SWOUTP

SWOUTN

SWINP

SWINN

S

5

S

2

S

1

S

4

S

3

DAC1282

www.ti.com

SBAS490

– DECEMBER 2011

OUTPUT SWITCH (SWINP, SWINN, SWOUTP, SWOUTN)

The DAC1282 has an integrated output switch. The switch can be used to route the DAC output signal to a

sensor for pulse, THD, and common-mode testing. The switch has low on-resistance and matched elements to

minimize signal distortion. The switch input voltage range extends to the analog power supply.

The switch is controlled by three register bits, SW[2:0], and is also controlled by the SW/TD input pin. The switch

integrates break-before-make operation when the register or the SW/TD input control is changed. The SW/TD

input can be used to force the switch open for precise timing control of sensor impulse testing; see the Switch

Control/DAC Data Input (SW/TD) section. Figure 37 and Table 8 describe the switch operation.

Figure 37. DAC1282 Signal Switch

Note that when the DAC is in power-down mode, the switch is forced open.

As shown in Figure 29, the switch on-resistance varies with the switch signal level. When the switch is used to

route the signal and a resistive load is connected to the switch output, the switch on-resistance variations interact

with the load resistance and cause the THD to degrade. Figure 27 illustrates the dependence of THD versus

switch load resistance. The dependence of THD data was taken with a full-scale signal.

Table 8. Switch Connections

DESCRIPTION

PIN CONNECTIONS

SWITCHES CLOSED

SW[2:0] REGISTER BITS

Open (default)

Open

None

000

Differential

SWINP to SWOUTP and SWINN to SWOUTN

S1, S3

001

Differential reverse

SWINP to SWOUTN and SWINN to SWOUTP

S2, S4

010

Common-mode positive

SWINP to SWOUTP and SWOUTN

S1, S2

011

Common-mode negative

SWINN to SWOUTP and SWOUTN

S3, S4

100

Single-ended positive

SWINP to SWOUTP

S1

101

Single-ended negative

SWINN to SWOUTN

S3

110

Output short

SWOUTP to SWOUTN

S5

111

Copyright

© 2011, Texas Instruments Incorporated

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