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Texas Instruments LM317LZ/LFT4
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- Part No.:
- LM317LZ/LFT4
- Manufacturer:
- Texas Instruments
- Package:
- TO-226-3, TO-92-3 (TO-226AA)
- Datasheet:
-
LM317LZ/LFT4.pdf
- Description:
- IC REG LIN POS ADJ 100MA TO92-3
- Quantity:
- Payment:
- Shipping:
Inventory:2,000
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Product details
Overview
LM317LZ/LFT4 from Texas Instruments is a 3-terminal, adjustable positive-voltage linear regulator delivering up to 100mA output current with 1.25V to 37V programmable output voltage range. It uses floating topology, sees only input-to-output differential voltage (max 45V), and requires no output capacitor for stability. It serves as a precision voltage or current regulator in low-power industrial power supplies and analog sensor conditioning circuits.
For engineers reviewing the LM317LZ/LFT4 datasheet, LM317LZ/LFT4 pinout, LM317LZ/LFT4 application, or LM317LZ/LFT4 equivalent, key selection considerations include its 100mA output capability, 1.25V reference voltage, ±3000V HBM ESD rating, –40°C to +125°C operating junction temperature, and TO-92 package compatibility with legacy designs requiring compact through-hole mounting.
Technical Context
The LM317LZ/LFT4 implements an NPN Darlington output stage with internal 1.25V bandgap reference, enabling precise feedback via external resistors. Its floating architecture allows operation with input voltages hundreds of volts above ground-provided the input-to-output differential remains ≤45V (CSO:RFB fabrication).
It integrates overcurrent and thermal-overload protection that remains active even if the ADJUST pin is disconnected. Regulation relies on maintaining ≥2.5V headroom (VI–VO) and consuming ≥1.28mA minimum load current-including ADJUST pin bias current (44–57µA)-to prevent output drift.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output current | Up to 100mA continuous; supports light-load regulation down to 1.28mA minimum output current. |
| Output voltage range | 1.25V to 37V adjustable; set by two external resistors using VOUT = 1.25V × (1 + R2/R1) + IADJ × R2. |
| Reference voltage | 1.256V typical (CSO:RFB); tight 1.22–1.292V tolerance enables <±1% output accuracy with proper resistor selection. |
| Input-to-output differential | Max 45V (CSO:RFB); enables high-side floating regulation in HVDC intermediate rails or battery stack monitoring. |
| Ripple rejection | 71.5dB at 120Hz (with 10µF ADJ-to-ground cap); improves noise immunity in AC/DC front-end or solar MPPT auxiliary supplies. |
| Operating temperature | –40°C to +125°C junction; validated for HVAC control modules and outdoor energy storage interface boards. |
| ESD rating | ±3000V HBM (CSO:RFB); meets industrial handling requirements without additional input protection circuitry. |
Pinout & Package
LM317LZ/LFT4 is supplied in TO-92 (LP) package: 3-pin, through-hole, 4.8mm × 3.68mm body with JEDEC-standard lead spacing. Pin 1 = INPUT, Pin 2 = OUTPUT, Pin 3 = ADJUSTMENT. All OUTPUT pins are internally connected; no NC pins present in this variant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 (INPUT) | Input supply voltage | Accepts unregulated DC input; must maintain ≥2.5V headroom above desired output for regulation. |
| Pin 2 (OUTPUT) | Regulated output voltage | Sources up to 100mA; connects directly to load or feedback divider; internal connection to all OUTPUT terminals. |
| Pin 3 (ADJUSTMENT) | Feedback voltage reference | Sinks 44–57µA bias current; sets output via resistor divider; bypassing with capacitor improves ripple rejection. |
Key Features
| Feature | Design Value |
|---|---|
| Floating topology | Enables high-side regulation with input voltages >100V when referenced to output-not ground-reducing isolation complexity. |
| No output capacitor required | Stable without COUT; optional 1µF ceramic improves transient response in analog sensor power domains. |
| Programmable current source | Single-resistor configuration (R = 1.25V / IOUT) delivers precision constant current for LED bias or battery charging. |
| Integrated protection | Thermal shutdown and current limiting remain fully functional even if ADJUST pin is open or shorted. |
| Low quiescent current drift | Adjust pin current variation ≤2.5µA over VI–VO = 2.8–35V and IO = 2.5–100mA (CSO:RFB), ensuring stable setpoint accuracy. |
Applications
| Solar Energy Power Management | HVAC Control Module Supply |
|---|---|
Use Scenario: Regulating auxiliary 5V/12V rail from variable PV array output under partial shading or low-light conditions. IC Role / Device Role / Timing Role: Adjustable floating regulator providing isolated, ripple-tolerant bias for microcontroller, sensors, and communication ICs. Use Value: Maintains regulation across wide input differentials (up to 45V) without requiring optocoupler feedback or transformer-based isolation. |
Use Scenario: Powering analog temperature/humidity sensor interfaces and relay drivers in wall-mounted thermostats. IC Role / Device Role / Timing Role: Low-noise, thermally robust linear regulator supplying stable 3.3V or 5V to precision ADCs and comparators. Use Value: –40°C to +125°C operation and 71.5dB ripple rejection ensure reliable performance in uncontrolled ambient environments. |
| Optical Network Terminal (ONT) | Analog Input Module |
Use Scenario: Generating clean ±5V rails for PON transceiver bias and laser diode control circuitry. IC Role / Device Role / Timing Role: Positive adjustable regulator paired with LM337 for symmetric dual-rail generation in compact ONT chassis. Use Value: TO-92 footprint enables dense layout; no output capacitor requirement simplifies BOM and reduces board area. |
Use Scenario: Providing programmable excitation voltage (e.g., 2.5V, 5V, 10V) for strain gauge or RTD bridge circuits. IC Role / Device Role / Timing Role: Precision voltage reference generator with <±0.5% line/load regulation for ratiometric measurement systems. Use Value: 1.25V reference tolerance and low 10µV/V output noise preserve signal integrity in 16-bit+ data acquisition paths. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM317LDR2G | SOIC-8 package; includes two NC pins; higher RθJA (97.1°C/W vs. 139.5°C/W for TO-92); same electrical specs. | Suitable for surface-mount production; requires PCB rework for through-hole replacement; thermal derating needed at >60mA. | Select LM317LDR2G for automated assembly where space permits and thermal management uses copper pour or heatsink. |
| LD1084V | 5A output current; fixed 5V/12V variants available; dropout voltage ~1.5V; no ADJUST pin-requires external feedback for adjustability. | Used in high-current applications like motor driver logic rails; not drop-in for LM317LZ/LFT4 due to different pinout and regulation method. | Choose LD1084V only when >100mA output is required and board layout allows redesign for SO-223 or TO-220 mounting. |
Compared with LM317LDR2G and LD1084V, the LM317LZ/LFT4 uniquely balances through-hole manufacturability, ultra-low minimum load (1.28mA), and floating topology-making it irreplaceable in legacy HVAC sensor nodes and solar charge controller auxiliary supplies where input differentials exceed 30V and PCB real estate is constrained.
