3-Terminal Adjustable Regulators: D E S C R I P T I O N
3-Terminal Adjustable Regulators: D E S C R I P T I O N
3-Terminal Adjustable Regulators: D E S C R I P T I O N
DESCRIPTION
The LM317 are adjustable 3-terminal positive-voltage regulators capable of supplying 1.5A over
a differential voltage range of 3V to 40V. They are exceptionally easy to use and require only two
external resistors to set the output voltage. Both input and output regulation is better than
standard fixed regulators.
In addition to higher performance than fixed regulators, these regulators offer full overload
protection available only in integrated circuits. Included on the chip are current limit, thermal
overload protection, and safe-area protection. All overload protection circuit remains fully
functional even if the adjustment terminal is disconnected. Normally, no capacitors are needed
unless the device is situated far from the input filter capacitors in which case an input bypass is
needed. An optional output capacitor can be added to improve transient response.
The primary applications of each of these regulators is that of a programmable output regulator,
but by connecting a fixed resistor between adjustment terminal and the output terminal, each
device can be used as a precision current regulator. Even though the regulator is floating and
sees only the input-to-output differential voltage, use of these devices to regulate output voltages
that would cause the maximum-rated differential voltage to be exceeded if the output became
shorted is not recommended
TO-220 PACKAGE
LM317T
FEATURES
!
INPUT
Output Voltage Range Adjustable from 1.2 V to 37V OUTPUT
!
ADJUSTMENT
Output Current Capability of 1.5A Max
! Input Regulation Typically 0.01% Per Input-Volt
Change
! Output Regulation Typically 0.1% A
Wing Shing Computer Components Co., (H.K.)Ltd. Tel:(852)2341 9276 Fax:(852)2797 8153
Homepage: http://www.wingshing.com E-mail: wsccltd@hkstar.com
LM317 3-TERMINAL ADJUSTABLE REGULATORS
ELECTRICAL CHARACTERISTICS
Uniess otherwise noted ,these specifications apply for the following test conditions: Vi-Vo=5V and Io=0.5A. For conditions
shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
VI IN OUT V0
ADJ R1 See Note 3
240
C1=0.1 F C2=1 F
See Note 1 R2 See Note 2
R2
Output voltage is calculated from VO = VREF { 1+
R1
}
1. Use of an input bypass capacitor is recommended if regulator is far from filter capacitors.
2. Use of an output capacitor improves transient response but is optional.
3. VREF equals the difference between the output and adjustment terminal voltages.
LM317 3-TERMINAL ADJUSTABLE REGULATORS
260 2
280 3 240
240
1 330
265 4
240
230