20V, 4MHz, synchronous dual-output 6A step-down regulator in a compact 4mm x 5mm QFN package

     Linear Technology Corporation, a division of Analog Devices, introduces the LTC3636 and LTC3636-1 high-efficiency, 4MHz synchronous dual-output step-down regulators. Both devices feature a unique constant frequency/controlled on-time, current mode control scheme with phase-locked switching frequencies. In addition, its innovative design architecture reduces conducted and radiative emissions. These devices can provide a continuous output current of up to 6A per channel or produce a two-phase single output of up to 12A.

     Both devices are available in a compact 4mm x 5mm QFN package for output voltages as low as 0.6V. Switching frequencies in the 500kHz to 4MHz range are user-programmable, allowing the use of slim, low-cost capacitors and inductors, which can also be synchronized to an external clock signal. The LTC3636/-1 operates in an input voltage range of 3.1V to 20V, while the LTC3636 has an output voltage detection range of 0.6V to 5V and the LTC3636-1 has an output voltage detection range of 1.8V to 12V. This makes it ideal for two-node lithium-ion applications and 5V and 12V intermediate bus systems.

     Each channel of the LTC3636/-1 uses internal switches with RDS (ON) of only 32mΩ and 18mΩ to provide up to 95% efficiency. Their unique control architecture enables these devices to achieve duty cycles as low as 5% while maintaining switching frequencies up to 2.25MHz, making them ideal for high buck ratio applications, such as 12VIN to 1.8VOUT conversion. The two channels operate at a 180 degree difference, thus minimizing the size of the input and output capacitors. The two outputs can be combined in a two-phase configuration to provide up to 12A output current.

     Running in Burst Mode maximizes efficiency at light loads, up to 600µA at no load. For applications that require minimal noise, the LTC3636/-1 can be configured to operate in forced continuous mode, reducing power ripple and potential RF interference. Other features include a chip temperature monitor, power supply good voltage indicator, output voltage tracking, individual soft start per channel, short circuit protection, input overvoltage and overheat protection.