MAX7219EWG+T

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1. Description

The MAX7219EWG+T/MAX7221 are compact, serial input/ output common-cathode display drivers that interface microprocessors (μPs) to 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual LEDs. Included on-chip are a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, and an 8x8 static RAM that stores each digit. Only one external resistor is required to set the segment current for all LEDs. The MAX7221 is compatible with SPI™, QSPI™, and MICROWIRE™, and has slew-rate-limited segment drivers to reduce EMI. A convenient 4-wire serial interface connects to all common μPs. Individual digits may be addressed and updated without rewriting the entire display. The MAX7219/MAX7221 also allow the user to select code-B decoding or no decode for each digit. The devices include a 150μA low-power shutdown mode, analog and digital brightness control, a scan-limit register that allows the user to display from 1 to 8 digits, and a test mode that forces all LEDs on. For applications requiring 3V operation or segment blinking, refer to the MAX6951 data sheet.

2. Features

    1. 10MHz Serial Interface

    2. Individual LED Segment Control

    3. Decode/No-Decode Digit Selection

    4. 150μA Low-Power Shutdown (Data Retained)

    5. Digital and Analog Brightness Control

    6. Display Blanked on Power-Up

    7. Drive Common-Cathode LED Display

    8. Slew-Rate Limited Segment Drivers for Lower EMI (MAX7221)

    9. SPI, QSPI, MICROWIRE Serial Interface (MAX7221)

  10. 24-Pin DIP and SO Packages

3. Applications

    1. Bar-Graph Displays

    2. Industrial Controllers

    3. Panel Meters

    4. LED Matrix Displays

4. Pin Configuration

5. MAX7219/MAX7221 Differences

The MAX7219 and MAX7221 are identical except for two parameters: the MAX7221 segment drivers are slew-rate limited to reduce electromagnetic interference (EMI), and its serial interface is fully SPI compatible

6. Pin Description

7. Serial addressing mode

For MAX7219, DIN serial data is sent in 16-bit packets, Are shifted into the internal 16-bit shift register, each The rising edge of CLK, regardless of the state of LOAD. for The CS of MAX7221 must be low to input or output clock data. Then the data is latched into the digital or control register On the rising edge of LOAD/CS. Load/CS must become higher At the same time or after the 16th clock rising edge, but Before the next rising edge of the clock or data will be lost. The data on DIN is propagated through the shift register and Appears at DOUT after 16.5 clock cycles. Data is timed Output on the falling edge of CLK. Data bits are marked D0–D15. D8-D11 contains the register address. D0-D7 contain data, D12-D15 are "don't care" Bit. The first received is D15, the most significant bit (MSB).

8. Digital and control registers

14 addressable digital and control registers. Digital registers through on-chip 8x8 Dual port SRAM. They are addressed directly in order to It is possible to update a single number and keep the data for as long as possible Because V+ usually exceeds 2V. Control registers include Decoding mode, display intensity, scan limit (quantity Scan number), shutdown and display test (all LEDs are on)

9. Shutdown mode

When the MAX7219 is in shutdown mode, the sweep oscillator is Stop, all segment current sources are pulled to ground, And all digital drivers are pulled to V+, thus blanking exhibit. MAX7221 is the same, except that the driver is High impedance. Data in digital and control registers constant. Shutdown can be used to save power Or as an alarm flashing display through continuous input And exit the shutdown mode. For minimum supply current In shutdown mode, the logic input should be grounded or V+ (CMOS logic level). Normally, MAX7219/ MAX7221 exits shutdown mode. The display driver can Programming in shutdown mode, then shutdown The mode can be covered by the display test function.