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SN74LS47N

BCD-to-7-segment decoder, active-LOW, common-anode, PDIP-16

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Manufacturer Part：

SN74LS47N

Package：

PDIP-16 (19.3 x 6.35 x 4.57mm, 2.54mm pitch, through-hole)

Brand：

Product Categories：

Integrated Circuits ICs, Interface ICs

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Description

Product Overview

The SN74LS47N from Texas Instruments is a BCD-to-7-segment decoder/driver with active-LOW outputs for common-anode LED displays, featuring ripple blanking for leading-zero suppression in a 16-pin PDIP package.

Key Specifications

Function	BCD-to-7-segment decoder/driver
Logic Family	LS (Low-power Schottky)
Supply Voltage	4.75V to 5.25V
Output Type	Active-LOW (for common-anode displays)
Output Sink Current	24mA per segment
Lamp Test (LT)	Active LOW (all segments on)
RBI/RBO	Ripple blanking in/out for leading-zero suppression
Operating Temperature	0°C to +70°C
Package	PDIP-16 (19.3 x 6.35mm)

Features

Drives common-anode 7-segment LED displays
24mA output sink current per segment
Ripple blanking for leading-zero suppression
Lamp test for display verification
Invalid BCD (10-15) displays unique patterns

Applications

Common-anode LED display driver
Digital panel meter display
Counter display system
Clock and timer displays

Product Introduction:SN74LS47N Product Introduction

The SN74LS47N from Texas Instruments is a BCD-to-7-segment decoder/driver with active-LOW (current-sinking) outputs designed to drive common-anode LED displays. In a common-anode display, the anodes of all LED segments connect to VCC, and each segment turns on when its cathode is pulled LOW. The 7447’s active-LOW outputs sink current through the segment, lighting it up. External current-limiting resistors (typically 330Ω at 5V) are required on each segment output. The 24mA sink capability provides adequate brightness for most indoor LED displays. The Ripple Blanking Input (RBI) and Output (RBO) allow automatic leading-zero suppression: when RBI is LOW and the BCD input is 0000, all segments are blanked AND RBO goes LOW, which can drive the RBI of the next lower digit. This causes leading zeros to be blanked automatically (005 displays as ‘ 5’). The N suffix denotes the PDIP-16 through-hole package.

Working Principle:SN74LS47N Working Principle

The SN74LS47N accepts a 4-bit BCD input (D,C,B,A) and decodes it into 7 active-LOW segment outputs (a-g). For BCD inputs 0-9, the segment outputs activate the appropriate pattern on a common-anode display. For inputs 10-15 (invalid BCD), unique patterns are displayed (not blank — the 7446/7447 displays patterns for 10-15, unlike the CD4511 which blanks them). The Lamp Test (LT, active LOW) overrides all other inputs and turns all segments on simultaneously — useful for verifying display integrity. The Blanking Input (BI, active LOW) forces all segments off — this can be used for display blanking or intensity modulation (PWM on BI). The Ripple Blanking Input (RBI) is used for leading-zero suppression: when RBI=LOW, LT=HIGH, and BCD input=0000, all segments are blanked AND RBO goes LOW. For a 3-digit display: connect the hundreds RBI to GND; hundreds RBO to tens RBI; tens RBO to units RBI. This blanks leading zeros: 007 displays as ‘ 7′, 070 displays as ’70’, 700 displays as ‘700’. Note: the units digit should never be blanked, so connect its RBI to VCC or leave it unconnected with a pull-up.

Pin Description:SN74LS47N Pin Definition and Functions

Pin	Name	Type	Description
1	B	Input	BCD input B (2^1)
2	C	Input	BCD input C (2^2)
3	LT	Input	Lamp test (active LOW, all segments on)
4	BI/RBO	I/O	Blanking input / Ripple blanking output
5	RBI	Input	Ripple blanking input (active LOW)
6	D	Input	BCD input D (MSB)
7	A	Input	BCD input A (LSB)
8	GND	Power	Ground
9	e	Output	Segment e (active LOW)
10	d	Output	Segment d (active LOW)
11	c	Output	Segment c (active LOW)
12	b	Output	Segment b (active LOW)
13	a	Output	Segment a (active LOW)
14	g	Output	Segment g (active LOW)
15	f	Output	Segment f (active LOW)
16	VCC	Power	Supply (5V)

Application Scenarios:In which products and applications isSN74LS47N used

4-Digit Display: 4× 7447; each driven by counter BCD output; 330Ω resistors on segment outputs; common-anode displays; RBI/RBO for leading zero blanking
Digital Clock: Hours and minutes from counter chain → BCD → 7447 → common-anode display; RBI suppresses leading zero in hours
Panel Meter: ADC BCD output → 7447 → display; LT pin for display test; BI for blanking during update

Alternative Models:What chips are recommended as replacements for SN74LS47N

Model	Manufacturer	Key Difference	Package	Supply
74LS47N	TI/Nexperia	Original TTL version with 5V-only supply, typical propagation delay 10-15ns	DIP-16	5V TTL
74LS47D	TI/Nexperia	Surface-mount SOIC version of LS with identical logic function	SOIC-16	5V TTL
74HC47D	TI/Nexperia	CMOS version with wide 2-6V supply range, lower power consumption and higher noise immunity	SOIC-16	2-6V CMOS
74HC47N	TI/Nexperia	Through-hole DIP version of HC family for prototyping and repair	DIP-16	2-6V CMOS
74HCT47D	TI/Nexperia	CMOS with TTL-compatible input levels, ideal for mixing with LS devices at 5V	SOIC-16	4.5-5.5V TTL-in
74HCT47N	TI/Nexperia	Through-hole DIP version of HCT family for prototyping and repair	DIP-16	4.5-5.5V TTL-in

The 7447 is a BCD-to-7-Segment Decoder/Driver. Family variants span from the original LS TTL (5V only) to modern LVC/AUP (down to 0.8V). HC and HCT versions offer 2-6V CMOS operation with HCT providing TTL-compatible input thresholds for mixed 5V systems. CD4000-series equivalents offer the widest 3-18V supply range at the cost of lower switching speed. DIP packages (N suffix) are through-hole; SOIC (D suffix) and TSSOP are surface-mount.