TC7107CPL Microchip Technology, TC7107CPL Datasheet - Page 18

• Manufacturer Part Number: TC7107CPL
• Description: IC ADC 3 1/2DGT LED DVR 40-DIP
• Manufacturer: Microchip Technology

Specifications of TC7107CPL

• Package / Case: 40-DIP (0.600", 15.24mm)
• Display Type: LED
• Configuration: 7 Segment
• Digits Or Characters: A/D 3.5 Digits
• Current - Supply: 800µA
• Voltage - Supply: 5V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Architecture: Dual Slope
• Input Type: Voltage
• Maximum Power Dissipation: 1230 mW
• Maximum Operating Temperature: + 70 C
• Mounting Style: Through Hole
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 158-1129; 158-1129

TC7106/A/TC7107/A
9.0
The TC7107A is designed to work from ±5V supplies.
However, if a negative supply is not available, it can be
generated from the clock output with two diodes, two
capacitors, and an inexpensive IC
FIGURE 9-1:
From +5V.
In selected applications a negative supply is not
required. The conditions to use a single +5V supply
are:
• The input signal can be referenced to the center
• The signal is less than ±1.5V.
• An external reference is used.
The TSC7660 DC-to-DC converter may be used to
generate -5V from +5V
FIGURE 9-2:
Generation with TC7660.
DS21455D-page 18
10 µF
of the Common mode range of the converter.
TC7107A
+
POWER SUPPLIES
2
4
V-
V+
OSC1
OSC2
OSC3
TC7660
GND
+5V
LED
DRIVE
8
3
V+
+
5
10 µF
TC7107A
Generating Negative Supply
Negative Power Supply
(-5V)
(Figure
V- = -3.3V
V+
V-
1
26
CD4009
V
V
COM
REF +
V
GND
REF -
V
9-2).
IN +
IN
-
(Figure
36
35
32
31
30
21
0.047
µF
9-1).
1N914
1N914
10
µF
V
IN
+
–
9.1
The TC7107A sinks the LED display current and this
causes heat to build up in the IC package. If the internal
voltage reference is used, the changing chip
temperature can cause the display to change reading.
By reducing the LED common anode voltage, the
TC7107A package power dissipation is reduced.
Figure 9-3
relationship between output current and output voltage
for a typical TC7107CPL. Since a typical LED has 1.8
volts across it at 7 mA, and its common anode is
connected to +5V, the TC7107A output is at 3.2V (point
A on
8.1 mA x 3.2V x 24 segments = 622 mW.
FIGURE 9-3:
Output Voltage.
Notice, however, that once the TC7107A output voltage
is above two volts, the LED current is essentially
constant as output voltage increases. Reducing the
output voltage by 0.7V (point B in
7.7 mA of LED current, only a 5 percent reduction.
Maximum power dissipation is only 7.7 mA x 2.5V x 24
= 462 mW, a reduction of 26%. An output voltage
reduction of 1 volt (point C) reduces LED current by
10% (7.3 mA) but power dissipation by 38% (7.3 mA x
2.2V x 24 = 385 mW).
Reduced power dissipation is very easy to obtain.
Figure 9-4
resistor, or a 1A diode placed in series with the display
(but not in series with the TC7107A). The resistor will
reduce the TC7107A output voltage, when all 24
segments are “ON,” to point “C” of
segments turn off, the output voltage will increase. The
diode, on the other hand, will result in a relatively
steady output voltage, around point “B”.
10.000
9.000
8.000
7.000
6.000
Figure
TC7107 Power Dissipation
Reduction
2.00
shows two ways: either a 5.1Ω, 1/4W
is a curve tracer display showing the
9-3). Maximum power dissipation is
C
2.50
B
Output Voltage (V)
TC7107 Output Current vs.
© 2008 Microchip Technology Inc.
3.00
Figure
A
Figure
3.50
9-3) results in
9-4. When
4.00