What is MAX7219 IC : Pin Configuration & Its Working

We know that generally number of LEDs can be controlled through the multiplexing technique. This technique allows you to control 64 LEDs through simply 16 pins. So, there are different methods are available to control the number of LEDs. From that, the MAX7219 Display Driver IC helps in driving several LEDs at a time. This article discusses an overview of MAX7219 IC and its working.

What is MAX7219 Display Driver IC?

MAX7219 IC is a serial input/output common-cathode display driver that is used to connect microprocessors with a 7-segment LED display or 64 individual LEDs or bar-graph displays. It includes multiplex scan circuitry, BCD code-B decoder, segment, digit drivers & an 8×8 stationary RAM that stores every digit. Here segment current of all LEDs can be simply set through one exterior resistor.

A suitable four-wire serial interface is used to connect all common microprocessors. Here separate digits may be addressed &updated exclusive of rewriting the whole display.

MAX7219 IC allows the operator to choose code-B decoding. This LED display driver IC comprises a 150μA low-power blackout mode, control of analog & digital brightness, a scan limit register that permits the operator to exhibit from 1- 8 digits & a test mode that strengthens all LEDs to activate.

MAX7219 IC Pin Configuration

The pin configuration of MAX7219 display driver IC is shown below. This IC includes 24 pins where each pin and its functionality are discussed below.

• Pin1 (DIN): DIN is the serial data i/p pin and this IC includes a 16-bit shift register where on each low to high CLK signal transition, the data can be loaded into this kind of register.
• Pins (2, 3, 5,6,7,8, 10, and 11): These are Digit Pins which are common o/p pins for all the segments of digits 0 to 7. These pins sink current from the display common cathode.
• Pins 4 & 9: These pins are GND pins
• Pin12 (LOAD (CS)): The operation of chip select pin is, for usual operation, is allied to less logic level to CLK data in/out. On the +Ve change of this input, the data can be latched into the CS. After the 16th increasing CLK edge, this input has to go high, or else all the data will be erased.
• Pin13 (CLK): This is the CLK serial i/p pin for the CLK signal. Once CS is low, this signal will be active. On the +Ve edge change of a clock signal, data can be moved into the inside shift register that is exhibited on the DOUT pin at the dropping edge of the CLK signal.
• Pins 14 to 17 & 20, 21 & 23: These pins are segments of digits like SEG_A to SEG_G
• Pin22: This pin is the segment pin for a decimal point like SEG DP
• Pin18 (ISET): This ISET pin is mainly used for setting the o/p current through connecting a resistor on this pin & the other pin is connected to the GND. So this resistor plays a key role in adjusting the current value.
• Pin19 (V+): It is +ve power supply terminal
• Pin24 (DOUT): Serial digital o/p pin

Specifications & Features

The specifications & features of MAX7219 Display Driver IC include the following.

• The range of operating voltage is +4.0 to +5.5V
• The suggested operating voltage is +5V
• Max voltage supply is 6V
• Max current through each pin is 100mA
• Max current through every DIGIT GND pin is 500mA
• Power utilization is low
• Delay Time from Data-to-Segment is 2.2mSec
• Operating temperature ranges from 0°C to +70°C
• Storage Temperature ranges from -65°C to +150°C
• This LED driver display IC through a 10MHz serial interface that allows the operator to choose the No-Decode or decode digit.
• It provides a feature like analog & digital brightness control & a 150µA of shutdown mode where the flow of current in all segments is dragged to GND.
• The utmost current for every section pin is 100mA & for every DIGIT GND pin is 500mA

How to use MAX7219 IC?

The MAX7219 IC is similar to any kind of shift register. The data transmission toward this chip can be done bit by bit. When the data transmission is over then the IC shifts this data into serial data o/p through CS pin. The working of this IC includes different steps.

