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HomeProductsIntegrated Circuits (ICs)Specialized ICsLT1117-3.3TR
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LT1117-3.3TR - LT

Manufacturer Part Number
LT1117-3.3TR
Manufacturer
LT
Allelco Part Number
32D-LT1117-3.3TR
Warranty
1 Year Allelco Warranty - Find out more
Stock Status:
5,200 pcs available, New & Original
Parts Description
DAC91001
Data sheet
-
Category
Integrated Circuits (ICs) > Specialized ICs
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In stock: 5200

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Specifications

LT1117-3.3TR Tech Specifications
LT - LT1117-3.3TR technical specifications, attributes, parameters and parts with similar specifications to LT - LT1117-3.3TR

Product Attribute Attribute Value
Part Number LT1117-3.3TR
Package DAC91001
Description DAC91001
Stock Condition Get 5200 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 LT
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 LT1117-3.3TR compare to other linear regulators in terms of dropout voltage when powering a 3.3V system from a 4V input?
The LT1117-3.3TR exhibits a typical dropout voltage of approximately 1.2V at full load current, which means it can maintain regulation down to an input voltage of about 4.5V. This is relatively moderate compared to older regulators but still limits its efficiency in low-voltage headroom scenarios. For a 4V input, the regulator may not achieve full output accuracy under higher loads due to insufficient margin above the dropout threshold. In contrast, modern LDOs with lower dropout voltages (e.g., under 0.3V) would be more suitable for such tight input-output differentials.
What are the thermal implications of using the LT1117-3.3TR in a compact SOT-223 package without a heatsink, assuming a 500mA load and ambient temperature of 25°C?
With a maximum junction-to-ambient thermal resistance (θJA) of around 59°C/W in the SOT-223 package, the LT1117-3.3TR will experience significant heating at 500mA load. The power dissipation is roughly (4.5V - 3.3V) × 0.5A = 0.6W, leading to a temperature rise of approximately 35°C above ambient—placing the junction at near 60°C. While this may not immediately trigger thermal shutdown, prolonged operation near these levels risks derating or accelerated degradation. A heatsink or forced airflow is advisable for sustained high-current applications.
Can the LT1117-3.3TR safely deliver 800mA continuously in a consumer electronics design, and what external components are critical for stable operation?
The LT1117-3.3TR is specified for up to 800mA output current, but continuous operation at this level requires careful attention to layout, input/output capacitance, and thermal management. The datasheet mandates specific ESR ranges for output capacitors—typically between 10mΩ and 220mΩ—to ensure stability. Using ceramic capacitors alone without series resistance may lead to oscillation. Additionally, input capacitance should be at least 10µF with similar ESR characteristics. Without proper decoupling and thermal relief, reliability could be compromised.
Why might someone choose the LT1117-3.3TR over a switching regulator despite its lower efficiency, and where does this trade-off make sense?
The LT1117-3.3TR offers simplicity, low noise, and transient response superior to many switchers, making it ideal for noise-sensitive analog circuits or microcontrollers requiring clean power rails. In battery-powered devices where EMI compliance is strict and efficiency is secondary to signal integrity, the linear approach outweighs the benefits of switching topology. However, for systems prioritizing energy conservation—such as IoT sensors with long sleep cycles—a buck converter would be more appropriate despite added complexity.
How do I determine whether the LT1117-3.3TR will remain stable when paired with a 10µF tantalum capacitor on the output?
Tantalum capacitors generally exhibit acceptable ESR within the recommended range (10–220mΩ), so a 10µF part often falls into this window and should work reliably with the LT1117-3.3TR. However, some low-ESR tantalums approach the upper end of the ESR limit, potentially pushing stability margins near the edge. To verify, consult the manufacturer’s datasheet for exact ESR values and consider adding a small series resistor (e.g., 0.1–1Ω) if oscillations occur during testing. Always perform bench validation under expected load transients.
What precautions should be taken during PCB layout to prevent instability or overshoot when using the LT1117-3.3TR?
