ICL7104-14CPL Intersil, ICL7104-14CPL Datasheet - Page 10

• Manufacturer Part Number: ICL7104-14CPL
• Description: 14 BIT A/D CONVERTER
• Manufacturer: Intersil

Specifications of ICL7104-14CPL

• Rohs Status: RoHS non-compliant
• Other names: NT5018

Buffer Gain
At the end of the auto-zero interval, the instantaneous noise
voltage on the auto-zero capacitor is stored, and subtracts from
the input voltage while adding to the reference voltage during
the next cycle. The result is that this noise voltage effectively is
somewhat greater than the input noise voltage of the buffer
itself during integration. By introducing some voltage gain into
the buffer, the effect of the auto-zero noise (referred to the
input) can be reduced to the level of the inherent buffer noise.
This generally occurs with a buffer gain of between 3 and 10.
Further increase in buffer gain merely increases the total offset
to be handled by the auto-zero loop, and reduces the available
buffer and integrator swings, without improving the noise per-
formance of the system. The circuit recommended for doing
this with the ICL8068/ICL7104 is shown in Figure 7. With care-
ful layout, the circuit shown can achieve effective input noise
voltages on the order of 1 to 2µV, allowing full 16-bit use with
full scale inputs of a low as 150mV. Note that at this level, ther-
moelectric EMFs between PC boards, IC pins, etc., due to local
temperature changes can be very troublesome. For further dis-
cussion, see Application Note AN030.
Full scale V
Buffer Gain
R
C
C
C
V
Resolution
REF
INT
INT
AZ
REF
ICL7104-16 POL
ICL7104-14
ICL8052/8068 WITH
-AN
I/P
IN
TABLE 4. TYPICAL COMPONENT VALUES (V++ = +15V, V+ = 5V, V- = 5V, V- = -15V, f
9
C
8
-
3
REF
+
6
7
HBEN
O/R
2
4
POL
B16
TABLE 3. THREE-STATE BYTE FORMATS AND ENABLE PINS
V
BUFFER
REF
+
-
B15
O/R
A1
B14
B14
0.33
200
100
100
R
3.1
10
10
1
INT
FIGURE 6D. PHASE III DEINTEGRATE
B13
B13
INTEGRATOR
MBEN
HBEN
+
-
A2
C
C
AZ
B12
B12
INT
ICL7104-16
ICL7104
1
0.33
800
400
43
12
1
1
1
B11
B11
10
COMP.
+
-
A3
ICL8052 vs ICL8068
The ICL8052 offers significantly lower input leakage currents
than the ICL8068, and may be found preferable in systems
with high input impedances. However, the ICL8068 has
substantially lower noise voltage, and for systems where
system noise is a limiting factor, particularly in low signal
level conditions, will give better performance.
Component Value Selection
For optimum performance of the analog section, care must
be taken in the selection of values for the integrator capaci-
tor and resistor, auto-zero capacitor, reference voltage, and
conversion rate. These values must be chosen to suit the
particular application.
B10
B10
CE/LD
B9
B9
4000
2000
0.33
200
61
1
1
1
CROSS.
ZERO
DET.
B8
B8
B7
B7
POL
100
0.1
6.1
10
47
10
50
1
B6
B6
ICL7104-14
CLOCK
B5
B5
LBEN
LBEN
D
CROSSING
= 200kHz)
ZERO
B4
B4
4000
2000
180
244
F/F
CL
0.1
CL
1
1
1
B3
B3
Q
B2
B2
UNIT
V/V
mV
mV
kΩ
µF
µF
µF
µV
B1
B1