*VCM =

VO1 + VO2

2

*BY DESIGN

RG

RG

VOCM

RL

VO

RF

RF

CL

RO

RO

EN

+

-

VI

a

VO1

VO2

VI2

VI1

RM

RT

RS

= a

VOCM

1 + AV

WHERE RM << RG

VICM = VOCM *

(RG + RM)

(RG + RM + RF)

2 VPP

VOCM

EN

100:

TWISTED PAIR

50:

2 VPP

1000

1000

500

500

GAIN = 2

50:

a

+

-

LMP8350

www.ti.com

SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015

Application Information (continued)

Figure 30. Fully-Differential Cable Driver

With up to 15 VPP differential output voltage swing and 80 mA of linear drive current, the LMP8350 makes an

excellent precision cable driver as shown in Figure 30. The LMP8350 is also suitable for driving differential

cables from a single-ended source.

8.1.2 Single Supply Operation

As shown in Figure 31, 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. The input common-mode voltage is calculated in Equation 2. 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 32.

VICM= Input common-mode voltage = (V

+

IN + V

−

IN)/2.

(2)

Figure 31. Relating AV to Input/Output Common-Mode Voltages

In Figure 31 the differential closed loop gain is = AV= RF/RG.

NOTE

In single-ended to differential operation VIN is measured single ended while VOUT is

measured differentially. This means that gain is really one-half, or 6 dB, less when

measured on either of the output pins separately.

Copyright © 2011–2015, Texas Instruments Incorporated

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