LT3080ET - 1.1A Adjustable Single-Resistor LDO Regulator | Analog Devices
MPN: LT3080ET ✓ ActiveLT3080ET Overview
An LDO (low-dropout) linear regulator is a type of voltage regulator that maintains a stable output voltage even when the input voltage is only marginally higher than the output. LDOs belong to the linear regulator family, which sits under the broader power management IC category and is one of the two dominant approaches to DC voltage regulation (the other being switching converters). Compared with switching regulators, LDOs add no high-frequency switching noise to the output, making them ideal for noise-sensitive analog and RF rails, at the cost of lower efficiency when VIN - VOUT is large.
Key features of the LT3080ET include a wide 1.3 V to 36 V input operating range (with the published maximum at 36 V), 1.2 V typical dropout at 1.1 A, an internal current source architecture that supports output down to 0 V, and a Kelvin-programmable output that is independent of PCB trace resistance. The 5-pin TO-220-5 package exposes the die tab for a low thermal resistance of about 30 C/W when properly heatsunk, allowing the part to dissipate several watts in continuous operation.
The LT3080 uses a precision current-source reference and a unity-gain voltage follower topology, so the output is set by the value of a single resistor from the SET pin to ground. This architecture permits multiple LT3080 chips to be paralleled directly without ballast resistors or PCB-trim components, simplifying multi-ampere high-current designs and allowing thermal spreading on thermally limited surface-mount boards. The internal protection includes current limiting, safe operating area foldback, and thermal shutdown.
Typical applications include adjustable point-of-load (POL) regulators after a switching pre-regulator, high-current tracking power for op-amps and references, USB and industrial 24 V bus rails, and bench lab supplies where a single wide-range LDO replaces several discrete regulators.
When designing, place a high-quality 10 uF (minimum) low-ESR output capacitor as close as possible to the OUT pin and select the SET resistor (typically 1 kohm to 200 kohm) using the formula VOUT = 10 uA x RSET, where the 10 uA is the internal SET pin current. Use Kelvin sense at the load when precise regulation under load is required.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes that are not present in the manufacturer datasheet.
Drop-in alternatives for LT3080ET — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
LT3080ET#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT3080ET#31PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT3080MP
✅ Drop-In📋 Reference alternative (not in catalog)
LT3080ET Maximum Ratings & Electrical Characteristics
| Regulator Type | LDO, Positive Adjustable |
| Number of Outputs | 1 |
| Output Voltage Range | 0 V to 36 V |
| Maximum Output Current | 1.1 A |
| Input Voltage Range (Max) | 36 V |
| Input Voltage Range (Min Operating) | 1.3 V (VOUT + dropout) |
| Dropout Voltage | 1.2 V typical at 1.1 A |
| SET Pin Current | 10 uA typical |
| Line Regulation | 0.001 mV/V typical |
| Load Regulation | 0.2 mV typical |
| Operating Temperature | -40C to +125C |
| Package | TO-220-5 (T) through-hole with tab |
| Mounting Type | Through Hole |
| RoHS Status | Compliant (PBF suffix variants) |
| Lead-Free | Yes (PBF suffix variants) |
LT3080ET Pin Configuration
| Pin 1 | IN — Input supply voltage (1.3 V to 36 V) |
| Pin 2 | OUT — Regulated output voltage (0 V to 36 V) |
| Pin 3 | SET — Output voltage set pin - connect resistor to ground (VOUT = 10 uA x RSET) |
| Pin 4 | NC — Not connected (per datasheet) |
| Pin 5 | TAB/IN — Exposed tab - internally connected to IN (use as heatsink and electrical connection) |
Typical Applications
LT3080ET is suitable for 6 applications: Adjustable Point-of-Load (POL) Regulator, Paralleled High-Current Lab Bench Supply, Industrial 24 V Bus Power Conditioning, Op-Amp and Reference Power Rail, USB-Powered Adjustable Bench Source, Post-Switching Ripple Filter for RF Rails.
