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LTC1778-1

Design Notes

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  High Performance Switch Mode Power Solutions for Altera Low Voltage FPGAs &mdash Design Solutions 43
  PDF, 158 Kb, File published: Jun 1, 2004
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  Design Solutions 43
  June 2004
  High Performance Switch Mode Power Solutions
  for Altera Low Voltage FPGAs
  by Mike Shriver
  INTRODUCTION
  The core voltages for FPGAs are moving lower as a result
  of advances in the fabrication process. The newest FPGA
  family from Altera, the StratixВ® II, now requires a core
  voltage of 1.2V and the Stratix, Stratix GX, HardCopyВ®
  Stratix and CycloneTM families require a core voltage of
  1.5V. This article discusses how to power the core and I/O
  of low voltage FPGAs using the latest step-down switch
  mode controllers from Linear Technology Corporation.
  To ensure correct selection of power management circuitry,
  it is recommended to use Altera’s PowerPlay Power Estimation Tools to obtain accurate results. Tools are available
  to help determine power consumption before and during
  the design process. More information on these tools is
  available from Altera’s website: http://www.altera.com/
  support/devices/estimator/pow-powerplay.html.
  Overview
  The load and input voltage requirements for FPGA systems vary considerably. A single FPGA typically requires
  less than 2A, but for systems using multiple FPGAs, the …

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  High Efficiency I/O Power Generation for Mobile Pentium III Microprocessors &mdash DN258
  PDF, 86 Kb, File published: May 3, 2001
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  advertisement High Efficiency I/O Power Generation for Mobile
  Pentimum III Microprocessors – Design Note 258
  Wei Chen
  The demand for higher performance notebook computers has fueled the development of faster and more
  power-hogging microprocessors. These microprocessors also require a faster input/output (I/O) bus and a
  faster clock. From a power management perspective,
  this means that core, I/O and clock power supplies
  should be able to handle more power. This requires that
  core and I/O DC/DC converters operate more efficiently
  and be as small as possible. Linear Technology recommends the LTC В®1778 to provide I/O power for the next
  generation Pentium III microprocessors. The I/O input
  voltage requirement is 1.25V; transient (AC) tolerance
  is В±9% and static (DC) tolerance is В±5%. Load current
  requirements are as follows:
  Processor V TT: 2.7A
  830M chipset V TT: 0.7A 1. Internal graphics using the 830M engine: 3.6A
  2. External AGP graphics: 1.6A
  Total maximum I/O current: 7.0A
  The LTC1778 is a synchronous step-down switching
  regulator controller that provides synchronous drive for
  two external N-channel MOSFET switches. The true current mode control architecture has an adjustable current
  limit, can be easily compensated, is stable with ceramic
  output capacitors and does not require a power-wasting …

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  Microprocessor Core Supply Voltage Set by I2C Bus Without VID Lines &mdash DN279
  PDF, 75 Kb, File published: Mar 1, 2002
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  advertisement Microprocessor Core Supply Voltage Set by I2C Bus
  without VID Lines – Design Note 279
  Mark Gurries
  Introduction
  Many modern CPUs run at two different clock speeds,
  where each speed requires a different core operating
  voltage to assure optimum performance. These voltages
  are documented in the manufacturer’s VID (voltage
  identification) section of the CPU specification. Some
  new DC/DC converters (the LTCВ®1909, for example) have
  built-in VID control that supports dual programmable
  output voltages, but many existing converters do not.
  The LTC1699 is a precision 2-state resistive divider that
  uses a simple SMBus interface to allow VID control on
  non-VID-enabled DC/DC converters. No dedicated VID
  lines are required.
  How it Works
  DC/DC converters maintain consistent output voltage
  by comparing the output voltage, through an accurate
  voltage divider, against an internal reference and adjusting the output to compensate for differences. The
  LTC1699 is a 2-state resistive divider that replaces the
  п¬Ѓxed voltage divider in the feedback circuit, thus allowing the circuit to support two different voltage outputs.
  It is speciп¬Ѓcally designed to work with DC/DC PWM …

Articles

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  Low Voltage, High Current DC/DC Power Supply with Load Sharing and Redundancy &mdash LT Journal
  PDF, 183 Kb, File published: Aug 9, 2004
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  DESIGN IDEAS Low Voltage, High Current DC/DC
  Power Supply with Load Sharing and
  Redundancy
  by Henry J. Zhang and Wei Chen
  Introduction
  As computer and networking systems
  get larger and faster, their supply
  currents continue to rise and their
  supply voltages continue to drop. Load
  currents are high enough to require
  that power supply designers use several power supply modules in parallel.
  High performance power supplies for
  data-processing and communication
  equipment must also provide exceptional reliability and fault tolerance.
  For example, power systems for mission-critical data processing systems
  are must be functional better than
  99.999% of the time. To satisfy the
  needs of these systems, the power
  management solution must provide
  load sharing, fault tolerance and redundancy.
  This article presents a power management solution that offers all of
  these features in a relatively simple
  circuit that uses the LTC3729 …

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  New No Rsense Controllers Deliver Very Low Output Voltages &mdash LT Journal
  PDF, 182 Kb, File published: Feb 1, 2001
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  DESIGN FEATURES New No RSENSE Controllers Deliver Very
  Low Output Voltages by Christopher B. Umminger
  Valley Current Control
  Digital system voltages are dropping of very high efficiency DC/DC step-Enables tON(MIN) < 100ns
  Introduction ever lower, yet battery voltages are
  not. This forces DC/DC step-down
  converters in portable products to
  operate at lower duty cycles. Unfortunately, low duty cycle operation
  decreases efficiency due to both
  increased switching losses and the
  increased importance of I2R losses at
  low output voltages. Furthermore,
  conventional control architectures
  often have difficulty operating with
  very short switch on-times. The
  LTC1778 and LTC3711 with VID
  address these problems with a new
  architecture for buck regulators that
  delivers the low output voltages and
  high efficiencies that modern portable supplies require.
  The LTC1778 is a step-down controller that provides synchronous
  drive for two external N-channel
  MOSFET switches. It comes with a …

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  SMBus Controls CPU Voltage Regulators without VID Pins &mdash LT Journal
  PDF, 148 Kb, File published: Sep 1, 2001
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  DESIGN IDEAS SMBus Controls CPU Voltage
  Regulators without VID Pins by Mark Gurries Introduction
  The LTC1699 allows a variety of nonVID equipped voltage regulators to be
  programmed to VID voltages via the
  SMBus. Many microprocessors
  require core voltage changes when
  switching from one clock frequency to
  another. These voltages are specified
  in 5-bit VID (voltage identification)
  tables. The LTC1699 is a precision,
  digitally programmed resistor divider
  that provides output voltage feedback to PWM controllers that have a
  reference voltage of 0.8V, such as the
  LTC1702, LTC1628, LTC1735 and
  the new LTC1778. It uses the SMBus
  to determine the two output voltages
  that can be selected by the SEL pin. A
  Power Good signal is provided to tell
  the system that CPU voltage is in
  regulation. An enhanced version of
  the part, the LTC1699EGN, expands
  the power sequencing to coordinate
  multiple DC/DC converters that manage other CPU system voltages such …

Model Line

Manufacturer's Classification

• Power Management > Switching Regulator > Step-Down (Buck) Regulators > External Power Switch Buck Controllers