LM317

Part: LM317 — Texas Instruments

Type: Adjustable Positive Linear Voltage Regulator

Description: 3-pin adjustable positive regulator supplying 1.5 A over a 1.25–37 V output range, with 0.01%/V typical line regulation and 0.1% typical load regulation.

Operating Conditions:

• Input-to-output differential voltage: 3–40 V
• Output voltage: 1.25–37 V
• Output current: 0.01–1.5 A
• Operating junction temperature: 0 to 125 °C

Absolute Maximum Ratings:

• Max input-to-output voltage differential: 40 V
• Storage temperature: -65 to 150 °C
• Operating virtual junction temperature (legacy chip): -65 to 150 °C
• Power dissipation: internally limited

Key Specs:

• Reference voltage: 1.25 V typ (1.2–1.3 V over 3 V ≤ VIN–VOUT ≤ 40 V, 10 mA ≤ IOUT ≤ 1500 mA, PD ≤ 20 W)
• Line regulation: 0.01 %/V typ, 0.04 %/V max (TJ = 25 °C, 3 V ≤ VIN–VOUT ≤ 40 V)
• Load regulation (new chip): 0.1 % VO typ, 0.5 % VO max at TJ = 25 °C; 0.3 % typ, 1.5 % max over full temperature range
• Adjustment pin current: 50 μA typ, 100 μA max
• Minimum load current: 3.5 mA typ, 10 mA max (VIN–VOUT = 40 V)
• Current limit: 1.5 A min, 2.2 A typ (VIN–VOUT ≤ 15 V); 0.15 A min, 0.4 A typ (VIN–VOUT = 40 V, TJ = 25 °C)
• Ripple rejection (new chip, VOUT = 10 V, 120 Hz, CADJ = 10 μF): 66 dB min, 80 dB typ
• Ripple rejection (legacy chip, CADJ = 10 μF): 62 dB min, 64 dB typ
• RMS output noise: 0.003 % of VOUT (10 Hz–10 kHz)
• ESD HBM: ±2500 V (legacy chip), ±3000 V (new chip)

Features:

• Adjustable output voltage from 1.25 V to 37 V
• 1.5 A output current
• Internal short-circuit current limiting
• Thermal overload protection
• Output safe-area compensation (new chip)
• Overload protection remains functional if the ADJUST pin is disconnected
• Usable as a precision current regulator

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 (6.5 mm × 7 mm)
• KTT: TO-263, 3-pin (10.16 mm × 15.24 mm)
• KCS, KCT: TO-220, 3-pin (10.16 mm × 4.55 mm), legacy chip

• 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.

$$V_{OUT} = 1.25V \times \left(1 + \frac{R_2}{R_1}\right) + I_{ADJ} \times (R_2)$$

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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