36V, with 55V Transient Protection, 500mA(IOUT), Step-Down DC/DC Converter with Integrated LDO

News Release ⎜ www.linear.com
36V, with 55V Transient Protection, 500mA(IOUT), Step-Down
DC/DC Converter with Integrated LDO
MILPITAS, CA – May 12, 2011 – Linear Technology Corporation announces the LT3645, a
500mA (IOUT), 36V step-down switching regulator and integrated LDO packaged in a
3mm x 3mm QFN or MSOP-12E. The LT3645 operates from a VIN range of 3.6V to 36V with
transient protection to 55V, making it ideal for load dump and cold-crank conditions found in
automotive applications. Its internal 0.75A internal switch can deliver up to 500mA of
continuous output current to voltages as low as 0.8V. The LT3645 uses a constant switching
frequency of 750kHz to minimize noise while optimizing efficiency. In addition to the primary
switcher channel, the integrated LDO can be used for an additional low noise output of up to
200mA of continuous current at voltages as low as 0.8V. Powering the LDO from the primary
switching output offers both high efficiency and low noise for applications such as
microprocessor core voltages. The LT3645 provides a compact, thermally efficient dual output
solution, with its 3mm x 3mm QFN-16 package (or thermally enhanced MSOP-12E) and high
switching frequency, which keeps external capacitors and inductor small,
The LT3645’s main switcher utilizes a high efficiency 750mA, 450mVCESAT switch, with
the necessary oscillator, control, logic circuitry and LDO integrated into a single die. Special
design techniques enable high efficiency over a wide input voltage range while its current mode
topology enables fast transient response and excellent loop stability. A current-limited DA pin
offers an additional level of protection to improve overall reliability. The linear regulator
operates from the VCC2 pin at voltages ranging from 1.2V to 16V with only a 310mV dropout
voltage. Other features of the LT3645 include a power good flag, soft-start and thermal
The LT3645EUD is offered in a 3mm x 3mm 16-lead QFN package and is priced at
$2.25 each. The LT3645EMSE is offered in a 12-lead, thermally enhanced MSOP package and
is priced at $2.35 each. Industrial grade versions, namely the LT3645IUD and the
LT3645IMSE, are tested and guaranteed to operate from a -40°C to 125°C operating junction
36V, with 55V Transient Protection, 500mA(IOUT), Step-Down
DC/DC Converter with Integrated LDO
page 2
temperature and are priced at $2.48 and $2.59 each, respectively. The LT3645HMSE is tested
and guaranteed to operate from a -40°C to 150°C operating junction temperature and is priced at
$2.84 each. All prices are for 1,000-piece quantities and all versions are available from stock.
For more information, visit www.linear.com/product/LT3645
Photo Caption: 36V, 500mA(IOUT), Step-Down DC/DC Converter with Integrated LDO
Summary of Features: LT3645
Wide Input Range: Operation from 3.6V to 36V, Overvoltage Lockout Protects Circuit through
55V Transients
500mA Output Current Switching Regulator
Constant Switching Frequency: 750kHz
200mA Low Dropout Linear Regulator 1.2V to 16V Input; 0.8V to 8V Output
310mV Dropout Voltage VCC2 to OUT2
Precision Undervoltage Lockout
Short-Circuit Robust
Internal Soft Start
<2μA Shutdown Current
Small Thermally Enhanced 16-Lead (3mm × 3mm) QFN & 12-Lead MSE Packages
About Linear Technology
Linear Technology Corporation, a member of the S&P 500, has been designing, manufacturing
and marketing a broad line of high performance analog integrated circuits for major companies
worldwide for three decades. The Company’s products provide an essential bridge between our
analog world and the digital electronics in communications, networking, industrial, automotive,
computer, medical, instrumentation, consumer, and military and aerospace systems. Linear
Technology produces power management, data conversion, signal conditioning, RF and interface
ICs, and µModule® subsystems.
LT, LTC, LTM, µModule and
are registered trademarks of Linear Technology Corp. All other trademarks are the
property of their respective owners.
Press Contacts:
North America / Worldwide
UK & Nordic
John Hamburger, Director Marketing
[email protected]
Tel: 408-432-1900 ext 2419
Alan Timmins
[email protected]
Tel: +44-1-252-629937
Doug Dickinson, Media Relations Manager
[email protected]
Tel: 408-432-1900 ext 2233