1 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

• 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

2 Applications

• Isolated power supply for CAN, RS-485, RS-422,

RS-232, SPI, I2C, low-power LAN

• Low-noise isolated USB supplies

• Process control

• Telecom supplies

• Radio supplies

• Distributed supplies

• Medical instruments

• Precision instruments

• Low-noise filament supplies

3 Description

The SN6505x 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 V DC 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 SN6505x consists of an oscillator

followed by a gate drive circuit that provides

the complementary output signals to drive groundreferenced

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.

SN6505x includes a soft-start feature that prevents

high inrush current during power up with large load

capacitors. SN6505A has a 160 kHz internal oscillator

for applications that need to minimize emissions

whereas SN6505B has a 420 kHz internal oscillators

for applications that require higher efficiency and

smaller transformer size. The SN6505x 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.