The MAX6974/MAX6975 high-precision current sinking, 24-output PWM LED driver can drive red, green, and/or blue LEDs for full-color information boards and video displays. Each output has 12-bit (MAX6974) or 14-bit (MAX6975) PWM luminance (color) control and 7-bit (MAX6974) or 5-bit (MAX6975) PWM global brightness control. The MAX6974/MAX6975 also include an LED open-circuit fault detection circuit and a watchdog timer.
The drive has three sets of eight outputs, each of which drives a specific color in an RGB application. The full-scale current of each group of 8 outputs can be adjusted from 6mA to 30mA, and the adjustment level is 256 (0.3125% per level) for calibrating each color.
The MAX6974/MAX6975 can use the /MUX0 and /MUX1 output select multiplexers to drive external pnp transistors. The multiplexer extends the MAX6974/MAX6975 drivers to drive 48 LEDs.
The MAX6974/MAX6975 operate from a 3.0V to 3.6V supply and have an LED supply voltage range of 3V to 7V. LED drivers only need to provide a voltage higher than the LED's turn-on voltage drop of 0.8V, providing a separate supply voltage for each LED to maximize power consumption.
The serial interface uses differential signaling to transmit high-speed clocks and data to reduce EMI and ensure signal integrity. The MAX6974/MAX6975 provide buffering for all interfaces, simplifying device cascading in modules that require a large number of drivers. When the internal watchdog timer is enabled, if there is no input trigger signal within 40ms, the device will automatically clear the pixel data register and mask the display.
The MAX6974/MAX6975 are available in a 40-pin TQFN package and are specified over the automotive temperature range of -40°C to +125°C.
Key characteristics
24 channels of LED current absorption output (three groups of 8 channels)
Use a multiplexer to drive 48 LEDs
The 33MHz clock supports 63 frames per second of video transmission. The constant current output calibration is adjustable from 6mA to 30mA. The adjustment level is 256.
EZCascadeTM interface simplifies cascading of multiple drives without external buffers
12- or 14-bit PWM LED brightness control
7-bit or 5-bit display board PWM brightness control
+3V to +7V LED power supply
+3.0V to +3.6V logic power supply
LED open-circuit fault detection can select the watchdog timer, and the shielded display works in the temperature range of -40°C to +125°C when the connection fails.
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