ICL7129 Intersil, ICL7129 Datasheet - Page 10

• Manufacturer Part Number: ICL7129
• Description: 41/2 Digit LCD/ Single-Chip A/D Converter
• Manufacturer: Intersil

A single polarity power supply can be used to power the
ICL7129 in applications where battery operation is not
appropriate or convenient only if the power supply is isolated
from system ground. Measurements must be made with
respect to COMMON or some other voltage within its input
common-mode range.
Voltage References
The COMMON output of the ICL7129 has a temperature
coefficient of 80ppm/
able as a reference voltage for applications where ambient
temperature variations are expected to be minimal. When
the ICL7129 is used in most environments, other voltage ref-
erences should be considered. The diagram in the Typical
Application Schematic and Figure 15 show the ICL8069
1.2V band-gap voltage source used as the reference for the
ICL7129, and the COMMON output as its pre-regulator. The
reference voltage for the ICL7129 is set to 1.000V for both
2V and 200mV full-scale operation.
Multiple Integration A/D Converter
Equations
Oscillator Frequency
Oscillator Period
Integration Clock Period
Integration Period
60/50Hz Rejection Criterion
Optimum Integration Current
Full Scale Analog Input Voltage
f
C
f
or
f
t
t
t
t
OSC
OSC
OSC
OSC
CLOCK
INT(2V)
INT(200mV)
OSC
t
I
V
INT
INT
INFS
= 0.45/RC
(Typ) = 120kHz
= 120kHz Crystal (Recommended)
= 1/f
/t
> 50pF; R
= 13 A
60Hz
= 2
= 1000
(Typ) = 200mV or 2V
OSC
*
ZERO-INTEGRATE
= 10,000
t
OSC
or t
AND LATCH
*
t
INT
OSC
NOTE: Shaded area greatly expanded
in time and amplitude.
CLOCK
/t
o
*
50Hz
C typically. This voltage is only suit-
> 50k
t
CLOCK
= Integer
10,000 CLOCKS
1000 CLOCKS
INTEGRATE
(Range = 1)
(Range = 0)
INT
1
DE-INTEGRATE
CLOCKS
2000
DE
1
ICL7129
3-40
REST X10
Integrate Resistor
Integrate Capacitor
Integrator Output Voltage Swing
Display Count
Minimum V
Common Mode Input Voltage
Auto Zero Capacitor: C
Reference Capacitor: 0.1 F < C
V
Power Supply: Single 9V
Display: Triplexed LCD
Conversion Cycle (In Both Ranges)
COM
INTEGRATOR
(V- + 1V) < V
Biased Between V+ and V-.
V
Regulation lost when V+ to V- < 6.4V.
If V
V
V+ - V- = 9V
Digital supply is generated internally
V
Continuity Output On if
V
t
CYC
COUNT
C INT
V INT
COUNT
COM
COM
GND
INHI
VOLTAGE
RESIDUE
R
R
V
(2V Range)
(200mV Range)
INT
INT
INT
COM
= t
to V
DE
circuit will turn off.
=
Maximum Swing:
=
= V
(Typ) = 150k
CLOCK
V+ - 4.5V
V+ -2.9V
2
1000 CLOCKS
----------------------------------
----------------------------------
REF
=
is externally pulled down to (V+ to V-)/2, the
=
INLO
t INT I INT
t INT I INT
REST X10
INFS
10 000
10 000
C INT
V INT
IN
: 500mV
< 200mV
< (V+ - 0.5V)
x 30,000
/I
INT
---------------- - Range = 1
V REF
V IN 10
---------------------- - Range = 0
V IN
V REF
AZ
DE
3
not used
(V- + 0.5V) < V
ZERO-INTEGRATE
REF
< 1 F
INT
< (V+ - 0.7V)