LM1117 800-mA, Low-Dropout Linear Regulator
Texas Instruments
1 Features
- Newer drop-in alternative: TLV1117
- Drop-in replacements in fixed output SOT-223 package with improved functionality: TLV761
- Available in 1.8 V, 2.5 V, 3.3 V, 5 V, and adjustable versions
- Space-saving SOT-223 and WSON packages
- Current limiting and thermal protection
- Output current: 800 mA
- Line regulation: 0.2% (maximum)
- Load regulation: 0.4% (maximum)
- Temperature range: LM1117: 0°C to +125°C; LM1117I: -40°C to +125°C
2 Applications
- AC drive power stage modules
- Merchant network and server PSU
- Industrial AC/DC
- Ultrasound scanners
- Servo drive control modules
3 Description
The LM1117 is a low dropout voltage regulator with a dropout of 1.2 V at 800 mA of load current. It is available in an adjustable version, which can set the output voltage from 1.25 V to 13.8 V using two external resistors. It also comes in five fixed voltages: 1.8 V, 2.5 V, 3.3 V, and 5 V. The device features current limiting and thermal shutdown, with a Zener trimmed band-gap reference ensuring output voltage accuracy within ±1%. A minimum of 10-µF tantalum capacitor is required at the output for improved transient response and stability.
Package Information
| PART NUMBER | PACKAGE (1) | BODY SIZE (NOM) |
|---|---|---|
| LM1117, LM1117I | DCY (SOT-223, 4) | 6.50 mm × 3.50 mm |
| NDE (TO-220, 3) | 14.986 mm × 10.16 mm | |
| NDP (TO-252, 3) | 6.58 mm × 6.10 mm | |
| NGN (WSON, 8) | 4.00 mm × 4.00 mm | |
| KTT (TO-263, 3) | 10.18 mm × 8.41 mm |
(1) For all available packages, see the orderable addendum at the end of the data sheet.
4 Revision History
Changes from Revision P (July 2022) to Revision Q (January 2023): Added drop-in replacement bullet for TLV761 to Features section.
Changes from Revision O (June 2020) to Revision P (July 2022): Updated the numbering format for tables, figures, and cross-references throughout the document.
5 Device Comparison Table
| IOUT | PARAMETER | LM1117 | TLV1117 | UNIT |
|---|---|---|---|---|
| 800 mA | Input voltage range (max) | 15 | 15 | V |
| Load regulation accuracy | 1.6 | 1.6 | % | |
| PSRR (120 Hz) | 75 | 75 | dB | |
| Recommended operating temperature | 0–125 | -40–125 | °C | |
| SOT-223 TJA | 61.6 | 104.3 | °C/W | |
| TO-220 TJA | 23.8 | 30.1 | °C/W | |
| TO-252 TJA | 45.1 | 50.9 | °C/W | |
| TO-263 TJA | 41.3 | 27.5 | °C/W | |
| WSON-8 TJA | 39.3 | 38.3 | °C/W |
6 Pin Configuration and Functions
Figure 6-1. DCY Package, 4-Pin SOT (Top View) Figure 6-2. NDE Package, 3-Pin TO-220 (Top View) Figure 6-3. KTT Package, 3-Pin TO-263 (Top View) Figure 6-4. NDP Package, 3-Pin TO-252 (Top View) Figure 6-5. NGN Package, 8-Pin WSON (Top View) (When using the WSON package, pins 2, 3, and 4 must be connected together, and pins 5, 6, and 7 must be connected together.)
| NAME | PIN (TO-252, WSON, SOT-223, TO-263, TO-220) | I/O | DESCRIPTION |
|---|---|---|---|
| ADJ/GND | 1 (1, 1, 1, 1, 1) | -- | Adjust pin for adjustable output option. Ground pin for fixed output option. |
| VIN | 3 (2,3,4, 3, 3) | I | Input voltage pin for the regulator |
| VOUT | 2, TAB (5,6,7, TAB, 2,4, 2, TAB, 2, TAB) | O | Output voltage pin for the regulator |
7 Specifications
7.1 Absolute Maximum Ratings
| MIN | MAX | UNIT | |
|---|---|---|---|
| Maximum input voltage (VIN to GND) | 20 | V | |
| Power dissipation | Internally Limited | ||
| Junction temperature (TJ) | 150 | °C | |
| Storage temperature, Tstg | -65 | 150 | °C |
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) The maximum power dissipation is a function of TJ(max), RθJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max)−TA)/RθJA. All numbers apply for packages soldered directly into a PCB.
