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参数资料
| 型号： | TC7107CKW |
| 元件分类： | ADC |
| 英文描述： | 1-CH DUAL-SLOPE ADC, PQFP44 |
| 封装： | PLASTIC, QFP-44 |
| 文件页数： | 8/26页 |
| 文件大小： | 623K |
| 代理商： | TC7107CKW |
TC7106/A/TC7107/A
DS21455B-page 16
2002 Microchip Technology Inc.
9.0
POWER SUPPLIES
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).
FIGURE 9-1:
GENERATING NEGATIVE
SUPPLY 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
of the Common mode range of the converter.
The signal is less than ±1.5V.
An external reference is used.
The TSC7660 DC to DC converter may be used to gen-
erate -5V from +5V (Figure 9-2).
FIGURE 9-2:
NEGATIVE POWER
SUPPLY GENERATION
WITH TC7660
9.1
TC7107 Power Dissipation
Reduction
The TC7107A sinks the LED display current and this
causes heat to build up in the IC package. If the inter-
nal voltage reference is used, the changing chip tem-
perature can cause the display to change reading. By
reducing the LED common
anode voltage, the
TC7107A package power dissipation is reduced.
Figure 9-3 is a curve tracer display showing the rela-
tionship between output current and output voltage for
a typical TC7107CPL. Since a typical LED has 1.8 volts
across it at 7mA, and its common anode is connected
to +5V, the TC7107A output is at 3.2V (point A on
Figure 9-3). Maximum power dissipation is 8.1mA x
3.2V x 24 segments = 622mW.
FIGURE 9-3:
TC7107 OUTPUT
CURRENT VS. OUTPUT
VOLTAGE
Notice, however, that once the TC7107A output voltage
is above two volts, the LED current is essentially con-
stant as output voltage increases. Reducing the output
voltage by 0.7V (point B in Figure 9-3) results in 7.7mA
of LED current, only a 5 percent reduction. Maximum
power dissipation is only 7.7mA x 2.5V x 24 = 462mW,
a reduction of 26%. An output voltage reduction of 1
volt (point C) reduces LED current by 10% (7.3mA) but
power dissipation by 38% (7.3mA x 2.2V x 24 =
385mW).
Reduced power dissipation is very easy to obtain.
Figure 9-4 shows two ways: either a 5.1 ohm, 1/4 watt
resistor or a 1 Amp diode placed in series with the dis-
play (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 Figure 9-4. When
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.”
In addition to limiting maximum power dissipation, the
resistor reduces the change in power dissipation as the
display changes. This effect is caused by the fact that,
as fewer segments are “ON,” each “ON” output drops
more voltage and current. For the best case of six seg-
TC7107A
V+
OSC1
OSC2
OSC3
GND
V-
V+
CD4009
0.047
F
1N914
10
F
–
+
V- = -3.3V
GND
VIN-
VIN
VREF+
VREF-
COM
+5V
LED
DRIVE
36
1
35
32
31
30
26
V+
V-
21
TC7660
3
10
F
+
10
F
+
2
8
5
(-5V)
TC7107A
4
VIN+
C
B
A
6.000
7.000
8.000
9.000
10.000
2.00
2.50
3.00
3.50
4.00
Output Voltage (V)
O
u
tput
C
u
rr
ent
(m
A
)
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相关代理商/技术参数 |
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| TC7107CKW713 | 功能描述:LED显示驱动器 w/LED Driver RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
| TC7107CLW | 功能描述:LED显示驱动器 w/LED Driver RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
| TC7107CLW713 | 功能描述:LED显示驱动器 w/LED Driver RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
| TC7107CPL | 功能描述:LED显示驱动器 w/LED Driver RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
| TC7107CPL | 制造商:Microchip Technology Inc 功能描述:Leaded Process Compatible:No |
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