SN6505 Low-Noise Transformer Drivers

By Texas Instruments 76

SN6505 Low-Noise Transformer Drivers

Texas Instruments' SN6505 is a low-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 VDC power supply. Ultra-low noise and EMI are achieved by slew rate control of the output switch voltage and through spread spectrum clocking (SSC). The SN6505 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, under-voltage lockout, thermal shutdown, and break-before-make circuitry. SN6505 includes a soft-start feature that prevents high inrush current during power up with large load capacitors. The SN6505 is available in a small 6-pin SOT23/DBV package. The device operation is characterized for a temperature range from -55°C to 125°C.

TI Design Link: Reference Design for Isolated Gate Driver Power Stage with Active Miller Clamp for Solar Inverters

Features
  • 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 RON 0.25 Ω max at 4.5 V supply
  • Spread spectrum clocking
  • Precision internal oscillator options: 160 kHz (SN6505A) and 420 kHz (SN6505B)
  • Synchronization of multiple devices with external clock input
  • Ultra-low EMI 
  • Slew-rate control
Applications
  • Isolated power supply for CAN, RS-485, RS-422, RS-232, SPI, I2C, and low-power LAN
  • Low-noise isolated USB supplies
  • Process control
  • Telecom supplies
  • Radio supplies
  • Medical instruments
  • Distributed supplies
  • Medical instruments
  • Precision instruments
  • Low-noise filament supplies

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