Texas Instruments SN6505A transformer driver for isolated power supplies

The SN6505 is a low-noise, low-EMI push-pull transformer driver which is specifically designed for small form-factor, isolated power supplies. It drives low-profile, centre-tapped transformers from a 2.25 to 5 VDC power supply. Ultralow noise and EMI are achieved by slew rate control of the output switch voltage and through spread spectrum clocking (SSC).

The product consists of an oscillator followed by a gate drive circuit that provides the complementary output signals to drive ground-referenced N-channel power switches. The device includes two 1 A power-MOSFET switches to ensure start-up under heavy loads. The switching clock can also be provided externally for accurate placement of switcher harmonics or when operating with multiple transformer drivers.

The internal protection features include a 1.7 A current limiting, undervoltage lockout, thermal shutdown and break-before-make circuitry. A soft-start feature prevents high inrush current during power-up with large load capacitors. Available in a small 6-pin SOT23/DBV package, the device operation is characterised for a temperature range from -55 to +125°C.