Dual-Output Synchronous Controller Requires No Sense Resistor

The LTC3836 synchronous step-down switching controller can generate two independent output voltages as low as 0.6 V, allowing it to power the latest generation of low-voltage DSPs and microcontrollers. Operating from a low input voltage of 2.75 to 4 V, the 2-phase, current-mode device is well suited for use with 3.3-V, single-cell Li-ion, or multicell alkaline, or NiMH sources. The LTC3836 is composed of two synchronous buck regulator controllers, with on-chip high-side and low-side synchronous rectifier drivers for N-channel MOSFETs. It can run at up to a 95% duty cycle for low voltage drop out, extending operating time in battery-powered systems.

The controllers operate 180° out of phase in order to minimize ripple current. This cuts EMI and minimizes the required input capacitance. The high-side MOSFET current-sense architecture provides current limiting and overload protection, eliminating the need for a sense resistor and boosting efficiency. Switching frequency is programmable up to 750 kHz, so designers can use small, surface-mount inductors. For noise-sensitive applications, the controller can be externally synchronized up to 850 kHz. Designers can configure the device for pulse-skipping operation to improve efficiency at light loads. A tracking function allows output voltage control during power up and power down.

The LTC3836 comes in a 28-lead SSOP or a 28-lead 4- by 5-mm QFN package, with an operating temperature range of -0°C to 85°C. Prices start at $2.75 each for 1000 pieces.