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Design Notes

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  Power Supply Tracker Can Also Margin Supplies &mdash DN372
  PDF, 75 Kb, File published: Aug 10, 2005
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  advertisement Power Supply Tracker Can Also Margin Supplies – Design Note 372
  Dan Eddleman
  Power supply margining is a technique commonly used to
  test circuit boards in production. By adjusting power
  supply output voltages, electrical components are tested
  at the upper and lower supply voltage limits specified for
  a design. The LTCВ®2923 power supply tracking controller
  can be used to margin supplies in addition to its usual task
  of tracking multiple power supplies.
  The LTC2923 uses the simple tracking cell shown in
  Figure 1 to control the ramp-up and ramp-down behavior
  of multiple supplies. This cell servos the TRACK input to
  0.8V and mirrors the current supplied by that pin at the FB
  output pin. The FB pin connects to the feedback node of
  the slave power supply. Normally, a resistive divider
  connects the master signal to the TRACK pin. By selecting
  the appropriate resistor values, RTA and RTB, the relationship of the slave power supply is configured relative to the
  master signal.
  The supply margining application uses an LTC2923 tracking cell to margin a supply high and low under the control
  of a three-state I/O pin. illustration. If the feedback voltage, VFB, of the power
  supply is 0.8V, solve for the value of RFM1 that must be
  added in parallel with RF1 of the existing design to
  produce the desired high margin output. …

Articles

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  Dual 500mA µPower LDO Features Independent 1.8V-20V Inputs and Easy Sequencing in a 4mm × 3mm DFN &mdash LT Journal
  PDF, 312 Kb, File published: Apr 1, 2010
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  design ideas Dual 500mA µPower LDO Features Independent 1.8V–20V
  Inputs and Easy Sequencing in a 4mm Г— 3mm DFN
  Molly Zhu The LT3029 integrates
  two independent 500mA
  monolithic LDOs in a
  tiny 16-lead MSOP or
  4mm Г— 3mm Г— 0.75mm DFN
  package. Both regulators
  have a wide 1.8V to 20V
  input voltage range with
  a 300mV dropout voltage
  at full load. The output
  voltage is adjustable down
  to the 1.215V reference
  voltage. With an external
  bypass capacitor, the
  output voltage noise is less
  than 20ВµVRMS. A complete
  power supply requires only
  a minimum 3.3ВµF ceramic
  output capacitor for each
  channel to be stable.
  Quiescent current is 55ВµA per channel, dropping below 1ВµA in shutdown. …

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  Low Voltage Wizardry Provides the Ultimate Power-On Reset Circuit &mdash LT Journal
  PDF, 135 Kb, File published: Dec 1, 2003
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  DESIGN FEATURES Low Voltage Wizardry Provides the
  Ultimate Power-On Reset Circuit
  by Bob Jurgilewicz The Low Voltage
  Reset Problem VRST
  VIN Figure 2. Traditional NMOS pull-down circuit 14 5V
  3.3V DC/DC
  CONVERTER 2.5V
  1.8V SYSTEM
  LOGIC C1
  0.1ВµF
  C2
  0.1ВµF LTC2903B-2
  V1
  RST
  GND V4 V2 V3 Figure 1. Typical application using the LTC2903B for quad supply monitoring inside the chip). Second, there is a
  limit to how small the external resistor
  can be before the resistor overcomes
  the pull-up strength of the PMOS
  transistor. Third, low power systems
  will suffer while the reset node is logic
  high, since the external resistor will
  continuously dissipate power. With
  a 5V output and a 100kО© external …

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  Versatile Power Supply Tracking without MOSFETs &mdash LT Journal
  PDF, 376 Kb, File published: Feb 1, 2004
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  DESIGN FEATURES Versatile Power Supply Tracking
  by Dan Eddleman
  without MOSFETs
  Introduction Modern electronics systems often have
  complex power supply voltage tracking
  and sequencing requirements. Ignoring these requirements can result in
  the immediate destruction of devices,
  or worse yet, premature failures in the
  field.
  Voltage tracking requirements
  usually specify that the voltage difference between two power supplies
  must never exceed a certain limit. This
  constraint applies at all times: during
  power up, power down, and steady
  state operation. In contrast, supply sequencing requirements specify the order in which
  supplies power up and power down.
  Figure 1 shows various tracking
  and sequencing scenarios.
  The penalty for poor tracking or sequencing is often irreparable damage
  to devices in the system. FGPAs, PLDs,
  DSPs and microprocessors typically
  have diodes placed between the core
  and I/O supplies as a component of the …

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  Power Supply Tracking for Linear Regulators &mdash LT Journal
  PDF, 267 Kb, File published: Mar 25, 2005
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  DESIGN FEATURES Power Supply Tracking for
  Linear Regulators
  Introduction (see “Versatile Power Supply Tracking
  without MOSFETs” from Linear Technology Magazine, February, 2004 ) but
  it is easily adapted to linear regulators,
  including popular low-dropout (LDO)
  types. Summarized here are several
  techniques for controlling linear regulators with the LTC2923. The LTC2923 provides simple and
  versatile control over the power-up
  and power-down behavior of switching
  power supplies. It allows several supplies to track the voltage of a master
  supply, so that their relative voltages
  meet the stringent specifications for
  the power up of modern digital
  semiconductors, such as DSPs, microprocessors, FPGAs and ASICs. The
  LTC2923 is specifically designed to
  work with switching power supplies Monolithic Regulators
  Table 1 lists three popular monolithic
  linear regulators that have been tested
  with the LTC2923. Using these three Table 1. New monolithic linear regulators Regulator IOUT(MAX) (V) VIN(MIN) (V) VIN(MAX) (V) VDROPOUT (V) LT3020 100mA 0.9 10 0.15 LTC1844 150mA 1.6 6.5 0.11 LTC3025 300mA 0.9 5.5 0.045 3.3V IN
  2.2ВµF 3.3V CGATE
  0.1ВµF 0.1ВµF
  VCC GATE OFF ON ON SHDN …

Model Line

Manufacturer's Classification

• Monitor, Control and Protection > Sequencers, Trackers, and Margining Controllers
• Monitor, Control and Protection > Sequencers, Trackers, and Margining Controllers > Tracking Controllers

Other Names:

LTC2923CMSTRPBF, LTC2923CMS TRPBF