Datasheet

Data Sheet AD8338
Rev. A | Page 17 of 20
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 output amplifier’s summing nodes
(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).
Figure 47. Decreasing the Output Common-Mode Voltage
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.
Table 5. Resistor Values for Decreasing the Output
Common-Mode Voltage
VBAT (V ) Target V
OCM
(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 V
OCM
(V) Resistor Value (Ω) Tied to
Any 1.8 47,500 COMM
Any 2.0 28,500 COMM
Any 2.5 14,250 COMM
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
+ V
OUT
/2
+ V
OUT
/2
11279-150
l
OUT
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
+ V
OUT
/2
+ V
OUT
/2
11279-151
l
OUT