hi7131 Intersil Corporation, hi7131 Datasheet - Page 10

• Manufacturer Part Number: hi7131
• Description: 3 1/2 Digit, Low Power, High Cmrr, Lcd/led Display-type A/d Converters
• Manufacturer: Intersil Corporation

HI7131/33 vs ICL7136/37
Figure 5 shows the analog front end block diagram of both
HI7131/33 and ICL7136/37. The difference is the common
reference voltage generator connection and 2 extra analog
switches in the ICL7136. The HI7131 architecture uses the
INLO as the reference point of the integrator (non-inverting
input of the integrator amplifier) in all the phases of the con-
version cycle. The ICL7136 uses INLO as a reference point
only during integration cycle and COMMON pin is used as
the integrator reference point during auto-zero, deintegrate,
and zero integrate phases.
COMMON
COMMON
INLO
INLO
INHI
INHI
31
32
30
31
32
30
C
C
INT
INT
REF
REF
AZ
AZ
34
34
+
+
REFHI
REFHI
FIGURE 93B. ICL7136 AND ICL7137 ANALOG SECTION FUNCTIONAL DIAGRAM
36
FIGURE 93A. HI7131 AND HI7133 ANALOG SECTION FUNCTIONAL DIAGRAM
AZ AND
ZI
AZ AND
ZI
36
DE-
DE+
DE-
DE+
FIGURE 93. HI7131, HI7133 vs ICL7136, ICL7137 ANALOG SECTIONS
INPUT HIGH
INPUT HIGH
C
C
REF
REF
AZ AND
AZ AND
AZ AND DE
DE+
DE-
DE+
DE-
ZI
ZI
35
35
REFLO
REFLO
C
C
33
33
AND ZI
REF
REF
-
+
HI7131, HI7133
-
+
-
-
ZI
ZI
3-1835
28
28
BUFF
BUFF
R
R
INT
INT
The circuit configuration of the HI7131 results in a superior
120dB rejection of DC common mode on the inputs. How-
ever, the HI7131 has reduced AC common mode noise
rejection, since the noise on the INLO input can cause errors
during the deintegration phase.
The circuit configuration of the ICL7136 is unaffected by the
AC noise riding on the inputs, but the DC common mode
rejection on the input is only 86dB.
29
29
A-Z
A-Z
INTEGRATOR
INTEGRATOR
C
C
AZ
AZ
AZ
AZ
+
-
-
+
COMPARATOR
COMPARATOR
27
GENERATOR
GENERATOR
27
INT
INT
V
V
C
C
COMMON
COMMON
INT
INT
+
-
+
-
V +
V +
V+
V+
V -
V
V -
V -
26
-
26
1
1
DETECTOR
DETECTOR
CROSSING
CROSSING
FLIP-FLOP
FLIP-FLOP
POLARITY
POLARITY
ZERO
ZERO
TO
DIGITAL
SECTION
TO
DIGITAL
SECTION