# CD4543 BCD to 7-segment decoder: specs and pinout

> A CMOS BCD-to-seven-segment latch/decoder/driver for LCD displays that can also drive LEDs. It has a latch input, a blanking input and a phase input…

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A CMOS BCD-to-seven-segment latch/decoder/driver for LCD displays that can also drive LEDs. It has a latch input, a blanking input and a phase input that selects common-cathode or common-anode LEDs or an LCD backplane signal.

Every value cites its sourceOfficial pinout

[Buy on Compoden](https://compoden.com/products/cd4543-bcd-to-7-segment-decoder-ic-dip-16-package)

## Specs

| Spec | Value | Source |
|---|---|---|
| Supply voltage VDD | 3 V to 18 V recommended; absolute maximum -0.5 V to +20 V | source Recommended Operating Conditions, p.2; Maximum Ratings, p.1 |
| Input logic levels | VIH 3.5 V min and VIL 1.5 V max at VDD 5 V; 7 V and 3 V at 10 V | source Static Electrical Characteristics, p.3 |
| Output sink current | IOL 0.51 mA min (1 mA typ) at VO 0.4 V, VDD 5 V; 1.3 mA min at VDD 10 V, 25 C | source Static Electrical Characteristics, p.3 |
| Output source current | IOH -0.37 mA min (-0.75 mA typ) at VO 4.6 V, VDD 5 V; -0.8 mA min at VDD 10 V, 25 C | source Static Electrical Characteristics, p.3 |
| Quiescent current | 0.04 uA typ, 5 uA max at VDD 5 V, 25 C | source Static Electrical Characteristics, p.3 |
| Latch disable LD | LD high: outputs follow the BCD input; LD low: latches the last code | source Truth Table, p.5 |
| Blanking BI | BI high blanks all segments; codes 10 to 15 also display blank | source Truth Table, p.5 |
| Phase Ph | Ph = 0 for common-cathode LED readouts; Ph = 1 for common-anode; square wave for LCD readouts | source Truth Table and Description, p.1 and p.5 |
| Propagation delay | 600 ns typ (1200 ns max) high-to-low at VDD 5 V, 50 pF | source Dynamic Electrical Characteristics, p.4 |
| Operating temperature | -55 C to +125 C | source Maximum Ratings, p.1 |

## Power

| | Value | Source |
|---|---|---|
| Supply | VDD 3-18 V | source Recommended Operating Conditions p.2; Static Electrical Characteristics p.3 |
| Current | 0.04 uA typ quiescent at VDD 5 V (display current not included) | source Recommended Operating Conditions p.2; Static Electrical Characteristics p.3 |

## Pinout

This is a bare logic IC, not a module.

| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| LATCH DISABLE (1) | Latch input | high = transparent, low = hold | | source Terminal assignment p.1; Truth Table p.5 |
| C (2), B (3), D (4), A (5) | BCD data inputs | VIH 3.5 V min at VDD 5 V | A is the least significant bit, D the most | source Terminal assignment p.1; Truth Table p.5 |
| PHASE (6) | Phase input | 0 common-cathode, 1 common-anode | | source Terminal assignment p.1; Truth Table p.5 |
| BLANKING (7) | Blanking input | high = blank | | source Terminal assignment p.1; Truth Table p.5 |
| VSS (8) | Ground | | | source Terminal assignment, p.1 |
| a (9), b (10), c (11), d (12), e (13), g (14), f (15) | Seven-segment outputs | | Pin order as drawn on the terminal assignment diagram and Fig. 1 | source Terminal assignment p.1; Fig. 1 p.2 |
| VDD (16) | Supply | 3-18 V | | source Terminal assignment, p.1 |

## Build with it
Project ideas for the CD4543 BCD to 7-segment decoder. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.

- [BCD to segment tester](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20BCD%20to%20seven-segment%20tester%20that%20shows%20what%20the%20decoder%20outputs%20using%20an%20Uno%20and%20a%20CD4543%20chip): The Uno 5 V logic suits a VDD of 5 V; Ph is set to 0 for common-cathode style. Outputs are weak at 5 V (0.37-0.51 mA min), so use LEDs as dim indicators or add BC547 buffers.
- [Push-button counter display](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20push-button%20counter%20with%20a%20segment%20display%20using%20a%20CD4518%20counter%20and%20a%20CD4543%20decoder): The counter's BCD outputs feed the decoder directly; both are CMOS on the same VDD. The CD4518 counts in BCD (0 to 9), and the decoder blanks codes 10 to 15. Use a common-cathode display with Ph set to 0, one series resistor per segment from the resistor pack, and the breadboard supply set to 5 V for both chips. Outputs are weak at 5 V, so the display will be dim. A push button into the counter may bounce and count twice.
- [Segment driver with transistor buffers](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20seven-segment%20driver%20that%20lights%20bright%20LED%20segments%20using%20a%20CD4543%20and%20BC547%20transistors): A BC547 per segment (hFE 110 min) turns the decoder's sub-milliamp output into LED current; keep each segment well under the transistor's 100 mA limit. Use a common-cathode display with Ph set to 0; power the chips and display from the Uno 5 V pin, with series resistors from the resistor pack for the base of each BC547 and each segment.

## Common mistakes

- Connecting 3.3 V logic to a 5 V CD4543: at VDD 5 V the input high level is 3.5 V minimum, so a 3.3 V output does not meet it ([source](https://www.ti.com/lit/ds/symlink/cd4543b.pdf))
- Expecting strong LED drive at 5 V: the outputs sink 0.51 mA min and source 0.37 mA min at VDD 5 V, so a bare LED segment will be dim; use higher VDD or buffer transistors ([source](https://www.ti.com/lit/ds/symlink/cd4543b.pdf))
- Wrong Ph setting: Ph must be 0 for common-cathode LED displays and 1 for common-anode; an LCD needs a square wave on Ph and the backplane ([source](https://www.ti.com/lit/ds/symlink/cd4543b.pdf))

## Not covered by the official source

- The TI PDF is a scanned datasheet; values are from pages 1-5.

## Sources

- [link](https://www.ti.com/lit/ds/symlink/cd4543b.pdf) (TI/Harris CD4543B, SCHS086D, April 2004; maker)