The AT9917 is an advanced fixed frequency PWM IC designed to control single-switch, boost, SEPIC, and buck LED drivers in a constant current mode. The controller uses a peak current-mode control scheme (with programmable slope compensation) and includes an internal transconductance amplifier to control the output current with high accuracy. The IC includes a +/-1A gate driver that makes the AT9917 suitable for high power applications. An internal 40V linear regulator powers the IC eliminating the need for a separate power supply for the IC. The IC provides a FAULT output, which can be used to disconnect the LEDs in case of a fault condition (such as an alternator load dump in automobiles) using an external disconnect FET. AT9917 also provides a TTL compatible, low-frequency PWM dimming input that can accept an external control signal with a duty ratio of 0-100% and a frequency of up to several kilohertz. Temperature foldback of the output current is possible, using an external NTC resistor.
The AT9917-based LED driver is suited for automotive LED driver applications. The AT9917 based LED lamp drivers can achieve efficiencies in excess of 90% when buck or boost topologies are used.
Switch mode controller for boost, SEPIC & buck converters
Closed loop control of output current
High PWM dimming ratio
Internal 40V linear regulator
Internal 3% voltage reference
Constant frequency operation with programmable slope compensation