Datasheet

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AVAILABLE

EVALUATION KIT AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

For pricing, delivery, and

ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

General Description

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 I

C-compati-

ble 2-wire serial interface. The MAX6955 drives up to 16

digits 7-segment, 8 digits 14-segment, 8 digits 16-seg-

ment, 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 max-

imum segment current for the display digits is set using

a single external resistor. Digit intensity can be inde-

pendently 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.

Applications

Set-Top Boxes Automotive

Panel Meters Bar Graph Displays

White Goods Audio/Video Equipment

Features

 400kbps 2-Wire I

C-Compatible Interface

 2.7V to 5.5V Operation

 Drives Up to 16 Digits 7-Segment, 8 Digits

14-Segment, 8 Digits 16-Segment, 128 Discrete

LEDs, or a Combination of Digit Types

 Drives Common-Cathode Monocolor and Bicolor

LED Displays

 Built-In ASCII 104-Character Font for 14-Segment

and 16-Segment Digits and Hexadecimal Font for

7-Segment Digits

 Automatic Blinking Control for Each Segment

 10µA (typ) Low-Power Shutdown (Data Retained)

 16-Step Digit-by-Digit Digital Brightness Control

 Display Blanked on Power-Up

 Slew-Rate-Limited Segment Drivers for Lower EMI

 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

 36-Pin SSOP and 6mm x 6mm 40-Pin TQFN

Packages

 Automotive Temperature Range Standard

2-Wire Interfaced, 2.7V to 5.5V LED Display

Driver with I/O Expander and Key Scan

Ordering Information

PART TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX6955AAX -40°C to +125°C 36 SSOP A36-2

MAX6955ATL+ -40°C to +125°C 40 TQFN-EP* T4066- 5

Pin Configurations and Typical Operating Circuits appear

at end of data sheet.

ISET

OSC

OSC_OUT

BLINK

SCL

AD0

AD1

SDA

2-WIRE SERIAL INTERFACE

RAM

BLINK

CONTROL

CONFIGURATION

CHARACTER

GENERATOR

ROM

CURRENT

SOURCE

DIVIDER/

COUNTER

NETWORK

DIGIT

MULTIPLEXER

PWM

BRIGHTNESS

CONTROL

GPIO

AND KEY-SCAN

CONTROL

LED

DRIVERS

O0 TO O18

P0 TO P4/IRQ

MAX6955

Functional Diagram

SPI is a trademark of Motorola, Inc.

EP = Exposed paddle.

Denotes a lead-free package.

