TC7116CPL Microchip Technology Inc., TC7116CPL Datasheet - Page 8

• Manufacturer Part Number: TC7116CPL
• Description: 3-1/2 DIGIT A/D, W/ HOLD
• Manufacturer: Microchip Technology Inc.

Specifications of TC7116CPL

• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

TC7116/A/TC7117/A
3.0
(All Pin Designations Refer to 40-Pin PDIP.)
3.1
Figure 3-1 shows the block diagram of the analog sec-
tion for the TC7116/TC7116A and TC7117/TC7117A.
Each measurement cycle is divided into three phases:
(1) Auto-Zero (AZ), (2) Signal Integrate (INT), and
(3) Reference Integrate (REF), or De-integrate (DE).
3.1.1
High and low inputs are disconnected from the pins and
internally shorted to analog common. The reference
capacitor is charged to the reference voltage. A feed-
back loop is closed around the system to charge the
auto-zero capacitor (C
ages in the buffer amplifier, integrator, and comparator.
FIGURE 3-1:
3.1.3
The final phase is reference integrate, or de-integrate.
Input low is internally connected to analog common
and input high is connected across the previously
charged reference capacitor. Circuitry within the chip
ensures that the capacitor will be connected with the
correct polarity to cause the integrator output to return
to zero. The time required for the output to return to
zero is proportional to the input signal. The digital
reading displayed is:
EQUATION 3-1:
DS21457C-page 8
Common
Analog
DETAILED DESCRIPTION
Analog Section
V
V
IN
AUTO-ZERO PHASE
REFERENCE INTEGRATE PHASE
IN
+
-
32
31
30
V+
C
REF
1000 =
10μA
INT
AZ
INT
AZ
+
Analog Section of TC7116/TC7116A and TC7117/TC7117A
) to compensate for offset volt-
34
V
V
DE (+)
REF
V
REF
IN
36
DE
(–)
+
AZ
AZ & DE (±)
C
REF
DE (–)
DE
(+)
C
REF
33
AZ
-
V-
26
–
+
V
BUFF
V+ -3V
–
+
28
R
INT
Temp.
Zener
V
Since the comparator is included in the loop, AZ
accuracy is limited only by system noise. The offset
referred to the input is less than 10μV.
3.1.2
The auto-zero loop is opened, the internal short is
removed, and the internal high and low inputs are
connected to the external pins. The converter then inte-
grates the differential voltages between V
for a fixed time. This differential voltage can be within a
wide Common mode range: 1V of either supply. How-
ever, if the input signal has no return with respect to the
converter power supply, V
common to establish the correct Common mode
voltage. At the end of this phase, the polarity of the
integrated signal is determined.
Low
Drift
3.1.4
The positive reference voltage (V
analog common.
V+
REF
35
29
Auto-Zero
C
AZ
SIGNAL INTEGRATE PHASE
REFERENCE
Integrator
–
+
TC7116A
TC7117A
Comparator
TC7116
TC7117
27
V
C
INT
INT
+
© 2006 Microchip Technology Inc.
IN
- can be tied to analog
REF
Section
+) is referred to
Digital
To
IN
+ and V
IN
-