Linear Technology has introduced the LTC3867, a fixed frequency synchronous step-down DC/DC controller with nonlinear control, differential output voltage sensing and clock synchronisation. Nonlinear control minimises the output voltage excursion during load transient events by increasing the operating frequency, allowing the controller to recover from a large load step in only a few cycles. The controller's 4 to 38V input range encompasses many applications including most intermediate bus voltages, says the company. Strong onboard N-channel MOSFET gate drivers can use the high power external MOSFETs for high load current, up to 25A, claims the company. The output voltage range is 0.6 to 14V, making the controller suitable for telecomms, datacomms, automotive and industrial applications.
The controller's differential amplifier provides true remote output voltage sensing of both the positive and negative terminals, enabling regulation independent of IR losses up to ±300mV in trace runs, vias and interconnects. A 65ns minimum on-time allows for a high step-down ratio power supply at high frequency operation. The operating frequency is selectable from 200kHz to 1.2MHz or can be synchronised to an external clock. The output current is monitored by sensing the voltage drop across the output inductor DCR for high efficiency or by using a sense resistor. Additional features include DCR temperature compensation, an onboard bias voltage LDO (low-dropout), soft-start or tracking, adjustable current limit, soft recovery from an output over-current condition, over-voltage protection, external VCC control and ±1% reference voltage over a -40 to 125°C operating junction temperature range. The controller is available in a thermally enhanced 4x4mm QFN-24 package.
