MAX7219Eight-digit serial LED driver

Three control wires. Eight digits. A display that refreshes itself.

Manufacturer-referenced

Analog Devices · MAX7219ENG+

PDIP-2419-4452 · Rev. 6 · August 2021

MAX7219 combines an eight-digit LED driver, display memory and a serial interface in one 24-pin IC. It can control eight common-cathode seven-segment digits or 64 individual LEDs, refreshing the display while the host performs other work. A 16-bit command selects a digit or control register. Code-B decoding handles numbers and a small set of characters; raw segment mode gives direct control of each LED. RSET establishes peak current, while a separate intensity register adjusts PWM brightness. This page uses the industrial-temperature MAX7219ENG+ and MAX7219EWG+ packages with the same pin numbering. The example uses a 5 V host, eight red digits, both ground returns and local bypass capacitors. The MAX7219 clocks data regardless of LOAD, so it must not be treated as a MAX7221 with a clock-gating chip select.

Real View

MAX7219ENG+ black PDIP-24 package with silver contacts and readable marking.

Pinout

MAX7219PDIP-24Top view

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24Physical pins MAX7219ENG+PDIP-24 Manufacturer-referencedAnalog Devices

Pin diagram

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Package map

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MAX7219PDIP-24Top view

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PIN 1 · Serial controls

DIN

Input

Function

Accepts serial data on each rising CLK edge.

How to connect

Connect to a 5 V host MOSI output.

Electrical note

A guaranteed HIGH requires at least 3.5 V; use level translation with a 3.3 V host.

Key specifications

Eight display bytes remain in internal RAM. A scan engine selects one digit at a time, and the segment drivers supply the requested anodes. Brightness combines the RSET current setting with intensity PWM.

Display capacity8 digits / 64 LEDs

Operating supply4.0–5.5 V

Serial clock10 MHz maximum

PWM levels16 intensity settings

Operating profile

Supply, signals and operating conditions

MAX7219 operating profile
Parameter	Value	Conditions / notes
Physical package	PDIP-24	24 leads · same pin map
Selected E-grade range	−40 to +85°C	Thermal loading can reduce usable ambient range
Display topology	Common cathode	Segment sources + digit sinks

Package details

MAX7219ENG+ · PDIP-24

Selected package

Selected MAX7219 physical package
Property	Details
Manufacturer	Analog Devices
Part number	MAX7219ENG+
Package	PDIP-24
Connections	24 pins
Mounting	Through-hole
Lead pitch	2.54 mm
Package code	PDIP-24
Thermal reference	See operating and package limits

Supply and logic levels

Recommended operating conditions

Manufacturer specifications 7 parameters

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Parameter	Value	Conditions / notes
V+ operating range	4.0–5.5 V	Example uses regulated 5 V
Input HIGH / LOW	≥3.5 V / ≤0.8 V	DIN, CLK and LOAD; 3.3 V is not a guaranteed HIGH
Shutdown current	150 µA typical	25°C, logic inputs at a supply rail
Display refresh	800 Hz typical at eight digits	500–1300 Hz specified scan range
Selected E temperature grade	−40 to +85°C	C grade is 0–70°C
Bypass capacitors	100 nF ceramic + 10 µF bulk	Close to V+19 and ground
Ground contacts	Pins 4 and 9	Connect both; carry multiplexed display return current

Check power dissipation separately from the temperature grade.

Registers and command words

16 bits, MSB first: address byte then data byte

Manufacturer specifications 8 parameters

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Parameter	Value	Conditions / notes
0x00 · No-op	Data ignored	Use to pass a command through a daisy chain
0x01–0x08 · Digits	One display byte each	Addresses correspond to DIG0–DIG7
0x09 · Decode mode	One bit per digit	1 enables Code B; 0 selects raw segments
0x0A · Intensity	Low nibble 0x0–0xF	16 PWM settings
0x0B · Scan limit	0–7	Selects one through eight scanned digits
0x0C · Shutdown	0=blank / 1=normal	RAM and control contents retained
0x0F · Display test	0=normal / 1=all LEDs	Overrides shutdown and intensity; disable after testing
Unused command bits	D15–D12 ignored	D11–D8 address; D7–D0 data

MAX7219 has no readback register command. DOUT is the serial shift output.

Decode and segment mapping

Digit data is interpreted by the decode mask

Manufacturer specifications 7 parameters

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Parameter	Value	Conditions / notes
Raw D7…D0	DP, A, B, C, D, E, F, G	A set bit lights its segment during that digit slot
Code-B values 0x0–0x9	Numerals 0–9	Lower nibble selects the glyph
Code-B 0xA…0xF	−, E, H, L, P, blank	D4–D6 ignored
Decimal point	D7=1	Independent of Code-B decoding
Raw numeral 8	0x7F	All seven bars on; decimal point off
Raw blank	0x00	All segments off
Decoded blank	0x0F	Use only on Code-B-enabled digits

A raw matrix image needs decode mode 0x00.

