TC7126CPL Microchip Technology, TC7126CPL Datasheet - Page 15

• Manufacturer Part Number: TC7126CPL
• Description: IC ADC 3 1/2DGT LCD DVR 40-DIP
• Manufacturer: Microchip Technology

Specifications of TC7126CPL

• Display Type: LCD
• Configuration: 7 Segment
• Digits Or Characters: A/D 3.5 Digits
• Current - Supply: 55µA
• Voltage - Supply: 9V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 40-DIP (0.600", 15.24mm)
• Resolution (bits): 3.5bit
• Input Channel Type: Differential
• Data Interface: Parallel
• Supply Voltage Range - Analogue: 9V
• Supply Current: 55µA
• No. Of Pins: 40
• Operating Temperature Range: 0°C To +70°C
• Digital Ic Case Style: DIP
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: TC7126CPLR; TC7126CPLR

7.3
The analog common pin is set at a voltage potential
approximately 3V below V+. The potential is between
2.7V and 3.35V below V+. Analog common is tied inter-
nally to an N-channel FET capable of sinking 100μA.
This FET will hold the common line at 3V should an
external load attempt to pull the common line toward
V+. Analog common source current is limited to 1μA.
Therefore, analog common is easily pulled to a more
negative voltage (i.e., below V+ – 3V).
The TC7126A connects the internal V
inputs to analog common during the auto-zero phase.
During the reference integrate phase, V
nected to analog common. If V
nected to analog common, a Common mode voltage
exists, but is rejected by the converter’s 86dB Common
mode rejection ratio. In battery operation, analog com-
mon and V
mon mode voltage concerns. In systems where V
connected to power supply ground or to a given
voltage, analog common should be connected to V
The analog common pin serves to set the analog sec-
tion reference, or common point. The TC7126A is spe-
cifically designed to operate from a battery, or in any
measurement system where input signals are not refer-
enced (float) with respect to the TC7126A’s power
source. The analog common potential of V+ – 3V gives
a 7V end of battery life voltage. The common potential
has a 0.001%/% voltage coefficient and a 15Ω output
impedance.
With sufficiently high total supply voltage (V+ – V- > 7V),
analog common is a very stable potential with excellent
temperature stability (typically 35ppm/°C). This poten-
tial can be used to generate the TC7126A’s reference
voltage. An external voltage reference will be unneces-
sary in most cases because of the 35ppm/°C tempera-
ture coefficient. See Section 7.5 “TC7126A Internal
Voltage Reference”, TC7126A Internal Voltage
Reference discussion.
7.4
The TEST pin potential is 5V less than V+. TEST may
be used as the negative power supply connection for
external CMOS logic. The TEST pin is tied to the inter-
nally generated negative logic supply through a 500Ω
resistor. The TEST pin load should be no more than
1mA. See Section 5.0 “DIGITAL SECTION”, Digital
Section for additional information on using TEST as a
negative digital logic supply.
I
minus sign will be activated. DO NOT OPERATE IN
THIS MODE FOR MORE THAN SEVERAL MINUTES.
With TEST = V+, the LCD segments are impressed
with a DC voltage which will destroy the LCD.
© 2006 Microchip Technology Inc.
f TEST is pulled HIGH (to V+), all segments plus the
Analog Common (Pin 32)
TEST (Pin 37)
IN
- are usually connected, removing Com-
IN
- is not externally con-
IN
+ and V
IN
- is con-
IN
IN
- is
IN
-.
-
7.5
The TC7126A’s analog common voltage temperature
stability has been significantly improved (Figure 7-3).
The “A” version of the industry standard TC7126 device
allows users to upgrade old systems and design new
systems, without external voltage references. External
R and C values do not need to be changed. Figure 7-4
shows analog common supplying the necessary
voltage reference for the TC7126A.
FIGURE 7-3:
Coefficient
FIGURE 7-4:
Reference Connection
200
180
160
140
120
100
80
60
40
20
0
SET V
TC7126A Internal Voltage
Reference
26
V-
TC7126A
REF
TC7126A
Maximum
COMMON
Typical
9V
ANALOG
= 1/2 V
V
V
+
REF
REF
Analog Common Temp.
TC7126A Internal Voltage
V+
+
REF
1
-
Maximum
36
35
32
Specified
ICL7126
V
TC7126/A
Typical
REF
No
DS21458C-page 15
240kΩ
10kΩ
Maximum
Specified
ICL7136
Typical
No