Product Data Sheets
ISD2500 Series
1–83
1
SSD
SSA
OVF
CE
PD
EOM
XCLK
P/R
V
NC
NC
A0/M0
A1/M1
A2/M2
A3/M3
A4/M4
A5/M5
A6/M6
ANA OUT
ANA IN
AGC
MIC REF
MIC
V
SP–
NC
NC
SP+
V
V
AUX IN
A8
A7
NC
CCD
CCA
ISD2532/40/48/64
TSOP
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
SSD
SSA
A0/M0
A1/M1
A2/M2
A3/M3
A4/M4
A5/M5
A6/M6
NC
A7
A8
AUX IN
V
V
SP+
V
P/R
XCLK
EOM
PD
CE
OVF
ANA OUT
ANA IN
AGC
MIC REF
MIC
V
SP–
CCD
CCA
ISD2532
ISD2540
ISD2548
ISD2564
DIP/SOIC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
Microphone Input (MIC)
The microphone input transfers its signal to the on-
chip preamplifier. An on-chip Automatic Gain Con-
trol (AGC) circuit controls the gain of this
preamplifier from -15 to 24 dB. An external micro-
phone should be AC coupled to this pin via a series
capacitor. The capacitor value, together with the
internal 10 K ohm resistance on this pin, deter-
mines the low-frequency cutoff for the ISD2500
Series passband. See ISD's
Application Notes and
Design Manual in this book for additional informa-
tion on low-frequency cutoff calculation.
Microphone Reference Input (MIC REF)
The MIC REF input is the inverting input to the
microphone preamplifier. This provides a noise-
canceling or common-mode rejection input to the
device
when
connected
to
a
differential
microphone.
Automatic Gain Control Input (AGC)
The AGC dynamically adjusts the gain of the
preamplifier to compensate for the wide range of
microphone input levels. The AGC allows the full
range of whispers to loud sounds to be recorded
with minimal distortion. The “attack” time is deter-
mined by the time constant of a 5 K
Ω internal
resistance and an external capacitor (C2 on the
schematic on page 1-100) connected from the
AGC pin to VSSA analog ground. The “release”
time is determined by the time constant of an
external resistor (R2) and an external capacitor
(C2) connected in parallel between the AGC Pin
and VSSA analog ground. Nominal values of
470 K
Ω and 4.7 µF give satisfactory results in
most cases.
Analog Output (ANA OUT)
This pin provides the preamplifier output to the
user. The voltage gain of the preamplifier is deter-
mined by the voltage level at the AGC pin.
Analog Input (ANA IN)
The analog input pin transfers its signal to the chip
for recording. For microphone inputs, the ANA
OUT pin should be connected via an external
capacitor to the ANA IN pin. This capacitor value,
together with the 3.0 K
Ω input impedance of ANA
IN, is selected to give additional cutoff at the low-
frequency end of the voice passband. If the
desired input is derived from a source other than a
microphone, the signal can be fed, capacitively
coupled, into the ANA IN pin directly.
External Clock Input (XCLK)
The external clock input for the ISD2500 devices
has an internal pull-down device. These devices
are configured at the factory with an internal sam-
pling
clock
frequency
centered
to
±1% of
ISD2532/40/48/64* DEVICE PINOUTS
* Advance information: ISD2532/40/48/64 devices.
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