MAX6974/MAX6975 19-0555 Rev 2 10/07 24-Output PWM LED Drivers for Message Boards General Description Features 24 LED Current Sink Outputs (Three Banks of The MAX6974/MAX6975 precision current-sinking, Eight Outputs) 24-output PWM LED drivers drive red, green, and blue LEDs for full-color graphic message boards and video 48 LED Drive Option When Multiplexing displays. Each output has an individual 12-bit (MAX6974) 33MHz Clock Supports Up to 63 Frames per or 14-bit (MAX6975) PWM-intensity (hue) control and Second of Video 7-bit (MAX6974) or 5-bit (MAX6975) global PWM intensity Constant Output Current Calibration from 6mA to (luminance) control. The MAX6974/MAX6975 feature a 30mA in 256 Steps high-speed, fully buffered cascadable serial interface, EZCascade Interface Simplifies Multiple Driver open-circuit LED fault detection circuitry, as well as a Cascading Without External Buffers watchdog timer. 12-Bit or 14-Bit Individual PWM LED Intensity The driver has three banks of eight outputs, with each Controls bank intended to drive a different color in RGB applica- 7-Bit or 5-Bit Panel PWM-Intensity Control tions. The full-scale current for each bank of eight out- puts is adjustable from 6mA to 30mA in 256 steps +3V to +7V LED Power Supply (0.3125% per step) to calibrate each color. +3.0V to +3.6V Logic Supply The MAX6974/MAX6975 can optionally multiplex by Open-Circuit LED Fault Detection using outputs MUX0 and MUX1, which each drive an Optional Watchdog Timer Blanks Display if external pnp transistor. Multiplexing doubles the Interface Fails MAX6974/MAX6975 drive capability to 48 LEDs. Standard -40C to +125C Operating Temperature The MAX6974/MAX6975 operate from a 3.0V to 3.6V Range power supply. The LED power supply can range from Ordering Information 3V to 7V. The LED drivers require only 0.8V headroom above the LEDs forward-voltage drop. Using a sepa- PIN- PKG PART TEMP RANGE rate LED supply voltage for each LED minimizes power PACKAGE CODE consumption. MAX6974ATL+ -40C to +125C 40 TQFN-EP* T4066-3 The serial interface uses differential signaling for the MAX6975ATL+ -40C to +125C 40 TQFN-EP* T4066-3 high-speed clock and data signals to reduce EMI and *EP = Exposed paddle. improve signal integrity. The MAX6974/MAX6975 buffer +Denotes a lead-free package. all interface signals to simplify cascading devices in modules that use a large number of drivers. Pin Configuration An internal watchdog timer, when enabled, automatically clears the pixel-data registers and blanks the display if TOP VIEW any of the signal inputs fail to toggle within 40ms. 30 29 28 27 26 25 24 23 22 21 The MAX6974/MAX6975 are available in 40-pin TQFN AGND 31 20 G4 packages and operate over the -40C to +125C 32 19 G3 B7 temperature range. EP* 33 18 G2 B6 Refer to the MAX6972/MAX6973 data sheet for a B5 34 17 G1 16-output, 11mA to 55mA software-compatible device. B4 35 16 G0 EZCascade is a trademark of Maxim Integrated Products, Inc. MAX6974ATL/ 36 15 R7 B3 MAX6975ATL B2 37 14 R6 Applications B1 38 13 R5 LED Video Display Panels + 39 12 R4 B0 LED Message Boards 40 11 R3 V DD Variable Message Signs (VMS) 12 3 45 6 7 89 10 Signs Graphic Panels TQFN-EP *EP = EXPOSED PADDLE. Typical Operating Circuit appears at the end of data sheet. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE MUX0 MUX1 CLKI+ CLKO+ CLK0- CLKI- DIN+ DOUT+ DIN- DOUT- LOADO LOADI I.C. V DD G7 R0 G6 R1 G5 R224-Output PWM LED Drivers for Message Boards ABSOLUTE MAXIMUM RATINGS (All voltages with respect to GND.) Operating Temperature Range .........................-40C to +125C V ........................................................................-0.3V to +4.0V Junction Temperature......................................................+150C DD R0R7, G0G7, B0B7, MUX0, and MUX1 ...........-0.3V to +8.0V Storage Temperature Range .............................-65C to +150C All Other Pins..............................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10s) .................................+300C DD Continuous Power Dissipation (T = +70C) A 40-Pin TQFN (derate 37mW/C over +70C) .............2963mW Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = 3.0V to 3.6V, T = T to T , unless otherwise noted. Typical values are at V = 3.3V, T = +85C.) (Note 1) DD A MIN MAX DD A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Operating Supply Voltage V 3.0 3.6 V DD LEDs Anode Voltage (R0R7, G0G7, B0B7, MUX0, V 7V O and MUX1) f = 0Hz CLKO , DOUT loaded 200 CLKI 28 52 calibration DACs set to 0x01 f = 0Hz CLKO , DOUT loaded 200 CLKI Supply Current I 51 72 mA DD calibration DACs set to 0xFF f = 32MHz CLKO , DOUT loaded 200 CLKI 54 77 calibration DACs set to 0xFF 0.7 Input High Voltage LOADI V V IHC x V DD 0.3 Input Low Voltage LOADI V V ILC x V DD Differential Input Voltage Range V 0.15 1.20 V ID CLKI , DIN Common-Mode Input Voltage V V / 2 2.4 V CM I D CLKI , DIN Differential Input High Threshold VDIFF 8 100 mV TH Differential Input Low Threshold VDIFF -100 -8 mV TL Differential Output Voltage V Termination 200 at receiver + and - inputs 190 550 mV OD CLKO , DOUT Differential Output Offset V Termination 200 at receiver + and - inputs 1.125 1.25 1.375 V OS CLKO , DOUT Input Leakage Current I , I -1 +1 A IH IL CLKI , DIN , LOADI Input Capacitance 10 pF CLKI , DIN , LOADI Output Low Voltage LOADO V I = 5mA 0.05 0.25 V OLC SINK V V DD DD Output High Voltage LOADO V I = 5mA V OHC SOURCE - 0.5 - 0.2 2 MAX6974/MAX6975