ICL7135_14 Datasheet, PDF (13/15 Pages) Intersil Corporation – 41/2 Digit, BCD Output, A/D Converter

ICL7135
Design Information Summary Sheet
• CLOCK INPUT
The ICL7135 does not have an internal oscillator. It
requires an external clock.
f_CLOCK (Typ) = 120kHz
• CLOCK PERIOD
t_CLOCK = 1/f_CLOCK
• INTEGRATION PERIOD
t_INT = 10,000 x t_CLOCK
• 60/50Hz REJECTION CRITERION
t_INT/t_60Hz or t_INT/t_50Hz = Integer
• OPTIMUM INTEGRATION CURRENT
I_INT = 20μA
• FULL-SCALE ANALOG INPUT VOLTAGE
V_lNFS (Typ) = 200mV or 2V
• INTEGRATE RESISTOR
R_INT = ^V----_I-^I-_I-^NN----^F-_T--^S--
• INTEGRATE CAPACITOR
C_INT = ⁽---^t--^I--^N---_V-^T---_I-⁾-_N-⁽--^I-_T-^I--^N----^T----⁾
• INTEGRATOR OUTPUT VOLTAGE SWING
V_INT = ⁽---^t--^I--^N---_C-^T---_I-⁾-_N-⁽--^I-_T-^I--^N----^T----⁾
• V_INT MAXIMUM SWING:
(V- + 0.5) < V_INT < (V+ - 0.5V)
V_INT Typically = 2.7V
Typical Integrator Amplifier Output Waveform (INT Pin)
• DISPLAY COUNT
COUNT = 10, 000 × _V----^V-_R---^I--_EN----_F--
• CONVERSION CYCLE
t_CYC = t_CL0CK x 40002
when f_CLOCK = 120kHz, t_CYC = 333ms
• COMMON MODE INPUT VOLTAGE
(V- + 1V) < V_lN < (V+ - 0.5V)
• AUTO-ZERO CAPACITOR
0.01μF < C_AZ < 1μF
• REFERENCE CAPACITOR
0.1μF < C_REF < 1μF
• POWER SUPPLY: DUAL ±5V
V+ = +5V to GND
V- = -5V to GND
• OUTPUT TYPE
4 BCD Nibbles with Polarity and Overrange Bits
There is no internal reference available on the ICL7135. An
external reference is required due to the ICL7135’s 4¹/₂
digit resolution.
AUTO ZERO PHASE
(COUNTS)
30001 - 10001
INTEGRATE
PHASE FIXED
10000 COUNTS
DE-INTEGRATE PHASE
1 - 20001 COUNTS
TOTAL CONVERSION TIME = 40002 x t_CLOCK
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FN3093.4