Datasheet Linear Technology LTC1477

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LTC1478

Design Notes

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  70mOhm Protected Load Management Switch &mdash DN117
  PDF, 125 Kb, File published: Nov 1, 1995
  Extract from the document

  advertisement 70mΩ Protected Load Management Switch – Design Note 117
  Mitchell Lee and Tim Skovmand
  In an effort to conserve energy, simple shutdown schemes
  are incorporated into many battery-operated circuits. Not
  all circuits lend themselves to direct control, however, and
  instead the supply must be turned off by a switch. The
  LTC В®1477 high side switch is designed for this purpose
  and includes short-circuit current limit and thermal shutdown to guard against faulty loads. Figure 1 shows a
  simplified block diagram of the LTC1477.
  VIN V+
  D1 D2 D3 CHARGE
  PUMP
  ENABLE LTC1477
  S2 VOUT Figure 2 shows the LTC1477 and LTC699 conjoined in an
  undervoltage disconnect application. The LTC699 microprocessor supervisor disables the LTC1477 and hence the
  load whenever the input voltage falls below 4.65V. An
  external logic signal applied to the gate of Q1 can also
  disable the LTC1477. When enabled, the LTC1477 output
  ramps over a period of approximately 1ms, thereby limiting
  the peak current in the load capacitor to 500mA. This
  prevents glitches on the 5V source line that might otherwise affect adjacent loads.
  An LT В®1301 is used in Figure 3 to boost a 3.3V or 5V input
  to 12V, such as VPP for Flash memory. Although the …

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  New Micropower, Low Dropout Regulators Ease Battery Supply Designs &mdash DN121
  PDF, 85 Kb, File published: Jan 5, 1996
  Extract from the document

  New Micropower, Low Dropout Regulators Ease Battery
  Supply Designs – Design Note 121
  Mitchell Lee and John Seago
  Three new linear regulators simplify the design of
  battery-operated equipment. The LTВ®1521 is a 300mA,
  positive low dropout regulator with micropower quiescent current and shutdown. The LT1175 is a 500mA
  negative complement with adjustable current limit. A
  third product, the LT1118, has the unique capability of
  maintaining output regulation while sourcing or sinking
  load current.
  The LT1521 contains all of the features associated
  with battery-operated applications. In designs where
  memory must be powered continuously, the LT1521’s
  12ОјA quiescent current eliminates the need for a
  separate micropower backup supply. In shutdown the
  quiescent current drops to 6ОјA. Figure 1 shows an
  example application using the LTC В®1477 as a means
  of disconnecting all circuitry except for memory and
  ON/OFF control logic. The LTC1477 protected high
  side switch draws only 10nA in shutdown, eliminating
  itself as well as its load as a factor in battery shelf life.
  In battery-backed memory applications, the output of
  the LT1521 can be held up by the backup battery while …

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  Short-Circuit Protection for Boost Regulators &mdash DN154
  PDF, 77 Kb, File published: May 1, 1997
  Extract from the document

  advertisement Short-Circuit Protection for Boost Regulators – Design Note 154
  Jeff Witt
  The basic boost regulator topology provides no shortcircuit protection. When the output is pulled low, a large
  current can flow from the input through the inductor
  and catch diode, limited only by the series resistance
  of these parts. The result may be damage to the boost
  regulator, the load or the power source. This design note
  presents several solutions to this potential problem.
  Short-Circuit Protection and Load Disconnect
  with the LTC1477
  The LTC В®1477 protected high side switch contains
  an internal, low loss NMOS power switch. It provides
  protection to external circuits in two ways: switch
  current is limited to 0.85A, 1.5A or 2A (depending on
  configuration) and thermal shutdown circuitry turns
  the switch off when power dissipation raises the die
  temperature to 130В°C. In Figure 1, the LTC1477 protects
  an LTВ®1304 micropower boost regulator and its load
  from excessive currents. An increasing load current will
  п¬Ѓrst be limited to 0.85A; as more power is dissipated
  in the switch, the LTC1477 will cycle the switch to limit
  average current and dissipation to an acceptable level.
  The enable pin can be used to disconnect the output. …

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Manufacturer's Classification

• Monitor, Control and Protection > High Side Switches & MOSFET Drivers