ICL71C03 Datasheet, PDF (9/19 Pages) Intersil Corporation – Precision 4 1/2 Digit, A/D Converter

ICL8052/ICL71C03, ICL8068/ICL71C03
once and only once for each measurement cycle starting
101/11 pulses after the end of the full measurement cycle.
Digit 5 (MSD) goes high at the end of the measurement
cycle and stays on for 201/21 counts. In the center of this
digit pulse (to avoid race conditions between changing BCD
and digit drives) the first STROBE pulse goes negative for
1_{/2 clock pulse width. Similarly, after Digit 5, Digit 4 goes}
high (for 200/20 clock pulses) and 100/10 pulses later the
STROBE goes negative for the second time. This continues
through Digit 1 (LSD) when the fifth and last STROBE pulse
is sent. The digit drive will continue to scan (unless the
previous signal was over-range) but no additional STROBE
pulses will be sent until a new measurement is available.
Busy (Pin 28)
BUSY goes high at the beginning of signal integrate and
stays high until the first clock pulse after zero-crossing (or
after end of measurement in the case of an OVER-RANGE).
The internal latches are enabled (i.e., loaded) during the first
clock pulse after BUSY and are latched at the end of this
clock pulse. The circuit automatically reverts to auto-zero
when not BUSY so it may also be considered an A-Z signal.
A very simple means for transmitting the data down a single
wire pair from a remote location would be to AND BUSY with
clock and subtract 10,001/1,001 counts from the number of
pulses received - as mentioned previously there is one “NO-
count” pulse in each Reference Integrate cycle.
Over-Range (Pin 4)
This pin goes positive when the input signal exceeds the
range (20,000/2,000) of the converter. The output F-F is set
at the end of BUSY and is reset to zero at the beginning of
Reference Integrate in the next measurement cycle.
Under-Range (Pin 13)
This pin goes positive when the reading is 9% of range or
less. The output F-F is set at the end of BUSY (if the new
reading is 1800/180 or less) and is reset a the beginning of
Signal Integrate of the next reading.
Polarity (Pin 3)
This pin is positive for a positive input signal. It is valid even for a
zero reading. In other words, +0000 means the signal is posi-
tive but less than the least significant bit. The converter can be
used as null detector by forcing equal (+) and (-) readings. The
null at this point should be less than 0.1 LSB. This output
becomes valid at the beginning of Reference Integrate and
remains correct until it is revalidated for the next measurement.
Digit Drives (Pins 19, 24, 25, 26, and 27)
Each digit drive is a positive-going signal which lasts for
200/20 clock pulses. The scan sequence is D₅(MSD), D₄,
D₃, D₂, and
operating in
D₁
the
(LSD). All
3¹/₂ digit
five digits are scanned
mode, and this scan is
even when
continuous
unless and OVER-RANGE occurs. Then all Digit drives are
blanked from the end of the STROBE sequence until the
beginning of Reference Integrate, at which time D₅ will start
the scan again. This gives a blinking display as a visual
indication of OVER-RANGE.
BCD (Pins 20, 21, 22 and 23)
The Binary coded decimal bit B₈, B₄, B₂, and B₁ are positive
logic signals that go on simultaneously with the Digit driver.
INTEGRATOR
OUTPUT
AUTO
ZERO
10,001
/ 1,001
COUNTS
SIGNAL
INTEG.
10,000
/ 1,000
COUNTS
REFERENCE
INTEGRATE
20,001 / 2,001
COUNTS MAX
FULL MEASUREMENT CYCLE
40,002/4,002 COUNTS
BUSY
OVER-RANGE
WHEN APPLICABLE
UNDER-RANGE
WHEN APPLICABLE
DIGIT SCAN
FOR OVER-RANGE
STROBE
DIGIT SCAN
FOR OVER-RANGE
EXPANDED SCALE BELOW
D₅
D₄
D₃
D₂
D₁
1000†/100 COUNTS
†FIRST D₅ OF AZ AND REF INT
ONE COUNT LONGER
AUTO ZERO
D₅
SIGNAL
INTEGRATE
REFERENCE
INTEGRATE
D₄
D₃
D₂
D₁
FIGURE 5. TIMING DIAGRAM FOR OUTPUTS
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