MAX6978AUE+ Maxim Integrated, MAX6978AUE+ Datasheet

MAX6978AUE+

Manufacturer Part Number

MAX6978AUE+

Description

LED Display Drivers 8-Port, 5.5V CC LED Driver w/Fault Det

Manufacturer

Maxim Integrated

Datasheet

1.MAX6978AUE.pdf (13 pages)

Specifications of MAX6978AUE+

Rohs

yes

Number Of Segments

Mounting Style

SMD/SMT

Package / Case

TSSOP-16

Operating Supply Voltage

3 V to 5.5 V

Maximum Supply Current

25 mA

Maximum Operating Temperature

+ 125 C

Minimum Operating Temperature

- 40 C

Low Level Output Current

60 mA

Power Dissipation

1702 mW

Current page: 1 of 13
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The MAX6978 serial-interfaced LED driver provides

eight open-drain, constant-current sinking LED driver

outputs rated at 5.5V. The MAX6978 operates from a 3V

to 5.5V supply. The MAX6978 supply and the LEDs’

supply can power up in any order. The constant-current

outputs are programmed together to up to 55mA using

a single external resistor. The MAX6978 operates with a

25Mb, industry-standard, 4-wire serial interface.

The MAX6978 includes circuitry that automatically

detects open-circuit LEDs. Fault status is loaded into the

serial-interface shift register when LE goes high and is

automatically shifted out on DOUT when the next data

transmission is shifted in.

The MAX6978 includes a fail-safe feature for safety-

related applications, which blanks the display if the ser-

ial interface fails. If the serial interface becomes

inactive for more than 1s, all driver output latches are

automatically cleared. This turns off all LEDs connected

to the outputs. The shift register data is not disturbed.

The outputs remain off until the driver output latches are

updated with data turning them on, so recovery is auto-

matic if the transmission failure is temporary. The

watchdog function requires no software change to the

application driving the MAX6978.

The MAX6978 uses the industry-standard shift-register-

plus-latch-type serial interface. The driver accepts data

shifted into an 8-bit shift register using data input DIN

and clock input CLK. Input data appears at the output

DOUT eight clock cycles later to allow cascading of

multiple MAX6978s. The latch-enable input LE loads

the 8 bits of shift-register data into an 8-bit output latch

to set which LEDs are on and which are off. The output-

enable input OE gates all eight outputs on and off, and

is fast enough to be used as a PWM input for LED

intensity control.

The MAX6978 is one of a family of 12 shift-register-plus-

latch-type LED drivers. The family includes 8-port and

16-port types, with 5.5V- or 36V-rated LED outputs, with

and without open-circuit LED detection and watchdog.

All versions operate from a 3V to 5.5V supply, and are

specified over the -40°C to +125°C temperature range.

19-3578; Rev 2; 7/05

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

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

8-Port, 5.5V Constant-Current LED Driver with

Variable Message Signs

Marquee Displays

Point-of-Order Signs

Traffic Signs

Gaming Features

Architectural Lighting

________________________________________________________________ Maxim Integrated Products

General Description

LED Fault Detection and Watchdog

Applications

o 25Mb Industry-Standard 4-Wire Serial Interface at 5V

o 3V to 5.5V Logic Supply

o 8 Constant-Current LED Outputs Rated at 5.5V

o Up to 55mA Continuous Current per Output

o Output Current Programmed by Single Resistor

o 3% Current Matching Between Outputs

o 6% Current Matching Between ICs

o Watchdog Clears Display if Interface Fails

o Reports Open-Circuit LED Faults

o -40°C to +125°C Temperature Range

*EP = Exposed pad.

Typical Application Circuit and Selector Guide appear at

end of data sheet.

MAX6978AUE

MAX6978APE

MAX6978AAE

PART

TOP VIEW

OUT0

OUT1

OUT2

OUT3

GND

CLK

DIN

-40°C to +125°C

TEMP RANGE

TSSOP/PDIP/SSOP

Ordering Information

MAX6978AUE

MAX6978APE

MAX6978AAE

Pin Configuration

PIN-PACKAGE

16 TSSOP-EP*

16 PDIP

16 SSOP

V+

SET

DOUT

OUT7

OUT6

OUT5

OUT4

Features

Related parts for MAX6978AUE+

MAX6978AUE+ Summary of contents

Page 1

... Marquee Displays Point-of-Order Signs Traffic Signs Gaming Features Architectural Lighting ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. o 25Mb Industry-Standard 4-Wire Serial Interface 5.5V Logic Supply o 8 Constant-Current LED Outputs Rated at 5 ...

Page 2

Constant-Current LED Driver with LED Fault Detection and Watchdog ABSOLUTE MAXIMUM RATINGS Voltage (with respect to GND) V+ ............................................................................-0.3V to +6V OUT_ .......................................................................-0.3V to +6V DIN, CLK, LE, OE, SET ................................-0.3V to (V+ + 0.3V) DOUT Current ..................................................................±10mA ...

Page 3

Constant-Current LED Driver with LED Fault Detection and Watchdog 5V TIMING CHARACTERISTICS (Typical Operating Circuit 4.5V to 5.5V, T PARAMETER SYMBOL CLK Clock Period CLK Pulse-Width High CLK Pulse-Width Low DIN Setup Time DIN Hold Time ...

Page 4

Constant-Current LED Driver with LED Fault Detection and Watchdog 3.3V TIMING CHARACTERISTICS (Typical Operating Circuit 5.5V, T PARAMETER SYMBOL CLK Clock Period CLK Pulse-Width High CLK Pulse-Width Low DIN Setup Time DIN Hold Time ...

Page 5

Constant-Current LED Driver with LED Fault Detection and Watchdog (T = +25°C, unless otherwise noted.) A SUPPLY CURRENT vs. SUPPLY VOLTAGE (INTERFACE IDLE, ALL OUTPUTS ON 360Ω) SET +125° +85°C A ...

Page 6

Constant-Current LED Driver with LED Fault Detection and Watchdog PIN NAME 1 GND Ground 2 DIN Serial-Data Input. Data is loaded into the internal 8-bit shift register on CLK’s rising edge. 3 CLK Serial-Clock Input. Data is loaded ...

Page 7

Constant-Current LED Driver with LED Fault Detection and Watchdog Detailed Description The MAX6978 LED driver comprises a 4-wire serial interface driving eight constant-current sinking open- drain output ports. The outputs drive LEDs in either sta- tic or multiplex ...

Page 8

Constant-Current LED Driver with LED Fault Detection and Watchdog OE is independent of the operation of the serial inter- face. Data can be shifted into the serial-interface shift register and latched regardless of the state of OE. DOUT ...

Page 9

Constant-Current LED Driver with LED Fault Detection and Watchdog LE t LRF OUT_ LE t LRR OUT_ CLK t CRF OUT_ CLK t CRR OUT_ Figure 3. LE and CLK to OUT_ Timing tain the same data (validating ...

Page 10

Constant-Current LED Driver with LED Fault Detection and Watchdog NO. OF PART OUTPUTS MAX6968 MAX6977 8 MAX6978 MAX6970 8 MAX6981 MAX6980 MAX6969 MAX6984 16 MAX6979 MAX6971 16 MAX6982 MAX6983 +5V µC V+ SCLK CLK MOSI DIN MISO DOUT ...

Page 11

Constant-Current LED Driver with LED Fault Detection and Watchdog (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information www.maxim-ic.com/packages ______________________________________________________________________________________ Package Information PACKAGE ...

Page 12

Page 13

... Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 © 2005 Maxim Integrated Products ...

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