ISD1200 SERIES
PIN NAME
RECLED
PIN NO.
FUNCTION
Record LED
: The
RECLED
output is LOW during a record
cycle. It can be used to drive an LED to indicate a record cycle
25
is in progress. In addition,
RECLED
pulses LOW
momentarily when an end-of-message is encountered in a
playback operation.
XCLK
26
External Clock
: The external clock input has an internal pull-
down resistor. The ISD1100 is configured at the factory with
an internal sampling clock frequency that guarantees its
minimum nominal record/playback time. For instance, an
ISD1110 operating within specification will be observed to
always have a minimum of 10 seconds of recording time. The
sampling frequency is then maintained to a variation of
±
2.25
percent over the commercial temperature and operating
voltage ranges while still maintaining the minimum duration
specified. As a result some devices will have a few percent
more than nominal recording time. If greater precision is
required, the device can be clocked through the XCLK pin as
follows:
EXTERNAL CLOCK SAMPLE RATES
Part Number
ISD1110
ISD1112
Sample Rate
6.4 kHz
5.3 kHz
Required Clock
819.2 kHz
682.7 kHz
These recommended clock rates should not be varied
because the anti-aliasing and smoothing filters are fixed, and
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.
If the
XCLK is not used, this pin must be grounded.
Please see
Application Information for the ISD1100 series for more details
on external clocking.
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