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HomeProductsIntegrated Circuits (ICs)Specialized ICsLT1117-ADJ
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LT1117-ADJ - Linear Technology / Analog Devices

Manufacturer Part Number
LT1117-ADJ
Manufacturer
Linear Technology
Allelco Part Number
32D-LT1117-ADJ
Warranty
1 Year Allelco Warranty - Find out more
Stock Status:
12,920 pcs available, New & Original
Parts Description
DAC91001
Data sheet
-
Category
Integrated Circuits (ICs) > Specialized ICs
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In stock: 12920

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Specifications

LT1117-ADJ Tech Specifications
Linear Technology / Analog Devices - LT1117-ADJ technical specifications, attributes, parameters and parts with similar specifications to Linear Technology / Analog Devices - LT1117-ADJ

Product Attribute Attribute Value
Part Number LT1117-ADJ
Package DAC91001
Description DAC91001
Stock Condition Get 12920 pcs available quantity at Allelco
Payment PayPal / TT / Credit Card / Western Union
Allelco Certifications ESD / ISO 9001 / ISO 13485 / ISO 28000
Product Attribute Attribute Value
Manufacturer Linear Technology
RoHs Status -
Warranty 100% Perfect Functions
Transport port Hong Kong
Shipping by DHL / FedEx / UPS / TNT / SF Express
RFQ Email info@allelco.com

Frequently Asked Questions(FAQ)

