MAX6974_07 Datasheet, PDF (1/23 Pages) Maxim Integrated Products – 24-Output PWM LED Drivers for Message Boards

19-0555; Rev 2; 10/07
EVAALVUAAILTAIOBNLEKIT
24-Output PWM LED Drivers
for Message Boards
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 applica-
tions. The full-scale current for each bank of eight out-
puts 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 sepa-
rate 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.
EZCascade is a trademark of Maxim Integrated Products, Inc.
Applications
LED Video Display Panels
LED Message Boards
Variable Message Signs (VMS)
Signs
Graphic Panels
Typical Operating Circuit appears at the end of data sheet.
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
Ordering Information
PART
TEMP RANGE ^PIN-
PACKAGE
PKG
CODE
MAX6974ATL+ -40°C to +125°C 40 TQFN-EP* T4066-3
MAX6975ATL+ -40°C to +125°C 40 TQFN-EP* T4066-3
*EP = Exposed paddle.
+Denotes a lead-free package.
Pin Configuration
TOP VIEW
30 29 28 27 26 25 24 23 22 21
AGND 31
20 G4
B7 32
B6 33
19 G3
EP*
18 G2
B5 34
17 G1
B4 35
B3 36
B2 37
MAX6974ATL/
MAX6975ATL
16 G0
15 R7
14 R6
B1 38
+
B0 39
13 R5
12 R4
V_DD 40
11 R3
1 2 3 4 5 6 7 8 9 10
*EP = EXPOSED PADDLE.
TQFN-EP
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.