AD8290

Rev. B | Page 16 of 20

APPLICATIONS INFORMATION

TYPICAL CONNECTIONS

Figure 45 shows the typical connections for single-supply

operation when used with a sensor bridge.

CURRENT EXCITATION

(RSET).

The AD8290 is internally set by the factory to provide the

current excitation described by the previous formula (within the

respectively.

ENABLE/DISABLE FUNCTION

Pin 3 (ENBL) provides the enabling/disabling function of the

AD8290 to conserve power when the device is not needed. A

Logic 1 turns the part on and allows it to operate normally. A

Logic 0 disables the output and excitation current and reduces

the quiescent current to less than 10 μA.

The turn-on time upon switching Pin 3 high is dominated

by the output filters. When the device is disabled, the output

becomes high impedance, enabling the muxing application of

multiple AD8290 instrumentation amplifiers.

OUTPUT FILTERING

switching noise present at the output. The recommended

For bandwidths greater than 10 Hz, an additional single-pole

RC filter of 235 Hz is required on the output, which is also

recommended when driving an ADC requiring an antialiasing

filter. Internal to the AD8290 is a series 10 kΩ resistor at the

output (R3 in Figure 43) and using an external 68 nF capacitor

to ground produces an RC filter of 235 Hz on the output as well.

These two filters produce an overall bandwidth of approximately

160 Hz for the output signal.

In addition, when driving low impedances, the internal series

10 kΩ resistor creates a voltage divider at the output. If it is

necessary to access the output of the internal amplifier prior

to the 10 kΩ resistor, it is available at the CF2 pin.

For applications with low bandwidths (<10 Hz), only the first

frequency noise from the auto-zero amplifier (output amplifier)

is not filtered before the following stage.

CLOCK FEEDTHROUGH

The AD8290 uses two synchronized clocks to perform

autocorrection. The input voltage-to-current amplifiers

are corrected at 60 kHz.

Trace amounts of these clock frequencies can be observed at

the output. The amount of feedthrough is dependent upon the

gain because the autocorrection noise has an input- and output-

referred term. The correction feedthrough is also dependent

NOTES

LAYOUT CONSIDERATIONS:

1. KEEP C1 CLOSE TO PIN 2 AND PIN 10.

NC = NO CONNECT

ENBL

VOUT

VCC

VINP

VINN

IOUT

RSET

GND

AD8290

4

3

2

10

11

15

14

13

C1

0.1µF

CF2

CF1

5

6

C2

68nF

692Ω TO 3kΩ

5.0V

NC

NC

NC

NC

NC

NC

16

1

12

9

7

8

6.8nF

Figure 45. Typical Single-Supply Connections