Datasheet

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SBOS289A − NOVEMBER 2003 − REVISED DECEMBER 2003
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11
APPLICATION INFORMATION
This section provides practical information for designing
the PGA2500 into end applications.
BASIC CIRCUIT CONFIGURATION
A typical applications circuit, without the input and output
circuitry, is shown in Figure 6. Power-supply bypass and
DC servo capacitors are shown with recommended
values. All capacitors should be placed as close as
possible to the PGA2500 package to limit inductive noise
coupling. Surface-mount capacitors are recommended
(X7R ceramic for the 0.1µF and 1µF capacitors, and low
ESR tantalum for the 4.7µF capacitors).
The PGA2500 can be placed on a split ground plane, with
the package located over the split. However, there must be
a low impedance connection between the analog and
digital grounds at a common return point.
The DC common-mode input, V
COM
IN (pin 25), can be
connected to analog ground or a DC voltage (such as the
reference or common voltage output of an audio ADC).
When biasing this input to a DC voltage, keep in mind that
both the analog output and input pins are level-shifted by
the value of the bias voltage.
GPO1
GPO2
GPO3
GPO4
OVR
1
2
3
4
5
PGA2500
To
Relay Drivers,
Switches, or Indicators
AGND
28
DGND
6
To/From
MPU, MCU,
DSP, or Logic
DCEN
0dB
ZCEN
SDI
CS
SCLK
V
OUT
+
V
OUT
−
10
11
12
VD
−
14
VA
−
15
To
Analog Output
Circuit
17
16
V
IN
+
V
IN
−
From
Analog Input
Circuit
To
Optional
Common−Mode
Voltage
0
Ω
(1)
27
26
SDO
13
7
8
9
C
S21
C
S22
22
21
10
Ω
0.1
µ
F
VA
−
VA
−
20
0.1
µ
F
0.1
µ
F
+
4.7
µ
F
+
4.7
µ
F
VA
−
19
0.1
µ
F
1
µ
F
C
S11
C
S12
24
23
1
µ
F
VA
−
VA+
18
0.1
µ
F
+
4.7
µ
F
V
COM
IN
25
= Analog Ground
= Digital Ground
0.1
µ
F
(1)
NOTE: (1) Install a 0
Ω
shunt or jumper only when connecting V
COM
IN
to analog ground. Install a 0.1
µ
F ceramic capacitor (X7R type) only
when connecting V
COM
IN to a DC common−mode voltage source.
Connect Digital and Analog Grounds at
one common return point in the circuit.
Figure 6. Basic Circuit Configuration for the PGA2500