LM317DCYR - 1.5A Adjustable Positive Regulator | Texas Instruments
MPN: LM317DCYR β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.45 | $0.45 |
| 10 | $0.38 | $3.80 |
| 100 | $0.3 | $30.00 |
| 500 | $0.25 | $125.00 |
| 1,000 | $0.21 | $210.00 |
Drop-in alternatives for LM317DCYR β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
LM317QDCYRQ1
β Drop-Inβ In Stock
$0.31 / Unit
View Datasheet βLM317KCSE
β Drop-Inπ Reference alternative (not in catalog)
LM317DCYR
β Drop-Inβ In Stock
$0.21 / Unit
View Datasheet βLM317MSTT3G
β Drop-Inπ Reference alternative (not in catalog)
TL783KCSE
β‘ Same Packageπ Reference alternative (not in catalog)
LM317DCYR Maximum Ratings & Electrical Characteristics
| Output Type | Adjustable positive |
| Output Voltage Range | 1.25 V to 37 V |
| Maximum Output Current | 1.5 A |
| Maximum Input Voltage | 40 V |
| Reference Voltage | 1.25 V (VOUT to ADJ) |
| Line Regulation (typ) | 0.01% |
| Load Regulation (typ) | 0.1% |
| Dropout Voltage (typ) | 2.5 V at 1.5 A |
| Protection Features | Current limiting, thermal overload, safe-area compensation |
| Operating Junction Temperature | 0 C to 125 C |
| Package | SOT-223-4 (DCY) |
| Mounting Type | Surface Mount |
| Number of Terminals | 3 (plus tab) |
| RoHS Status | Compliant |
| Quiescent Current | [DATA_NEEDED: quiescent current] |
| Thermal Resistance | [DATA_NEEDED: theta JA for SOT-223-4] |
LM317DCYR Pin Configuration
| Pin 1 | ADJ β Adjustment pin - reference node for resistor divider |
| Pin 2 | VOUT β Regulated output voltage (also connected to tab) |
| Pin 3 | VIN β Input supply voltage, up to 40V |
| Pin Tab | VOUT β Tab electrically connected to output for heatsinking |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
LM317DCYR is suitable for 6 applications: Adjustable Bench Power Supplies, Battery Chargers, LED Constant-Current Drivers, Audio Equipment Power Rails, Industrial Control Systems, Test and Measurement Instrumentation.
Adjustable Bench Power Supplies
The LM317DCYR is the classic core of lab-style adjustable supplies: two resistors program any output from 1.25V to 37V, with 0.01% line and 0.1% load regulation holding the rail steady as load and input vary. Its built-in current limiting and thermal shutdown make it forgiving against accidental shorts during prototyping. A 10uF output capacitor plus an ADJ bypass capacitor improves transient response and ripple rejection to about 80 dB with adequate input filtering.
Recommended
Battery Chargers
Because the LM317 holds a fixed 1.25V between OUT and ADJ, a single resistor converts it into a constant-current charger, ideal for NiCd/NiMH cells or lead-acid float configurations with an added resistor network. The 1.5A capability suits multi-cell chargers, and safe-area compensation protects during deep-discharge conditions where current is highest. Limit dissipation by sizing the input source so the (VIN - VBAT) differential stays thermally manageable in the SOT-223 package.
Recommended
LED Constant-Current Drivers
The LM317DCYR makes a minimal LED driver: one resistor from 1.25V/R sets LED current precisely, e.g., 3.6 ohms for 350mA. No feedback loop or controller IC is required, keeping BOM cost near zero. The device inherently limits current through LED temperature drift, protecting the diode. The main trade-off is efficiency: power above the LED forward voltage is dissipated as heat, so this topology suits low-to-medium power indicator and small-luminaire applications rather than high-power lighting.
