36V Input with 60V Transient 700mA, Micropower Step-Down Regulator Has On-Chip Power-On Reset & Watchdog Timer

News Release ⎜ www.linear.com
36V Input with 60V Transient 700mA, Micropower Step-Down Regulator
Has On-Chip Power-On Reset & Watchdog Timer
MILPITAS, CA – August 27, 2009 – Linear Technology Corporation announces the LT3689, a
700mA, 36V input step-down switching regulator with a power-on reset and watchdog timer. Its
Burst Mode® operation keeps quiescent current under 85uA in no load standby conditions. The
LT3689’s 3.6V to 36V input voltage range, with 60V transient ride through, makes it ideal for
load dump and cold crank conditions commonly found in automotive applications. Its 1.2A
internal switch can deliver up to 700mA of continuous output current at voltages as low as 0.8V.
The LT3689’s Burst Mode® operation provides ultralow quiescent current, well suited for
applications such as automotive or telecom systems, which demand always-on operation and
optimum battery life. Switching frequency is user programmable from 350kHz to 2.2MHz,
enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency
bands. The LT3689’s 3mm x 3mm QFN-14 (or thermally enhanced MSOP-16) package and high
switching frequency keeps external inductors and capacitors small, providing a very compact,
thermally efficient footprint.
The integrated microprocessor supervisor functions support high reliability applications
such as automotive electronic control units.The reset and watchdog timeout periods are
independently adjustable using external capacitors. Tight accuracy specifications and glitch
immunity ensure reliable reset operation of a system without false triggering. The open collector
RST will pull down if output voltage drops 10% below the programmed value. The watchdog
timer is pin-selectable for window or timeout modes. In timeout mode, WDO pulls low if too
long a period passes before a watchdog transition is detected. In window mode, the LT3689
monitors for WDI falling edges grouped too close together or too far apart.
The LT3689 utilizes a high efficiency 1.2A, 450mV switch, with an integrated boost
diode, oscillator, control and logic circuitry integrated into a single die. Low ripple Burst Mode
operation maintains high efficiency at low output currents while keeping output ripple below
36V Input with 60V Transient 700mA, Micropower Step-Down Regulator
Has On-Chip Power-On Reset & Watchdog Timer
page 2
15mVPK-PK. Special design techniques and a new high voltage process enable high efficiency
over a wide input voltage range, and current mode topology enables fast transient response and
excellent loop stability. Other features include external synchronization (from 350kHz to
2.2MHz), a power good flag and soft-start capability.
The LT3689EUD and LT3689EMSE are priced starting at $3.20 and $3.25 each,
respectively, for 1,000 piece quantities. The LT3689IUD and LT3689IMSE are tested and
guaranteed to operate from a -40°C to 125°C operating junction temperature and are priced at
$3.56 and $3.61 each, respectively, in 1,000 piece quantities. Finally, the LT3689HMSE is tested
and guaranteed to operate from a -40°C to 150°C operating junction temperature and is priced at
$3.86 each in 1,000 piece quantities. All versions are available from stock. For more
information, visit www.linear.com.
Photo Caption: 36V (60V Transient Protection), 700mA Step-Down Regulator with Power-On
Reset and Watchdog Timer
Summary of Features: LT3689
Wide Input Range: Operation from 3.6V to 36V, Overvoltage Lockout Protects Circuits through
60V Transients
700mA Output Switching Regulator with Internal Power Switch
Low Ripple (<15mVP-P) Burst Mode® Operation: IQ= 85uA IQ at (12VIN to 3.3VOUT)
Programmable, Defeatable Watchdog Timer with Window or Timeout Control
Programmable Power-On Reset Timer (POR)
Synchronizable, Adjustable 350kHz to 2.2MHz Switching Frequency
Adjustable Output Voltage
800mV Feedback Voltage
Programmable Input Undervoltage Lockout with Hysteresis
16-Pin 3mm × 3mm QFN & 16-Pin MSOP Packages
36V Input with 60V Transient 700mA, Micropower Step-Down Regulator
Has On-Chip Power-On Reset & Watchdog Timer
page 3
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,
uModule® 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.
LT, LTC, LTM, uModule, Burst Mode 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]
408-432-1900 ext 2233