Product Data Sheets

ISD1000A Series

1–5

1

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. It has a

maximum gain of about 24 dB for small input sig-

nal levels.

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 2.7 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.

Optional External Clock Input (XCLK)

ISD1000A devices are configured at the factory

with an internal sampling clock frequency cen-

tered to

±1% of specification. The frequency is

maintained to a total variation of

±2.25% toler-

ance over the entire commercial temperature and

4.5 to 5.5 voltage ranges. The internal clock has a

±5% tolerance over the industrial temperature

range and 4.5 to 5.5 voltage range. A regulated

power supply is recommended for industrial-tem-

perature-range parts. If greater precision is

required, the device can be clocked through the

XCLK pin as follows.

These recommended clock rates should not be

varied because the antialiasing and smoothing fil-

ters are fixed, and aliasing problems can occur if

the sample rate differs from the one recom-

mended. The duty cycle on the input clock is not

critical, as the clock is immediately divided by

CONNECTED TO GROUND

.

Speaker Outputs (SP+/SP-)

All devices in the ISD1000A Series include an on-

chip differential speaker driver, capable of driving

50 milliwatts into 16

Ω from AUX IN (12.2 mW from

memory).

record and power down. It is therefore not possi-

ble to parallel speaker outputs of multiple

ISD1000A devices or the outputs of other speaker

drivers.

NOTE

Connection of speaker outputs in parallel

may cause damage to the device.

While a single output may be used alone (includ-

ing a coupling capacitor between the SP pin and

the speaker), these outputs may be used individ-

ually with the output signal taken from either pin.

Using the differential outputs results in a 4:1

improvement in output power.

NOTE

Never ground or drive an output.

Auxiliary Input (AUX IN)

The Auxiliary Input is multiplexed through to the

output amplifier and speaker output pins when CE

is HIGH and Playback has ended, or if the device

is in overflow. When cascading multiple ISD1000A

devices, the AUX IN pin is used to connect a Play-

back signal from a following device to the

previous output speaker drivers. For noise consid-

erations, it is suggested that the Auxiliary Input not

be driven when the storage array is active.

Address/Mode Inputs (Ax/Mx)

The Address/Mode Inputs provide two functions in

the ISD1000A Series: 1. Message address (either

Part

Number

Sample Rate

Required Clock

ISD1016A

8.0 KHz

1024 KHz

ISD1020A

6.4 KHz

819.2 KHz

06.DataBook_1000A Dsht Page 5 Friday, September 27, 1996 10:44 AM