Descripción

The LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37 V. It requires only two external resistors to set the output voltage. The device features a typical line regulation of 0.01% and typical load regulation of 0.1%. It includes current limiting, thermal overload protection, and safe operating area protection. Overload protection remains functional even if the ADJUST terminal is disconnected.

 

Características

Output voltage range adjustable from 1.25 V to 37 V

Output current greater than 1.5 A

Internal short-circuit current limiting

Thermal overload protection

Output safe-area compensation

 

Aplicaciones

ATCA solutions

DLP: 3D biometrics, hyperspectral imaging, optical networking, and spectroscopy

DVR and DVS

Desktop PCs

Digital signage and still cameras

ECG electrocardiograms

EV HEV chargers: levels 1, 2, and 3

Electronic shelf labels

Energy harvesting

Ethernet switches

Femto base stations

Fingerprint and iris biometrics

HVAC: heating, ventilating, and air conditioning

High-speed data acquisition and generation

Hydraulic valves

IP phones: wired and wireless

Intelligent occupancy sensing

Motor controls: brushed DC, brushless DC, lowvoltage, permanent magnet, and stepper motors

Point-to-point microwave backhauls

Power bank solutions

Power line communication modems

Power over ethernet (PoE)

Power quality meters

Power substation controls

Private branch exchanges (PBX)

Programmable logic controllers

RFID readers

Refrigerators

Signal or waveform generators

Software-defined radios (SDR)

Washing machines: high-end and low-end

X-rays: baggage scanners, medical, and dental

 

Descripción detallada

Visión general

The LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying up to 1.5 A over an output-voltage range of 1.25 V to 37 V. It requires only two external resistors to set the output voltage. The device features a typical line regulation of 0.01% and typical load regulation of 0.1%. It includes current limiting, thermal overload protection, and safe operating area protection. Overload protection remains functional even if the ADJUST terminal is disconnected.

The LM317 device is versatile in its applications, including uses in programmable output regulation and local oncard regulation. Or, by connecting a fixed resistor between the ADJUST and OUTPUT terminals, the LM317 device can function as a precision current regulator. An optional output capacitor can be added to improve transient response. The ADJUST terminal can be bypassed to achieve very high ripple-rejection ratios, which are difficult to achieve with standard three-terminal regulators.

Descripción

NPN Darlington Output Drive

NPN Darlington output topology provides naturally low output impedance and an output capacitor is optional. 3-V headroom is recommended (VI – VO) to support maximum current and lowest temperature.

Overload Block

Over-current and over-temperature shutdown protects the device against overload or damage from operating in excessive heat.

Programmable Feedback

Op amp with 1.25-V offset input at the ADJUST terminal provides easy output voltage or current (not both) programming. For current regulation applications, a single resistor whose resistance value is 1.25 V/IO and power rating is greater than (1.25 V)2/R should be used. For voltage regulation applications, two resistors set the output voltage.

Device Functional Modes

Normal Operation The device OUTPUT pin will source current necessary to make OUTPUT pin 1.25 V greater than ADJUST terminal to provide output regulation.

Operation With Low Input Voltage

The device requires up to 3-V headroom (VI – VO) to operate in regulation. The device may drop out and OUTPUT voltage will be INPUT voltage minus drop out voltage with less headroom.

Operation at Light Loads

The device passes its bias current to the OUTPUT pin. The load or feedback must consume this minimum current for regulation or the output may be too high. See the Electrical Characteristics table for the minimum load current needed to maintain regulation.

Operation In Self Protection

When an overload occurs the device shuts down Darlington NPN output stage or reduces the output current to prevent device damage. The device will automatically reset from the overload. The output may be reduced or alternate between on and off until the overload is removed.

Información sobre la solicitud

The flexibility of the LM317 allows it to be configured to take on many different functions in DC power applications.