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NTE8374

Integrated Circuit Seven–Segment Latch/Decoder/Driver for Common Anode LED’s

NTE Electronics 

Functional Description:

The NTE8374 is a 7–segment decoder/driver with latches on the address inputs and active LOW

constant current outputs 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 pro-

duces 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 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

input from MOS time clocks, DVMs, calculator chips, etc. Data inputs are multiplexed while the dis-

plays are in static mode. This lowers component and insertion costs, since several circuits–seven

resistors per display, strobe drivers, a separate display voltage source, and clock failure detect cir-

cuits–traditionally found in multiplexed display systems are eliminated. It also allos low strobing rates

to be used without display flicker.

Another NTE8374 feature is the reduced loading on the data inputs when the Latch Enable is HIGH

(only 10µA typ). This allows many NTE8374s to be driven from a MOS device in multiplex mode with-

out the need for drivers on the data lines. The NTE8374 also provides automatic blanking capability

0060.0300 would be displayed 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 RBI input grounded; and since

suppression 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 pro-

vide automatic suppression of trailing–edge zeros. 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 generated for this purpose by forming a variable frequency multivibrator with a cross

coupled pair of TTL or DTL gates.

DC Characteristics: (TA = 0 to +70°C unless otherwise specified)

Parameter

Symbol

Test Conditions

Min Typ Max Unit

Output Voltage, Applied (OFF)

Output LOW Current, a – g

Output HIGH Current, a – g

Power Supply Current

VOUT Separate LED Supply

–

IOL

VCC = 5V, VOL = 3V, TA = +25°C

12

IOH

VCC = Max, VOUT = 5.5V

–

ICC

VCC = Max, VIN = GND, VOUT = 3V –

–

10

V

–

18 mA

– 250 µA

–

50 mA

AC Characteristics: (VCC = +5VTA = +25°C unless otherwise specified)

Parameter

Symbol

Test Conditions

Min Typ Max Unit

Propagation Delay, An to a – g

Propagation Delay, LE to a – g

tPLH, tPHL CL = 15pF, RL = 1kΩ

tPLH, tPHL CL = 15pF, RL = 1kΩ

–

– 140 ns

–

– 140 ns

AC Operating Requirements: (VCC = +5VTA = +25°C unless otherwise specified)

Parameter

Symbol

Test Conditions

Min Typ Max Unit

Setup Time HIGH or LOW, An to LE

Hold Time HIGH or LOW, An to LE

LE Pulse Width LOW

ts (H)

ts (L)

th (H)

th (L)

tw (L)

75

–

30

–

0

–

0

–

85

–

–

ns

–

ns

–

ns

–

ns

–

ns

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