Initially, pins like DIN, CLK & CS need to connect to control this IC. Choose an appropriate resistor for pin18 to drive the display based on different parameters This IC can be used in two ways by transmitting data in bit by bit form and using libraries

As we have mentioned above regarding the data transmission. This data can be stored within registers till the complete data is received. Once data sending is completed, need to set the CS pin to move all the received data within its register to the o/p.

When the serial data is moved through the IC then it will illuminate the equivalent LEDs to exhibit the result.

A 4-digit Seven Segment LED Display Control with a MAX7219

The following circuit shows how to show numerals over a 4-digit seven-segment display through a MAX7219IC. This IC is an LED display driver with 8-digits, so it connects & controls 8-digits. This circuit is used to control a four-digit seven-segment display. The required components to build this circuit are MAX7219 IC, resistor – 40 kilo-ohm, capacitors- 10μF &100nF, four-digit seven segments LED display.

The MAX7219 IC pinout & its work are already discussed above. This LED display includes 12-pins where the 8pins are used for controlling 8 LEDs on a seven-segment display, which includes A to G & decimal point (DP) & four pins signify each of the four digits from D1to D4.

This IC requires 5V to function, thus we connect both the pins like V+ & pin-19 to 5V whereas the GND pins, pin-4&9 to GND. In the circuit, we connect two capacitors like 100nF & 10μF in parallel to the GND terminal to assist to filter the noise from the power supply & also to confirm the power supply is stable.

All of the segment pins in the circuit can be connected to the equivalent segment over the LED display. Thus Segment A is connected to the A-pin of the LED display. Segment B & C connects to B, C & so on until you fix to segment G & DP to cover 8 connections.

Similar to segment connections, digits can also be connected. Here the Max7219IC digits can be connected to the equivalent digits of the LED display. So, Digit 0 on the MAX IC connects to the 12th pin like D1 of the display. Digit-1 on the MAX IC is connected to the D2 pin. Digit-2 is connected to D3. This IC works through the microcontroller which is connected to a CLK signal.

The instructions are executed on the increasing edge of the CLK signal. So the CLK pin of the IC, pin-13 is connected to the Arduino board’s digital pin-13. In this way, both the IC & microcontroller can function in synchrony.

The ISET pin allows fixing the current toward the segment pins & digits. These pins provide current toward the output device like a 4-digit 7-segment display. So ISET pin is set using an exterior resistor that is connected to V+.

Here a 40KΩ resistor is connected to V+ to supply 10mA of current to the display. In the MAX7219 IC, Pin1 & DIN pins are connected to pin 11 on the Arduino.

In Arduino board, pin11 like MOSI (Master Out Slave In) allows to converse & transmit data toward the chip. In the above circuit diagram, the communication between the IC & the microcontroller can be done simply one way.

The Arduino board simply needs to transmit instructions toward the IC on how to manage the o/p device without using IC to transmit data toward the microcontroller. The load or chip select pin is pin12; the load/CS must be below to load the data into IC.

Where to use/Applications

The applications of MAX7219 Display Driver IC include the following.

• Used for controlling more display segments through a connecting number of chips within serial.
• This IC plays a key role in converting the data from serial to parallel
• This IC controls 64 LEDs with 3-pins
• It is used to decrease the usage of the I/O pin of a processor/ controller.
• SHIFT operation
• Digital systems
• Servers
• Networking
• Memory units
• Instruments Measurement
• Digital Electronics
• LED Matrix for LED lights controlling
• Panel Meters
• Industrial Controllers
• Bar-Graph based Displays

Thus, this is all about an overview of aMAX7219 display driver IC datasheet. This IC includes serial I/O pins and also a variable current capacity that can be set through simply one exterior resistor & a 4 wire serial interface that is simply interfaced to all microprocessors which drive 64 LEDs which are connected on its o/p pins through simply four wires with the help of an Arduino. This IC drives displays with dot matrix, bar graphs & Seven segments displays. Here is a question for you, what are the advantages of MAX7219IC?