Data Sheet

AD8338

Rev. B | Page 17 of 19

ADJUSTING THE OUTPUT COMMON-MODE

VOLTAGE

The output common-mode voltage of the AD8338 differential

outputs is nominally set to 1.5 V, the voltage at Pin VREF. This

output common-mode voltage can be adjusted by connecting a

resistor from each of the summing nodes of the output amplifier

(Pin FBKP and Pin FBKM) to either Pin COMM or Pin VBAT.

Connecting a resistor from Pin FBKP and Pin FBKM to Pin VBAT

decreases the output common-mode voltage, whereas connecting

a resistor from Pin FBKP and Pin FBKM to Pin COMM increases

the output common-mode voltage (see Figure 47 and Figure 48).

FBKM

OUTP = 1.5V –

OUTM = 1.5V –

FBKP

9.5kΩ

VREF = 1.5V

VBAT

VBAT

(VBAT – 1.5V) × 9.5kΩ

R2

R2

R1

9.5kΩ

(VBAT – 1.5V) × 9.5kΩ

R1

Figure 47. Decreasing the Output Common-Mode Voltage

FBKM

OUTP = 1.5V –

OUTM = 1.5V –

FBKP

9.5kΩ

VREF = 1.5V

COMM

COMM

(0 – 1.5V) × 9.5kΩ

R2

R2

R1

9.5kΩ

(0 – 1.5V) × 9.5kΩ

R1

Figure 48. Increasing the Output Common-Mode Voltage

Table 5 and Table 6 show suggested values for the external

resistors shown in Figure 47 and Figure 48, respectively.

Table 5. Resistor Values for Decreasing the Output

Common-Mode Voltage

VBAT (V)

Resistor Value (Ω)

Tied to

5.0

0.9

55,417

VBAT

3.3

0.9

28,500

VBAT

3.0

0.9

23,750

VBAT

Table 6. Resistor Values for Increasing the Output

Common-Mode Voltage

VBAT (V)

Resistor Value (Ω)

Tied to

Any

1.8

47,500

COMM

Any

2.0

28,500

COMM

Any

2.5

14,250

COMM