Rainbow Electronics MAX6975 - 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 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.
Applications
LED Video Display Panels
LED Message Boards
Variable Message Signs (VMS)
Signs
Graphic Panels
Features
♦ 24 LED Current Sink Outputs (Three Banks of
Eight Outputs)
♦ 48 LED Drive Option When Multiplexing
♦ 33MHz Clock Supports Up to 63 Frames per
Second of Video
♦ Constant Output Current Calibration from 6mA to
30mA in 256 Steps
♦ EZCascade™ Interface Simplifies Multiple Driver
Cascading Without External Buffers
♦ 12-Bit or 14-Bit Individual PWM LED Intensity
Controls
♦ 7-Bit or 5-Bit Panel PWM-Intensity Control
♦ +3V to +7V LED Power Supply
♦ +3.0V to +3.6V Logic Supply
♦ Open-Circuit LED Fault Detection
♦ Optional Watchdog Timer Blanks Display if
Interface Fails
♦ Standard -40°C to +125°C Operating Temperature
Range
MAX6974/MAX6975
24-Output PWM LED Drivers
for Message Boards
________________________________________________________________ Maxim Integrated Products 1
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
35
36
34
33
12
11
13
14
1 2
+
B5
4 5 6 7
27 28
EP*
*EP = EXPOSED PADDLE.
29 30 26 24 23 22
B4
B3
G2
G1
G0
R7
3
25
37 B2 R6
38
39
40
B1
B0
V DD
R5
R4
R3
B6
32
15
G3 B7
31
16
17
18
19
20 G4
8 9 10
21
AGND
R2 R1 R0 I.C.
LOADI
DIN- DIN+ CLKI- CLKI+ MUX0
CLKO+ CLK0- DOUT+ DOUT- LOADO V
DD
G7 G6 G5 MUX1
Pin Configuration
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
EZCascade is a trademark of Maxim Integrated Products, Inc.