Recommended
Audio Equipment Power Rails
Linear regulation with no switching artifacts makes the LM317 attractive for op-amp and preamp supply rails. Its 0.01% line regulation rejects supply fluctuations, and adding a bypass capacitor on ADJ raises ripple rejection to roughly 80 dB, cleaning up residual ripple from rectified transformers. For best results, feed it from a filtered supply with at least 3V of headroom. Low-noise demanding designs may prefer a dedicated LDO post-stage for the final microvolt-level cleanup.
Recommended
Industrial Control Systems
In industrial controllers, the LM317DCYR derives local logic or sensor rails from 24V or 12V buses, with its 40V input rating providing comfortable margin on 24V systems. Thermal overload and current limiting add fault tolerance for harsh environments. For unattended equipment, the automotive-qualified LM317QDCYRQ1 variant extends temperature range. Keep input-output differential above 3V and verify worst-case dissipation at maximum load and minimum input in the SOT-223 thermal layout.
Recommended
Test and Measurement Instrumentation
Bench instruments and sensor front ends use the LM317 for trimmable reference rails and bias sources; the 1.25V reference itself serves as a stable low-voltage source with approximately 0.01% line regulation. In ADC front ends, an LM317-generated clean analog rail combined with good decoupling reduces noise coupling into precision conversions. For highest precision requirements, pair it with a dedicated reference IC rather than relying on the regulator alone.
Recommended
Recommended Products Summary
Engineering reference data for LM317DCYR β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM317QDCYRQ1 | LM317DCYR (UMW) | LM317MSTT3G | TL783KCSE |
|---|---|---|---|---|---|
| Package | SOT-223-4 (DCY) | SOT-223-4 (DCY) - same | SOT-223 - same | SOT-223 - same | SOT-223-4 - same |
| Brand | Texas Instruments | Texas Instruments | UMW | onsemi | Texas Instruments |
| Output Voltage Range | 1.25 V to 37 V | 1.25 V to 37 V | 1.25 V to 37 V | 1.25 V to 37 V | 1.25 V to 125 V |
| Output Current | 1.5 A | 1.5 A | 1.5 A | 1.5 A | 0.7 A |
| Maximum Input Voltage | 40 V | 40 V | 40 V | 40 V | 125 V |
| Automotive Grade (AEC-Q100) | No | Yes (Q1) | No | No | No |
| Operating Temperature | 0 C to 125 C (TJ) | -40 C to 125 C | [DATA_NEEDED] | -40 C to 125 C | 0 C to 125 C |
| Reference Voltage | 1.25 V | 1.25 V | 1.25 V | 1.25 V | 1.25 V |
Key Differentiators
- Industry-standard simplicity with two-resistor programming (vs LM317MSTT3G)
- Automotive-qualified same-footprint upgrade path (vs LM317QDCYRQ1)
- Higher current than TL783 in same package (vs TL783KCSE)
Design Notes
Power dissipation is (VIN - VOUT) x IOUT. At 12V in, 5V out, 1A load, the LM317DCYR dissipates 7W, which exceeds SOT-223 capability even with a generous copper pour. Calculate required copper area per TI thermal guidelines and keep junction temperature below 125C. For large differentials, use a switching pre-regulator or reduce load current. Severeity: this is the most common cause of field failures with the LM317.
The SOT-223 tab is electrically connected to VOUT, so the copper pour used for heatsinking is at output potential - check clearance to adjacent traces. Place a 0.1uF input capacitor close to VIN if the input supply is far away, plus 10uF bulk at input and output. Keep the ADJ resistor divider short and use 1% or better resistors for output accuracy.
Maintain at least 3V dropout headroom (typical dropout 2.5V at 1.5A). Add a bypass capacitor (10uF) on ADJ to boost ripple rejection to about 80 dB, and include protection diodes (e.g., 1N4002) from output to input and ADJ to output when large output capacitance can discharge into the device during input short or output fault conditions, per the TI datasheet application section.
Compliance Information
RoHS compliant per distributor listings (DigiKey, LCSC). For full REACH and material declarations, consult TI quality documents.
