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LT8709 - Negative Input Synchronous Multi-Topology DC/DC Controller

The LT®8709 is a synchronous PWM controller for negativeto- negative or negative-to-positive DC/DC conversion, with rail-to-rail output current monitor and control. The LT8709 is ideal for many local power supply designs. It can be easily configured in buck, boost, buck-boost, and inverting topologies with negative input voltages.

In addition, the LT8709’s rail-to-rail output current sense allows the part to be configured in current limited applications such as battery or capacitor charging. The PG pin is used for power good indication.

The LT8709’s switching frequency range can be set between 100kHz and 750kHz. The part may be clocked internally at a frequency set by the resistor from the RT pin to the –VIN pin, or it may be synchronized to an external clock.

The LT8709 also features innovative EN/FBIN pin circuitry that allows for slowly varying input signals and an adjustable undervoltage lockout function. The pin is also used as input voltage regulation to avoid collapsing a high impedance input supply. Additional features such as frequency foldback, thermal shutdown and soft-start are integrated. The LT8709 is available in a 20-lead TSSOP package.

Features Wide Negative Input Range: –4.5V to –80V Rail-to-Rail Output Current Monitor and Control Input Voltage Regulation for High Impedance Inputs Power Good Indication Pin MODE Pin for Forced CCM (Continuous Conduction Mode) or Pulse-Skipping/DCM (Discontinuous Conduction Mode) Operation Switching Frequency Up to 750kHz Easily Configurable as a Buck, Boost, Buck-Boost, or Inverting Converter with a Single Feedback Pin Can be Synchronized to an External Clock High Gain EN/FBIN Pin Accepts Slowly Varying Input Signals 20-Lead TSSOP Package Typical Application

Applications High Power Negative Input, Negative Output Power Supplies High Power Negative Input, Positive Output Power Supplies Telecom Equipment Power Supplies Cathodic Protection Power Supplies Packaging

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