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Design Notes

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  The LTC1267 Dual Switching Regulator Controller Operates from High Input Voltages &mdash DN114
  PDF, 121 Kb, File published: Sep 3, 1995
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  advertisement The LTC1267 Dual Switching Regulator Controller Operates
  from High Input Voltages – Design Note 114
  Randy G. Flatness and Craig Varga Linear Technology offers three versions of the LTC1267, all
  in the space-saving 28-lead SSOP package. The LTC1267
  provides fixed output voltages of 3.3V and 5V with individual shutdown capability. The LTC1267-ADJ provides
  two user-programmable output voltages set by external
  resistive dividers. The LTC1267-ADJ5 is configured with a
  fixed 5V output and a programmable output set by an
  external resistor divider.
  High Efficiency with Dual Output Voltages
  To boost efficiency, a unique EXT VCC pin on the LTC1267
  (also present on the single output LTC1159) allows the
  MOSFET drivers and control circuitry to be powered from
  an external source, such as the output of the regulator
  itself. Obtaining control and driver power from VOUT improves efficiency at high input voltages, since the resulting
  current drawn from VIN is scaled by the duty cycle of the
  regulator. During start-up and short-circuit conditions,
  operating power is supplied by an internal 4.5V low dropout regulator. This regulator automatically turns off when
  the EXT VCC pin rises above 4.5V.
  This 28-pin controller uses Linear Technology’s high performance, current mode architecture and Burst ModeTM
  operation. The LTC1267 automatically switches to Burst
  Mode operation at low output currents to maintain high
  efficiency over two decades of load current range. The wide …

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  New Comparators Feature Micropower Operation Under All Conditions &mdash DN137
  PDF, 443 Kb, File published: Sep 2, 1996
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  New Comparators Feature Micropower Operation
  Under All Conditions – Design Note 137
  Jim Williams
  Some micropower comparators have operating modes
  that allow excessive current drain. In particular, poorly
  designed devices can conduct large transient currents
  during switching. Such behavior causes dramatically
  increased power drain with rising frequency, or when
  the inputs are nearly balanced, as in battery monitoring
  applications. resulting in greatly reduced power consumption versus
  frequency, or when the inputs are nearly balanced. Figure 2’s
  plot contrasts the LTC1440’s power consumption versus
  frequency with that of another comparator specified as a
  micropower component. The LTC1440 has about 200 times
  lower current consumption at higher frequencies, while
  maintaining a significant advantage below 1kHz. Figure 1 shows a popular micropower comparator’s current
  consumption during switching. Trace A is the input pulse,
  trace B is the output response and trace C is the supply
  current. The device, specified for micropower level supply drain, pulls 40mA during switching. This undesirable
  surprise can upset a design’s power budget or interfere
  with associated circuitry’s operation. Table 1 shows some LTC1440 family characteristics. A voltage reference and programmable hysteresis are included
  in some versions, with 5Вµs response time for all devices. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks
  of Linear Technology Corporation. All other trademarks are the property of their …

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  Dual PowerPathв„ў Controller Simplifi es Power Management &mdash DN160
  PDF, 78 Kb, File published: Aug 1, 1997
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  Dual PowerPathв„ў Controller Simplifies Power Management
  Design Note 160
  Jaime Tseng
  As the demand for portable electronics with multiple
  batteries continues to grow, so does the need for simple
  and efficient solutions for switching between batteries. The LTC ®1473 simplifies the design of circuitry
  for switching between two batteries or a battery and
  an AC adapter. protection shuts off the gate drive when a fault condition exceeds the user-programmable time limit, inrush
  current limiting limits the current flowing into or out of
  the system bypass capacitor and a diode default mode
  allows power to flow from the highest potential until
  the inputs can be defined. The LTC1473 is designed to drive two sets of low loss,
  back-to-back N-channel MOSFET switches to route
  power where needed, typically to the input of the main
  system switching regulator. An internal micropower
  boost regulator supplies the gate drive for the N-channel
  MOSFET switches. Automatic Switchover Between Battery and AC
  Adapter
  A protected automatic switchover between a battery and
  a power source connected at DCIN can be constructed
  using the circuit in Figure 1. Under normal conditions,
  this circuit will route the voltage at DCIN to the output. The LTC1473 simplifies the designer’s task by incorporating a number of protection features. Short-circuit L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks
  and PowerPath is a of Linear Technology Corporation. All other trademarks are the …

Articles

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  Low Voltage PowerPath Driver Switches from a 3.3V or 5V Supply to Battery Backup &mdash LT Journal
  PDF, 116 Kb, File published: Jun 1, 1999
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  DESIGN IDEAS Low Voltage PowerPath Driver
  Switches from a 3.3V or 5V
  by Peter Guan and
  Supply to Battery Backup
  Tim Skovmand
  The LTC1473L solves the problem
  of seamless power switching between
  3.3V or 5V supplies and backup battery packs (3-or 4-cell NiMH) at high
  current levels. By driving two sets of
  back-to-back N-channel MOSFET
  switches, the LTC1473L routes power
  to the input of a low voltage (3.3V to
  10V) system efficiently and inexpensively. An internal micropower boost
  regulator is included to fully enhance
  the external NMOS switches, even at
  low operating voltages. An external
  1mH inductor and 1ВµF capacitor
  charge VGG to approximately 8.5V
  above V+, providing ample drive for
  the external MOSFETs. The LTC1473L
  includes inrush-current limiting during supply switchover to produce
  smooth transitions between the DC
  supply and the battery backup and to …

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Manufacturer's Classification

• Signal Conditioning > Comparators > Micropower Comparators | Application Specific Comparators
• Signal Conditioning > Voltage References > Reference Plus Comparator or Amplifier