Datasheet

Analog and Digital Power Supplies
3-2
3.1 Analog and Digital Power Supplies
All analog and digital power supplies are connected through terminal block J4.
Recommended power-supply connections are shown in Figure 3−1.
Figure 3−1. Recommended Power-Supply Connections
Phantom Power
Source, +48V
J2
J4
VCC EGND
GND VCOM VA+ VA
−
+5V Digital
Chassis (Earth) Ground
Common Ground
+5V Analog
−
5V Analog
Common Ground
0V to +2.5V
Primary
Power Supply
V
COM
IN
Power Supply
The PGA2500EVM requires two analog supplies and one digital power supply.
The analog supplies are VA+ and VA−, respectively. VA+ is typically set to
+5.0V DC, while VA− is typically set to −5.0V DC. The analog supplies power
the PGA2500 microphone preamplifier integrated circuit. The digital power
supply, VCC, is typically set to +5.0V DC. The VCC supply powers the
SN74AHCT541 buffer IC (U2) and the associated pull-up resistors for the digi-
tal section of the board.
An optional third analog power supply may be utilized for the PGA2500 com-
mon-mode DC voltage input, V
COM
IN (pin 25). The common-mode input can
be connected to analog ground by shorting pins 3 and 4 of Jumper JMP3. Al-
ternatively, the common-mode input can be connected to the VCOM supply
terminal of connector J4 by shorting pins 1 and 2 of Jumper JMP3. The VCOM
supply will typically be set to a DC voltage within the 0V to +2.5V DC range
(with respect to GND). The common-mode voltage biases both the output and
input terminals of the PGA2500, with the output pins being biased to the V
CO
-
M
IN voltage level and the input pins being biased to approximately V
COM
IN −
0.65V.
The GND terminal of connector J4 serves as the common ground connection
for both the analog and digital sections of the PGA2500EVM. The EGND
(earth ground) terminal should be connected to the earth or chassis ground of
the power supply. The common ground (GND) and earth ground (EGND) are
connected to one another using a 0.1µF capacitor (C3).