The LT3795 is a DC/DC controller designed to regulate a constant-current or constant-voltage and is ideal for driving LEDs. It drives a low side external N-channel power MOSFET from an internal regulated 7.7V supply. The fixed frequency and current mode architecture result in stable operation over a wide range of supply and output voltages. Spread spectrum frequency modulation (SSFM) can be activated for improved electromagnetic compatibility (EMC) performance. Ideally suitable for a wide variety of applications, including automotive, industrial and architectural lighting.
The LT3795 from Linear Technology is an 110V, high-side current sense DC/DC converter designed to regulate a current or voltage to a constant value, ideal for driving high brightness (HB) LEDs. Its 4.5V to 110V input voltage range makes it appropriate for a wide variety of applications, including automotive, industrial and architectural lighting.
This device uses an external low side N-channel MOSFET and can drive up to 90V of white LEDs from a nominal 12V input, delivering in excess of 50 watts. Spread spectrum frequency modulation reduces EMI emissions, while an internal PMOS switch driver delivers robust short-circuit protection in boost and buck-boost topologies.
The LT3795 incorporates a high-side current sense, enabling it to be used in boost, buck, buck-boost or SEPIC topologies. Additionally it offers both input and output current limiting and monitoring for added reliability and design flexibility.
This DC/DC controller can deliver efficiencies of over 94% in boost mode, minimizing the need for external heat sinking. A frequency adjust pin permits the user to program the frequency between 100kHz and 1MHz, optimizing efficiency while minimizing external component size and cost. Combined with a thermally enhanced TSSOP-28 package, the LT3795 offers a very compact HB LED driver or charger solution.
The LT3795 uses PWM dimming, which delivers constant LED color with dimming ranges of up to 3,000:1. For less demanding dimming requirements, the CTRL pin can be used to offer a 10:1 analog dimming range. Its fixed frequency, current mode architecture offers stable operation over a wide range of supply and output voltages. Robust open and short-circuit protection maximize overall system reliability, while C/10 detection optimizes both battery and SuperCap charging designs.
The ground referred voltage FB pin serves as the input for several LED protection features, and also allows the converter to operate as a constant-voltage source. The maximum output current is set by an external resistor, and the output current amplifier has a rail-to-rail common mode range. The LT3795 also includes a separate input current sensing amplifier that is used to limit input current. The TG pin inverts and level shifts the PWM signal to drive the gate of the external PMOS.
Additional features include input and output current reporting, frequency synchronization, programmable UVLO and a programmable fault restart timer.
The LT3795EFE is available in a thermally enhanced TSSOP-28 package. Pricing starts at $3.45 each. An extended temperature version or I-grade, the LT3795IFE, is also available with pricing starting at $3.86 each.
Finally, a high temperature, or H-grade, the LT3795HFE is available, the pricing starts at $4.11 each. All prices are in 1,000-piece quantities and all versions are available from stock.
For more information on the LT3795, visit www.linear.com/product/LT3795.
Summary of Features of the LT3795:
- 3000:1 True Color PWM™ Dimming
- Wide Input Voltage Range: 4.5V to 110V
- Input & Output Current Reporting
- PMOS Switch Driver for PWM & Output Disconnect
- Internal Spread Spectrum Frequency Modulation
- ±2% Constant Voltage Regulation
- ±3% Constant Current Regulation: 0V = VOUT = 110V
- Programmable Input Current limit
- CTRL Inputs Linearly Adjust LED Current
- Adjustable Frequency: 100kHz to 1MHz
- Programmable Open LED Protection with OPENLED Flag
- Short-Circuit Protection & SHORTLED Flag
- Programmable Undervoltage Lockout with Hysteresis
- Soft-Start with Programmable Fault Restart Timer
- C/10 Detection for Battery Charging
- Available in 28-Lead TSSOP Package
Typical Application
Applications
- High Power LED, High Voltage LED
- Battery Chargers
- Accurate Current Limited Voltage Regulators
About Linear Technology
Linear Technology Corporation, a manufacturer of high performance linear integrated circuits, was founded in 1981, became a public company in 1986 and joined the S&P 500 index of major public companies in 2000. Linear Technology products include high performance amplifiers, comparators, voltage references, monolithic filters, linear regulators, DC-DC converters, battery chargers, data converters, communications interface circuits, RF signal conditioning circuits, µModule products, and many other analog functions. Applications for Linear Technology’s high performance circuits include telecommunications, cellular telephones, networking products such as optical switches, notebook and desktop computers, computer peripherals, video/multimedia, industrial instrumentation, security monitoring devices, high-end consumer products such as digital cameras and MP3 players, complex medical devices, automotive electronics, factory automation, process control, and military and space systems.
Linear Technology (UK) Limited
Tel: +44 (0)1628 477066
E-mail: uksales@linear.com
Web site: www.linear.com
Website for product information: http://www.linear.com/product/LT3795
