LM317LDR2G — 100mA Adjustable Voltage Regulator (SOIC-8, onsemi)

What Are the Technical Specifications of the LM317LDR2G?

Key numbers that matter. The EC table is tested at a 625mW dissipation ceiling, and the current limit engages anywhere from 100mA to 300mA. That spread is the design rule: a load that needs 120mA “should be fine” on one sample and trips protection on the next.

And the temperature floor is 0°C. The commercial LM317L is specified down to freezing — nothing lower. If the design ever sits in an unheated enclosure, this is the spec that sends you to the automotive grade or the TI part.

When Should You Use (and NOT Use) the LM317LDR2G?

What Are the Alternatives to the LM317LDR2G?

The dual-source decision in one line. LM317LDR2G and LM317LMX/NOPB share a pinout, a 5mA minimum load, and a 625mW test ceiling. What actually differs: the temperature floor (0°C vs −40°C) and the brand on the reel. That's why dual-approving both costs nothing and buys an allocation-proof supply.

And don't let the 200mA typical current limit seduce you. The guaranteed floor is 100mA, and the EC table means it: 100mA is the rated output, full stop. Past that you're sampling, not designing.

What Are the Typical Applications of the LM317LDR2G?

4–20mA current loop transmitters. In precision current-regulator mode, I = 1.25V / R. A 62.5Ω resistor gives exactly 20mA — the classic two-wire transmitter trick. The 5mA minimum load is irrelevant here because the loop itself loads the output.

Reel-quantity production rails. At 2,500 per reel the LM317LDR2G drops into a standard SMT feeder with no rework. If your contract manufacturer already runs SOIC-8 parts, an adjustable rail adds zero setup time.

Dual-sourced bias supplies. Op-amp rails, reference supplies, and sensor excitation at 5–15mA draw. Approve both this part and the TI twin, and purchasing always has a working alternative — the layout, the test fixtures, and the firmware don't care which brand is populated.

Indoor instruments and lab gear. Benchtop PSUs, calibrators, and panel meters live at room temperature. The 0°C junction floor never matters indoors, and the 80dB ripple rejection with a 10µF ADJ cap keeps rails clean enough for 12-bit ADCs.

Why Buy LM317LDR2G from ICMASS?

Both twins, one warehouse. We stock LM317LDR2G and LM317LMX/NOPB side by side, so a dual-source BOM ships in one carton with one invoice. Swap between brands without changing anything downstream.

Reel integrity that matters on the line. We track lot codes through the full reel — 2,500 pieces that belong together stay together. Mixed-lot reels cause exactly the kind of mystery field failures nobody has time for.

The automotive grade when you need it. If the temperature floor question comes up, NCV317LBDR2G (−40°C, AEC-qualified) is on the shelf too. One conversation, no cross-vendor sourcing sprint.

Frequently Asked Questions About the LM317LDR2G

Q1: Is the LM317LDR2G a drop-in replacement for the TI LM317LMX/NOPB?

A: Yes — the SO-8 pinouts are identical. Pin 1 VIN, pins 2/3/6/7 VOUT, pin 4 ADJ, pins 5/8 NC on both parts. Same 1.25V reference and the same 5mA max minimum load. The one real difference: onsemi specifies 0°C to +125°C, TI −40°C to +125°C. Check your cold-start spec before swapping in a freezer-class design.

Q2: What does the DR2G suffix mean?

A: D = SOIC-8 package, R2 = 2,500-piece 13-inch reel, G = Pb-free. Same part, other suffixes: LM317LZREG is the TO-92 through-hole version, and the NCV317LB prefix marks the automotive-qualified −40°C variant. The suffix tells you package and reel, not silicon.

Q3: What's the minimum load current for the LM317LDR2G?

A: 3.5mA typical, 5mA maximum — same as the TI part. Below that, the internal quiescent current charges the output cap and the voltage drifts above the set point. Size the divider to draw at least 5mA, or hang a small permanent load on the rail.

Q4: Can the LM317LDR2G run below freezing?

A: Not on the datasheet — the commercial LM317L is specified from 0°C junction. For −40°C cold starts use the NCV317LBDR2G (automotive) or the TI LM317LMX/NOPB. Outside the specified range the part doesn't suddenly die, but you're on your own — not a place to be in a design review.

Q5: How much current can I really draw from an LM317LDR2G?

A: 100mA guaranteed — the current limit engages anywhere from 100mA to 300mA. The 200mA typical is where protection usually trips, but the guarantee stops at 100mA. TI's own engineers give the same advice for the LM317L-N: keep the load below the minimum current limit. Above 100mA, move to an LM317T or LM317G-AA3-R.

Q6: How do I get the best ripple rejection from the LM317LDR2G?

A: Add 10µF from ADJ to ground — rejection reaches 80dB typ at 120Hz. That's the onsemi datasheet number with C_ADJ in place, 60dB minimum. It fades above 120Hz, so for switching-frequency noise keep the input bypass close to the pins.

Q7: Can the LM317LDR2G drive a 4–20mA loop?

A: Yes — it's a classic. In current-source mode I = 1.25V / R, and a 62.5Ω resistor yields 20mA. Published LM317 loop converters hit 0.02% linearity, and full transmitter designs add an external boost transistor to keep IC dissipation low. At 20mA with a few volts across the part, the LM317L handles the loop comfortably.

Q8: SO-8 or TO-92 — which LM317L should I buy?

A: SO-8 for production, TO-92 for hand work — same die. Standalone, the TO-92 cools slightly better (160°C/W vs 180°C/W minimum-pad SO-8). But the SO-8's junction-to-case is 45°C/W versus 83°C/W — four VOUT pins pull heat into board copper, so on a real PCB it wins.

Q9: Do the LM317L suffix variants — DR2G, ZREG, LFT, NOPB — perform differently?

A: No — the die is identical; suffixes mark package and packing only. The LM317LDR2G (SO-8, 2,500/reel), LM317LZREG (TO-92), and TI's LM317L-N LFT/NOPB variants are functionally the same part, as TI's own E2E engineers confirm. Choose by package and reel, not performance.

Q10: How much input-output voltage difference does the LM317LDR2G need?

A: Specs assume a 5V differential, with 3V as the test-condition minimum. Design to 2.5–3V of headroom in practice. This is a classic regulator, not an LDO — tight-rail designs belong on AMS1117-class parts.