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 active-low MUX0 and active-low 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.
Key Features
Applications/Uses
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
* Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses. Note that "+", "#", "-" in the part number suffix describes RoHS status. Package drawings may show a different suffix character.
Devices:
1-6
of
6
MAX6974
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Package:
TYPE PINS FOOTPRINT
DRAWING CODE/VAR *
Temp
RoHS/Lead-Free? Materials Analysis
MAX6974ATL+
THIN QFN;40 pin;37 mm²
Dwg: 21-0141I (PDF)
Use pkgcode/variation: T4066+3*
MAX6971 16-Port, 36V Constant-Current LED Driver MAX6979 16-Port, 5.5V Constant-Current LED Driver with LED Fault Detection and Watchdog MAX6969 16-Port, 5.5V Constant-Current LED Driver MAX6974, MAX6975 24-Output PWM LED Drivers for Message Boards MAX6960, MAX6961, MAX6962, MAX6963 4-Wire Serially Interfaced 8 x 8 Matrix Graphic LED Drivers
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