Place input and output capacitors as close as possible to the IC pins to minimize parasitic inductance. Keep traces short and wide, especially for ground return paths. Avoid routing sensitive feedback lines near noisy components. The LT1117-3.3TR relies on low-impedance ground planes for stability; a solid ground plane beneath the device significantly improves performance. Also, ensure that any bypass capacitors use vias directly adjacent to their pads to reduce loop area and suppress high-frequency noise.
Is it feasible to parallel multiple LT1117-3.3TR units to share current in a high-power application, and what challenges arise?
Direct paralleling of LT1117-3.3TR devices without balancing resistors or active current-sharing techniques leads to unequal current distribution because of slight variations in VBE and manufacturing tolerances. One unit may carry most of the load while others remain underutilized or overstressed. Implementing ballast resistors (e.g., 0.1–0.5Ω) in series with each regulator can help balance currents but introduces additional power loss and defeats some efficiency goals. Therefore, parallel operation is generally discouraged unless absolutely necessary and carefully managed.
How does the LT1117-3.3TR respond to rapid load transients, and what capacitor value helps maintain regulation during sudden current demands?
The LT1117-3.3TR has good line and load regulation specifications—typically ±2% for load steps—but its ability to handle fast transients depends heavily on output capacitance. A minimum of 10µF with sufficient ESR dampens oscillations and prevents droop. During sudden load increases (e.g., from 10mA to 500mA in <10µs), the output may briefly dip below 3.3V if capacitance is inadequate. Adding a small ceramic capacitor (e.g., 0.1µF) in parallel with the main output cap improves high-frequency response without affecting stability.
What environmental factors could degrade the performance or lifespan of the LT1117-3.3TR in industrial versus consumer applications?
Operating temperature range extends from -40°C to +125°C, making it suitable for industrial environments. However, elevated ambient temperatures increase junction temperature for a given power dissipation, reducing available headroom before thermal protection activates. Humidity and mechanical stress in harsh conditions may affect solder joints over time, especially in drop-prone consumer devices. Proper conformal coating and robust PCB assembly practices mitigate these risks and extend operational life.
When selecting between fixed and adjustable versions of similar regulators, why might the LT1117-3.3TR be preferred over an adjustable variant like the LT1117CST?
The fixed 3.3V version (LT1117-3.3TR) eliminates the need for external resistors, simplifying design and reducing component count. It also avoids potential issues with resistor tolerance affecting output accuracy. For digital systems requiring exactly 3.3V (e.g., 3.3V logic families), the fixed output ensures consistent rail voltage without calibration concerns. Adjustable variants introduce minor overhead in BOM cost and board space, which may not justify marginal flexibility unless future reconfigurability is anticipated.
How accurate is the 3.3V output of the LT1117-3.3TR across temperature and aging, and does this impact precision analog designs?
Output voltage accuracy is typically ±2% initially, with minimal drift over temperature due to internal compensation. Over time, aging effects are negligible for most applications. However, in precision analog circuits sensitive to supply ripple or DC offset (e.g., data converters), even 66mV deviation from nominal could affect performance. If tighter control is needed, post-regulation using reference buffers or LDO cascading may be required, though this adds complexity beyond what the LT1117-3.3TR provides natively.
Can the LT1117-3.3TR operate reliably from a Li-ion battery discharging down to 3.5V?
No. With a dropout voltage of ~1.2V at full load, the LT1117-3.3TR requires at least 4.5V input to regulate properly. At 3.5V, the output will fall below 3.3V under load, causing undefined behavior in downstream circuits. For Li-ion applications with discharge curves reaching 3.2–3.3V, a low-dropout regulator with <0.4V dropout (like the LP2985) or a buck-boost converter is far more appropriate. Attempting to use the LT1117-3.3TR in this scenario results in unreliable operation.
What role does input voltage ripple play in the stability of the LT1117-3.3TR, and how should it be mitigated?
