AD8338ACPZ-R7 datasheet(17/19 Pages) AD

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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 – 1.5V) × 9.5kΩ

9.5kΩ

(VBAT – 1.5V) × 9.5kΩ

+ VOUT/2

lOUT

Figure 47. Decreasing the Output Common-Mode Voltage

FBKM

OUTP = 1.5V –

OUTM = 1.5V –

FBKP

9.5kΩ

VREF = 1.5V

COMM

(0 – 1.5V) × 9.5kΩ

9.5kΩ

(0 – 1.5V) × 9.5kΩ

+ VOUT/2

lOUT

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)

Target VOCM (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)

Target VOCM (V)

Resistor Value (Ω)

Tied to

Any

1.8

47,500

COMM

Any

2.0

28,500

COMM

Any

2.5

14,250

COMM

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