Adjustable Point-of-Load (POL) Regulator
The LT3080ET's wide 0 V to 36 V output range and 1.1 A current make it an excellent final-stage POL regulator when placed after a switching pre-regulator. The single-resistor output setting simplifies BOM and layout, while the 1.2 V dropout at 1.1 A leaves enough headroom for 5 V or 12 V intermediate bus rails. The internal current-source architecture means the output is stable with any low-ESR ceramic or tantalum output capacitor above 10 uF, and Kelvin sense at the SET pin keeps regulation accurate even with PCB trace losses. In a typical 24 V industrial bus stepping down to a 5 V logic rail at 1 A, the LT3080 dissipates about 19 W and needs a small clip-on heatsink, but adds no switching ripple to the output.
Recommended
Paralleled High-Current Lab Bench Supply
Two or more LT3080ETs can be paralleled directly on the same output without external ballast resistors, which is the headline feature of this part. Each device shares load current in proportion to its SET resistor value, so wiring five LT3080ETs at RSET = 100 kohm (1 V out) yields 5.5 A of usable current with heat spread across five TO-220 tabs. The Kelvin SET pin connection makes the parallel combination behave like a single low-impedance regulator, and the wide 0 V to 36 V output is ideal for laboratory adjustable supplies that need to cover sub-1 V analog and 30 V bench voltages. This topology is documented in the Analog Devices datasheet 3080fc as a primary use case for higher-current designs.
Recommended
Industrial 24 V Bus Power Conditioning
Factory-automation PLCs and sensor hubs often run on a 24 V industrial bus that must be regulated down to 5 V, 12 V, or 15 V for downstream analog and digital circuits. The LT3080ET accepts up to 36 V on the input and can deliver a clean 1.1 A regulated output for relays, signal-conditioning ADCs, and motor-driver logic rails. The LDO's lack of switching noise keeps it suitable for the analog front-end ADCs, while the 0 V to 36 V adjustability lets one stock part serve 5 V, 12 V, and 15 V rails by swapping a single SET resistor. The -40 C to +125 C operating range covers most factory-floor enclosures, and the TO-220 tab bolts directly to a chassis or aluminum plate for additional cooling.
Recommended
Op-Amp and Reference Power Rail
Precision op-amps and voltage references are notoriously sensitive to supply-rail noise and ripple. Using the LT3080ET to drop a 12 V or 15 V rail to a clean 5 V or 10 V analog supply gives the downstream op-amp a low-noise, well-regulated source with no switching-frequency artifacts. The 0.001 mV/V line regulation and 0.2 mV typical load regulation keep the analog circuit's bias points stable even when the upstream switching converter pulses heavily, which is exactly the role Analog Devices designed the LT3080 family to fill. Designers commonly use one LT3080ET per analog rail, sharing a single SET resistor value across PCBs.
Recommended
USB-Powered Adjustable Bench Source
USB ports deliver 5 V at up to 0.5 A, which is enough headroom to feed the LT3080ET to produce a clean 0 V to 5 V adjustable source for prototyping analog circuits. The internal current-source architecture gives a true 0 V output, unlike classic three-terminal regulators that bottom out around 1.25 V, so the LT3080ET is one of the few LDOs that can pull a node all the way to ground for calibrating zero-offset sensors. A 10 uF output cap and a 100 kohm to 1 Mohm SET potentiometer deliver a wide-range low-current bench aid that runs from any laptop. This use case is documented in the Analog Devices evaluation-kit literature for the LT3080 family.
Recommended
Post-Switching Ripple Filter for RF Rails
In RF transceivers, switching pre-regulators are efficient but their 100 kHz to 2 MHz ripple can leak into local oscillators and degrade phase noise. Placing an LT3080ET between the switching pre-regulator and the RF supply pin cleans that ripple by 60 dB or more at low frequencies, with no added switching noise of its own. The 1.1 A current capability is sufficient for power-hungry PAs and LNAs, and the 0 V to 36 V output range lets the same part generate 3.3 V, 5 V, or 8 V RF rails by changing a single resistor. The TO-220 package provides a solid ground return and a heatsink-able tab, which matters when the LDO is dissipating several watts at high VIN - VOUT differentials.
