Datasheet Linear Technology LT1776

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Design Notes

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  The LT1776 Provides Power for the IEEE1394 Fire Wire &mdash DN191
  PDF, 605 Kb, File published: Oct 1, 1998
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  The LT1776 Provides Power for the IEEE1394 “FireWire”
  Design Note 191 Ajmal Godil
  Faster microprocessors, more memory and better graphics have fueled the rapid growth of the personal computer
  industry. However, many of the peripheral connections
  use older interface technologies that are starting to limit
  performance and growth for future applications.
  The IEEE1394 High Performance Serial Bus (“FireWire”)
  addresses these interface issues by providing a flexible and
  cost-effective way to share real time information among
  data-intensive applications, such as digital camcorders,
  digital VCRs and digital video disks (DVDs). This serial bus
  supports data transfer rates of 100Mbps, 200Mbps and
  400Mbps. It also provides unregulated 8VDC to 40VDC
  at up to 1.5A. As many as sixteen devices can be connected to the IEEE1394 bus, with cable segments between
  devices of up to 4.5 meters. The junction or node where
  a device connects to the bus may be a power source, a
  power sink or neither. Since there may be more than one
  power source, all power sources are diode connected. SUPPLY 1 NODE 1 SUPPLY 2 NODE 2 IEEE1394
  BUS Figure 3 is a schematic of a circuit that produces a regulated 5V at 500mA from a FireWire input (8V to 40V).
  The LTВ®1776 is a high voltage, high efficiency buck converter IC. The IC includes an onboard power switch, oscillator, control and protection circuitry. The part can accept
  an input voltage as high as 40V and the power switch is
  rated at 700mA peak current. Current mode control offers
  excellent dynamic input supply rejection and overcurrent …

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  60V, High Efficiency Buck Switching Regulators in SO-8 &mdash DN202
  PDF, 104 Kb, File published: Apr 1, 1999
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  advertisement 60V, High Efficiency Buck Switching Regulators in SO-8
  Design Note 202
  Ajmal Godil
  The LT®1676/LT1776 are wide input range, high efficiency buck (step-down) switching regulators in SO-8
  packages. Typical applications include automotive
  DC/DC conversion, telecom 48V step-down and
  IEEE1394 (FireWire) step-down converters. Since both parts allow such a wide input voltage range,
  they use two techniques to optimize efficiency. First,
  the internal control circuitry draws power from the VCC
  pin, which is normally connected to the output supply.
  During start-up, the controllers draw power from VIN.
  When the output voltage exceeds 2.9V, the bias power
  comes from the output. This reduces quiescent power
  consumption by hundreds of milliwatts when operating at high input voltage. Second, the switch circuitry
  maintains a fast rise time at high loads (see Figure 2).
  Both of these factors help in maximizing efficiency with
  high input voltages. At light loads, the switch rise time
  slows down (see Figure 3) to avoid pulse skipping, thus
  maintaining a constant frequency from heavy to light
  loads. This helps significantly in reducing the output Both the LT1676 and the LT1776 can accept input
  voltages from 7V to 60V. The LT1676 has a nominal
  switching frequency of 100kHz whereas the LT1776
  runs at 200kHz. For higher input voltage applications, …

Articles

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  Wide Input Range, High Efficiency Step-Down Switching Regulators &mdash LT Journal
  PDF, 257 Kb, File published: Nov 1, 1998
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  DESIGN FEATURES Wide Input Range, High Efficiency
  Step-Down Switching Regulators
  by Jeff Schenkel
  Introduction
  The LT1676 and LT1776 are Linear
  Technology’s latest offerings for high
  efficiency step-down switching regulator applications. These two parts
  are pin-for-pin compatible and virtually identical in operation, the only
  difference being their internal oscillator frequencies—100kHz for the
  LT1676 vs 200kHz for the LT1776.
  They operate in a fixed frequency
  mode (as opposed to constant offtime or on-time, for instance) and can
  be externally synchronized to a higher
  switching frequency.
  The internal output switch is rated
  at a nominal peak current of 700mA,
  which typically accommodates DC
  output currents of up to 500mA. The
  input voltage range is 7.4V to 60V.
  Maintaining acceptable efficiency in
  the upper half of this input voltage
  range requires very fast output-switch
  edge rates. The LT1676/LT1776 contain specialized output circuitry to …

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Manufacturer's Classification

• Power Management > Switching Regulator > Step-Down (Buck) Regulators > Internal Power Switch Buck | High Input Voltage Buck