2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan

 

Part Number	Replacement	Explanation

Description

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The MAX6955 is a compact display driver that interfaces microprocessors to a mix of 7-segment, 14-segment, and 16-segment LED displays through an I²C-compatible 2-wire serial interface. The MAX6955 drives up to 16 digits 7-segment, 8 digits 14-segment, 8 digits 16-segment, or 128 discrete LEDs, while functioning from a supply voltage as low as 2.7V. The driver includes five I/O expander or general-purpose I/O (GPIO) lines, some or all of which can be configured as a key-switch reader. The key-switch reader automatically scans and debounces a matrix of up to 32 switches.

Included on chip are full 14- and 16-segment ASCII 104-character fonts, a hexadecimal font for 7-segment displays, multiplex scan circuitry, anode and cathode drivers, and static RAM that stores each digit. The maximum segment current for the display digits is set using a single external resistor. Digit intensity can be independently adjusted using the 16-step internal digital brightness control. The MAX6955 includes a low-power shutdown mode, a scan-limit register that allows the user to display from 1 to 16 digits, segment blinking (synchronized across multiple drivers, if desired), and a test mode, which forces all LEDs on. The LED drivers are slew-rate limited to reduce EMI.

For an SPI-compatible version, refer to the MAX6954 data sheet. An evaluation kit (EV kit) for the MAX6955 is available.

MAX6955: Functional Diagram Enlarge+

Key Features

• Simplifies Driving 5 x 7 Matrix LED Displays
  • Drives Common-Cathode Monocolor and Bicolor LED Displays
  • Drives Up to 16 Digits 7-Segment, 8 Digits 14-Segment, 8 Digits 16-Segment, 128 Discrete LEDs, or a Combination of Digit Types
  • 2.7V to 5.5V Operation
• Standard 2-Wire Interface Supports a Variety of Microprocessor Architectures
  • 400kbps 2-Wire I²C-Compatible Interface
• Integrated Flexibility Supports Different Application Requirements
  • Built-In ASCII 104-Character Font for 14-Segment and 16-Segment Digits and Hexadecimal Font for 7-Segment Digits
  • 16-Step Digit-by-Digit Digital Brightness Control
  • Display Blanked on Power-Up
  • Automatic Blinking Control for Each Segment
  • 10µA (typ) Low-Power Shutdown (Data Retained)
• Five GPIO Port Pins Can Be Configured as Key-Switch Reader to Scan and Debounce Up to 32 Switches with n-Key Rollover
  • IRQ Output when a Key Input Is Debounced
• Slew-Rate-Limited Segment Drivers for Lower EMI
• 36-Pin SSOP and 40-Pin DIP and TQFN Packages
• Automotive Temperature Range Standard Covers Usage in Harsh Environments

Applications/Uses

• Audio/Video Equipment
• Bar Graph Displays
• Panel Meters
• Set-Top Boxes
• White Goods