Recommended
Recommended Products Summary
Engineering reference data for LT3080ET — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT3080ET#PBF | LT3080ET#31PBF | LT3080MP | LM1085 |
|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | TO-220-5 (T) | TO-220-5 - same | TO-220-5 - same | TO-220-5 - same | TO-220-3 - different (not pin-compatible) |
| Output Current | 1.1 A | 1.1 A | 1.1 A | 1.1 A | 3.0 A (but different package) |
| Output Voltage Range | 0 V to 36 V | 0 V to 36 V | 0 V to 36 V | 0 V to 36 V | 1.25 V to 28 V |
| Input Voltage Max | 36 V | 36 V | 36 V | 36 V | 30 V |
| Dropout at Full Load | 1.2 V typical | 1.2 V | 1.2 V | 1.2 V | 1.3 V (3 A) |
| Terminal Finish | Matte Tin (Pb-free) | Matte Tin (Pb-free) | SnPb (Flow 31) | Matte Tin (Pb-free) | Matte Tin (Pb-free) |
| RoHS Compliant | Depends on suffix | Yes | No (SnPb finish) | Yes | Yes |
| Operating Temperature | -40C to +125C | -40C to +125C | -40C to +125C | -55C to +150C (military) | -40C to +125C |
| Unit Price (1k qty) | $2.79 | $2.79 (ADI 1ku list) | Similar to PBF | Higher (military grade) | Lower |
Key Differentiators
- Direct paralleling without external sense resistors (vs LM1085 (Analog Devices))
- True 0 V minimum output voltage (vs LM1085 (Analog Devices))
- Wide input range to 36 V on a single LDO (vs LM7805L-TA3-T (various))
Design Notes
The LT3080ET dissipates (VIN - VOUT) x ILOAD as heat. Estimated: at VIN = 12 V, VOUT = 5 V, and ILOAD = 1.1 A, dissipation is about 7.7 W, which requires a clip-on TO-220 heatsink rated at less than 10 C/W. For inputs above 24 V or loads above 0.8 A, add a switching pre-regulator in front of the LT3080ET to keep dissipation under 3 W.
Place a 10 uF (minimum) low-ESR ceramic or tantalum capacitor directly on the OUT pin with traces kept short and wide to maintain stability. The SET pin is a high-impedance node (10 uA bias), so keep SET traces short and away from switching or noisy signals; route the SET resistor's ground return directly to the device's OUT ground for best regulation accuracy.
The TO-220 tab is internally connected to IN. When using the tab as a heatsink, ensure the insulator (if used) does not short the input rail to ground. The TO-220-5 case style typically achieves about 30 C/W theta_JA with the tab soldered to several square inches of 2 oz copper - adequate for 1 A loads at moderate VIN-VOUT differentials.
Estimated: Do not leave the SET pin floating - the output will rise to the input voltage and may damage the load. Do not use RSET below about 1 kohm, which forces the SET pin to sink 10 mA and exceeds the internal current source limit. Do not apply reverse input voltage; place a Schottky diode from OUT to IN if the load can back-feed the regulator.
The tab pin (pin 5) is internally tied to IN, so the PCB heatsink area is at input potential. Route the OUT and SET traces on the opposite side of the package from the tab to avoid injecting input noise into the feedback path. For paralleled LT3080ETs, star-ground all SET resistors at a single point near the load to share current accurately.
Compliance Information
RoHS-compliant for the LT3080ET#PBF and LT3080MP variants per Analog Devices product page. The LT3080ET#31PBF (Flow 31) carries a SnPb finish and is not RoHS-compliant. AEC-Q100 does not apply - this is an industrial-grade part; use LT3080MP for extended temperature.
