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.
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