Excessive input ripple, especially at frequencies near the regulator’s crossover frequency, can couple into the output through internal pass transistor dynamics. Although the LT1117-3.3TR has good PSRR (~60dB at 1kHz), poor input filtering allows noise to propagate. A bulk electrolytic capacitor (e.g., 47–100µF) combined with a ceramic bypass capacitor near the input helps attenuate high-frequency transients. Layout parasitics must also be minimized to prevent resonant interactions between input capacitance and trace inductance.
How does the enable functionality (if available) or lack thereof impact system power sequencing when using the LT1117-3.3TR?
The LT1117-3.3TR does not feature a dedicated enable pin; instead, it powers up when input voltage exceeds the turn-on threshold (~1.2V). This means it cannot participate in controlled power-up sequences without external circuitry. In systems requiring staggered startup or shutdown, additional components like comparators or supervisor ICs must manage sequencing. Failure to sequence properly risks brownout conditions or latch-up in downstream ICs during undervoltage events.
In what scenarios would the LT1117-3.3TR be unsuitable despite its high output current capability?
Applications demanding high efficiency over wide load ranges, such as battery-operated devices running for months on coin cells, are poor fits due to linear regulation losses. Similarly, space-constrained wearables benefit more from ultra-thin switching regulators. The SOT-223 package, while compact, dissipates heat less effectively than larger TO-220 variants, limiting use in densely populated boards without thermal vias. Lastly, RF-sensitive environments may require post-LDO filtering beyond what the LT1117-3.3TR inherently provides.
How should one interpret the absolute maximum ratings for input-to-output reverse bias conditions involving the LT1117-3.3TR?
The LT1117-3.3TR is not designed to tolerate reverse polarity between input and output. Applying a voltage greater than the input while holding the output at a higher potential (e.g., back-driving the regulator) can damage internal ESD structures or cause latch-up. Absolute maximum ratings specify that input voltage should never exceed output by more than a few volts. If bidirectional protection is needed, external diodes or dedicated reverse-bias tolerant regulators should be used instead of relying on the LT1117-3.3TR alone.
What diagnostic tools or measurements are most effective for verifying LT1117-3.3TR performance during prototype validation?
Key metrics include output voltage under full and light loads, dropout voltage measurement, thermal rise under worst-case conditions, and transient response using electronic loads capable of simulating step changes. Oscilloscope probing with bandwidth-limited techniques reveals ringing or overshoot indicative of stability issues. Simultaneously monitoring input current helps assess efficiency and identify unexpected loading. Comparing measured values against datasheet graphs validates compliance and identifies layout-related anomalies early in development.
Why might two seemingly identical LT1117-3.3TR units behave differently under the same test conditions?
Minor variations in internal fabrication cause differences in threshold voltages, quiescent current, and thermal characteristics. These tolerances manifest as slight discrepancies in output voltage, startup delay, or thermal shutdown thresholds. Additionally, PCB layout inconsistencies—such as trace length mismatches or ground plane discontinuities—can amplify individual part variation. Therefore, always assume statistical distribution of parameters and design margins accordingly rather than expecting uniform behavior across production lots.

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Common Countries Logistic Time Reference
Region Country Logistic Time(Day)
America United States 5
Brazil 7
Europe Germany 5
United Kingdom 4
Italy 5
Oceania Australia 6
New Zealand 5
Asia India 4
Japan 4
Middle East Israel 6
DHL & FedEx Shipment Charges Reference
Shipment charges(KG) Reference DHL(USD$)
0.00kg-1.00kg USD$30.00 - USD$60.00
1.00kg-2.00kg USD$40.00 - USD$80.00
2.00kg-3.00kg USD$50.00 - USD$100.00
Note:
The above table is for reference only. There may have some data bias for the uncontrollable factors.
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LT1117-3.3TR

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32D-LT1117-3.3TR

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