Simplified Block Diagram
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- 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
- Graphic Panels
- LED Message Boards
- LED Video Display Panels
- Variable Message Signs (VMS)
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.