Datasheet

PGA2500 Product Overview
1-2
1.1 PGA2500 Product Overview
The PGA2500 is a digitally-controlled, microphone preamplifier integrated cir-
cuit designed for amplifying the output of dynamic and condenser micro-
phones and driving high-performance audio analog-to-digital (A/D) convert-
ers. A functional block diagram of the PGA2500 is shown in Figure 1−1.
Figure 1−1. PGA2500 Functional Block Diagram
SERIAL
PORT and
LOGIC
CONTROL
C
S1
and C
S2
are external DC servo integrator capacitors,
and are connected across the C
S11
/C
S12
and C
S21
/C
S22
pins, respectively.
CS
SCLK
SDI
SDO
OVR
V
COM
IN
V
OUT
+
V
OUT
−
VD
−
DCEN
0dB
ZCEN
GPO1
GPO2
GPO3
GPO4
PGA
DC
Servo
C
S1
C
S2
DGND
V
IN
+
V
IN
−
AGND
VA+
VA
−
VA+
VA
−
Gain Range
0dB or
+10dB to +65dB
1dB per step
The analog input to the preamplifier is provided differentially at the V
IN
+ and
V
IN
− inputs (pins 27 and 26, respectively). The programmable gain amplifier
can be programmed to either pass through the signal at unity gain, or apply
10dB to 65dB of gain to the input signal. The gain of the amplifier is adjustable
over the full 10dB to 65dB range in 1dB steps. The differential output of the
PGA2500 is made available at V
OUT
+ and V
OUT
− (pins 17 and 16, respective-
ly). Gain is controlled using a serial port interface.
The 4-wire serial port interface is used to program the PGA2500 gain and sup-
port functions. A 16-bit control word is utilized to program these functions; see
Figure 1−2. A serial data output pin provides support for daisy-chaining multi-
ple PGA2500 devices on a single serial interface bus.