ISD4004 SERIES
PIN NAME
PIN NO.
FUNCTION
SOIC /
TSOP
PDIP
AM CAP
14
22
AutoMute™ Feature: The AutoMute feature only applies
for playback operation and helps to minimize noise (with 6
dB of attenuation) when there is no signal (i.e. during
periods of silence). A 1 µF capacitor to ground is
recommended to connect to the AM CAP pin.
This capacitor becomes a part of an internal peak detector
which senses the signal amplitude. This peak level is
compared to an internally set threshold to determine the
AutoMute trip point. For large signals, the AutoMute
attenuation is set to 0 dB automatically but 6 dB of
attenuation occurs for silence. The 1 µF capacitor also
affects the rate at which the AutoMute feature changes with
the signal amplitude (or the attack time).
The AutoMute feature can be disabled by connecting the
AM CAP pin directly to VCCA..
ANA IN-
16
24
Inverting Analog Input: This pin transfers the signal into
the device during recording via differential-input mode.
In this differential-input mode, a 16 mVp-p maximum input
signal should be capacitively coupled to ANA IN- for
optimal signal quality, as shown in Figure 1: ANA IN
Modes. This capacitor value should be equal to that used
on ANA IN+ pin. The input impedance at ANA IN- is
normally 56 KΩ.
In the single-ended mode, ANA IN- should be capacitively
coupled to VSSA through a capacitor equal to that used on
the ANA IN+ pin.
ANA IN+
17
25
Non-Inverting Analog Input: This pin is the non-inverting
analog input that transfers the signal to the device for
recording. The analog input amplifier can be driven single
ended or differentially.
In the single-ended input mode, a 32 mVp-p (peak-to-peak)
maximum signal should be capacitively connected to this
pin for optimal signal quality. The external capacitor
associated with ANA IN+ together with the 3 KΩ input
impedance are selected to give cutoff at the low frequency
end of the voice passband.
In the differential-input mode, the maximum input signal at
ANA IN+ should be 16 mVp-p capacitively coupled for
optimal signal quality. The circuit connections for the two
modes are shown in Figure 1.
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