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SN74LS47N

BCD-to-7seg decoder, active-low, common-anode LED, RBI/RBO, LT, 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 (current-sinking) outputs for driving common-anode LED displays directly, including ripple-blanking and lamp-test functions 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 (5V nominal)
Output Type	Active-low (current sink, open-collector)
Output Sink Current	24mA max per segment
Propagation Delay	100ns typical
Input (BCD)	4-bit binary-coded decimal (A, B, C, D)
Ripple Blanking Input (RBI)	Blanks leading zeros when LOW
Ripple Blanking Output (RBO)	Goes LOW when RBI=LOW and BCD=0
Lamp Test (LT)	Active-low; lights all segments when LOW
Display Type	Common-anode LED displays
Operating Temperature	0°C to +70°C
Package	PDIP-16 (19.3 x 6.35mm)

Features

BCD-to-7-segment decoding for digits 0-9
Active-low outputs for common-anode displays
Direct LED drive: 24mA per segment
Ripple blanking for leading/trailing zero suppression
Lamp test function (all segments ON)
Blanking on invalid BCD codes (10-15)

Applications

7-segment LED display driving
Digital counter/meter displays
Clock and timer displays
Instrumentation readout
Multi-digit display with zero suppression

Product Introduction:SN74LS47N Product Introduction

The SN74LS47N from Texas Instruments is a BCD-to-7-segment decoder/driver designed to drive common-anode LED displays directly. The 4-bit BCD input (A, B, C, D) is decoded into the seven segment outputs (a through g) that drive the display. The active-low (current-sinking) outputs connect to the LED segments through current-limiting resistors; the common anode of the display connects to VCC. The 24mA per-segment sink capability can drive most standard LED displays at full brightness. The ripple-blanking feature suppresses leading or trailing zeros in multi-digit displays: the RBI (ripple-blanking input) of the most significant digit is grounded, and if that digit is 0, all segments are blanked and RBO (ripple-blanking output) goes LOW, which cascades to the next digit’s RBI. The lamp-test (LT) input, when pulled LOW, turns on all seven segments regardless of the BCD input, useful for verifying display function. Invalid BCD codes (10-15) produce blanked or special patterns. The N suffix denotes the PDIP-16 through-hole package.

Working Principle:SN74LS47N Working Principle

The SN74LS47N takes a 4-bit BCD input (D=MSB, A=LSB) and decodes it to activate the appropriate combination of the seven segment outputs (a-g) to display digits 0-9. The outputs are active-low open-collector NPN transistors: when a segment should be lit, the corresponding output transistor turns ON, sinking current from the LED through a current-limiting resistor to ground. For a common-anode display, the LED anodes are connected to VCC, and the cathodes connect to the 74LS47 outputs through resistors. The resistor value sets the LED current: R = (VCC – VLED – VOL) / ILED ≈ (5V – 1.7V – 0.3V) / 10mA = 300Ω. The ripple-blanking logic works as follows: when RBI is LOW and the BCD input is 0000 (digit 0), all segment outputs are turned off (blanked) and RBO goes LOW. This RBO is connected to the RBI of the next-lower digit, cascading the blanking. The most significant digit has its RBI grounded, so if it displays 0, it is blanked and the blanking ripples down. The lamp-test (LT) input overrides all other inputs; when LT is LOW, all segment outputs are ON, illuminating all segments.

Pin Description:SN74LS47N Pin Definition and Functions

Pin	Name	Type	Description
1	B	Input	BCD input B (bit 1)
2	C	Input	BCD input C (bit 2)
3	Lamp Test (LT)	Input	Lamp test (active LOW, all segments ON)
4	RBI	Input	Ripple-blanking input (active LOW)
5	RBO	Output	Ripple-blanking output (active LOW, cascade to next RBI)
6	D	Input	BCD input D (MSB, bit 3)
7	A	Input	BCD input A (LSB, bit 0)
8	GND	Power	Ground
9-15	e,d,c,b,a,g,f	Output	7-segment outputs (active LOW, open-collector)
16	VCC	Power	Supply (4.75V to 5.25V)

Application Scenarios:In which products and applications isSN74LS47N used

4-Digit Counter: 4× 74LS47 + 4× common-anode displays; counter IC feeds BCD; RBI/RBO cascades zero suppression
Clock Display: Hours:minutes; leading zero blanked on tens-of-hours; LT button for display test
DVM Readout: A/D converter BCD output → 74LS47 → display; RBI on MSB blanks leading zeros
Temperature Display: MCU outputs BCD on 4 GPIO pins per digit; 74LS47 decodes to 7-segment
Single Digit: One 74LS47 drives one common-anode display; 300Ω resistors set 10mA per segment

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.