LM1117-3.3 Reference Tables, Pins & Specifications

Pin reference

Signal names, electrical functions and connection guidance

TO-220

Physical pin numbers3 pins

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LM1117-3.3 pin functions and connections
Signal	Type	Function & connection
GND	Ground reference	Return for the internal reference, feedback divider and bias current in the fixed 3.3 V version. Connection guidance Connect to the input-supply return, load return and both capacitor returns. This is GND on the fixed-output part. The adjustable LM1117 uses this lead as ADJ and is a different circuit.
OUTPUT	Regulated output	Supplies the nominal 3.3 V rail. The metal tab is electrically connected to this output. Connection guidance Connect the load and a suitable output capacitor close to the regulator. The output capacitor is part of the stability requirements: TI specifies at least 10 µF tantalum with ESR from 0.3 Ω to 22 Ω. The tab is not ground.
INPUT	DC input	Feeds the pass stage and bias circuit from a supply above the output by sufficient headroom. Connection guidance Use a regulated 5 V source for the example and a local 10 µF input bypass. Check input tolerance, ripple and dropout at the intended load and temperature. The 20 V absolute maximum is not the 15 V recommended maximum.

TI LM1117-3.3 · fixed-output grade

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Nominal output	3.3 V	Fixed 3.3 V option
Output at 25°C	3.267 / 3.3 / 3.333 V	Minimum / typical / maximum; VIN = 5 V, IOUT = 10 mA
Output across specified conditions	3.235–3.365 V	0–800 mA; VIN = 4.75–10 V; TJ = 0–125°C
Output current	Up to 800 mA	Requires headroom and adequate thermal design
Junction operating range	0–125°C	Selected LM1117 grade
Recommended input maximum	15 V	Must also satisfy thermal and dropout constraints

The LM1117I grade has a different temperature range. This reference follows the selected non-I devices.

Retain the measurement conditions

Manufacturer-referenced values5 parameters

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Parameter	Value	Conditions / notes
Line regulation	1 mV typical; 6 mV maximum	IOUT = 0 mA, VIN = 4.75–15 V; typical at 25°C, maximum over 0–125°C
Load regulation	1 mV typical; 10 mV maximum	VIN = 4.75 V, IOUT = 0–800 mA; typical at 25°C, maximum over 0–125°C
Ground current	5 mA typical; 10 mA maximum	VIN ≤ 15 V; typical at 25°C, maximum over 0–125°C
Dropout criterion	Output falls by 100 mV	Referenced to VOUT measured with VIN = VOUT + 1.5 V
Current limiting	Built in	An overload protection feature, not an extra operating-current allowance

Dropout changes with output current and junction temperature; use TI’s table and curves when choosing the supply margin.

Capacitance and ESR both matter

Manufacturer-referenced values5 parameters

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Parameter	Value	Conditions / notes
Input bypass	10 µF tantalum	TI’s suitable input capacitor for most applications
Output capacitor	At least 10 µF tantalum	Required for the selected fixed-output circuit
Output capacitor ESR	0.3–22 Ω	Manufacturer stability guidance
Low-ESR substitution	Check before changing technology	A ceramic capacitor is not automatically a valid drop-in replacement
Placement	Short input, output and ground paths	Keep the load return and regulator ground well connected

Check capacitance, ESR, voltage rating and temperature behavior for the actual capacitor part.

100 mA nominal resistive load

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Supply	Regulated 5 V DC	Feed pin 3 INPUT
Return	Pin 1 GND	Common with input supply, capacitors and load
Output	Pin 2 OUTPUT	Nominal 3.3 V; tab is the same net
Example load	33 Ω · at least 1 W	3.3 / 33 = 0.10 A; resistor power = 0.33 W
Pass-stage loss	0.17 W	(5 − 3.3) × 0.10
Including typical ground current	Approximately 0.195 W	0.17 + 5 × 0.005

These are nominal calculations, not measured results. Output tolerance and actual ground current change the values.

Package ratings require a thermal context

Manufacturer-referenced values7 parameters

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Parameter	Value	Conditions / notes
Power estimate	PD ≈ (VIN − VOUT) × ILOAD + VIN × IGND	Include both loss terms
Junction estimate	TJ ≈ TA + PD × RθJA	Only for the board and airflow represented by the thermal resistance
TO-220 RθJA / RθJC(bottom)	23.8 / 1.5°C/W	TI thermal characterization conditions
D²PAK RθJA / RθJC(bottom)	41.3 / 1.3°C/W	TI thermal characterization conditions
Input absolute maximum	20 V	Stress rating, not the recommended operating maximum
Junction absolute maximum	150°C	Recommended operation ends at 125°C
Storage range	−65 to +150°C	Unpowered

The output-connected tab must not be shorted to a grounded heatsink. Thermal shutdown does not replace cooling design.