100mA synchronous buck converter with 150V input eliminates TVS

May 13, 2013 // By Graham Prophet
Linear Technology's LTC3639 is a 150V input-capable synchronous buck converter that delivers up to 100mA of continuous output current. It operates from an input voltage range of 4.5V to 150V, eliminating the need for an external transient suppression device.

It uses internal synchronous rectification and a programmable peak current-mode design to optimise efficiency over a broad range of output currents. It delivers efficiencies as high as 92% and requires only 12 µA of quiescent current, maximising battery run time and eliminating thermal issues. A user-programmable output current limit can set output current from 10mA to 100mA to minimise the need to oversize external components and protect high impedance sources. The LTC3639 can be programmed with fixed output voltages of 1.8V, 3.3V or 5V or a resistor divider can be used to program outputs from 0.8V to VIN. The LTC3639’s thermally enhanced MSOP package offers the additional pin spacing required for high voltage inputs. The combination of its MSOP package with only three small external components provides a highly compact solution footprint for a broad range of applications.

The LTC3639’s internal high side and synchronous power switches, drawing only 12µA at no load while maintaining output voltage regulation, make it ideal for always-on battery-powered applications. Due to the inherent stability of the converter, no external compensation is required, simplifying the design and minimising the solution footprint. Additional features include a precise 0.8V +1% feedback voltage reference, internal or external soft-start and a feedback comparator output which enables multiple LTC3639s to be connected in parallel for higher current applications.

Pricing for the LTC3639EMSE starts at $3.65 91000). An industrial temperature grade version, the LTC3639IMSE is guaranteed to operate from -40°C to 125°C operating junction temperature, and costs $4.02. An automotive temperature grade, the LTC3639HMSE is guaranteed to operate over a -40°C to 150°C operating junction temperature range, at $4.27. Finally, a high reliability military plastic version, the LTC3639MPMSE, is tested and guaranteed to operate from -55°C to 150°C operating junction temperature, priced at $10.84.

Linear Technology, www.linear.com