7.2 ESD Ratings
| VALUE | UNIT | |
|---|---|---|
| Electrostatic discharge (Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)) | ±2000 | V |
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Pins listed as ±2000 V may actually have higher performance.
7.3 Recommended Operating Conditions
| MIN | MAX | UNIT | |
|---|---|---|---|
| Input voltage (VIN to GND) | 15 | V | |
| Junction temperature (TJ)(1) | LM1117: 0 | 125 | °C |
| LM1117I: -40 | 125 |
(1) The maximum power dissipation is a function of TJ(max), RθJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max)−TA)/RθJA. All numbers apply for packages soldered directly into a PCB.
7.4 Thermal Information
| THERMAL METRIC(1) | DCY (SOT-223) 4 PINS | NDE (TO-220) 3 PINS | NDP (TO-252) 3 PINS | NGN (WSON) 8 PINS | KTT (TO-263) 3 PINS | UNIT |
|---|---|---|---|---|---|---|
| Junction-to-ambient thermal resistance (RθJA) | 61.6 | 23.8 | 45.1 | 39.3 | 41.3 | °C/W |
| Junction-to-case (top) thermal resistance (RθJC(top)) | 42.5 | 16.6 | 52.1 | 31.4 | 44.1 | °C/W |
| Junction-to-board thermal resistance (RθJB) | 10.4 | 5.3 | 29.8 | 16.5 | 24.2 | °C/W |
| Junction-to-top characterization parameter (ΨJT) | 2.9 | 3.1 | 4.5 | 0.3 | 10.9 | °C/W |
| Junction-to-board characterization parameter (ΨJB) | 10.3 | 5.3 | 29.4 | 16.7 | 23.2 | °C/W |
| Junction-to-case (bottom) thermal resistance (RθJC(bot)) | -- | 1.5 | 1.3 | 5.6 | 1.3 | °C/W |
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC package thermal metrics application report.
7.5 LM1117 Electrical Characteristics
Unless otherwise specified, TJ = 25°C
| PARAMETER | TEST CONDITIONS | MIN(1) | TYP(2) | MAX(1) | UNIT | |
|---|---|---|---|---|---|---|
| Reference voltage (VREF) | LM1117-ADJ: IOUT = 10 mA, VIN – VOUT = 2 V, TJ = 25°C | 1.238 | 1.25 | 1.262 | V | |
| LM1117-ADJ: 10 mA ≤ IOUT ≤ 800 mA, 1.4 V ≤ VIN – VOUT ≤ 10 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 1.225 | 1.25 | 1.27 | V | |
| Output voltage (VOUT) | LM1117-1.8: IOUT = 10 mA, VIN = 3.8 V, TJ = 25°C | 1.782 | 1.8 | 1.818 | V | |
| LM1117-1.8: 0 ≤ IOUT ≤ 800 mA, 3.2 V ≤ VIN ≤ 10 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 1.746 | 1.8 | 1.854 | V | |
| LM1117-2.5: IOUT = 10 mA, VIN = 4.5 V, TJ = 25°C | 2.475 | 2.5 | 2.525 | V | ||
| LM1117-2.5: 0 ≤ IOUT ≤ 800 mA, 3.9 V ≤ VIN ≤ 10 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 2.45 | 2.5 | 2.55 | V | |
| LM1117-3.3: IOUT = 10 mA, VIN = 5 V TJ = 25°C | 3.267 | 3.3 | 3.333 | V | ||
| LM1117-3.3: 0 ≤ IOUT ≤ 800 mA, 4.75 V ≤ VIN ≤ 10 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 3.235 | 3.3 | 3.365 | V | |
| LM1117-5.0: IOUT = 10 mA, VIN = 7 V, TJ = 25°C | 4.95 | 5 | 5.05 | V | ||
| LM1117-5.0: 0 ≤ IOUT ≤ 800 mA, 6.5 V ≤ VIN ≤ 12 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 4.9 | 5 | 5.1 | V | |
| LM1117-ADJ: IOUT = 10mA, 1.5V ≤ VIN-VOUT ≤ 13.75V | TJ = 25°C | 0.035% | 0.2% | |||
| Line regulation (AVOUT) | LM1117-1.8: IOUT = 0 mA, 3.2 V ≤ VIN ≤ 10 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 6 | mV | |
| LM1117-2.5: IOUT = 0 mA, 3.9 V ≤ VIN ≤ 10 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 6 | mV | ||
| LM1117-3.3: IOUT = 0 mA, 4.75 V ≤ VIN ≤ 15 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 6 | mV | ||
| LM1117-5.0: IOUT = 0 mA, 6.5 V ≤ VIN ≤ 15 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 10 | mV | ||
| LM1117-ADJ: VIN – VOUT = 3 V, 10 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 0.2% | 0.4% | |||
| Load regulation (AVOUT) | LM1117-1.8: VIN = 3.2 V, 0 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 10 | mV | |