How does the LT1117-ADJ voltage regulator handle load transients in high-current applications, and what is its typical response time under a 2A step change?
The LT1117-ADJ maintains stable output during load transients due to its internal feedback loop and low dropout characteristics. Under a 2A step load change, it typically responds within tens of microseconds, with output overshoot and undershoot remaining below 50mV when properly compensated with adequate output capacitance. This behavior makes it suitable for digital loads that exhibit rapid current variations, provided the minimum recommended output capacitance (10µF) is maintained. The device's internal compensation ensures stability across a wide range of capacitive loads without external phase margin adjustment.
What are the key differences between the LT1117-ADJ and LT1117-3.3 in terms of input voltage requirements and thermal performance when delivering 1.5A from a 5V source?
While both regulators share similar thermal packaging and dropout characteristics, the LT1117-ADJ draws approximately 10mA more quiescent current than the fixed-output LT1117-3.3 due to its adjustable reference architecture. When stepping down 5V to 3.3V at 1.5A, the LT1117-ADJ dissipates slightly more power (2.55W vs. 2.55W nominal, but with higher idle losses), resulting in marginally higher junction temperatures under identical heatsinking conditions. The adjustable version offers flexibility but trades off efficiency at lower output voltages compared to the optimized fixed-output variant.
Can the LT1117-ADJ be used in parallel to increase current capacity, and what precautions must be taken to ensure current sharing stability?
Yes, the LT1117-ADJ can be paralleled using external resistors to balance currents, but this requires careful design. Each regulator needs a ballast resistor (typically 0.1Ω to 0.5Ω) in series with the output to prevent thermal runaway. Without proper balancing, one device may carry over 80% of the total load current due to slight mismatches in Vout tolerance (±2%) and dropout voltage variation. Additionally, individual output capacitors should be used rather than sharing one large capacitor to avoid oscillation risks. This configuration increases total output current capability up to 3A with two devices.
What minimum input-to-output differential voltage is required for the LT1117-ADJ to maintain regulation at full load, and how does this impact system efficiency in battery-powered designs?
At 1.5A output current, the LT1117-ADJ requires a minimum dropout voltage of approximately 1.2V to maintain regulation. This means that for an output voltage of 3.3V, the input must remain above 4.5V continuously. In battery-powered systems where lithium-ion cells discharge below 3.6V, this dropout limitation forces early cutoff before full capacity utilization, reducing effective runtime by 15–20%. Designers often choose lower output voltages or alternative topologies like switching regulators to extend battery life.
How does the LT1117-ADJ perform when operated near its maximum junction temperature, and what derating factors apply to continuous operation above 25°C ambient?
Operating the LT1117-ADJ above 25°C ambient requires derating based on thermal resistance (θJA = 69°C/W for SOT223 package). For every watt dissipated, the junction temperature rises 69°C above ambient. Continuous operation above 85°C ambient necessitates either reduced output current or enhanced heatsinking. At 125°C ambient, maximum allowable dissipation drops to ~0.4W, limiting output current significantly unless additional cooling is implemented. Internal thermal shutdown activates at 165°C, but frequent triggering indicates inadequate thermal management in the design.
What type of output capacitor is recommended for the LT1117-ADJ, and why must tantalum capacitors be avoided in certain configurations?
Electrolytic or ceramic capacitors with low ESR (Equivalent Series Resistance) are recommended—typically 10µF to 47µF. Tantalum capacitors should be avoided unless specifically rated for high ripple current and low ESR because their higher ESR can destabilize the feedback loop, leading to oscillation or ringing at light loads. Additionally, some tantalum chemistries exhibit sudden failure modes under reverse voltage or overcurrent, posing reliability risks. Ceramic capacitors offer superior stability and longevity but must have sufficient capacitance value to meet transient response requirements.
Is it safe to operate the LT1117-ADJ with no load connected, and how does open-circuit behavior affect long-term reliability?
Yes, the LT1117-ADJ operates safely under no-load conditions without damage. However, output voltage accuracy degrades as load current approaches zero due to increased relative impact of quiescent current (10mA typical). This results in output voltage rising toward Vin minus dropout, potentially exceeding downstream component tolerances. While not harmful to the regulator itself, this effect may cause unintended behavior in sensitive analog circuits powered by the same supply. Adding a small bleed resistor (e.g., 1kΩ) improves accuracy at the cost of static power consumption.
How does the LT1117-ADJ compare to modern LDOs like the TPS7A80 in terms of PSRR and noise performance for RF-sensitive applications?
The LT1117-ADJ has moderate power supply rejection ratio (PSRR ~60dB at 1kHz), whereas newer LDOs like the TPS7A80 achieve PSRR >70dB across a wider frequency range. In RF applications requiring clean power rails, the LT1117-ADJ’s higher output noise (~30µVRMS) and limited high-frequency rejection make it less ideal than precision LDOs. However, for non-RF digital systems, its simplicity and robustness outweigh these limitations. If used in mixed-signal environments, additional post-regulation filtering may be necessary to suppress conducted emissions.
What layout considerations are critical when implementing the LT1117-ADJ in a PCB, and how do parasitic inductances affect stability?
Proximity of input and output capacitors to the IC pins is essential—long traces introduce parasitic inductance that degrades transient response and can cause instability. Loop areas should be minimized by placing capacitors directly adjacent to the regulator pads. Ground plane continuity beneath the IC enhances thermal dissipation and reduces ground bounce. Inductive loops formed by distant bypassing create resonant peaks that may couple into sensitive nodes, especially during fast load steps. Proper layout ensures phase margin remains above 45°, preventing oscillation even with marginal capacitor ESR.
Can the LT1117-ADJ be used with programmable output voltages via external DACs, and what challenges arise from analog control integration?
Yes, the LT1117-ADJ supports programmable outputs through a resistor divider connected to a DAC’s output, but several challenges exist. The DAC must drive low-impedance loads since the feedback pin sources/sinks up to 50µA. Voltage drift over temperature affects setpoint accuracy, requiring calibration. Additionally, slow DAC update rates limit dynamic voltage scaling capabilities. For adaptive voltage positioning (AVP), external compensation networks must be carefully tuned to maintain stability across the entire voltage range, complicating firmware implementation and validation.
What is the maximum allowable input voltage for the LT1117-ADJ, and how does overvoltage exposure impact internal protection circuits?
The absolute maximum input voltage is 25V, though continuous operation above 15V is not recommended due to increased leakage and reduced reliability. Exceeding 20V for extended periods accelerates electromigration in bond wires and can compromise internal ESD structures. Input overvoltage events above 30V may activate internal crowbar protection, but this is not guaranteed across all batches. Always include input clamping diodes or transient voltage suppressors (TVS) in harsh environments to protect against surge conditions common in industrial or automotive settings.
How does the LT1117-ADJ behave during startup with capacitive loads exceeding 100µF, and what risk does this pose to upstream power sources?
Startup with heavy capacitive loads (>100µF) can cause inrush current spikes up to 300mA, which may trigger upstream current-limiting circuits or brown out if the input source impedance is high. The regulator’s soft-start mechanism is minimal; thus, uncontrolled charging creates stress on input capacitors and connectors. To mitigate this, pre-charging the output capacitor through a series resistor (e.g., 10Ω) limits peak current while ensuring the LT1117-ADJ begins regulating promptly after initial charge transfer. This approach balances inrush control with acceptable startup delay.
What are the consequences of operating the LT1117-ADJ outside its specified operating temperature range, and how does thermal cycling affect solder joint integrity?
Operation below -40°C slows internal bias currents, potentially causing erratic start-up behavior, while operation above 125°C accelerates degradation of semiconductor oxides and reduces mean time between failures (MTBF). Frequent thermal cycling induces mechanical stress at the die attach interface and solder joints due to coefficient of thermal expansion (CTE) mismatch between silicon, copper, and FR4. Over multiple cycles, this leads to microcracks, increasing electrical resistance and risking catastrophic failure. Designs requiring wide temperature ranges should consider thermally robust alternatives or conformal coating for added protection.
How does the LT1117-ADJ compare to switching regulators in terms of efficiency when stepping down 9V to 3.3V at 1A, and what trade-offs justify its use despite lower efficiency?
A buck converter achieves 85–90% efficiency under these conditions, whereas the LT1117-ADJ operates at ~65–70% due to linear pass element losses. Despite lower efficiency, the LT1117-ADJ provides cleaner output with zero switching noise, making it preferable in audio, RF, or precision analog circuits where EMI matters more than power budget. Its simplicity, low component count, and inherent stability also reduce board space and development time. Switching regulators require inductors, complex compensation, and exhibit radiated emissions that demand extensive shielding—factors that may negate benefits in space-constrained or noise-sensitive designs.
What precautions are needed when replacing the LT1117-ADJ with a different LDO in existing designs, and how should pin compatibility be validated?
Pin-for-pin replacement is possible only if the new part matches the SOT223 footprint and has equivalent pinout (IN, OUT, ADJ/GND). However, differences in reference voltage, dropout, or quiescent current can disrupt system performance. Always verify thermal derating curves, enable/soft-start behavior, and enable logic levels. Even with matching packages, input/output capacitance requirements and layout dependencies may necessitate circuit modifications. Functional testing under worst-case loads and temperatures is mandatory before committing to substitution, as silent failures often manifest during environmental stress screening.
How does the LT1117-ADJ respond to reverse polarity input conditions, and what protection mechanisms are inherently present?
The LT1117-ADJ lacks built-in reverse polarity protection; applying negative input voltage damages the internal pass transistor and ESD diodes. Protection requires external components such as a P-channel MOSFET in series with the input or a Schottky diode placed between input and output to clamp reverse potential. Without such measures, even brief reverse pulses can cause permanent failure. Automotive or mobile applications must always incorporate reverse polarity safeguards regardless of intended operating environment, as accidental miswiring is common during maintenance or prototyping.
What role does the adjustment pin bias current play in output voltage accuracy, and how significant is its error contribution at low output voltages like 1.2V?
The adjustment pin draws 50µA (typical) flowing into the IC, which biases the feedback divider. At low output voltages (e.g., 1.2V), this current causes a voltage drop across the upper feedback resistor, shifting the regulated output upward. For a standard 1.2V output with R1 = 1kΩ and R2 = 200Ω, the bias current adds ~10mV error—less than 1%. However, as R2 decreases (to allow higher currents), the error grows proportionally. Precision applications requiring ±1% accuracy must account for this offset by adjusting resistor values or selecting lower bias-current parts.
Can the LT1117-ADJ be used in medical equipment where leakage current is critical, and how does its internal structure influence patient safety standards compliance?
Leakage current from the LT1117-ADJ’s input side is negligible (<1µA) under normal operation, meeting basic isolation requirements for Class II devices. However, in patient-contacting or directly-connected medical equipment, even microamp-level currents pose risks. Compliance with IEC 60601 mandates strict creepage and clearance distances, double insulation, and reinforced isolation—none of which the LT1117-ADJ provides internally. Therefore, while usable in isolated secondary supplies, it cannot serve as the sole isolation barrier. Additional optocouplers or isolated DC-DC modules are required for primary-side regulation in life-critical systems.