Current, PWM and heat

Do not confuse peak and average LED current

Manufacturer specifications 8 parameters

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Parameter	Value	Conditions / notes
Eight-digit example RSET	64.9 kΩ	Near the 63.7 kΩ manufacturer-table value for 10 mA at 2.0 V LED drop
Maximum recommended peak	40 mA per segment	Check LED pulse rating and IC power budget
Minimum RSET	9.53 kΩ	Actual current also depends on LED forward voltage
Intensity code k	PWM duty = (2k+1)/32	k=0…15; applies during each digit slot
Per-LED average at eight digits	Approximately Ipeak × PWM duty / 8	Multiplexing is in addition to intensity PWM
One / two / three digits	Peak ≤10 / 20 / 30 mA	Manufacturer limits individual digit-driver dissipation
Package thermal resistance	PDIP: 75°C/W; SOIC: 85°C/W	Datasheet reference values; board and cooling matter
Current example	10 mA × 15/32 ÷ 8 ≈0.586 mA	Intensity code 7; approximate average per lit LED

Use scan limit for the real display topology; use intensity to dim.

Serial timing and cascading

LOAD is a latch strobe on MAX7219

Manufacturer specifications 7 parameters

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Parameter	Value	Conditions / notes
Serial clock maximum	10 MHz	At least 50 ns HIGH and 50 ns LOW
DIN setup / hold	25 ns / 0 ns	Relative to CLK rising
LOAD HIGH pulse	At least 50 ns	Latch after the last bit
LOAD rise to next CLK rise	At least 50 ns	MAX7219 requirement
DOUT progression	16.5 clock cycles behind DIN	Updates on falling CLK edges; always driven
Chain connection	DOUT → next DIN	Share CLK and LOAD; send farthest-device word first
MAX7221 distinction	CS gates clocking; outputs slew-limited	Do not assume those behaviors for MAX7219

Use a defined idle clock and latch only after a complete transfer.

Eight-digit startup example

Example values for decoded numbers

Manufacturer specifications 8 parameters

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Parameter	Value	Conditions / notes
Blank during setup	0x0C, 0x00	Shutdown while configuring
Disable test	0x0F, 0x00	Avoid the all-on override
Enable Code B	0x09, 0xFF	All eight digits decoded
Select eight digits	0x0B, 0x07	DIG0 through DIG7
Set moderate PWM	0x0A, 0x07	15/32 slot duty
Initialize display RAM	0x01…0x08 with 0x0F	Blank every decoded digit
Write a zero on DIG0	0x01, 0x00	Use 0x80 to include its decimal point
Enable display	0x0C, 0x01	Normal scanning begins

Commands are two bytes each, followed by LOAD rising.

Connections by function

Select a pin for its function, connection guidance and electrical notes.

Serial controls4 pins

Digit cathodes8 pins

Ground2 pins

Segment anodes8 pins

Current setting1 pin

Supply1 pin

MAX7219 working principle: illustrated functional stages, basic circuit and connections — Select the diagram to read it at full resolution.

How it works

3 stages · Explore one step at a time

Step 1 / 3

Wire the display by function

Segment anodes share A–G/DP buses; each digit has its own common cathode.

Step 2 / 3

Load bytes through DIN and CLK

Send address then data, MSB first, and latch with LOAD rising.

Step 3 / 3

Scan and dim in hardware

RAM preserves the pattern while internal scanning and PWM drive the LEDs.

MAX7219 narrow 24-pin IC connected to a 5 V microcontroller and eight common-cathode digits, with 64.9 kohm ISET resistor and supply bypass capacitors. — Matching net names connect. Segment buses are eight separate wires; digit buses are eight separate returns.

Connect it, step by step

Follow the component values and pin connections

Power and bypass

Use both ground pins and place 100 nF plus 10 µF close to V+.

Connect the digit and segment buses

Use common-cathode displays and map each output by its name.

Configure then enable

Initialize mode, scan limit, RAM and brightness before leaving shutdown.

Compact MAX7219 cutaway with shift register, address decoder, 8 by 8 RAM, Code B bypass, PWM, scan engine and LED drivers. — Original functional illustration, not a transistor-level die schematic.

Explore the circuit

Select a stage to see its role and connections

Receive and latch

CLK shifts the command; LOAD selects the destination register.

Store and decode

Each digit has a RAM byte; Code B can be enabled individually.

Drive the display

RSET controls peak segment current; scanning selects digit cathodes.

Selected packagePDIP-24MAX7219ENG+

Physical connections24 pinsPackage-specific numbering

Reference collection7 tables45 parameters & pin functions