DAC1282_15 Datasheet, PDF (22/46 Pages) Texas Instruments – Low Distortion Digital-to-Analog Converter for Seismic

DAC1282, DAC1282A
SBAS490B – DECEMBER 2011 – REVISED MAY 2015
www.ti.com
8.2.5 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.
S₁
SWINP
S₂
SWOUTP
S₅
S₃
SWINN
S₄
SWOUTN
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.
DESCRIPTION
Open (default)
Differential
Differential reverse
Common-mode positive
Common-mode negative
Single-ended positive
Single-ended negative
Output short
Table 8. Switch Connections
PIN CONNECTIONS
Open
SWINP to SWOUTP and SWINN to SWOUTN
SWINP to SWOUTN and SWINN to SWOUTP
SWINP to SWOUTP and SWOUTN
SWINN to SWOUTP and SWOUTN
SWINP to SWOUTP
SWINN to SWOUTN
SWOUTP to SWOUTN
SWITCHES CLOSED
None
S1, S3
S2, S4
S1, S2
S3, S4
S1
S3
S5
SW[2:0] REGISTER BITS
000
001
010
011
100
101
110
111
22
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