4.5V to 36V, 1A, High-Efficiency, Synchronous Step-Down DC-DC Converter

The MAX17645 is a high-efficiency, high voltage, synchronous step-down DC-DC converter with integrated MOSFETs, operates over a 4.5V to 36V input. It can deliver up to 1A load current. The MAX17645 operates at 650kHz switching frequency. The MAX17645B operates in pulse-width modulation (PWM) mode at all loads. The MAX17645D operates in pulse-frequency modulation (PFM) mode at light loads. The output voltage is programmable from 0.9V up to 89% of VIN. Built-in control loop compensation across the output voltage range eliminates the need for external compensation components. The feedback voltage regulation accuracy over -40°C to +125°C is ±1.1%.

The device features a peak-current-mode control architecture. In this architecture, while operating in PWM mode the part sets the duty cycle using a transconductance error amplifier, a PWM comparator, a high-side current-sense amplifier, and a slope-compensation generator. At each rising edge of the clock, the high-side MOSFET turns on and remains on until either the appropriate or maximum duty cycle is reached, or the peak current limit is detected. During the high-side MOSFET’s on-time, the inductor current ramps up. During the rest of the switching cycle, the high-side MOSFET remains off and the low-side MOSFET remains on, inductor current ramps down. An appropriate dead time is implemented between the high-side and low-side state transitions to avoid cross conduction.

A fixed soft-start time of 3.15ms (typ) allows users to reduce input inrush current. The device also features an enable/undervoltage lockout pin (EN/UVLO) that allows the user to turn on the part at the desired input-voltage level. An open-drain active-low RESET feature provides a power-good signal to the system upon achieving successful regulation of the output voltage.

Applications

* Factory Automation * Aftermarket Market Automation * General Point of Load

* Reduces External Components and Total Cost

* No Schottky—Synchronous Operation * Internal Control Loop Compensation * Internal Soft-Start * All Ceramic Capacitors, Ultra-Compact Layout

* Reduces Number of DC-DC Regulators to Stock

* Wide 4.5V to 36V Input Voltage Range * Adjustable Output from 0.9V up to 89% of VIN * Delivers Up to 1A Load Current

* High Efficiency

* 90% Full-Load Efficiency (VIN = 24V, VOUT = 5V, IOUT = 1A) * 2.2μA (typ) Shutdown Current * High Light-Load Efficiency with PFM Mode (MAX17645D)

* Flexible Design

* Programmable EN/UVLO Threshold * Monotonic Startup into Prebiased Output * Open-Drain Output (Actiive-Low RESET) for Output Status Monitoring

* Robust Operation

* Built-In Hiccup Mode Overload Protection * Overtemperature Protection * CISPR32 Class B Compliant * Wide -40°C to +125°C Ambient Operating Temperature/-40°C to +150°C Junction Temperature