Dual output synchronous step-down controller produces 1.5-V output from up to 24-V input at 2-MHz

November 15, 2011 // By Paul Buckley
Linear Technology Corporation has introduced a high frequency controlled on-time dual output synchronous step-down DC/DC controller with differential output voltage sensing and clock synchronization. The controlled on-time, valley current-mode architecture enables a fast transient response by increasing its operating frequency during a transient event, enabling the LTC3838 to recover from a large load step in only a few clock cycles.

The operating frequency is selectable from 200 kHz to 2 MHz or can be synchronized to an external clock. A low 30 ns minimum on-time allows for a high step-down ratio power supply at high operating frequencies.

The LTC3838 operates over a 4.5 V to 38 V input voltage range, encompassing a wide variety of applications including most intermediate bus voltages. Strong onboard N-channel MOSFET gate drivers allow the use of high power external MOSFETs for output currents up to 25 A per channel, at output voltages ranging from 0.6 V to 5.5 V, making it ideal for point-of-load requirements.

The LTC3838’s differential amplifier provides true remote output voltage sensing of both the positive and negative terminals, enabling high accuracy regulation independent of board IR losses (up to ±500 mV). The output current is monitored by sensing the voltage drop across the output inductor (DCR) for highest efficiency or by using a sense resistor for extra precision. Additional features include an onboard bias voltage LDO, soft-start or tracking, adjustable current limit, overvoltage protection, current limit foldback and external V CC control.

The LTC3838 offers superior total regulation accuracy and is specified to account for all error sources including line, load and differential sensing. The LTC3838 total differential output voltage accuracy is ±0.25% at 25°C, ±0.67% from 0 to 85°C and ±1% maximum DC error over the full -40 to 125°C operating junction temperature range.

More information about the LTC3838 synchronous step-down DC/DC controller at www.linear.com/product/LTC3838