Rainbow Electronics MAX6975 User Manual

General Description

The MAX6974/MAX6975 precision current-sinking, 24-output PWM LED drivers drive red, green, and blue LEDs for full-color graphic message boards and video displays. Each output has an individual 12-bit (MAX6974) or 14-bit (MAX6975) PWM-intensity (hue) control and 7-bit (MAX6974) or 5-bit (MAX6975) global PWM intensity (luminance) control. The MAX6974/MAX6975 feature a high-speed, fully buffered cascadable serial interface, open-circuit LED fault detection circuitry, as well as a watchdog timer.

The driver has three banks of eight outputs, with each bank intended to drive a different color in RGB applications. The full-scale current for each bank of eight outputs is adjustable from 6mA to 30mA in 256 steps (0.3125% per step) to calibrate each color.

The MAX6974/MAX6975 can optionally multiplex by using outputs MUX0 and MUX1, which each drive an external pnp transistor. Multiplexing doubles the MAX6974/MAX6975 drive capability to 48 LEDs.

The MAX6974/MAX6975 operate from a 3.0V to 3.6V power supply. The LED power supply can range from 3V to 7V. The LED drivers require only 0.8V headroom above the LEDs’ forward-voltage drop. Using a separate LED supply voltage for each LED minimizes power consumption.

The serial interface uses differential signaling for the high-speed clock and data signals to reduce EMI and improve signal integrity. The MAX6974/MAX6975 buffer all interface signals to simplify cascading devices in modules that use a large number of drivers.

An internal watchdog timer, when enabled, automatically clears the pixel-data registers and blanks the display if any of the signal inputs fail to toggle within 40ms.

The MAX6974/MAX6975 are available in 40-pin TQFN packages and operate over the -40°C to +125°C temperature range.

Refer to the MAX6972/MAX6973 data sheet for a 16-output, 11mA to 55mA software-compatible device.

Applications

LED Video Display Panels LED Message Boards Variable Message Signs (VMS) Signs Graphic Panels

Features

o 24 LED Current Sink Outputs (Three Banks of

Eight Outputs)

o 48 LED Drive Option When Multiplexing o 33MHz Clock Supports Up to 63 Frames per

Second of Video

o Constant Output Current Calibration from 6mA to

30mA in 256 Steps

o EZCascade™ Interface Simplifies Multiple Driver

Cascading Without External Buffers

o 12-Bit or 14-Bit Individual PWM LED Intensity

Controls

o 7-Bit or 5-Bit Panel PWM-Intensity Control o +3V to +7V LED Power Supply o +3.0V to +3.6V Logic Supply o Open-Circuit LED Fault Detection o Optional Watchdog Timer Blanks Display if

Interface Fails

o Standard -40°C to +125°C Operating Temperature

Range

MAX6974/MAX6975

24-Output PWM LED Drivers

for Message Boards

________________________________________________________________

Maxim Integrated Products

19-0555; Rev 0; 5/06

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.

Typical Operating Circuit appears at the end of data sheet.

EP = Exposed pad.

Denotes lead-free package.

MAX6974ATL/

MAX6975ATL

TQFN-EP

TOP VIEW

4567

2728

EP*

*EP = EXPOSED PADDLE.

2930 26 24 23 22

8910

AGND

I.C.

LOADI

DIN-

DIN+

CLKI-

CLKI+

MUX0

CLKO+

CLK0-

DOUT+

DOUT-

LOADO

VDDG7G6G5

MUX1

Pin Configuration

Ordering Information

PART

TEMP RANGE

PINPACKAGE

PKG

CODE

T4066-3

EZCascade is a trademark of Maxim Integrated Products, Inc.

MAX6974ATL+ -40°C to +125°C 40 TQFN-EP*

MAX6975ATL+ -40°C to +125°C 40 TQFN-EP*

MAX6974/MAX6975

24-Output PWM LED Drivers for Message Boards

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

(All voltages with respect to GND.) V

........................................................................-0.3V to +4.0V

R0–R7, G0–G7, B0–B7, MUX0, and MUX1 ...........-0.3V to +8.0V

All Other Pins..............................................-0.3V to (V

+ 0.3V)

Continuous Power Dissipation (T

= +70°C)

40-Pin TQFN (derate 37mW/°C over +70°C) .............2963mW

Operating Temperature Range .........................-40°C to +125°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(VDD= 3.0V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VDD= 3.3V, TA= +85°C.) (Note 1)

Operating Supply Voltage V

LEDs Anode Voltage (R0–R7, G0–G7, B0–B7, MUX0, and MUX1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Current I

Input High Voltage LOADI V

Input Low Voltage LOADI V

Differential Input Voltage Range CLKI_, DIN_

Common-Mode Input Voltage CLKI_, DIN_

Differential Input High Threshold VDIFF

Differential Input Low Threshold VDIFF

Differential Output Voltage CLKO_, DOUT_

Differential Output Offset CLKO_, DOUT_

Input Leakage Current CLKI_, DIN_, LOADI

Input Capacitance CLKI_, DIN_, LOADI

Output Low Voltage LOADO V

Output High Voltage LOADO V

IHC

ILC

, I

OLCISINK

OHCISOURCE

3.0 3.6 V

= 0Hz; CLKO_, DOUT_ loaded 200Ω;

