LM317QDCYRQ1 - 500mA 40V Adjustable LDO | TI | Automotive
MPN: LM317QDCYRQ1 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.62 | $0.62 |
| 10 | $0.56 | $5.60 |
| 100 | $0.45 | $45.00 |
| 500 | $0.38 | $190.00 |
| 1,000 | $0.31 | $310.00 |
LM317QDCYRQ1 Overview
An adjustable linear regulator (LDO-style series pass regulator) is a type of voltage regulator that maintains a stable output voltage by controlling the voltage drop across an internal series pass transistor. Within the power management IC hierarchy, the LM317 family sits in the classic NPN-darlington floating regulator category, renowned for decades of use across industrial and automotive power rails. The 'Q1' suffix indicates AEC-Q100 qualification and automotive temperature support.
Key features include a wide input voltage tolerance up to 40 V, 500 mA output current capability, internal thermal overload protection (thermal shutdown), and safe-operating-area current limiting. The floating architecture allows operation at high voltages, and the adjustable output enables a single design to cover multiple rail voltages simply by changing two resistors.
Technically, the device regulates the 1.25 V bandgap reference between the output and adjustment (ADJ) pin. The load and line regulation benefit from the low reference current, and the ADJ pin current of approximately 50 uA must be accounted for in the output divider calculation for best accuracy. Standard 1% resistors typically achieve output accuracy within a few percent.
Typical applications include automotive body electronics and infotainment auxiliary rails, industrial 12 V and 24 V bus post-regulation, and general-purpose adjustable bench or bias supplies where simplicity and robustness outweigh efficiency.
Design consideration: the device is a linear regulator, so power dissipation equals (VIN - VOUT) x ILOAD. The SOT-223 tab should be soldered to a generous copper pour; verify junction temperature stays below the datasheet maximum at worst-case load and input voltage.
Drop-in alternatives for LM317QDCYRQ1 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LM317QDCYRQ1 (same form factor and footprint) — differing in Maximum Output Current, Output Type, Protection Features, Reference Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LM317MQDCYRM3Q1
✅ Drop-In📋 Reference alternative (not in catalog)
LM317MQDCYR
✅ Drop-In📋 Reference alternative (not in catalog)
LM317MDCYR
✅ Drop-In📋 Reference alternative (not in catalog)
AP317K
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LM317QDCYRQ1 Maximum Ratings & Electrical Characteristics
| Output Type | Positive Adjustable |
| Number of Outputs | 1 |
| Maximum Output Current | 500 mA |
| Maximum Input Voltage | 40 V |
| Reference Voltage | 1.25 V (typical, LM317 family) |
| Regulation Type | Linear (series pass) |
| Qualification | Automotive (AEC-Q100, Q1) |
| Package | SOT-223-4 (DCY) |
| Mounting Type | Surface Mount |
| Protection Features | Thermal shutdown, current limit (LM317 family) |
LM317QDCYRQ1 Pin Configuration
| Pin 1 | ADJ — Adjust pin - 1.25 V reference between this pin and output; set output with resistor divider |
| Pin 2 | VOUT (Tab) — Regulated output voltage; tab doubles as thermal path |
| Pin 3 | VIN — Input supply voltage, up to 40 V |
| Pin 4 | GND/NC (Tab connection) — Package tab mounting surface; tie per reference layout |
Typical Applications
LM317QDCYRQ1 is suitable for 6 applications: Automotive Auxiliary Power Rails, Industrial 24V Bus Post-Regulation, Adjustable Bench and Lab Supplies, Bias Supplies for Amplifiers and Sensors, Battery-Powered Equipment Charging / Float Rails, Infotainment and Cluster Subsystem Power.
Automotive Auxiliary Power Rails
The LM317QDCYRQ1 fits 12 V automotive battery-rail post-regulation because its Q1 automotive qualification and 40 V input tolerance handle harsh vehicle supply conditions. Placed after a pre-regulator or protected battery rail, it produces clean adjustable 3.3 V to 12 V auxiliary supplies for modules and sensors. As a linear regulator it adds no switching ripple, though dissipation of (VIN-VOUT) x ILOAD must be thermally verified.
