UCC561

SLUS413B -- MAY 1999 -- REVISED NOVEMBER 2002

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4

APPLICATION INFORMATION

The resistor stack with the 1.75-V and 0.75-V reference gives the correct differential impedance, bias voltage,

common mode differential impedance, and common mode voltage as show in Table 1.

Table 1. UCC561 Resistor Stack vs. Standard (SPI--2 through SPI--4)

PARAMETER

UCC561

STANDARD

UNITS

Differential Impedance

107.3

100 to 110

W

Differential bias voltage

112.9

100 to 125

mV

Common-mode differential impedance

237

100 to 300

W

Common-mode voltage

1.25

1.2to1.3

V

UDG--98096

1.3 V ±100 mV

1.75 V ±50 mV

200 mA SOURCE/SINK

L1+

L27--

L27+

SOURCE/SINK REGULATOR

REF

1.3V

7

DIFSENS

DIFSENS: SOURCE ONLY FROM TERMPWR

2TERMPWR

4PGND

L1--

121 1%

121 1%

6

REF

1.75V

4.7

mF

REG1

3

REG2

SOURCE/SINK REGULATOR

REF

0.75V

200mA SOURCE/SINK

4.7

mF

DIFSENS

475 1%

475 1%

475 1%

475 1%

4.7

mF

TERMPWR

2.7V TO 5.25V

0.75 V ±50 mV

Figure 1. Low-Voltage Differential Discrete Resistor Stack