User Manual

ISD1800 SERIES

Publication Release Date: June 7, 2005

- 11 - Revision 0.3

RECLED

operation

The

RECLED

output pin provides an active-LOW signal, which can be used to drive an LED as a

“record-in-progress” indicator. It returns to a HIGH state when the REC pin is released LOW or when

the recording is completed due to the memory being filled. This pin also pulses LOW to indicate the

end of a message has been reached.

9. ROSC operation

The duration of the device can be varied by changing the value of R2 (R

OSC

). This means the ISD1800

device can actually be between 6 to 16 seconds duration. See the curve below, which charts typical

durations when the R

OSC

is varied from 80 K to 160 K.

This feature allows frequency shifting where a recorded voice or sound can be played back faster or

slower than normal for special effects. For example, use a 100 K resistor to make the recording and

then playback with either an 80 K resistor for faster “chipmunk” talk or with a 120 K resistor for a

slower, lower voice.

Another feature is a “Pause” or interrupt function that can be done by taking the R

OSC

resistor to V

stop playback momentarily, resuming when the resistor is connected back to ground.

Chart 1: ISD Duration Versus R

OSC

at T

= 25°C and V

= 3.0V

6 8 10 12 14 16

80 100 120 140 160

Typical R

OSC

(K )

Typical Duration (sec)

Ω