ICL71C03 Datasheet, PDF (16/19 Pages) Intersil Corporation – Precision 4 1/2 Digit, A/D Converter

ICL8052/ICL71C03, ICL8068/ICL71C03
R
37.5kΩ
f_OSC = 0.45/RC
C
100pF
FIGURE 12. CMOS OSCILLATOR
16kΩ
0.22µF
16kΩ
+5V
56kΩ
2
+
8
7
LM311
-
1
34
1kΩ
30kΩ
390pF
FIGURE 13. LM311 OSCILLATOR
D
S 2N5461
+15V -15V
100K
D
S 2N5458
0.22µF
-BUF IN BUF OUT -INT IN INT OUT
REF
OUT ₆
87 1
10
BUFFER
9
11
14
INTEG.
300pF
INT.
3 _REF.
-
COMP.
-
REF
A1
COMP
+
A2
+
-
A3
COMP
OUT
8052A/
8068A
+
2
-1.2V
5 +BUF IN 13
+INT IN 12
TO ICL71C03
FIGURE 14. GROSS OVERVOLTAGE PROTECTION CIRCUIT
Interfacing with UARTs and
Microprocessors
Figure 15 shows a very simple interface between a free-run-
ning 8068/8052/71C03A and a UART. The five STROBE
pulses start the transmission of the five data words. The digit
5 word is 0000XXXX, digit 4 is 1000XXXX, digit 3 is
0100XXXX, etc. Also, the polarity is transmitted indirectly by
using it to drive the Even Parity Enable Pin (EPE). If EPE of
the receiver is held low, a parity flag at the receiver can be
decoded as a positive signal, no flag as negative. A complex
arrangement is shown in Figure 14. Here the UART can
instruct the A/D to begin a measurement sequence by a
word on RRI. The Busy signal resets the Data Ready Reset
(DRR). Again STROBE starts the transmit sequence. A
quad 2 input multiplexer is used to superimpose polarity,
over-range, and under-range onto the D₅ word since in this
instance it is known that B₂ = B₄ = B₈ = 0.
For correct operation it is important that the UART clock be
fast enough that each word is transmitted before the next
STROBE pulse arrives. Parity is locked into the UART at
load time but does not change in this connection during an
output stream.
Circuits to interface the 71C03(A) directly with three popular
microprocessors are shown in Figures 17, 18 and 19. The
main differences in the circuits are that the IM6100 with its
12-bit word capability can accept polarity, over-range, under-
range, 4 bits of BCD and 5 digits simultaneously where the
8080/8048 and the MC6800 groups with 8-bit words need to
have polarity, over-range and under-range multiplexed onto
the Digit 5 word - as in the UART circuits. In each case the
microprocessor can instruct the A/D when to begin a mea-
surement and when to hold this measurement.
Application Notes
NOTE #
DESCRIPTION
AnswerFAX
DOC. #
AN016 “Selecting A/D Converters”
9016
AN017 “The Integrating A/D Converter”
9017
AN018 “Do’s and Don’ts of Applying A/D
Converters”
9018
AN023 “Low Cost Digital Panel Meter Designs”
9023
AN028 “Build an Auto-Ranging DMM Using the
8052A / 7103A A/D Converter Pair,” by
Larry Goff
9028
3-49