LM317

Part: LM317 from Texas Instruments (implied)

Type: Adjustable Positive-Voltage Regulator

Description: The LM317 is an adjustable three-pin, positive-voltage regulator capable of supplying more than 1.5A over an output voltage range of 1.25V to 37V, featuring typical line regulation of 0.01%/V and load regulation of 0.1%.

Operating Conditions:

• Supply voltage: 4.25–40 V (Input voltage range)
• Operating temperature: 0 to 125 °C (Virtual junction temperature)
• Output voltage range: 1.25–37 V
• Output current: 0.01–1.5 A

Absolute Maximum Ratings:

• Max input-output voltage differential: 40 V
• Max junction/storage temperature: 150 °C

Key Specs:

• Reference voltage: 1.2 V (min) to 1.3 V (max) over 3V ≤ (V IN - V OUT ) ≤ 40V, 10mA ≤ I OUT ≤ 1500mA, P D ≤ 20W
• Line regulation: 0.02 %/V (typ) over 3V ≤ (V IN - V OUT ) ≤ 40V (over full operating temperature range)
• Load regulation (New chip): 0.1 %V O (typ) for 10mA ≤ I OUT ≤ I MAX, T J = 25°C
• Adjustment pin current: 50 μA (typ) to 100 μA (max) over full operating temperature range
• Minimum load current: 3.5 mA (typ) to 10 mA (max) for (V IN - V OUT ) = 40V (over full operating temperature range)
• Current limit: 1.5 A (min) to 2.2 A (typ) for (V IN - V OUT ) ≤ 15V, P D < P MAX
• Ripple rejection ratio (New chip): 80 dB (typ) for V OUT = 10V, f = 120Hz, C ADJ = 10μF (over full operating temperature range)
• Long-term stability: 0.3 %/1k hr (typ) to 1 %/1k hr (max) at T J = 25°C

Features:

• Adjustable output voltage: 1.25V to 37V
• Output current: 1.5A
• Internal short-circuit current limiting
• Thermal overload protection
• Output safe-area compensation (new chip)
• PSRR: 80dB at 120Hz for CADJ = 10μF (new chip)

Applications:

• Multifunction printers
• AC drive power stage modules
• Electricity meters
• Servo drive control modules
• Merchant network and server PSU

Package:

• DCY (SOT-223, 4-pin)
• KTT (TO-263, 3-pin)
• KCS, KCT (TO-220, 3-pin)

• Output voltage range:
• -Adjustable: 1.25V to 37V
• Output current: 1.5A
• Line regulation: 0.01%/V (typ)
• Load regulation: 0.1% (typ)
• Internal short-circuit current limiting
• Thermal overload protection
• Output safe-area compensation (new chip)
• PSRR: 80dB at 120Hz for CADJ = 10μF (new chip)
• Packages:
• -4-pin, SOT-223 (DCY)
• -3-pin, TO-263 (KTT)
• -3-pin, TO-220 (KCS, KCT), legacy chip

• Multifunction printers
• AC drive power stage modules
• Electricity meters
• Servo drive control modules
• Merchant network and server PSU

☎

†† See Equation 1.

t text {See Equation 1.} V o u T = 1 . 2 5 V × ≤ft ( 1 + frac { R _ { 2 } } { R _ { 1 } } right ) + I _ { A D J } × ( R _ { 2 } ) ( 1 )Typical Application

Figure 5-2. KCS or KCT Package, 3-Pin TO-220 (Top View), Legacy Chip

Figure 5-1. DCY Package, 4-Pin SOT-223 (Top View)

Figure 5-3. KTT Package, 3-Pin TO-263 (Top View)

some specifications apply over the full operating temperature range as noted; unless otherwise specified, T J = 25°C, V IN VOUT = 5V, and IOUT = 10mA (1)

over operating free-air temperature range (unless otherwise noted) (1) (2)

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

• (1) For more information, see the Mechanical, Packaging, and Orderable Information .
• (2) The package size (length × width) is a nominal value and includes pins, where applicable.
• (3) Legacy chip.

Battery-Charger Circuit

The regulator is floating and detects only the input-to-output differential voltage. Thus, supplies of several hundred volts are regulated as long as the maximum input-to-output differential is not exceeded. That is, avoid short-circuiting the output.

By connecting a fixed resistor between the adjustment pin and output, the LM317 is also able to be used as a precision current regulator. Supplies with electronic shutdown are achieved by clamping the adjustment terminal to ground, which programs the output to 1.25V where most loads draw little current.

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