| LM1117-2.5: VIN = 3.9 V, 0 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 10 | mV | ||
| LM1117-3.3: VIN = 4.75 V, 0 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 10 | mV | ||
| LM1117-5.0: VIN = 6.5 V, 0 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 1 | 15 | mV |
7.5 LM1117 Electrical Characteristics (continued)
Unless otherwise specified, TJ = 25°C
| PARAMETER | TEST CONDITIONS | MIN(1) | TYP(2) | MAX(1) | UNIT | |
|---|---|---|---|---|---|---|
| Dropout voltage(4) | IOUT = 100 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 1.1 | 1.2 | V | |
| IOUT = 500 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 1.15 | 1.25 | V | ||
| IOUT = 800 mA | TJ = 25°C over the junction temperature range 0°C to 125°C | 1.2 | 1.35 | V | ||
| Current limit (ILIMIT) | VIN – VOUT = 5 V, TJ = 25°C | 800 | 1200 | 1500 | mA | |
| Minimum load current(5) | LM1117-ADJ: VIN = 15 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 1.7 | 5 | mA | |
| LM1117-1.8: VIN ≤ 15 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 5 | 10 | mA | ||
| Quiescent current | LM1117-2.5: VIN ≤ 15 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 5 | 10 | mA | |
| LM1117-3.3: VIN ≤ 15 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 5 | 10 | mA | ||
| LM1117-5.0: VIN ≤ 15 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 5 | 10 | mA | ||
| Thermal regulation | TA = 25°C, 30-ms pulse | 0.01 | 0.1 %/W | |||
| Ripple regulation | fRIPPLE = 120 Hz, VIN – VOUT = 3 V VRIPPLE = 1 Vpp | TJ = 25°C over the junction temperature range 0°C to 125°C | 75 | 60 | dB | |
| Adjust pin current | TJ = 25°C over the junction temperature range 0°C to 125°C | 60 | 120 | µA | ||
| 10 ≤ IOUT ≤ 800 mA, 1.4 V ≤ VIN – VOUT ≤ 10 V | TJ = 25°C over the junction temperature range 0°C to 125°C | 0.2 | 5 | µA | ||
| Temperature stability | 0.5% | |||||
| Long term stability | TA = 125°C, 1000 hours | 0.3% | ||||
| RMS output noise | (% of VOUT), 10 Hz ≤ f ≤ 10 kHz | 0.003% |
(1) All limits are ensured by testing or statistical analysis.
(2) Typical Values represent the most likely parametric normal.
(3) Load and line regulation are measured at constant junction room temperature.
(4) The dropout voltage is the input/output differential at which the circuit ceases to regulate against further reduction in input voltage. This voltage is measured when the output voltage has dropped 100 mV from the nominal value obtained at VIN = VOUT + 1.5 V.
(5) The minimum output current required to maintain regulation.
7.6 LM1117I Electrical Characteristics
Unless otherwise specified, TJ = 25°C
| PARAMETER | TEST CONDITIONS | MIN(1) | TYP(2) | MAX(1) | UNIT | |
|---|---|---|---|---|---|---|
| Reference voltage (VREF) | LM1117I-ADJ: IOUT = 10 mA, VIN – VOUT = 2 V, TJ = 25°C | 1.238 | 1.25 | 1.262 | V | |
| LM1117I-ADJ: 10 mA ≤ IOUT ≤ 800 mA, 1.4 V ≤ VIN – VOUT ≤ 10 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 1.2 | 1.25 | 1.29 | V | |
| Output voltage (VOUT) | LM1117I-3.3: IOUT = 10 mA, VIN = 5 V, TJ = 25°C | 3.267 | 3.3 | 3.333 | V | |
| LM1117I-3.3: 0 ≤ IOUT ≤ 800 mA, 4.75 V ≤ VIN ≤ 10 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 3.168 | 3.3 | 3.432 | V | |
| LM1117I-5.0: IOUT = 10 mA, VIN = 7 V, TJ = 25°C | 4.95 | 5 | 5.05 | V | ||
| LM1117I-5.0: 0 ≤ IOUT ≤ 800 mA, 6.5 V ≤ VIN ≤ 12 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 4.8 | 5 | 5.2 | V | |
| LM1117I-ADJ: IOUT = 10 mA, 1.5 V ≤ VIN – VOUT ≤ 13.75 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 0.035% | 0.3% | |||
| Line regulation (AVOUT) | LM1117I-3.3: IOUT = 0 mA, 4.75 V ≤ VIN ≤ 15 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 1 | 10 | mV | |
