Dual output multiphase synchronous step-down DC/DC controller with 6-bit voltage identification

Linear Technology Corporation introduces the LTC3877, a dual output multiphase synchronous step-down DC/DC controller with 6-bit voltage identification (VID) control that enables 10mV output voltage step resolution, a necessary feature when powering FPGAs and ASICs with tight input voltage requirements. The LTC3877 operates over an input voltage range of 4.5V to 38V and produces a fixed output voltage from 0.6V to 1.23V when using VID and up to 5V without VID. Up to 12 phases can be paralleled and clocked out-of-phase to minimize filtering. When outputs are paralleled, the LTC3877 maintains better than ±2.5% current mismatch between phases, making it ideal for very high current requirements up to 300A. Applications include high current power distribution, redundant (n+1) supplies, industrial systems and processor power.

The LTC3877 maintains ±1% output voltage accuracy (including internal resistor divider and differential remote sense amplifier errors) over a –40°C to 125°C temperature range. Dual onboard differential amplifiers enable remote output voltage sensing for both outputs. High step-down ratios at high operating frequencies are possible with its 40ns minimum on-time. The LTC3877 has a selectable fixed operating frequency from 250kHz to 1MHz or it can be synchronized to an external clock. Powerful 1.1Ω onboard all N-channel gate drivers minimize MOSFET switching losses.

The LTC3877 operates with true current mode control and can be used with very low DC resistance (DCR) power inductors down to 0.3mΩ with its novel sensing scheme that enhances the signal-to-noise ratio of the current sense signal. This sensing scheme dramatically reduces the switching jitter normally associated with low DCR resistance applications and its adjustable current limit can be configured for very low sense voltages from 10mV to 30mV to minimize power loss. DCR temperature compensation maintains a constant current limit threshold over a broad temperature range. Additional features include adjustable soft-start or tracking, foldback current limit, short-circuit soft recovery, output overvoltage protection and two power good output voltage signals.

The LTC3877 is available in a 44-lead 7mm x 7mm QFN package. The 1,000-piece price starts at $3.94 each.