Datasheet

3Maxim Integrated
Low Power, 3
1
⁄2 Digit A/D Converter
with Display Hold
MAX136
Detailed Description
The MAX136 3½ digit ADC is similar to the Maxim
ICL7136 except for the addition of a Hold pin. For a
detailed product description, and applications informa-
tion (other than the operation of the Hold pin described
below), refer to Maxim's ICL7136 data sheet.
Hold Input
The Hold input is a digital input with a logic thresh-
old approximately midway between V+ and Test. The
MAX136 continuously performs conversions, indepen-
dent of the Hold input. When the Hold input is at V+ the
display latch pulse is inhibited, and the display latches
are not updated; when the Hold input is low or at the
Test voltage, the display is updated at the end of each
conversion. The MAX136 maintains low-power dissipa-
tion even during display hold by eliminating the pulldown
resistor between Hold and Test present on the ICL7116.
The Hold input is CMOS compatible, and can also be
driven by a switch connected between Test and V+
(Figure 1).
Reference Input
Unlike the ICL7136, the MAX136 does not have a refer-
ence low input. Apply the reference voltage between
Reference High (REF HI) and
Figure 1. MAX136 Typical Operating Circuit, 200mV Full Scale
Figure 2. MAX136 Typical Operating Circuit, 2.0V Full Scale
MAX136
ANALOG
INPUT
9V
V
REF
TO ANALOG
COMMON (P32)
LCD DISPLAY
BACKPLANE
DRIVE
SEGMENT
DRIVE
0.47µF
C
+
REF
OSC
2
R
OSC
C
OSC
OSC
3
OSC
1
C
-
REF
0.47µF
0.01µF
0.047µF
1MI
180kI
180kI
150kI
100kI
31
34 33
20
21 MINUS SIGN
RUN
HOLD
37
35
36
26
1
IN HI
2-19
22-25
PDL
BP
TEST
HOLD
REF HI
V
+
V
-
IN LO
COMMON
BUFF
A/Z
INT
30
32
28
29
39 38 40
50pF
27
MAX136
ANALOG
INPUT
9V
V
REF
TO ANALOG
COMMON (P32)
LCD DISPLAY
BACKPLANE
DRIVE
SEGMENT
DRIVE
0.47µF
C
+
REF
OSC
2
R
OSC
C
OSC
OSC
3
OSC
1
C
-
REF
0.47µF
0.01µF
0.047µF
1MI
180kI
180kI
150kI
100kI
31
34 33
20
21 MINUS SIGN
RUN
HOLD
37
35
36
26
1
IN HI
2-19
22-25
PDL
BP
TEST
HOLD
REF HI
V
+
V
-
IN LO
COMMON
BUFF
A/Z
INT
30
32
28
29
39 38 40
50pF
27