ISDMICROTAD-16ME データシートの表示（PDF） - Information Storage Devices

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ISDMICROTAD-16ME

Single-Chip Voice Record/Playback Device 16-Minute Duration

Information Storage Devices 

ISD MicroTAD-16M

ROW ADDRESS CLOCK (RAC)

This is an open drain output pin that provides a

signal with a 400 ms period at the 4 KHz sampling

frequency. (This represents a single row of memo-

ry and there are 2400 rows of memory in the ISD

MicroTAD-16M devices.) This signal stays HIGH for

350 ms and stays LOW for 50 ms when it reaches

the end of a row.

TRAC

ROW (400 ms)

RAC

50 ms

TRACLO

The RAC pin stays HIGH for 218.76 µsec and stays

LOW for 31.26 µsec in Message Cueing mode

(see page 5 for a more detailed description of

Message Cueing). Refer to the AC Parameters

table for RAC timing information on other sam-

ple rate products.

When a record command is first initiated, the

RAC pin remains HIGH for an extra TRACLO period.

This is due to the need to load sample and hold

circuits internal to the device. This pin can be

used for message management techniques.

EXTERNAL CLOCK INPUT (XCLK)

The external clock input for the ISD MicroTAD-

16M product has an internal pull-down device.

These products are configured at the factory

with an internal sampling clock frequency cen-

tered to ±1 percent of specification. The fre-

quency is then maintained to a variation over

the entire commercial temperature and oper-

ating voltage ranges as defined by the min-

imum/maximum limits in the applicable AC

Parameters table. The internal clock has a toler-

ance, over the extended temperature, industrial

temperature and voltage ranges as defined by

the minimum/maximum limits in the applicable

AC Parameters table. A regulated power supply

is recommended for industrial temperature

range parts. If greater precision is required, the

device can be clocked through the XCLK pin in

Table 1.

Table 1:

External Clock Input Clocking

Table

Part Number Sample Rate Required Clock

ISD MicroTAD-16M

4.0 KHz

512 KHz

This recommended clock rate should not be var-

ied because the antialiasing and smoothing filters

are fixed. Thus, aliasing problems can occur if the

sample rate differs from the one recommended.

The duty cycle on the input clock is not critical,

as the clock is immediately divided by two inter-

nally. If the XCLK is not used, this input should be

connected to ground.

AUTOMUTE™ FEATURE (AM CAP)

This pin is used in controlling the AutoMute fea-

ture. The AutoMute feature attenuates the signal

when it drops below an internally set threshold.

This helps to eliminate noise (with 6 dB of attenu-

ation) when there is no signal (i.e., during periods

of silence). A 1 µF capacitor to ground should be

connected to the AM CAP pin. This capacitor

becomes a part of an internal peak detector

which senses the signal amplitude (peak). 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 while 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 Auto-

mute feature can be disabled by connecting

the AM CAP pin to VCCA.

4

Voice Solutions in Silicon™

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