SN6505B - Low-noise 1-A, 420kHz transformer driver for isolated power supplies

The SN6505x is alow-noise, low-EMI push-pull transformer driver, specifically designed for small form factor,isolated power supplies. It drives low-profile, center-tapped transformers from a 2.25 V to
5 V DC power supply. Ultra-low noise and EMI are achieved by slew rate control of the output switch voltage and throughSpread Spectrum Clocking (SSC). The SN6505x consists of an oscillator followed by a gate drive circuit thatprovides the complementary output signals to drive ground-referenced N-channel power switches. Thedevice includes two 1-A Power-MOSFET switches to ensure start-up under heavy loads. The switchingclock can also be provided externally for accurate placement of switcher harmonics, or whenoperating with multiple transformer drivers. The internal protection features include a 1.7 Acurrent limiting, under-voltage lockout, thermal shutdown, and break-before-make circuitry.SN6505x includes a soft-startfeature that prevents high inrush current during power up with large load capacitors. The SN6505 isavailable in a small 6-pin SOT23/DBV package. The device operation is characterized for atemperature range from –55°C to125°C.

• Push-Pull Driver for transformers
• Wide Input Voltage Range: 2.25 V to 5.5 V
• High Output Drive: 1 A at 5 V Supply
• Low R_ON 0.25 Ω Max at 4.5 V Supply
• Ultra-Low EMI
• Spread Spectrum Clocking
• Precision Internal Oscillator Options: 160 kHz (SN6505A) and 420 kHz (SN6505B)
• Synchronization of Multiple Devices with External Clock Input
• Slew-Rate Control
• 1.7 A Current-Limit
• Low Shutdown Current: <1 µA
• Thermal Shutdown
• Wide Temperature Range: –55°C to 125°C
• Small 6-Pin SOT23 (DBV) Package
• Soft-Start to reduce In-rush current

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