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부품번호 | DM9374 기능 |
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기능 | 7-Segment Decoder/Driver/Latch | ||
제조업체 | Fairchild Semiconductor | ||
로고 | |||
전체 8 페이지수
March 1989
Revised March 2000
DM9374
7-Segment Decoder/Driver/Latch
with Constant Current Sink Outputs
General Description
The DM74 is a 7-segment decoder driver incorporating
input latches and output circuits to directly drive common
anode LED displays.
Ordering Code:
Order Number Package Number
Package Description
DM9374N
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Connection Diagram
Logic Symbol
Pin Descriptions
VCC = Pin 16
GND = Pin 8
Pin
Names
A0–A3
LE
RBI
RBO
a –g
Description
Address (Data Inputs)
Latch Enable Input (Active LOW)
Ripple Blanking Input (Active LOW)
Ripple Blanking as Output (Active LOW)
as Input (Active LOW)
Constant Current Outputs (Active LOW)
© 2000 Fairchild Semiconductor Corporation DS010210
www.fairchildsemi.com
http://www.Datasheet4U.com
Applications
It is possible with common anode 7-segment LED displays
and constant current sink decoder drivers to save substan-
tial amounts of power by carefully choosing operating
points on display supply voltage. First, examine the power
used in the normal display driving method where the dis-
play and decoder driver are both operated from a +5.0V
regulated supply (VCC = VS).
The power dissipated by the LED and the driver outputs is
(VCC x Iseg x n Segments). The total power dissipated with
a 15 mA LED displaying an eight (8) would be:
PTOT = 5.0V x 15 mA x 7
= 525 mW
Of this 525 mW, the power actually required to drive the
LED is dependent on the VF drop of each segment. Most
GaAsP LEDs exhibit either a 1.7V or a 3.4V forward volt-
age drop. Therefore, the required total power for seven
segments would be:
P(1.7) = 1.7V x 15 mA x 7
= 178.5 mW
P(3.4)= 3.4V x 15 mA x 7
= 357 mW
The remaining power is dissipated by the driver outputs
which are maintaining the 15 mA constant current required
by the LEDs. Most of this power is wasted, since the driver
can maintain approximately 15 mA with as little as 0.5V
across the output device. By using a separate power
source (VS, Figure 1) for the LEDs, which is set to the LED
VF plus the offset voltage of the driver, as much as 280 mW
can be saved per digit. i.e.,
VS = VF (Max) + Voffset
= 2.0V + 0.5V
= 2.5V
PT= 2.5V x 14 mA (from Figure 6) x 7
= 245 mW
These figures show that using a separate supply to drive
the LEDs can offer significant display power savings. In
battery powered equipment, two rechargeable nickel-cad-
mium cells in series would be sufficient to drive the display,
while four such cells would be needed to operate the logic
units.
Another method to save power is to apply intensity modula-
tion to the displays (Figure 2). It is well known that LED dis-
plays are more efficient when operated in pulse mode.
There are two reasons: one, the quantum efficiency of the
LED material is better; secondly the eye tends to peak
detect. Typically a 20% off duty cycle to displays (GaAsP)
will produce the same brightness as operating under dc
conditions.
FIGURE 1. Separate Supply for LED Displays
All Inverters are DTL 9936 or Open Collector TTL 7405
FIGURE 2. Intensity Control by RBO Pulse Duty Cycle
www.fairchildsemi.com
4
http://www.Datasheet4U.com
4페이지 Switching Characteristics
VCC = +5.0V, TA = +25°C
Symbol
Parameter
tPLH Propagation Delay
tPHL An to a–g
tPLH Propagation Delay
tPHL LE to a–g
Typical Performance Characteristics
CL = 15 pF
RL = 1 kΩ
Min Max
140
140
140
140
Units
ns
ns
FIGURE 5. Output Voltage Safe Operating Area
FIGURE 6. Typical Constant Segment Current
Versus Output Voltage
7 www.fairchildsemi.com
http://www.Datasheet4U.com
7페이지 | |||
구 성 | 총 8 페이지수 | ||
다운로드 | [ DM9374.PDF 데이터시트 ] |
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구매 문의 | 일반 IC 문의 : 샘플 및 소량 구매 ----------------------------------------------------------------------- IGBT, TR 모듈, SCR 및 다이오드 모듈을 포함한 광범위한 전력 반도체를 판매합니다. 전력 반도체 전문업체 상호 : 아이지 인터내셔날 사이트 방문 : [ 홈페이지 ] [ 블로그 1 ] [ 블로그 2 ] |
부품번호 | 상세설명 및 기능 | 제조사 |
DM9374 | 7-Segment Decoder/Driver/Latch | National Semiconductor |
DM9374 | 7-Segment Decoder/Driver/Latch | Fairchild Semiconductor |
DataSheet.kr | 2020 | 연락처 | 링크모음 | 검색 | 사이트맵 |