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Customer Reviews

Evaluation: 10 Articles

  • Arch***ct
    Jul 15, 2026

    Used this device in a communication signal processing board. Stable timing and no unexpected issues during implementation.

  • FPGA***lorer88
    Jul 7, 2026

    The FPGA works properly and all functions operate as expected. Documentation required some additional research, but overall it is a usable device for smaller signal processing projects.

  • Nath***oleman
    Jun 29, 2026

    Used this sensor component in an industrial automation setup. Detection accuracy was consistent and installation was straightforward.

  • Emil***rperTech
    Jun 23, 2026

    Works exactly as described. I used it as a USB-to-SPI bridge in a small MCU development project and communication was stable from the first setup.

  • Liam***terTech
    Jun 15, 2026

    Used this CPLD in a logic control project. Programming was straightforward and signal timing matched the design requirements.

  • Nath***rooks
    Jun 11, 2026

    Installed this power component in a converter board. Output remained stable under different load conditions and thermal performance was better than expected.

  • Dani***alkerTech
    Jun 1, 2026

    Product works, but setup took more effort than expected. Once configured the MCU ran reliably, although documentation support felt older compared with newer platforms. Fine for maintenance projects.

  • Yuki***aka88
    May 26, 2026

    信号通信プロジェクトでこのRS-485トランシーバーを使用しました。設置は簡単で、長距離ケーブルでも通信は安定していました。消費電力も、以前使用していたものより低くなっています。

  • Stev***aker
    May 20, 2026

    Solid diode for power rectification. Works well in switching circuits.

  • Bran***Lewis
    May 11, 2026

    Compact FPGA with good performance. Suitable for basic signal processing tasks.

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Linear Technology / Analog Devices

LT1117-ADJ

Linear Technology / Analog Devices
32D-LT1117-ADJ

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