74145 BCD to Decimal Decoder 5V 7mA IC PDIP-16

74145
BCD to Decimal
Decoder/driver IC PDIP-16

The 74145 is a 4-to-10 (BCD-to-decimal) decoder/driver implemented in Low-Power Schottky (LS) TTL. It decodes a 4-bit BCD input (A, B, C, D) into one active low output among ten (Y0Y9); all outputs are held off for invalid BCD codes. The device integrates pairs of inverters and four-input NAND gates to implement full BCD decoding and uses high-breakdown N-PN output transistors (open-collector) so the outputs can be pulled up to external voltages (the HD74LS145 supports up to 15 V on the off-state outputs), making it suitable to interface directly to indicators, lamp loads or relays when used with appropriate pull-ups.

Because the outputs are open-collector, the HD74LS145
sinks
current rather than sourcing; each output is designed for high low-side drive (sink capability up to 80 mA for heavy indicator/relay drive). Inputs are TTL-level compatible and include clamp diodes for termination/speed control. The device comes in common 16-pin packages (DIP and SOP) and is a drop-in LS replacement for classic 74LS145 parts used in numeric display and driver applications.

Features:

Decodes 4-bit BCD to one-of-ten active-LOW outputs.

Open-collector outputs for high-voltage pull-ups (off-state up to 15 V).

High-breakdown N-PN output transistors designed for indicator/relay driving.

All outputs remain off for invalid BCD inputs (prevents false outputs).

Low-Power Schottky TTL process (TTL input compatibility, faster switching).

Specifications:

Parameter

Symbol

Min

Typ

Max

Unit

Supply voltage (recommended operating):

VCC

5.0

V

Off-state output voltage (allowed pull-up):

VO(off)

15

V

Output low sink current (per output, max):

IOL (max)

80

mA

Output low voltage @ IOL = 12 mA:

VOL

0.4

V

Output low voltage @ IOL = 24 mA:

VOL

0.5

V

Output low voltage @ IOL = 80 mA:

VOL

3.0

V

Off-state output current @ 15 V:

IO(off)

250

A

Input VIH / VIL (TTL levels):

2.0

0.8

V

Supply current (outputs open):

ICC

7

13

mA

propagation delay:

~50

ns

Pinout:

Pin

Name

Description

1

Y0

Decimal output 0 (active LOW, open-collector)

2

Y1

Decimal output 1

3

Y2

Decimal output 2

4

Y3

Decimal output 3

5

Y4

Decimal output 4

6

Y5

Decimal output 5

7

Y6

Decimal output 6

8

GND

Ground

9

Y7

Decimal output 7

10

Y8

Decimal output 8

11

Y9

Decimal output 9

12

D

BCD input D (MSB)

13

C

BCD input C

14

B

BCD input B

15

A

BCD input A (LSB)

16

VCC

+5V supply

Applications:

Driving 10-digit indicator lamps or vacuum/filament indicators.

Driving relay coils or other loads that require a low-side switch (with appropriate pull-ups and flyback protection).

Numerical display multiplexing and legacy display drivers.

Open-collector logic interfacing where one-of-ten decoding is required (industrial counters, scoreboards, selectors).

Packages:

1x 74145 BCD to Decimal Decoder 5V 7mA IC PDIP-16.

Documents:

74145 Datasheet.