Datasheet Linear Technology LTC1642

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Design Notes

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  Hot Swap Circuit Meets InfiniBand Specification &mdash DN265
  PDF, 81 Kb, File published: Aug 2, 2001
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  Hot Swap Circuit Meets InfiniBand Specification
  Design Note 265
  Pat Madden
  and Local Power Enable (active high). The LTC1642
  Hot Swapв„ў controller IC performs four functions in
  this circuit. It controls pass transistor Q1’s gate in
  response to both signals; it limits Q1’s drain current; it
  monitors VB_In for both overvoltage and undervoltage
  conditions; and starts the DC/DC converter downstream.
  The LTC1642 was selected because it can respond
  to two control inputs and its voltage range suits the
  application’s requirements. Although the backplane
  supplies 12V nominally, the InfiniBand specification
  requires steady-state operation to 14V DC and up to
  16V for 1ms transients; this is satisfactory because the
  LTC1642 is fully specified for operation up to 16.5V. Its An InfiniBand backplane distributes bulk power at 12V
  DC to a number of plug-in modules, each having a DC/
  DC converter that steps the 12V supply down to the
  voltages required locally. A pass transistor on each
  module isolates the converter’s input capacitors during
  module plug-in, allowing modules to be added without
  disturbing others on the backplane. The requirements
  governing module hardware design are found in the …

Articles

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  Hot Swap Circuit Gets InfiniBand Power onto your Module &mdash LT Journal
  PDF, 230 Kb, File published: May 1, 2001
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  DESIGN IDEAS Hot Swap Circuit Gets InfiniBand
  by Pat Madden
  Power onto your Module
  An InfiniBandв„ў backplane distributes bulk power at 12VDC to a number
  of plug-in modules, each having a
  DC/DC converter that steps the 12V
  supply down to the voltages required
  locally. A pass transistor on each
  module isolates the converter’s input
  capacitors during module plug-in,
  allowing modules to be added without
  disturbing others on the backplane.
  The requirements governing module
  hardware design are found in the
  InfiniBand Architecture Specification,
  Volume 2, Release 1.0. This article
  describes a circuit fully implementing the specification for sequencing
  bulk power. The power conversion
  problem is not discussed here.
  Figure 1 shows the circuit. Power
  is supplied from the backplane at
  InfiniBand is a trademark of the InfiniBand
  Manufacturers Association. 12VDC between VB_In and VB_Ret. …

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  LTC1642: a Hot Swap Controller with Foldback Current Limiting and Overvoltage Protection &mdash LT Journal
  PDF, 162 Kb, File published: Nov 1, 1999
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  DESIGN FEATURES LTC1642: a Hot Swap Controller
  with Foldback Current Limiting
  and Overvoltage Protection by Pat Madden
  Hot Circuit Insertion limit the charging current when a
  board is plugged into a hot backplane. In this application, the
  backplane voltage is 12V, but the
  chip will operate with any supply
  voltage between 3.0V and 16.5V. When
  power is first applied to VCC, the chip
  holds Q1’s gate at ground. After a
  programmable debounce delay, an
  internal 25ВµA current source begins
  to charge the external capacitor C2,
  generating a voltage ramp of 25ВµA/
  C2 V/s at the GATE pin. Because Q1
  acts as a source follower while its gate
  ramps, the current charging the
  board’s bypass capacitance, CLOAD, is
  limited to 25ВµA CLOAD/C2. An internal charge pump supplies the 25ВµA
  gate current, ensuring sufficient gate
  drive to Q1. Resistor R3 protects
  against high frequency FET oscillations; capacitor C1 sets the debounce
  delay, ∆TD, before the GATE pin voltage begins ramping: ∆TD(ms) = 615 C1(ВµF). The ON pin is the chip’s control input; when it is below 1.22V, the When a circuit board is inserted into …

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• Monitor, Control and Protection > Hot Swap Controllers > Low Voltage Hot Swap Controllers