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ICL7139CPL Datasheet PDF : 13 Pages
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ICL7139, ICL7149
Reference Voltage Source
A voltage divider connected to V+ and Common is the sim-
plest source of reference voltage. While minimizing external
component count, this approach will provide the same volt-
age tempco as the ICL7139 and ICL7149 Common - about
100PPM/oC. To improve the tempco, an ICL8069 bandgap
reference may be used (see Figure 13). The reference volt-
age source output impedance must be ≤ RDElNT/4000.
V+
10M
10K
10M
ICL8069
10K 1M
TRIPLE POINT
EXTERNAL
DEINTEGRATE
REFERENCE
INTEGRATE VOLT/Ω
INTEGRATE CURRENT
REFERENCE INPUT
ANALOG COMMON
Applications, Examples, and Hints
A complete autoranging 33/4 digit multimeter is shown in
Figure 14. The following sections discuss the functions of
specific components and various options.
Meter Protection
The ICL7139 and ICL7149 and their external circuitry should
be protected against accidental application of 110/220V AC
line voltages on the Ω and current ranges. Without the nec-
essary precautions, both the ICL7139 and ICL7149 and their
external components could be damaged under such fault
conditions. For the current ranges, fast-blow fuses should be
used between S5A in Figure 14 and the 0.1Ω and 9.9Ω
shunt resistors. For the Ω ranges, no additional protection
circuitry is required. However, the 10kΩ resistor connected
to pin 7 must be able to dissipate 1.2W or 4.8W for short
periods of time during accidental application of 110V or
220VAC line voltages respectively.
FIGURE 13. EXTERNAL VOLTAGE REFERENCE CONNECTION
TO ICL7139 AND ICL7149
10MΩ
3.3nF
0.1µF
120kHz
CRYSTAL
13 14 15 21 22
INPUTS
V/Ω
S4A
A
S5A
TRIPLE CAZ CINT OSC OSC
9 POINT
OUT IN
DEINT
10MΩ 12
INT (V/Ω)
V
Ω
10kΩ 7
DISPLAY 1-3
DRIVE 23-40
OUTPUTS
LOΩ
A
1MΩ 8
HIΩ
µA
1MΩ 11
INT (I)
16
BEEPER
4
mA
9.9Ω
V+
ICL7139
ICL7149
+
1µF
LO BAT
AC
mAVµA
kΩMΩ
BEEPER
+
9V
BATTERY
-
PIN 4
10kΩ
COMMON
30K-
50K
0.1Ω
2W
V+ µA V+
V-
V
Ω
A S4B
mA
10
COMMON
18
V/Ω/A
17
mA/µA
5
V-
6
VREF
19
HIΩ-DC/LOΩ-AC
20
HOLD
ON/OFF S1
S3
V+
S3
V+
4.7µF +
10kΩ
TANT
ICL8069
PIN 10
S2 CLOSED: HIΩ-DC
S3 CLOSED: HOLD READING
NOTES:
1. Crystal is a Statek or SaRonix CX-IV type.
2. Multimeter protection components have not been shown.
3. Display is from LXD, part number 38D8R02H (or Equivalent).
4. Beeper is from muRata, part number PKM24-4A0 (or Equivalent).
FIGURE 14. BASIC MULTIMETER APPLICATION CIRCUIT FOR ICL7139 AND ICL7149
3-44
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