Datasheet

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SBOS289A − NOVEMBER 2003 − REVISED DECEMBER 2003
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10
DAISY-CHAINING MULTIPLE PGA2500
PREAMPLIFIERS
Since the serial port interface may be viewed as a serial in,
serial out shift register, multiple PGA2500 preamplifiers
may be connected in a cascaded or daisy-chained fashion,
as shown in Figure 4. The daisy-chained PGA2500
devices behave as a 16 x N-bit shift register, where N is the
number of cascaded PGA2500 devices. To program all of
the devices, simply force CS
low for 16 x N serial clock
periods and clock in 16 x N bits of control data. The CS
input is then forced high to latch in the new settings.
A timing diagram for the daisy-chain application is shown
in Figure 5.
CS
SCLK
SDI
SDO
V
OUT
+
V
OUT
−
V
IN
+
V
IN
−
PGA2500
#1
CS
SCLK
SDI
SDO
V
OUT
+
V
OUT
−
V
IN
+
V
IN
−
PGA2500
#2
CS
SCLK
SDI
SDO
V
OUT
+
V
OUT
−
V
IN
+
V
IN
−
PGA2500
#N
CS
DATACLK
DOUT
DIN
Micro
or DSP
Figure 4. Daisy-Chain Configuration for Multiple PGA2500 Preamplifiers
SCLK
CS
SDI
DC G0
DC G0DC
Device #1
Device #2Device #N
G0
Figure 5. Serial Port Operation for Daisy-Chain Operation