Ordering Information

19-2548; Rev 3; 2/08

MAX6955

Summary of content (43 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX6955 LE AVAILAB 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan General Description Features 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.
PAGE 2
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan ABSOLUTE MAXIMUM RATINGS Voltage (with Respect to GND) V+ .........................................................................-0.3V to +6V SCL, SDA, AD0, AD1 ...........................................-0.3V to +6V All Other Pins............................................-0.3V to (V+ + 0.3V) Current O0–O7 Sink Current ......................................................935mA O0–O18 Source Current ...............
PAGE 3
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan DC ELECTRICAL CHARACTERISTICS (continued) (Typical Operating Circuit, V+ = 2.7V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS -32 -40 -48 mA VLED = 2.2V, V+ = 3.3V Segment Drive Source Current Segment Current Slew Rate Segment Drive Current Matching ISEG VLED = 2.2V, V+ = 2.7V TA = +25°C ∆ISEG/∆t TA = +25°C, V+ = 3.
PAGE 4
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan TIMING CHARACTERISTICS (Typical Operating Circuit, V+ = 2.7V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 400 kHz TIMING CHARACTERISTICS Serial Clock Frequency fSCL Bus Free Time Between a STOP and a START Condition tBUF 1.3 µs Hold Time (Repeated) START Condition tHD, tSTA 0.6 µs Repeated START Condition Setup Time tSU, tSTA 0.
PAGE 5
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Typical Operating Characteristics (V+ = 3.3V, LED forward voltage = 2.4V, Typical Application Circuit, TA = +25°C, unless otherwise noted.) INTERNAL OSCILLATOR FREQUENCY vs. TEMPERATURE 4.2 4.0 3.8 RSET = 56kΩ CSET = 22pF MAX6954 toc03 RSET = 56kΩ CSET = 22pF MAX6955 toc02 RSET = 56kΩ CSET = 22pF 4.4 OSCILLATOR FREQUENCY (MHz) MAX6955 toc01 4.
PAGE 6
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Pin Description PIN NAME FUNCTION SSOP TQFN-EP 1, 2, 34, 35 36, 37, 33, 34 P0–P3 3 38 AD0 Address Input 0. Sets device slave address. Connect to GND, V+, SCL, or SDA to give four logic combinations. See Table 5. 4 39 SDA I2C-Compatible Serial Data I/O 5 40 SCL I2C-Compatible Serial Clock Input 6 1 AD1 Address Input 1. Sets device slave address.
PAGE 7
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan 1a 1b 1f 2f 2b 1g 1e a 2a f 2g 2e 1c i j g1 e 2c 1dp h a1 m l k h i g1 g2 2dp 2d 1d f b a2 c e m j b g2 l k c dp d dp d2 d1 Figure 1. Segment Labeling for 7-Segment Display, 14-Segment Display, and 16-Segment Display Table 1.
PAGE 8
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 2.
PAGE 9
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan SDA tSU, STA tSU, DAT tLOW tBUF tHD, STA tHD, DAT tSU, STO SCL tHIGH tHD, STA tR tF START CONDITION REPEATED START CONDITION STOP CONDITION START CONDITION Figure 2. 2-Wire Serial Interface Timing Details SDA SCL S P START CONDITION STOP CONDITION Figure 3. Start and Stop Conditions SDA 1 START MSB SCL 1 0 A3 A2 A1 A0 R/W ACK LSB Figure 4.
PAGE 10
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Operation with Multiple Masters Table 5.
PAGE 11
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan The data in the digit registers does not control the digit segments directly for 14- and 16-segment displays. Instead, the register data is used to address a character generator that stores the data for the 14- and 16segment fonts (Tables 8 and 9). The lower 7 bits of the digit data (D6 to D0) select the character from the font.
PAGE 12
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan range. The first 16 characters of the 16-segment ROM map cover 7-segment displays. These 16 characters are numeric 0 to 9 and characters A to F (i.e., the hexadecimal set). Multiplex Clock and Blink Timing The OSC pin can be fitted with capacitor CSET to GND to use the internal RC multiplex oscillator, or driven by an external clock to set the multiplex clock frequency and blink rate.
PAGE 13
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 7.
PAGE 14
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 7.
PAGE 15
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 7.
PAGE 16
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan D15 COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION D14 D13 D12 D11 D10 D9 D8 ACKNOWLEDGE FROM MAX6955 S SLAVE ADDRESS 0 A COMMAND BYTE A R/W P ACKNOWLEDGE FROM MAX6955 Figure 7.
PAGE 17
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan START OF NEXT CYCLE ONE COMPLETE 1.
PAGE 18
