AD8290

Rev. B | Page 18 of 20

PRESSURE SENSOR BRIDGE APPLICATION

Given its excitation current range, the AD8290 provides a good

match with pressure sensor circuits. Two such sensors are the

Fujikura FGN-615PGSR and the Honeywell HPX050AS. Figure 47

shows the AD8290 paired with the Honeywell bridge and the

to the circuit to ensure that the maximum output voltage of the

AD8290 is not exceeded. Depending on the sensors specifications,

The specifications for the bridge are show in Table 5 and the

chosen conditions for the AD8290 are listed in Table 6.

Given these specifications, calculations should be made to ensure

that the AD8290 is operating within its required ranges. The

to ensure that the conditions stay within the minimum and

maximum specifications of the AD8290. For this example,

because the specifications of the HPX050AS are for a bridge

excitation voltage of 3.0 V, care must be taken to scale the

resulting voltage calculations to the actual bridge voltage. The

required calculations are shown in Table 7.

ENBL

VOUT

VCC

NC

NC

VINP

VINN

IOUT

RSET

GND

NC

AD8290

NC

NC

NC

16

1

4

3

2

12

9

10

11

15

14

13

6.8nF

C1

0.1µF

CF2

CF1

5

6

7

8

C2

68nF

0.1µF

2.7kΩ

2kΩ

3.3V

4

5

6

8

HPX050AS

2

NC = NO CONNECT

Figure 47. HPX050AS Pressure Sensor Application

Table 5. HPX050AS Specifications

Bridge Impedance (Ω)

Rated Offset (mV)

Rated Output Span (mV)

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Bridge Excite Voltage (V)

4000

6000

−30

+30

0

80

3.0

Table 6. Typical AD8290 Conditions for Pressure Sensor Circuit

Excitation Current (μA)

3.3 (2.6 to 5.5)

333.3 (300 to 1300)

2000

Table 7. Pressure Sensor Circuit Calculations Compared to AD8290 Minimum/Maximum Specifications

Specification

Calculation

Unit

Allowable Range of AD8290

Supply Current

1.867

mA

2700

Ω

692 Ω to 3000 Ω

Minimum Equivalent Resistance to IOUT Pin

1333

Ω

Maximum Equivalent Resistance to IOUT Pin

1500

Ω

Minimum Current into Bridge

83.333

μA

Maximum Current into Bridge

111.111

μA

Minimum Bridge Midpoint Voltage (Excluding Offset/Span)

0.222

V

Maximum Bridge Midpoint Voltage (Excluding Offset/Span)

0.250

V

Minimum Voltage at Current Output Pin (IOUT)

0.444

V

>0.0 V

Maximum Voltage at Current Output Pin (IOUT)

0.500

V

<2.3 V

Input Voltage Minimum

0.218

V

>0.2 V

Input Voltage Maximum

0.266

V

<1.6 V

Output Voltage Minimum

0.643

V

>0.075 V

Output Voltage Maximum

1.852

V

<3.225 V