of visible correction feedthrough

is dependent on the values of the filters set by R2/C2. Use

ADC OUT to create a filter using R3/C3 to further reduce

correction feedthrough as described in the Output Filtering

section.

POWER SUPPLY BYPASSING

The AD8293G80/AD8293G160 use internally generated clock

signals to perform autocorrection. As a result, proper bypassing

is necessary to achieve optimum performance. Inadequate or

improper bypassing of the supply lines can lead to excessive

noise and offset voltage.

A 0.1 μF surface-mount capacitor should be connected between

the supply lines. This capacitor is necessary to minimize ripple

from the correction clocks inside the IC. For dual-supply operation,

a 0.1 μF (ceramic) surface-mount capacitor should be connected

from each supply pin to GND.

For single-supply operation, a 0.1 μF surface-mount capacitor

should be connected from the supply line to GND.

All bypass capacitors should be positioned as close to the DUT

supply pins as possible, especially the bypass capacitor between

the supplies. Placement of the bypass capacitor on the back of

the board directly under the DUT is preferred.

INPUT OVERVOLTAGE PROTECTION

All terminals of the AD8293G80/AD8293G160 are protected

against ESD. In the case of a dc overload voltage beyond either

supply, a large current would flow directly through the ESD

protection diodes. If such a condition can occur, an external resistor

should be used in series with the inputs to limit current for voltages

beyond the supply rails. The AD8293G80/AD8293G160 can safely

handle 5 mA of continuous current, resulting in an external

resistor selection of

1

8

7

5

6

4

ADC OUT

FILT

I

1.8V

–IN

+IN

R1

4kΩ

R2

160kΩ

R3

5kΩ

+3.3V

10µF

0.1µF

C3

39nF

OUT

C2

1.3nF

AD8293G80

REF

GND

3

2

IN-AMP

ADC

REF

LOAD

DC-DC

+5V

0.1µF

Figure 21. Measuring Current Through a Shunt Resistor (Filter Is Set to 500 Hz)