ICL7136_14 Datasheet, PDF (6/15 Pages) Intersil Corporation – 31/2 Digit LCD, Low Power Display, A/D Converter with Overrange Recovery

ICL7136
Pin Descriptions
PIN NUMBER
44 PIN
40 PIN DIP FLATPACK
1
8
2
9
3
10
4
11
5
12
6
13
7
14
8
15
9
16
10
17
11
18
12
19
13
20
14
21
15
22
16
23
17
24
18
25
19
26
20
27
21
28
22
29
23
30
24
31
25
32
26
34
27
35
28
36
29
37
30
38
31
39
32
40
33
41
34
42
35
43
36
44
37
3
38
4
39
6
40
7
NAME
V+
D1
C1
B1
A1
F1
G1
E1
D2
C2
B2
A2
F2
E2
D3
B3
F3
E3
AB4
POL
BP/GND
G3
A3
C3
G2
V^-
INT
BUFF
A-Z
IN LO
IN HI
COMMON
C_REF-
C_REF+
REF LO
REF HI
TEST
OSC3
OSC2
OSC1
FUNCTION
Supply
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Supply
Output
Output
Input
Input
Supply/
Output
DESCRIPTION
Power Supply.
Driver Pin for Segment “D” of the display units digit.
Driver Pin for Segment “C” of the display units digit.
Driver Pin for Segment “B” of the display units digit.
Driver Pin for Segment “A” of the display units digit.
Driver Pin for Segment “F” of the display units digit.
Driver Pin for Segment “G” of the display units digit.
Driver Pin for Segment “E” of the display units digit.
Driver Pin for Segment “D” of the display tens digit.
Driver Pin for Segment “C” of the display tens digit.
Driver Pin for Segment “B” of the display tens digit.
Driver Pin for Segment “A” of the display tens digit.
Driver Pin for Segment “F” of the display tens digit.
Driver Pin for Segment “E” of the display tens digit.
Driver pin for segment “D” of the display hundreds digit.
Driver pin for segment “B” of the display hundreds digit.
Driver pin for segment “F” of the display hundreds digit.
Driver pin for segment “E” of the display hundreds digit.
Driver pin for both “A” and “B” segments of the display thousands digit.
Driver pin for the negative sign of the display.
Driver pin for the LCD backplane/Power Supply Ground.
Driver pin for segment “G” of the display hundreds digit.
Driver pin for segment “A” of the display hundreds digit.
Driver pin for segment “C” of the display hundreds digit.
Driver pin for segment “G” of the display tens digit.
Negative power supply.
Integrator amplifier output. To be connected to integrating capacitor.
Input buffer amplifier output. To be connected to integrating resistor.
Integrator amplifier input. To be connected to auto-zero capacitor.
Differential inputs. To be connected to input voltage to be measured. LO and HI
designators are for reference and do not imply that LO should be connected to lower
potential, e.g., for negative inputs IN LO has a higher potential than IN HI.
Internal voltage reference output.
Connection pins for reference capacitor.
Input
Input
Output
Output
Input
Input pins for reference voltage to the device. REF HI should be positive reference to
REF LO.
Display test. Turns on all segments when tied to V+.
Device clock generator circuit connection pins.
Detailed Description
Analog Section
Figure 2 shows the Analog Section for the ICL7136. Each
measurement cycle is divided into four phases. They are (1)
auto-zero (A-Z), (2) signal integrate (INT) and (3) de-
integrate (DE), (4) zero integrate (ZI).
Auto-Zero Phase
During auto-zero three things happen. First, input high and low
are disconnected from the pins and internally shorted to analog
COMMON. Second, the reference capacitor is charged to the
reference voltage. Third, a feedback loop is closed around the
system to charge the auto-zero capacitor C_AZ to compensate
for offset voltages in the buffer amplifier, integrator, and
comparator. Since the comparator is included in the loop, the A-
Z accuracy is limited only by the noise of the system. In any
case, the offset referred to the input is less than 10µV.
Signal Integrate Phase
During signal integrate, the auto-zero loop is opened, the
internal short is removed, and the internal input high and low
6
FN3086.6
July 21, 2005