Document
TC7126/A
3-1/2 Digit Analog-to-Digital Converters
Features:
• Internal Reference with Low Temperature Drift: - TC7126: 80ppm/°C, Typical - TC7126A: 35ppm/°C, Typical
• Zero Reading with Zero Input • Low Noise: 15VP-P • High Resolution: 0.05% • Low Input Leakage Current: 1pA Typ., 10pA Max. • Precision Null Detectors with True Polarity at Zero • High-Impedance Differential Input • Convenient 9V Battery Operation with Low-Power
Dissipation: 500W Typ., 900W Max.
Applications:
• Thermometry • Bridge Readouts: Strain Gauges, Load Cells,
Null Detectors • Digital Meters and Panel Meters:
- Voltage/Current/Ohms/Power, pH • Digital Scales, Process Monitors
Device Selection Table
Package Code
Package
Temperature Range
CPL IPL CKW CLW
40-Pin PDIP 40-Pin PDIP (TC7126 Only)
44-Pin PQFP 44-Pin PLCC
0C to +70C -25C to +85C 0C to +70C 0C to +70C
General Description:
The TC7126A is a 3-1/2 digit CMOS Analog-to-Digital Converter (ADC) containing all the active components necessary to construct a 0.05% resolution measurement system. Seven-segment decoders, digit and polarity drivers, voltage reference, and clock circuit are integrated on-chip. The TC7126A directly drives a Liquid Crystal Display (LCD), and includes a backplane driver.
A low-cost, high resolution indicating meter requires only a display, four resistors, and four capacitors. The TC7126A’s extremely low-power drain and 9V battery operation make it ideal for portable applications.
The TC7126A reduces linearity error to less than 1 count. Rollover error (the difference in readings for equal magnitude, but opposite polarity input signals) is below ±1 count. High-impedance differential inputs offer 1pA leakage current and a 1012 input impedance. The 15VP-P noise performance ensures a “rock solid” reading, and the auto-zero cycle ensures a zero display reading with a 0V input.
The TC7126A features a precision, low drift internal voltage reference and is functionally identical to the TC7126. A low drift external reference is not normally required with the TC7126A.
2002-2012 Microchip Technology Inc.
DS21458D-page 1
TC7126/A
Package Type
44-Pin PLCC
44-Pin PQFP
A1 B1 C1 D1 V+ NC OSC1 OSC2 OSC3 TEST VREF+ VREF+ VREFCREF+ CREFANALOG COMMON VIN+ VINCAZ VBUFF VINT V-
6 5 4 3 2 1 44 43 42 41 40
F1 7
39 VREF-
G1 8
38 CREF+
E1 9 D2 10 C2 11 NC 12
TC7126CLW TC7126ACLW
37 CREF-
36
ANALOG COMMON
35 VIN+
34 NC
B2 13
33 VIN-
A2 14
32 CAZ
F2 15
31 VBUFF
E2 16
30 VINT
D3 17
29 V-
18 19 20 21 22 23 24 25 26 27 28
44 43 42 41 40 39 38 37 36 35 34
NC 1 NC 2 TEST 3 OSC3 4 NC 5 OSC2 6 OSC1 7 V+ 8 D1 9 C1 10 B1 11
TC7126CKW TC7126ACKW
33 NC 32 G2 31 C3 30 A3 29 G3 28 BP 27 POL 26 AB4 25 E3 24 F3 23 B3
12 13 14 15 16 17 18 19 20 21 22
B3 F3 E3 AB4 POL NC BP G3 A3 C3 G2 A1 F1 G1 E1 D2 C2 B2 A2 F2 E2 D3
40-Pin PDIP (Normal)
V+ 1
D1 2
C1 3
B1 4
1's
A1 5
F1 6
G1 7
E1 8
D2 9
C2 10 B2 11 10's A2 12 F2 13
E2 14
100's
D3 15 B3 16 F3 17
E3 18
1000's
AB4 19
POL 20 (Minus Sign)
Normal Pin
40 OSC1
Configuration 39 OSC2
38 OSC3
37 TEST
36 VREF+
35 VREF-
TC7126CPL 34 CREF+
TC7126ACPL 33 CREF-
TC7126IPL TC7126AIPL
32
ANALOG COMMON
31 VIN+
30 VIN-
29 CAZ
28 VBUFF
27 VINT
26 V-
25 G2
24 C3 23 A3
100's
22 G3
21 BP (Backplane)
44-Pin PDIP (Reverse)
OSC1 1 OSC2 2
40 V+ Reverse Pin Configuration 39 D1
OSC3 3
38 C1
TEST 4
37 B1
VREF+ 5
36 A1 1's
VREF- 6
35 F1
CREF+ 7 TC7126RCPL 34 G1
CREF- 8 TC7126ARCPL 33 E1
ANALOG COMMON
9
VIN+ 10
TC7126RIPL TC7126ARIPL
32 31
D2 C2
VIN- 11 CAZ 12
30 B2 10's
29 A2
VBUFF 13 VINT 14
28 F2 27 E2
100's
V- 15 G2 16 C3 17 A3 18
26 D3 25 B3 24 F3 23 E3
100's
G3 19
22 AB4 1000's
BP 20 (Backplane)
21 POL (Minus Sign)
NC = No Internal Connection
DS21458D-page 2
2002-2012 Microchip Technology Inc.
TC7126/A
Typical Application
+
Analog Input –
1MΩ 0.01μF
180kΩ 0.15μF
0.1μF
TC7126
34
33
TC7126A
CREF+ 31
VIN+
CREF2–19 Segment
22–25 Drive
LCD
30 VIN-
32
ANALOG COMMON
POL BP V+
20 Minus Sign
21
1
Backplane
28 VBUFF
240kΩ
0.33 μF
29 CAZ
27 VINT
VREF+ 36 VREF- 35
V- 26
OSC2 OSC3 OSC1
39 38 COSC 40
10kΩ
+ 9V
1 Conversion/Sec
ROSC 50pF
To Analog Common (Pin 32)
560kΩ
Note: Pin numbers refer to 40-pin DIP.
2002-2012 Microchip Technology Inc.
DS21458D-page 3
TC7126/A
Functional Block Diagram
DS21458D-page 4
Typical Segment Output V+
0.5mA
2mA
Segment Output
LCD
TC7126A
CREF+
CREF
VREF+
VREF-
34 36
35
RINT
CREF- VBUFF
V+
33
28 1
10 μA
31 VIN+
INT
Analog 32 Common
VININT
ZI & AZ
ZI &
–
AZ
+
ZI
DE DE (–) (+)
DE (+) DE (–) AZ & DE (±)
– + V+ – 2.8V
26 V-
Low Temp Co VREF
CAZ
29 Integrator
CINT VINT 27
–
To Digital
+
Section
+
–
AZ
Comparator
Thousands
BP 21
LCD Segment Drivers
7-Segment Decode
7-Segment Decode
7-Segment Decode
¸ 200
Data Latch
Hundreds
Tens
Units
40 OSC1
To Switch Dri.