New from Allegro MicroSystems Europe, the A6279 Series is a family of 16-bit constant-current latch LED driver ICs with built-in facilities for open LED detection.
Each BiCMOS device includes a 16-bit CMOS shift register, accompanying data latches, and 16 n-p-n constant-current sink drivers. The CMOS shift register and latches allow direct interfacing with microprocessor-based systems. With a 3.3 V or 5 V logic supply, typical serial data-input rates are up to 25 MHz.
The LED drive current is determined by the user's selection of a single resistor. Once set, the current will remain constant regardless of the LED voltage variation, supply voltage variation, or other circuit parameters that could otherwise affect LED current.
A CMOS serial data output permits cascade connections in applications requiring additional drive lines. Open LED connections can be detected and information fed back to the host microprocessor through the serial data-out pin.
The A6279 includes an internal undervoltage lockout circuit that disables the driver's outputs in the event of the logic supply voltage dropping below a minimum acceptable level, thereby preventing the display of erroneous information.
The device has a 20 ns delay between each output. The staggering of the outputs reduces the inrush of currents onto the power and ground planes to aid power-supply decoupling and to minimise EMI/EMC effects.
The A6279 Series consists of three devices with different package styles and allowable package power dissipation: through-hole DIP (suffix 'A'), surface-mount SOIC (suffix 'LW'), and exposed pad TSSOP (suffix 'LP').
Under normal operating conditions, the device's copper lead frame and low logic power dissipation allow the dual in-line package to sink maximum rated current (90 mA at 0.75 V drop) through all outputs continuously over the operating temperature range (-40° to +85°C).