DM9374N Fairchild Semiconductor, DM9374N Datasheet - Page 3

• Manufacturer Part Number: DM9374N
• Description: IC DECODER/DRVR/LATCH 7SEG 16DIP
• Manufacturer: Fairchild Semiconductor
• Series: 7400r

Specifications of DM9374N

• Display Type: LED
• Configuration: 7 Segment
• Current - Supply: 50mA
• Voltage - Supply: 4.75 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 16-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -
• Digits Or Characters: -
• Other names: DM9374

Functional Description
The DM9374 is a 7-segment decoder/driver with latches on
the address inputs and active LOW constant current out-
puts to drive LEDs directly. This device accepts a 4-bit
binary code and produces output drive to the appropriate
segments of the 7-segment display. It has a decode format
which produces numeric codes “0” through “9” and other
codes.
Latches on the four data inputs are controlled by an active
LOW Latch Enable, LE. When LE is LOW, the state of the
outputs is determined by the input data. When LE goes
HIGH, the last data present at the inputs is stored in the
latches and the outputs remain stable. The LE pulse width
necessary to accept and store data is typically 50 ns, which
allows data to be strobed into the DM9374 at normal TTL
speeds. This feature means that data can be routed
directly from high speed counters and frequency dividers
into the display without slowing down the system clock or
providing intermediate data storage.
The latch/decoder combination is a simple system which
drives LED displays with multiplexed data inputs from MOS
time clocks, DVMs, calculator chips, etc. Data inputs are
multiplexed while the displays are in static mode. This low-
ers component and insertion costs, since several circuits—
seven resistors per display, strobe drivers, a separate dis-
play voltage source, and clock failure detect circuits—tradi-
tionally
Logic Diagram
found
in
multiplexed
display
systems
are
3
eliminated. It also allows low strobing rates to be used with-
out display flicker.
Another DM9374 feature is the reduced loading on the
data inputs when the Latch Enable is HIGH (only 10 A
typ). This allows many DM9374s to be driven from a MOS
device in multiplex mode without the need for drivers on
the data lines. The DM9374 also provides automatic blank-
ing of the leading and/or trailing-edge zeroes in a multidigit
decimal number, resulting in an easily readable decimal
display conforming to normal writing practice. In an 8-digit
mixed integer fraction decimal representation, using the
automatic blanking capability 0060.0300 would be dis-
played as 60.03. Leading-edge zero suppression is
obtained by connecting the Ripple Blanking Output (RBO)
of a decoder to the Ripple Blanking Input (RBI) of the next
lower stage device. The most significant decoder stage
should have the RIB input grounded; and since suppres-
sion of the least significant integer zero in a number is not
usually desired, the RBI input of this decoder stage should
be left open. A similar procedure for the fractional part of a
display will provide automatic suppression of trailing-edge
zeroes. The RBO terminal of the decoder can be OR-tied
with a modulating signal via an isolating buffer to achieve
duration intensity modulation. A suitable signal can be gen-
erated for this purpose by forming a variable frequency
multivibrator with a cross coupled pair of TTL or DTL gates.
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