5V, 2.5A, 35V input buck regulator powers USB, with cable drop compensation

October 10, 2014 // By Graham Prophet
LT3697 is a 35V input capable step-down switching regulator (with 60V transient protection) designed to power 5V USB applications.

The LT3697 delivers precise 5V regulation at 2.5A to a remote USB port using programmable cable drop compensation to accurately correct the voltage drop from a long connecting cable regardless of variations in load current, with terminal output voltage being in the range 5.0V to 6.1V. The 5V output accuracy at the USB port is ±1.0% over the -40°C to 125°C temperature range.

The LT3697 uses an accurate and programmable output current limit, a power-good indicator and an output current monitor pin to improve system reliability and safety. This also allows the user to implement latchoff or auto-retry functionality, which can eliminate the need for a USB switch IC. An internal high efficiency switch delivers 90% efficiency and can be programmed to switch at 2 MHz, keeping switching noise out of critical frequency bands such as AM radio. The combination of its 16-lead thermally enhanced MSOP package and high switching frequency ensures that external inductors and capacitors are small, providing a compact, thermally efficient footprint.

The LT3697 uses a high efficiency power switch with the necessary oscillator, control, and cable compensation circuitry integrated into a single die. Internal cable compensation is programmable to accommodate the length and gauge of the cable, and dual input feedback allows an additional level of protection during fault conditions, further protecting USB devices. Other features include an FLT flag, short-circuit and thermal protection.

The LT3697EMSE is packaged in a thermally enhanced MSOP-16 package and is priced at $2.75. An industrial temperature version, the LT3697IMSE, operates from -40°C to 125°C junction temperature and is priced at $3.03. (Both 1000).

Linear Technology; www.linear.com/product/LT3697