Datasheet
R
G
R
G
V
OCM
R
L
V
O
R
F
R
F
C
L
R
O
EN
+
-
V
I
a
R
M
R
T
R
S
R
IN
=
R
G
1-
R
F
2 * (R
F
+ R
G
)
R
O
SET R
M
= R
T
||R
S
SET R
T
=
1
1
R
S
-
1
R
IN
¨
¨
©
§
¨
¨
©
§
¨
¨
©
§
¨
¨
©
§
LMP8350
www.ti.com
SNOSB80B –FEBRUARY 2011–REVISED MARCH 2013
With up to 15 V
PP
differential output voltage swing and 80 mA of linear drive current, the LMP8350 makes an
excellent precision cable driver as shown in Figure 31. The LMP8350 is also suitable for driving differential
cables from a single ended source.
Figure 32. Single Ended in Differential Out
SINGLE ENDED INPUT TO DIFFERENTIAL OUTPUT
Figure 32 shows a typical application where an LMP8350 is used to produce a differential signal from a single
ended source. It should be noted that compared to differential input, using a single ended input will reduce gain
by 1/2, so that the closed loop gain will be; Gain = A
V
= 0.5 * R
F
/R
G
.
In single ended input operation the output common mode voltage is set by the V
OCM
pin. Also, In this mode the
common mode feedback circuit must recreate the signal that is not present on the unused differential input pin.
The common mode feedback circuit is responsible for ensuring balanced output with a single ended input.
Balance error is defined as the amount of input signal that couples into the output common mode. It is measured
as the undesired output common mode swing divided by the signal on the input. Balance error can be caused by
either a channel to channel gain error, or phase error. Either condition will produce a common mode shift. As
mentioned in the previous FULL BANDWIDTH LIMITATIONS section, the overall bandwidth is limited due to the
V
OCM
buffer bandwidth limitations in this configuration.
Supply and V
OCM
pin bypassing are also critical in this mode of operation.
SINGLE SUPPLY OPERATION
As shown in Figure 33, the input common mode voltage is less than the output common voltage. It is set by
current flowing through the feedback network from the device output. The input common mode voltage range
places constraints on gain settings. Possible solutions to this limitation include AC coupling the input signal,
using split power supplies and limiting stage gain. AC coupling with single supply is shown in Figure 34.
V
ICM
= Input common mode voltage = (V
+
IN
+V
−
IN
)/2.
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