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Texas Instruments LM317DCYR — Power Management (PMIC / Gate Driver)

LM317DCYR adjustable voltage regulator, 1.5 A, SOT-223-4

MPNLM317DCYR
Active

Texas Instruments LM317 series, adjustable positive voltage regulator, LM317DCYR, 1.5 A output, 1.25 V to 37 V output range, 40 V input max, PSRR 64 dB to 57 dB at 120 Hz, SOT-223-4 surface-mount package, 0 °C to 125 °C operating temperature.

$0.8000Ref. price · indicative, final on quote
Texas Instruments LM317DCYR datasheet (PDF)
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

LM317DCYR specifications
ParameterValue
Output typeAdjustable
MountingSurface Mount
Voltage - input40V
Voltage - output37V
Voltage - output (Min (Fixed))1.25V
Output current1.5A
Current - quiescent10 mA
Operating temperature0°C~125°C
PSRR64dB ~ 57dB (120Hz)
PackageTape & Reel (TR); Cut Tape (CT)
CaseTO-261-4, TO-261AA
Protection featuresOver Current, Over Temperature, Short Circuit
Number of regulators1
Output configurationPositive

Product details

1.5 A adjustable regulator in SOT-223 — thermal budget is the real limit

The LM317DCYR is Texas Instruments' surface-mount variant of the classic LM317 adjustable positive voltage regulator, delivering up to 1.5 A output current in a SOT-223-4 package. The SOT-223-4 footprint (TO-261AA) is the key difference from the through-hole LM317T in TO-220. The surface-mount case has higher junction-to-ambient thermal resistance, so the 1.5 A rating is achievable only with adequate copper area on the PCB and airflow — at elevated ambient temperatures the output current must be derated. For a 24 V to 5 V conversion at 1 A, the power dissipation is roughly 19 W; the SOT-223 package cannot sustain that without a heatsink or forced air, so plan the thermal path early.

PSRR at 120 Hz — ripple rejection for analog rails

The LM317DCYR provides 64 dB of ripple rejection at 120 Hz, dropping to 57 dB as the output current increases. This is the line-frequency (full-wave rectified) rejection that matters when the regulator is cleaning up a bulk capacitor's ripple before feeding an analog load — op-amp supplies, ADC reference buffers, or audio preamp rails. The 57 dB floor means about 0.14% of the input ripple couples through; if the input has 1 Vpp of 120 Hz ripple, the output sees roughly 1.4 mVpp. For a 5 V rail feeding a 16-bit ADC with a 5 V reference, that ripple is about 0.5 LSB at the converter input — acceptable for many designs, but a lower-noise post-filter may be needed for precision chains.

Protection and quiescent current — built-in ruggedness

The LM317DCYR integrates overcurrent, overtemperature, and short-circuit protection, so no external crowbar or foldback circuit is needed. The quiescent current is 10 mA typical, which is the current the regulator consumes to bias its internal reference and error amplifier — this flows to ground regardless of load and must be included in the total supply budget. In a battery-powered system drawing 50 mA from the output, the 10 mA Iq represents a 20% overhead; for line-powered designs it is negligible.

No official successor or replacement part has been issued.

Frequently asked questions

What is the output current of LM317DCYR?

The LM317DCYR is rated for 1.5 A output current. This is the maximum continuous output, but the SOT-223-4 package's thermal resistance means the achievable current at elevated ambient temperatures is lower — derating is required based on PCB copper area and airflow.

Is LM317DCYR equivalent to LM317T?

The LM317DCYR and LM317T share the same LM317 adjustable regulator core — same 1.5 A output, same 1.25 V to 37 V range, same protection features. The difference is package: the LM317DCYR is in SOT-223-4 (surface mount), while the LM317T is in TO-220 (through-hole). The pin functions are the same (adjust, output, input), but the pin numbering and physical footprint differ. The SOT-223 variant has higher thermal resistance, so it cannot dissipate as much power without a heatsink or copper pour.