Recommended
Industrial 24V Bus Post-Regulation
The 40 V maximum input rating gives the LM317QDCYRQ1 comfortable headroom on industrial 24 V buses, where it provides low-noise adjustable rails for analog circuitry and control logic. Because linear regulation avoids switching noise, it suits sensor excitation and op-amp supplies. At large VIN-VOUT deltas and currents above 100 mA, thermal management via copper pour or a pre-regulator is essential.
Recommended
Adjustable Bench and Lab Supplies
The classic two-resistor adjustable architecture (VOUT = 1.25 V x (1 + R2/R1)) makes the LM317QDCYRQ1 ideal for general-purpose adjustable supplies and module bias rails. Internal current limit and thermal shutdown provide inherent short-circuit robustness valued in bench and test equipment. The 500 mA rating covers most prototype loads, and the SOT-223 tab simplifies heatsinking on small PCBs.
Recommended
Bias Supplies for Amplifiers and Sensors
Analog signal chains benefit from the LM317QDCYRQ1's ripple-free linear regulation when biasing amplifiers, ADC references, and sensor bridges from higher unregulated rails. The adjustable output allows tight tailoring of supply voltage to minimize device power dissipation in precision analog parts. Its 1.25 V reference stability and low output impedance keep bias points quiet across load transients.
Recommended
Battery-Powered Equipment Charging / Float Rails
The LM317QDCYRQ1 can serve as a simple constant-voltage source for float-charging lead-acid or NiMH packs, with the resistor divider programmed to the required float voltage. Current limiting protects against deep-discharge loads, and thermal shutdown guards against fault conditions. The 40 V rating tolerates wide battery input ranges common in vehicle and portable industrial equipment.
Recommended
Infotainment and Cluster Subsystem Power
Automotive infotainment modules use the LM317QDCYRQ1 to derive quiet local rails for tuner, audio, and display backlight bias circuits downstream of a main buck converter. The Q1 qualification supports AEC-Q100 supplier requirements, and the SOT-223 package mounts on standard infotainment PCBs. Post-regulation improves PSRR beyond what switching converters alone achieve for sensitive analog loads.
Recommended
Recommended Products Summary
Engineering reference data for LM317QDCYRQ1 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM317MQDCYRM3Q1 | LM317MQDCYR | LM317MDCYR |
|---|---|---|---|---|
| Package | SOT-223-4 (DCY) | SOT-223-4 (DCY) - same | SOT-223-4 (DCY) - same | SOT-223-4 (DCY) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Output Current | 500 mA | 500 mA | 500 mA | 500 mA |
| Output Type | Positive Adjustable | Positive Adjustable | Positive Adjustable | Positive Adjustable |
| Automotive Qualification | Yes (Q1) | Yes (Q1) | No | No |
| Output Configuration | 1 output, 3-terminal floating regulator | 1 output, 3-terminal floating regulator | 1 output, 3-terminal floating regulator | 1 output, 3-terminal floating regulator |
| Reference Voltage | 1.25 V (typical) | 1.25 V (typical) | 1.25 V (typical) | 1.25 V (typical) |
Key Differentiators
- Automotive AEC-Q100 qualification (vs LM317MQDCYR)
- Simplified drop-in second source (vs LM317MQDCYRM3Q1)
- 40 V input tolerance in SOT-223 (vs LM317MDCYR)
Design Notes
Power dissipation equals (VIN - VOUT) x ILOAD. The SOT-223-4 tab must be soldered to a copper pour of at least 1 square inch for reliable dissipation above roughly 1 W. For example, 24 V in to 5 V out at 200 mA dissipates 3.8 W - too much for this package without a pre-regulator. Verify junction temperature against the datasheet maximum in worst-case hot conditions.
Place the output divider resistors close to the ADJ pin and use the standard LM317 practice of sizing divider current (typically 5 mA minimum) so the ADJ pin current error term is negligible. Add 0.1 uF and 10 uF input/output ceramics per the LM317M datasheet application section; output capacitance improves transient response and stability.
Do not exceed the 40 V absolute maximum input, including automotive load-dump transients - add upstream clamping if required. Without a bypass capacitor on ADJ, ripple rejection degrades; adding approximately 10 uF on ADJ improves PSRR but requires a protection diode for output short-circuit conditions, as described in classic LM317 application notes.
Compliance Information
Q1 suffix denotes automotive qualification per TI product page. RoHS/REACH/lead-free status not stated in verified web data - confirm on TI product page.