CLKI

calibration DACs set to 0x01

= 0Hz; CLKO_, DOUT_ loaded 200Ω;

CLKI

calibration DACs set to 0xFF

= 32MHz; CLKO_, DOUT_ loaded 200Ω;

CLKI

calibration DACs set to 0xFF

0.7

x V

±0.15 ±1.20 V

| V

I D

-100 -8 mV

Termination 200Ω at receiver _+ and _- inputs ±190 ±550 mV

Termination 200Ω at receiver _+ and _- inputs 1.125 1.25 1.375 V

= 5mA 0.05 0.25 V

= 5mA

- 0.5

28 52

51 72

54 77

0.3

x V

/ 2| 2.4 V

8 100 mV

-1 +1 µA

10 pF

- 0.2

MAX6974/MAX6975

24-Output PWM LED Drivers

for Message Boards

_______________________________________________________________________________________ 3

Note 1: All parameters tested at TA= +85°C. Specifications over temperature are guaranteed by design.

Note 2: Specification limits apply to devices at the same T

for TA= T

MIN

to T

MAX

Note 3: Guaranteed by design.

ELECTRICAL CHARACTERISTICS (continued)

(VDD= 3.0V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VDD= 3.3V, TA= +85°C.) (Note 1)

TIMING CHARACTERISTICS

(VDD= 3.0V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at 3.3V, TA= +85°C.) (Note 1)

Output Slew Time LOADO 20% to 80%, 80% to 20%, load = 10pF 3 ns Output Low Voltage MUX_ V

Open-Circuit Detection V

Output Voltage Slew Time R0–R7, G0–G7, B0–B7

Full-Scale Port Output Current R0–R7, G0–G7, B0–B7

Port-to-Port Current Matching R0–R7, G0–G7, B0–B7

Output Load Regulation ΔI

Output Power-Supply Rejection ΔI

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

= 40mA 0.4 V

OLM

OCD

SINK

80% to 20%, load = 50pF, calibration DACs set to 0xFF

SINKFS

VDD = 3.3V, VO = 1.2V, calibration DACs set to 0xFF

TA = +85°C 28 30 32

= T

MIN

to T

MAX

TA = +125°C (Note 3)

TA = +85°C ±0.7 2

= -40°C

ΔI

VDD = 3.3V, VO = 1.2V, calibration DACs set to 0xFF

SINK

= 30mA (Note 2)

SINK

(Note 3)

OLR

OPSR

= 3.3V , V O = 1.2V to 3.0V ,

D D

calibration DACs set to 0x80, I

= 18mA

SINK

= 3.0 V to 3.6V , V O = 1.2V ,

D D

calibration DACs set to 0x80, I

= 18mA

SINK

TA = +85°C 0.3 1.15

= T

MIN

to T

MAX

TA = +85°C 0.6 1.7

= T

MIN

to T

MAX

200 mV

100 ns

26 34

±0.7 2.7

±0.9 3.3

1.5

2.0

mA/V

CLKI_ Input Frequency f

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

CLKI

33 MHz

CLKI_ Duty Cycle 40 60 %

CLKO_ Output Delay t

DIN_ Setup Time t

DIN_ Hold Time t

DOUT_ Output Delay t

LOADO Output Delay t

LOADI Hold Time t

PD-CLKO

SU-DIN

HD-DIN

PD-DOUT

PD-LOADO

HD-LOADI

0.5 ns

5ns

8ns

16 ns

15 ns

18 ns

Watchdog Period When enabled 40 125 300 ms

MAX6974/MAX6975

24-Output PWM LED Drivers for Message Boards

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VDD= 3.3V, TA= +25°C, unless otherwise noted.)

OPERATING CURRENT CONSUMPTION

vs. SUPPLY VOLTAGE V

MAX6974 toc01

SUPPLY VOLTAGE VDD (V)

(mA)

3.43.33.23.1

3.0 3.5 3.6

TA = -40°C

TA = +25°C

TA = +125°C

TA = +85°C

CLKI

= 32MHz

CALDAC = 0xFF

OPERATING CURRENT CONSUMPTION

vs. SUPPLY VOLTAGE V

MAX6974 toc02

SUPPLY VOLTAGE VDD (V)

(mA)

3.53.43.33.23.1

3.0 3.6

TA = -40°C

TA = +25°C

TA = +85°C

TA = +125°C

CLKI

= 0MHz

CALDAC = 0x00

LED OUTPUT SINK CURRENT

vs. OUTPUT VOLTAGE

MAX6974 toc03

OUTPUT VOLTAGE (V)

SINK

(mA)

564321

TA = -40°C

TA = +125°C

TA = +25°C

TA = +85°C

LED OUTPUT SINK CURRENT

vs. OUTPUT VOLTAGE

MAX6974 toc04

OUTPUT VOLTAGE (V)