Availability
LM317LZ/LFT4 is available at Aetrix Electronics and suitable for solar energy converters, HVAC control modules, and optical network terminal units requiring stable component supply with long-lifecycle support and traceable sourcing.
Supply support for LM317LZ/LFT4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and communications markets.
The LM317L series was designed as a cost-effective, robust adjustable linear regulator for low-power industrial subsystems-emphasizing simplicity, thermal resilience, and compatibility with legacy TO-92 footprints in field-deployed equipment.
FAQ
What is the maximum input-to-output differential voltage supported by LM317LZ/LFT4?
The LM317LZ/LFT4 supports a maximum input-to-output differential voltage of 45V, applicable to devices fabricated at TI's CSO:RFB facility. This rating enables safe operation in high-side floating configurations-for example, regulating 24V output from a 69V PV string-provided thermal limits are observed and minimum load current (≥1.28mA) is maintained.
Can LM317LZ/LFT4 be used as a constant-current source?
Yes, the LM317LZ/LFT4 can function as a precision constant-current source. Connect a single resistor R between OUTPUT and ADJUST pins; output current equals 1.25V / R. For example, a 25Ω resistor delivers 50mA. The LM317LZ/LFT4 maintains this current across varying load voltages up to its 45V differential limit and 100mA absolute maximum rating.
Does LM317LZ/LFT4 require an output capacitor for stability?
No, the LM317LZ/LFT4 does not require an output capacitor for stability-unlike many other linear regulators. An optional 1µF ceramic capacitor may be added to improve transient response in dynamic load applications such as microcontroller wake-up events, but it is not necessary for loop stability or basic regulation functionality.
What is the operating junction temperature range for LM317LZ/LFT4?
The LM317LZ/LFT4 is characterized for operation across a junction temperature range of –40°C to +125°C. This specification applies to the CSO:RFB fabrication version and ensures reliable performance in demanding environments such as outdoor solar inverters, industrial HVAC controllers, and telecom ONT enclosures exposed to wide ambient swings.
How is the output voltage calculated for LM317LZ/LFT4?
The output voltage of LM317LZ/LFT4 is calculated using VOUT = 1.25V × (1 + R2/R1) + IADJ × R2, where R1 connects ADJUST to ground and R2 connects OUTPUT to ADJUST. With typical IADJ = 44–57µA, this term contributes <0.5% error for R2 ≤ 10kΩ and is often omitted in initial design calculations.
LM317LZ/LFT4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA)
- Packaging:
- Cut Tape (CT)
- Product Status:
- Active
- Output Configuration:
- Positive
- Output Type:
- Adjustable
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.2V
- Voltage - Output (Max):
- 37V
- Voltage Dropout (Max):
- -
- Current - Output:
- 100mA
- Current - Quiescent (Iq):
- 5 mA
- Current - Supply (Max):
- -
- PSRR:
- 80dB ~ 65dB (120Hz)
- Control Features:
- -
- Protection Features:
- Over Current, Over Temperature, Short Circuit
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
LM317LZ/LFT4 FAQ
1.How can I place an order for LM317LZ/LFT4 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM317LZ/LFT4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LM317LZ/LFT4 reliable?
The price and inventory of LM317LZ/LFT4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM317LZ/LFT4 is usually 5 days.
3.What payment methods are accepted for LM317LZ/LFT4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM317LZ/LFT4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM317LZ/LFT4?
LM317LZ/LFT4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM317LZ/LFT4 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LM317LZ/LFT4?
For technical support, including LM317LZ/LFT4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM317LZ/LFT4 requirements.
6.How does Aetrix verify that LM317LZ/LFT4 is sourced from the original manufacturer or authorized distributors?
All LM317LZ/LFT4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LM317LZ/LFT4 meets industry standards.
7.What is the process for return or replacement of LM317LZ/LFT4?
All LM317LZ/LFT4 units undergo pre-shipment inspection (PSI). If there is an issue with LM317LZ/LFT4, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LM317LZ/LFT4 part is unused and in its original packaging.
Return procedure for LM317LZ/LFT4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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