LT1763 - 500mA, Low Noise, LDO Micropower Regulators

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Study on LT1763 - 500mA, Low Noise, LDO Micropower Regulators

Study on LT1763 - 500mA, Low Noise, LDO Micropower Regulators

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  • LT1763 - 500mA, Low Noise, LDO (low drop out) Micropower Regulators
  • Welcome to the training module on LTC1763. This module introduces the features and application of LT1763 - 500mA, Low Noise, LDO (low drop put) Micropower Regulators.
  • The LT1763 series low noise, low dropout voltage regulators are devices capable of supplying 500mA of output current with a dropout voltage of 300mV. A key feature of the LT1763 regulator is low output noise. With the addition of an external 0.01μF bypass capacitor, output noise drops to 20μVRMS over a 10Hz to 100kHz bandwidth.
  • LTC1763 is Designed for use in battery-powered systems, their low 30μA quiescent current makes them an ideal choice. Quiescent current is well controlled; it does not rise in dropout, as it does with many other regulators. It extends application in areas like cellular phones, battery powered system, and noise sensitive instrumentation systems.
  • This slide illustrates the curves of Typical performance characteristics of the LTC1763. the slide illustrates dropout voltage Vs output current and current limit Vs input voltage.
  • This slide offers information on how to connect Kelvin sense to the input of LTC1763. Optimum regulation will be obtained at the point where the SENSE pin is connected to the OUT pin of the regulator. In critical applications, small voltage drops are caused by the resistance (RP) of PC traces between the regulator and the load.
  • The adjustable version of the LT1763 has an output voltage range of 1.22V to 20V. The output voltage is set by the ratio of two external resistors, as shown. The value of R1 should be no greater than 250k to minimize errors in the output voltage caused by the ADJ pin bias current. The current in R1 is then equal to 1.22V/R1 and the current in R2 is the current in R1 plus the ADJ pin bias current.
  • The LT1763 regulators are designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. A minimum output capacitor of 3.3μF with an ESR of 3Ω, or less, is recommended to prevent oscillations. When used with a 5V regulator, a 16V 10μF capacitor can exhibit an effective value as low as 1μF to 2μF for the DC bias voltage applied and over the operating temperature range.
  • The LT1763 regulators incorporate several protection features which make them ideal for use in battery-powered circuits. The devices are protected against reverse input voltages, reverse output voltages and reverse voltages from output to input. The top resistor of the resistor divider must be chosen to limit the current into the ADJ pin to less than 5mA when the ADJ pin is at 7V. If the input is powered by a voltage source, the output will source the short-circuit current of the device and will protect itself by thermal limiting.
  • This page shows a typical application circuit diagram . The first figure shows a 3.3V Low Noise Regulator and the other shows paralleling of regulator for higher output current. A key feature of the LT1763 regulator is low output noise. With the addition of an external 0.01μF bypass capacitor, output noise drops to 20μVRMS over a 10Hz to 100kHz. Small ceramic capacitors can be used without the series resistance required by other regulators.
  • Demonstration circuit DC368 is a low noise micropower voltage regulator using the LT1763 in the 8-lead SO package. These circuits are used primarily in cellular phones, voltage controlled oscillators, RF power supplies , and, in larger systems, as local regulators. The ability to tolerate a wide variety of output capacitors makes them ideal in space- and cost-sensitive systems.
  • Thank you for taking the time to view this presentation on “ LT1763IDE ” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the Linear Technology site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility. You may visit Element 14 e-community to post your questions.

Transcript

  • 1. LT1763 - 500mA, Low Noise, LDO Micropower Regulators
    • Source: Linear Technology
  • 2. Introduction
    • Purpose
      • Study on LT1763 - 500mA, Low Noise, LDO Micropower Regulators
    • Outline
      • Features and Application.
      • Typical performance characteristics
      • Adjustable operation and Kelvin sense connection.
      • Application Information.
      • Demonstration circuit DC368.
    • Content
      • 12 pages
  • 3. Features
    • Low Noise: 20μVRMS (10Hz to 100kHz)
    • Output Current: 500mA
    • Low Quiescent Current: 30μA
    • Wide Input Voltage Range: 1.8V to 20V
    • Low Dropout Voltage: 300mV
    • Very Low Shutdown Current: < 1μA
    • No Protection Diodes Needed
    • Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3V, 3.3V, 5V
    • Adjustable Output from 1.22V to 20V
    • Stable with 3.3μF Output Capacitor
    • Stable with Aluminum, Tantalum or Ceramic Capacitors
    • Reverse Battery Protection
    • No Reverse Current
    • Over current and Over temperature Protected
    • 8-Lead SO and 12-Lead (4mm × 3mm) DFN Packages
  • 4. Applications
    • Cellular Phones
    • Battery-Powered Systems
    • Noise-Sensitive Instrumentation Systems
  • 5. Typical Performance Characteristics Dropout Voltage Current Limit Load Regulation Output Noise Spectral Density
  • 6. Kelvin Sense Connection
    • For fixed voltage versions of the LT1763
    • the SENSE pin is the input to the error
    • amplifier.
    • Optimum regulation will be obtained at the
    • point where the SENSE pin is connected to
    • the OUT pin of the regulator.
    • Voltage drop across the external PC traces
    • will add to the dropout voltage of the regulator.
    • The SENSE pin bias current is 10μA at the nominal rated output voltage. The SENSE pin can be pulled below ground.
    Kelvin Sense Connection
  • 7. Adjustable Operation Adjustable Operation
    • The adjustable version of the LT1763 has an output voltage range of 1.22V to 20V.
    • The output voltage is set by the ratio of two external resistors, as shown here.
    • The device servos the output to maintain the ADJ pin voltage at 1.22V referenced to ground. The current in R1 equal to 1.22V/R1 and the current in R2 is the current in R1 plus the ADJ pin bias current.
  • 8. Applications Information
    • The LT1763-X is a micro power device and output transient response will be a function of output capacitance.
    • The shaded region in the figure defines the range over which the LT1763 regulators are stable.
    • Bypass capacitors, used to decouple individual components powered by the LT1763-X, will increase the effective output capacitor value.
    • The most common dielectrics used are specified with EIA temperature characteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances
    Ceramic Capacitor DC Bias Characteristics Stability
  • 9. Protection Features
    • The devices are protected against reverse
    • input voltages, reverse output voltages and
    • reverse voltages from output to input.
    • Current limit protection and thermal overload
    • protection are intended to protect the device
    • against current overload conditions at the
    • output of the device.
    • The input of the device will withstand reverse
    • voltages of 20V. Current flow into the device
    • will be limited to less than 1mA and no negative voltage will appear at the output.
    • The output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage or is left open-circuit.
    Reverse Output Current
  • 10. Typical Application Paralleling of Regulators for Higher Output Current 3.3V Low Noise Regulator
  • 11. Demonstration Circuit DC368 LT1763 500mA Low Noise Micropower LDO Regulator Component Side Diagram
  • 12. Additional Resource
    • For ordering LT1763IDE , please click the part list or
    • Call our sales hotline
    • For more product information go to
      • http:// www.linear.com/pc/productDetail.jsp?navId =H0,C1,C1010,C1778,C1764,P1778
    • Visit Element 14 to post your question
      • www.element-14.com
    • For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility