Sunday, 29 January 2012

Synchronous Step-Down DC/DC Controller Delivers Up to 95% Efficiency with 2MHz Operating Frequency

Synchronous Step-Down DC/DC Controller Delivers 
Up to 95% Efficiency with 2MHz Operating Frequency

MILPITAS, CA – January 17, 2012 – Linear Technology Corporation introduces the LTC3839,
a high frequency controlled on-time single output dual phase synchronous  step-down DC/DC
controller that can achieve up to 92% efficiency with a 25A output when operating at 2MHz. The
operating frequency is selectable from 200kHz to 2MHz or can be synchronized to an external
clock. A low 30ns minimum on-time allows for a high step-down ratio at very high operating
frequencies. The controlled on-time, valley current-mode architecture and Detect Transient
Release feature provide a very fast transient response by increasing operating frequency during a
transient event, enabling the output voltage to recover in only a few clock cycles. Up to 12
phases can be paralleled and clocked out of phase for high current applications (up to 250A).
The LTC3839 operates over a 4.5V to 38V input voltage range, encompassing a wide
variety of applications including most intermediate bus voltages. Strong onboard N-channel
MOSFET gate drivers allow the use of high power external MOSFETs for output currents up to
50A, at output voltages ranging from 0.6V to 5.5V, making the device ideal for point-of-load
requirements. The LTC3839’s differential amplifier provides true remote output voltage sensing
of both the positive and negative terminals, enabling high accuracy regulation independent of
PCB IR losses (up to ±500mV). The output current is monitored by sensing the voltage drop
across the output inductor (DCR) for highest efficiency or by using a sense resistor for extra
precision. Additional features include an onboard bias voltage LDO, soft-start or tracking,
adjustable current limit, overvoltage protection, current limit foldback and external VCC control. 
The LTC3839 offers superior total regulation accuracy and is specified to account for all
error sources including line, load and differential sensing. The LTC3839 total output voltage
accuracy is +/-0.25% at 25°C, +/-0.67% from 0ºC to 85ºC, and ±1% maximum DC error over the
full -40°C to 125°C operating junction temperature range. The LTC3839 is available in a
thermally enhanced 5mm x 5mm QFN-32 package. The 1,000-piece price starts at $3.18 each.
For more information, visit

Synchronous Step-Down DC/DC Controller Delivers        page 2
Up to 95% Efficiency with 2MHz Operating Frequency

Photo Caption: High Frequency/High Efficiency Step-Down DC/DC Controller

Summary of Features: LTC3839

•  Controlled On-Time, Valley Current-Mode Control for Very Fast Transient Response
•  Programmable Operating Frequency from 200kHz to 2MHz, Synchronizable to an External Clock
•  Wide VIN Range: 4.5V to 38V
•  VOUT Range: 0.6V to 5.5V
•  Up to 50A Output Current
•  High Step-Down Ratio: 30ns Minimum On-Time
•  Up to 12 Phase Operation
•  Detect Transient Release Feature
•  Differential Amplifier for Remote Output Voltage Sensing
•  ±0.67% Output Voltage Accuracy over Temperature
•  RSENSE or DCR Current Sensing
•  Output Voltage Tracking or Programmable Soft Start
•  Adjustable Current Limit
•  Overvoltage Protection
•  Foldback Current Limit

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®

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