SINK

(mA)

564321

VDD = +3.0V

VDD = +3.3V

VDD = +3.6V

MAX6974/MAX6975

24-Output PWM LED Drivers

for Message Boards

_______________________________________________________________________________________ 5

Pin Description

PIN NAME FUNCTION

1 MUX0 Multiplex 0 Active-Low, Open-Drain Output. Use MUX0 to drive a pnp transistor.

2 CLKI+ PWM and Serial-Interface Noninverting Clock LVDS Input

3 CLKI- PWM and Serial-Interface Inverting Clock LVDS Input

4 DIN+ Serial-Interface Noninverting Data LVDS Input

5 DIN- Serial-Interface Inverting Data LVDS Input

6 LOADI Serial-Interface Load CMOS Input

7 I.C. Internally Connected. Connect to GND.

8–15 R0–R7 Red LED Drive Outputs. R0 to R7 are open-drain, constant-current sinks.

16–23 G0–G7 Green LED Drive Outputs. G0–G7 are open-drain, constant-current sinks.

24, 40 V

25 LOADO Serial-Interface Load CMOS Output

26 DOUT- Serial-Interface Inverting Data LVDS Output

27 DOUT+ Serial-Interface Noninverting Data LVDS Output

28 CLKO- PWM and Serial-Interface Inverting Clock LVDS Output

29 CLKO+ PWM and Serial-Interface Noninverting Clock LVDS Output 30 MUX1 Multiplex 1 Active-Low, Open-Drain Output. Use MUX1 to drive a pnp transistor.

31 AGND Analog Ground. Connect to GND.

32–39 B7–B0 Blue LED Drive Outputs. B0 to B7 are open-drain, constant-current sinks.

EP GND Power Ground. Exposed pad on package underside must be connected to GND.

Positive Supply Voltage. Bypass VDD to GND with a 0.1µF ceramic capacitor.

MAX6974/MAX6975

24-Output PWM LED Drivers for Message Boards

6 _______________________________________________________________________________________

MAX6974 Block Diagram

R LED OUTPUTS

EXT. PNP

MUX0

R CALDAC

OUTPUT

PWM

COUNTERS

SYNC

CONTROL

LOADI

CLKI

DIN

8-BIT

R6 R5 R4 R3 R2 R1 R0

R LED DRIVERS

SET

R7–R0

0/1

LOAD OE

SYNC DETECT

G CALDAC

7-BIT GLOBAL-INTENSITY PDM MODULATOR

MUX0 PIXEL PWM OLD DATA LATCH

MUX0 PIXEL PWM NEW DATA LATCH MUX1 PIXEL PWM NEW DATA LATCH

G LED OUTPUTS

G7 G6 G5 G4 G3 G2 G1 G0

8-BIT

12-BIT INDIVIDUAL PWM MODULATOR

288

G LED DRIVERS

SET

G7–G0

288-BIT DATA SHIFT REGISTER

B CALDAC

MAX6974

B LED OUTPUTS

B7 B6 B5 B4 B3 B2 B1 B0

8-BIT

LOAD

B LED DRIVERS

SET

MUX1 PIXEL PWM OLD DATA LATCH

B7–B0

288

24-BIT NEW HEADER

SHIFT REGISTER

EXT. PNP

MUX1

OUTPUTS

8 8

CALIBRATION

DATA LATCH

GLOBAL-

INTENSITY

DATA LATCH

LOADO

CLKO

DOUT

MAX6974/MAX6975

24-Output PWM LED Drivers

for Message Boards

_______________________________________________________________________________________ 7

MAX6975 Block Diagram

LOADI

CLKI

DIN

EXT. PNP

MUX0

OUTPUT

8-BIT

R CALDAC

PWM

COUNTERS

SYNC

CONTROL

R LED OUTPUTS

R6 R5 R4 R3 R2 R1 R0

R LED DRIVERS

SET

R7–R0

0/1

LOAD OE

SYNC DETECT

G LED OUTPUTS

G7 G6 G5 G4 G3 G2 G1 G0

8-BIT

G CALDAC

5-BIT GLOBAL-INTENSITY PDM MODULATOR

14-BIT INDIVIDUAL PWM MODULATOR

MUX0 PIXEL PWM OLD DATA LATCH

MUX0 PIXEL PWM NEW DATA LATCH MUX1 PIXEL PWM NEW DATA LATCH

336

SET

G LED DRIVERS

G7–G0

8-BIT

B CALDAC

LOAD

MAX6975

336-BIT DATA SHIFT REGISTER

B LED OUTPUTS

B7 B6 B5 B4 B3 B2 B1 B0

B LED DRIVERS

SET

B7–B0

336

MUX1 PIXEL PWM OLD DATA LATCH

336

24-BIT NEW HEADER

SHIFT REGISTER

CALIBRATION

DATA LATCH

INTENSITY

DATA LATCH

EXT. PNP

MUX1

OUTPUTS

8 8

GLOBAL-

LOADO

CLKO

DOUT

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