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan LED OUTPUT O0 SW A0 SW B0 SW C0 SW D0 LED0 LED OUTPUT O1 SW A1 SW B1 SW C1 SW D1 SW A2 SW B2 SW C2 SW D2 LED OUTPUT O2 LED1 LED OUTPUT O3 SW A3 SW B3 SW C3 SW D3 LED2 LED OUTPUT O4 SW A4 SW B4 SW C4 SW D4 LED3 LED OUTPUT O5 SW A5 SW C5 SW B5 SW D5 LED4 LED OUTPUT O6 SW A6 SW C6 SW B6 SW D6 LED5 LED OUTPUT O7 SW A7 VCC SW C7 SW B7 SW D7 LED SEGMENT IS OPTIONAL AND BASED ON APPLICATION.
PAGE 19
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Key Debounced Registers The Key_A debounced, Key_B debounced, Key_C debounced, and Key_D debounced read-only registers (Table 35) show which keys have been detected as debounced by the key-scanning circuit. Each bit in the register corresponds to one key switch. The bit is set if the switch has been correctly debounced since the register was read last.
PAGE 20
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Choosing Supply Voltage to Minimize Power Dissipation The MAX6955 drives a peak current of 40mA into LEDs with a 2.2V forward-voltage drop when operated from a supply voltage of at least 3.0V. The minimum voltage drop across the internal LED drivers is therefore (3.0V 2.2V) = 0.8V. If a higher supply voltage is used, the driver absorbs a higher voltage, and the driver’s power dissipation increases accordingly.
PAGE 21
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 8. 16-Segment Display Font Map MSB LSB x000 x001 x010 x011 x100 x101 x110 x111 Table 9.
PAGE 22
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 10.
PAGE 23
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 12.
PAGE 24
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 14. Example Configurations for Display Digit Combinations REGISTER DATA DIGIT-TYPE REGISTER SETTING ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 Digits 7 to 0 are 16-segment or 7segment digits. 0x0C 0 0 0 0 0 0 0 0 Digit 0 is a 14-segment digit, digits 7 to 1 are 16-segment or 7segment digits.
PAGE 25
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 16.
PAGE 26
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 17. Configuration Register Format MODE Configuration Register Table 18. Shutdown Control (S Data Bit DO) Format REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 REGISTER DATA MODE P I R T E B X D7 D6 D5 D4 D3 D2 D1 D0 Shutdown P I R T E B X 0 Normal Operation P I R T E B X 1 S Table 19.
PAGE 27
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 24. Global Intensity (I Data Bit D6) Format REGISTER DATA MODE D7 D6 D5 D4 D3 D2 D1 D0 Intensity for all digits is controlled by one setting in the global intensity register. P 0 R T E B X S Intensity for digits is controlled by the individual settings in the intensity10 and intensity76 registers. P 1 R T E B X S Table 25.
PAGE 28
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 28.
PAGE 29
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 30. Odd Individual Segment Intensity Format DUTY CYCLE TYPICAL SEGMENT CURRENT (mA) ADDRESS CODE (HEX) D7 D6 D5 D4 1/16 (min on) 2.5 0x10 to 0x17 0 0 0 0 0x0X 2/16 5 0x10 to 0x17 0 0 0 1 0x1X 3/16 7.5 0x10 to 0x17 0 0 1 0 0x2X 4/16 10 0x10 to 0x17 0 0 1 1 0x3X 5/16 12.5 0x10 to 0x17 0 1 0 0 0x4X 6/16 15 0x10 to 0x17 0 1 0 1 0x5X 7/16 17.
PAGE 30
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 33.
PAGE 31
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Table 35.
PAGE 32
MAX6955 2-Wire Interfaced, 2.7V to 5.
PAGE 33
MAX6955 2-Wire Interfaced, 2.7V to 5.
PAGE 34
MAX6955 2-Wire Interfaced, 2.7V to 5.
PAGE 35
MAX6955 2-Wire Interfaced, 2.7V to 5.
PAGE 36
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Typical Operating Circuits 3.
PAGE 37
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Typical Operating Circuits (continued) 3.
PAGE 38
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Typical Operating Circuits (continued) 3.
PAGE 39
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Pin Configurations BLINK 10 23 O10 EP* 22 O10 21 O9 20 O7 14 9 19 O8 23 24 8 O18 O17 O16 O15 O14 O13 O12 O11 25 V+ N.C.
PAGE 40
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Package Information SSOP.EPS (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 36 E DIM A A1 B C e E H L D H INCHES MILLIMETERS MAX MIN 0.096 0.104 0.004 0.011 0.012 0.017 0.009 0.013 0.0315 BSC 0.291 0.299 0.398 0.414 0.040 0.020 0.598 0.612 MAX MIN 2.65 2.44 0.29 0.10 0.44 0.30 0.23 0.
PAGE 41
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Package Information (continued) QFN THIN.EPS (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.
PAGE 42
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.
PAGE 43
MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 — Initial release — 1 — — — 2 12/06 — 3 3/08 — Corrected data sheet errors. 1, 2, 3, 6, 15, 16, 18, 19, 36, 37, 38 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.