CD4511 — BCD-to-7-Segment Latch/Decoder/Driver

Overview

The CD4511 (CD4511B / HEF4511B) is a classic BCD-to-7-segment latch/decoder/driver IC manufactured by Texas Instruments, ON Semiconductor, and Renesas. Designed to operate across a wide supply voltage range of 3.0V to 18.0V DC, it incorporates internal bipolar NPN transistor drivers that supply up to 25 mA per segment directly to common-cathode 7-segment LED displays.

Features include 4-bit BCD input latches ( $A, B, C, D$ ), an active-LOW Lamp Test input ( $\overline{LT}$ — lights up all 7 segments for display verification), and an active-LOW Blanking input ( $\overline{BL}$ — turns off all segments for zero-suppression or PWM intensity control).

Quick reference


Supply Voltage (`VDD - VSS`)	3.0 V to 18.0 V DC
Input Format	4-bit BCD ( $A, B, C, D$ — LSB to MSB)
Output Drive	7 Active-HIGH outputs ( $a \dots g$ , up to $25\text{ mA}$ source current per segment at $VDD = 15\text{V}$ )
Display Type	Common-Cathode 7-Segment LED Displays
Control Features	Latch Enable ( $\overline{LE}$ ), Lamp Test ( $\overline{LT}$ ), Blanking ( $\overline{BL}$ )
Package	16-pin DIP / SOIC-16

Pinout (DIP-16 Package)

text

             ┌───┴───┐
          B 1│ 1   16│ VDD (+3V to +18V)
          C 2│       │15 f
        /LT 3│ CD4511│14 g
        /BL 4│       │13 a
        /LE 5│       │12 b
          D 6│       │11 c
          A 7│       │10 d
   VSS(GND) 8│       │9  e
             └───────┘

Pin	Name	Type	Description
1	`B`	Input	BCD Bit 1 Input ( $2^1 = 2$ )
2	`C`	Input	BCD Bit 2 Input ( $2^2 = 4$ )
3	`\LT`	Input	Lamp Test Input (Active LOW: Low = Turn ON all segments $a \dots g$ )
4	`\BL`	Input	Blanking Input (Active LOW: Low = Turn OFF all segments $a \dots g$ )
5	`\LE`	Input	Latch Enable Input (Active LOW: Low = Pass-through; High = Latch BCD data)
6	`D`	Input	BCD Bit 3 Input ( $2^3 = 8$ , MSB)
7	`A`	Input	BCD Bit 0 Input ( $2^0 = 1$ , LSB)
8	`VSS`	Power	Digital Ground (0 V)
9–15	`e, d, c, b, a, g, f`	Output	7-Segment Active-HIGH LED Driver Outputs
16	`VDD`	Power	Positive Power Supply (+3.0V to +18.0V DC)

Application Notes

Current-Limiting Resistors: Always insert $220\ \Omega \dots 1\text{ k}\Omega$ series current-limiting resistors between pins $a \dots g$ and the common-cathode 7-segment display.
Unused BCD inputs ( $A, B, C, D$ ): Tie unused inputs to $V_{SS}$ (GND) or $V_{DD}$ .

Common mistakes

Leaving $\overline{LT}$ or $\overline{BL}$ un-connected: Control pins $\overline{LT}$ and $\overline{BL}$ are active-LOW inputs. Leaving them ungrounded or floating causes blank displays. Tie both $\overline{LT}$ and $\overline{BL}$ to VDD for normal operation.

Notes

CD4511 vs CD4055 / CD4543: CD4511 is designed specifically for active-HIGH common-cathode LED displays; CD4543 is designed with a phase input for driving LCDs and common-anode displays.