參數(shù)資料
型號： MM74C917
廠商： Fairchild Semiconductor Corporation
英文描述： Simplified Multi-Digit LED Display Controller(多數(shù)字式LED顯示控制器)
中文描述： 簡化的多位LED顯示控制器（多數(shù)字式的LED顯示控制器）
文件頁數(shù)： 7/26頁
文件大?。?/td> 639K
代理商： MM74C917
When a circuit design employs large segment currents, the
maximum dissipation should be calculated to ensure that the
power consumption of the controller or digit driver is within
the maximum limits. The display controller power dissipation:
P
C
= S(I
SEG
) (V
CC
V
SEG
)
where I
and V
are the peak segment current and seg-
ment voltage, as previously determined; and S is the maxi-
mum number of segments lit per digit. The maximum pack-
age dissipation for the controllers vs. temperature is shown
in Figure 13
To gain an understanding of how segment current affects the
controllers power dissipation, Figure 14 plots average and
peak LED segment current vs. package dissipation for both
the MM74C911 and the MM74C912/MM74C917. These typi-
cal curves are plotted using the typical segment driver output
currents and voltages from Figure 8
As the digit driver output voltage V
becomes larger, the
driver dissipates more power, thus the designer should also
ensure that the driver’s dissipation is not exceeded. Gener-
ally, the standard digit driver IC will dissipate around
1
2
W.
(See specific data sheets.) Driver power dissipation can be
calculated by:
P
D
= (V
DO
)(I
DIG
)
where V
and I
are the digit driver output voltage and
current. In a standard digit driver, one output will be active all
the time, but if discrete transistors are used, each transistor
is turned on 25% of the tiime. The average power dissipation
for each discrete transistor digit driver is
1
4
of the above
equation.
B. Common Anode LED Display
Although
connecting
MM74C917 to common anode displays is somewhat more
difficult than to common cathode displays, it can be done.
These controllers still provide all the necessary timing sig-
nals, but some extra buffering must be added to ensure the
correct logic levels and drive capability.
To drive common anode displays, the display controller’s
segment outputs must be inverted and the digit outputs must
be current buffered. Figure 15shows a simple circuit to inter-
face to most common anode displays. An 8-digit calculator
digit driver IC, DS8871, is used to drive the display seg-
the
MM74C911/MM74C912/
Display
Driver
Typical Range of
Segment Resistors
200
–800
300
–1500
*
150
–700
150
–1000
*
5
–50
5
–50
5
–40
Part No.
NSA1298
Height (In.)
0.110
No. of Digits
9
DS75494
NSA1558
0.140
8
DS75494
NSN381
NSB581
NS5931
0.3
0.5
0.5
2
2
6
DS75492
DS75492
DS75492
2N3904
DS75492
2N3904
NSN781
0.7
2
5
–30
FIGURE 11. MM74C912/MM74C917 Segment Resistor for Average Intensity for Various Displays
(
*
Using Red LED Filter over Display)
AN006030-11
AN006030-12
FIGURE 12. Typical Digit Driver Current vs. Output Voltage for (a) MM74C911 (b) MM74C912/MM74C917
7
www.fairchildsemi.com
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MM74C918 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual CMOS 30V Relay Driver
MM74C918J 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual CMOS 30V Relay Driver
MM74C918N 制造商:NATIONAL SEMICONDUCTOR 功能描述:SEMICONDUCTOR INTEGRATED CIRCUIT 制造商:National Semiconductor Corporation 功能描述:SEMICONDUCTOR INTEGRATED CIRCUIT
MM74C922 制造商:NSC 制造商全稱:National Semiconductor 功能描述:16, 20-Key Encoder
MM74C922N 功能描述:編碼器、解碼器、復(fù)用器和解復(fù)用器 16-Key Encoder RoHS:否 制造商:Micrel 產(chǎn)品:Multiplexers 邏輯系列:CMOS 位數(shù): 線路數(shù)量（輸入/輸出）:2 / 12 傳播延遲時間:350 ps, 400 ps 電源電壓-最大:2.625 V, 3.6 V 電源電壓-最小:2.375 V, 3 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Tray
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