Sunnyvale, Calif.—Maxim Integrated Products' MAX6971/MAX6983 16-port, and 8-port
MAX6970/MAX6980/MAX6981 constant-current LED drivers are rated at 36 volts for commercial lighting applications, including traffic signs, point-of-order and variable message signs, and marquee displays. Extra protection features support fail-safe application requirements.
These open-drain drivers feature a 25 MHz, 4-wire, industry-standard SPI-compatible serial interface. Each port, using a single external resistor with 2 percent current matching between outputs and 6 percent matching between cascaded devices, can sink up to
55 mA for all LEDs. The chips operate from a 3- to 5.5-volt supply and are rated for operation over -40 to +125°C.
The MAX6971/MAX6983 16-port drivers use the industry-standard, shift-register-plus-latch-type serial interface. The driver accepts data shifted into a 16-bit shift register using a data input and clock input. Input data appears at the output sixteen clock
cycles later to allow cascading of multiple devices. The latch-enable input loads the 16 bits of shift register data into a 16-bit output latch to determine which LEDs are on and which are off. The output-enable port gates all outputs on and off, and is fast enough to be used as a PWM input for LED intensity control.
The MAX6980 and MAX6983 deliver LED fault detection and fail-safe protection, allievating the need for external protective circuitry while cutting cost. The fault-detect feature reports open-circuit LED faults in the data stream. A watchdog timer clears the screen if the serial interface fails for more than 1 second.
Among the 8-port drivers, the MAX6970 provides standard, register-latched LED driver functionality. The MAX6981 adds LED open-circuit fault-detection.
The datasheets for the MAX6971 may be accessed by clicking here, and here for the MAX6983. The MAX6971 and MAX6983, in 24-pin TSSOP and 24-pin narrow PDIP packages, are priced at $1.98 and $2.14 each, respectively, both in 1k quantities. The MAX6970, MAX6980, and MAX6981, in 16-pin TSSOP and PDIP packages, are 99 cents, $1.11, and $1.03, respectively.
Maxim Integrated Products, 1-800-998-8800, www.maxim-ic.com