Low-noise, 1-A, 160-kHz transformer driver with soft start for isolated power supplies


Product details


Rating Catalog Output current (A) 1 Vin (Min) (V) 2.25 Vin (Max) (V) 5.5 Features Enable, Short-circuit protection, Spread spectrum clocking, Thermal shutdown, Slew-rate control Soft start Yes Operating temperature range (C) -55 to 125 Iout (Max) (A) 1.5 Switching frequency (Min) (kHz) 100 Switching frequency (Max) (kHz) 600 Vout (Max) (V) 16 Vout (Min) (V) 0 Switch current limit (Typ) (A) 2 open-in-new Find other Transformer drivers

Package | Pins | Size

SOT-23 (DBV) 6 5 mm² 2.9 x 1.6 open-in-new Find other Transformer drivers


  • 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

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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 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. 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.

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Technical documentation

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Type Title Date
* Data sheet SN6505x Low-Noise 1-A Transformer Drivers for Isolated Power Supplies datasheet (Rev. H) Apr. 18, 2019
Application note How to Isolate Signal and Power in Isolated CAN Systems (Rev. B) Oct. 08, 2020
Application note Isolated CAN Reference Design (Rev. E) Jul. 22, 2020
Application note Signal and Power Isolation with 3.3 V / 5 V Input and 12 V / 15 V Output Oct. 17, 2018
Application note How to isolate signal and power for an RS-485 system (Rev. B) Oct. 16, 2018
Application note How to isolate signal and power for I2C (Rev. A) Oct. 02, 2018
User guide SN6505A and SN6505B Evaluation Module User's Guide Dec. 10, 2015

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Hardware development

document-generic User guide
The evaluation module (EVM), featuring the SN6505A transformer driver, also contains a small form-factor transformer, simple rectifier circuit, and voltage regulator that can be used to simulate a complete isolated power-supply system suitable for many applications.
  • Low-noise 1-A transformer driver for isolated power supplies, 160-kHz internal clock
  • 5-V input, 5-V output isolated power
  • Simple rectifier circuit along with low droput (LDO) regulator gives rectified voltage of 5 V
  • Provision for feeding external clock to the device
  • EVM tested for device functionality (...)

Design tools & simulation

SLLM293.ZIP (11 KB) - IBIS Model
SLLM302A.ZIP (4 KB) - PSpice Model
PSpice® for TI design and simulation tool
PSPICE-FOR-TI — PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
  • Leverages Cadence PSpice Technology
  • Preinstalled library with a suite of digital models to enable worst-case timing analysis
  • Dynamic updates ensure you have access to most current device models
  • Optimized for simulation speed without loss of accuracy
  • Supports simultaneous analysis of multiple products
  • (...)
SPICE-based analog simulation program
TINA-TI TINA-TI provides all the conventional DC, transient and frequency domain analysis of SPICE and much more. TINA has extensive post-processing capability that allows you to format results the way you want them. Virtual instruments allow you to select input waveforms and probe circuit nodes voltages (...)
document-generic User guide

Reference designs

High-efficiency, low-emission, isolated DC/DC converter-based analog input module reference design
TIDA-010065 — This reference design is a simplified architecture for generating an isolated power supply for isolated amplifiers for measuring isolated voltages and currents. A fully integrated DC/DC converter with reinforced isolation operating from a 5-V input with configurable 5-V or 5.4-V output (headroom for (...)
document-generic Schematic document-generic User guide
Reference Design for 1200V Isolated I2C High Side Current Sensing for Solar Combiner Boxes
TIDA-01590 — This reference design is an isolated high-side current sensing design for a smart combiner box in a grounded or ungrounded system. The current sensing topology enables multichannel, sub ±1% error, isolated current sensing for high-voltage systems up to 1200-VDC, limited by the DC/DC transformer.
document-generic Schematic document-generic User guide
18-bit, 2-Msps Isolated Data Acquisition Reference Design to Achieve Maximum SNR and Sampling Rate
TIDA-00732 This “18-bit, 2-Msps Isolated Data Acquisition Reference Design to achieve maximum SNR and sampling rate”  illustrates how to overcome performance-limiting challenges typical of isolated data acquisition system design:
  • Maximizing sampling rate by minimizing propagation delay introduced by digital (...)
document-generic Schematic document-generic User guide

CAD/CAE symbols

Package Pins Download
SOT-23 (DBV) 6 View options

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