| LM1117I-5.0: IOUT = 0 mA, 6.5 V ≤ VIN ≤ 15 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 1 | 15 | mV | ||
| Load regulation (AVOUT) | LM1117I-ADJ: VIN – VOUT = 3 V, 10 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range -40°C to 125°C | 1 | 15 | mV | |
| LM1117I-3.3: VIN = 4.75 V, 0 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range -40°C to 125°C | 1 | 15 | mV | ||
| LM1117I-5.0: VIN = 6.5 V, 0 ≤ IOUT ≤ 800 mA | TJ = 25°C over the junction temperature range -40°C to 125°C | 20 | mV |
7.6 LM1117I Electrical Characteristics (continued)
Unless otherwise specified, TJ = 25°C
| PARAMETER | TEST CONDITIONS | MIN(1) | TYP(2) | MAX(1) | UNIT | |
|---|---|---|---|---|---|---|
| Dropout voltage(4) | IOUT = 100 mA | TJ = 25°C over the junction temperature range -40°C to 125°C | 1.1 | 1.2 | V | |
| IOUT = 500 mA | TJ = 25°C over the junction temperature range -40°C to 125°C | 1.15 | 1.35 | V | ||
| IOUT = 800 mA | TJ = 25°C over the junction temperature range -40°C to 125°C | 1.2 | 1.4 | V | ||
| Current limit (ILIMIT) | VIN – VOUT = 5 V, TJ = 25°C | 800 | 1200 | 1500 | mA | |
| Minimum load current(5) | LM1117I-ADJ: VIN = 15 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 1.7 | 5 | mA | |
| LM1117I-3.3: VIN ≤ 15 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 5 | 10 | mA | ||
| Quiescent current | LM1117I-5.0: VIN ≤ 15 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 5 | 10 | mA | |
| Thermal regulation | TA = 25°C, 30-ms pulse | 0.01 | 0.1 %/W | |||
| Ripple regulation | fRIPPLE = 120 Hz, VIN – VOUT = 3 V VRIPPLE = 1 Vpp | TJ = 25°C over the junction temperature range -40°C to 125°C | 75 | 60 | dB | |
| Adjust pin current | TJ = 25°C over the junction temperature range -40°C to 125°C | 60 | 120 | µA | ||
| 10 ≤ IOUT ≤ 800 mA, 1.4 V ≤ VIN – VOUT ≤ 10 V | TJ = 25°C over the junction temperature range -40°C to 125°C | 0.2 | 5 | µA | ||
| Temperature stability | 0.5% | |||||
| Long term stability | TA = 125°C, 1000 hours | 0.3% | ||||
| RMS output noise | (% of VOUT), 10 Hz ≤ f ≤ 10 kHz | 0.003% |
(1) All limits are ensured by testing or statistical analysis.
(2) Typical Values represent the most likely parametric normal.
(3) Load and line regulation are measured at constant junction room temperature.
(4) The dropout voltage is the input/output differential at which the circuit ceases to regulate against further reduction in input voltage. This voltage is measured when the output voltage has dropped 100 mV from the nominal value obtained at VIN = VOUT + 1.5 V.
(5) The minimum output current required to maintain regulation.
7.7 Typical Characteristics
Figure 7-1. Dropout Voltage (VIN – VOUT) vs Output Current (mA): A graph showing dropout voltage on the Y-axis and output current on the X-axis, with curves for TJ = 25°C and TJ = 125°C.
Figure 7-2. Short-Circuit Current vs Input/Output Differential (V): A graph showing short-circuit current on the Y-axis and input/output differential voltage on the X-axis, with curves for TJ = 25°C and TJ = 125°C.
Figure 7-3. Load Regulation vs Temperature (°C): A graph showing output voltage deviation (%) on the Y-axis and temperature (°C) on the X-axis.
Figure 7-4. LM1117-ADJ Ripple Rejection: A graph showing ripple rejection (dB) on the Y-axis and frequency (Hz) on the X-axis, with multiple curves indicating different capacitor configurations (Cadj, Cout).
Figure 7-5. LM1117-ADJ Ripple Rejection vs Current: A graph showing ripple rejection (dB) on the Y-axis and load current (mA) on the X-axis, with curves for different capacitor configurations.
Figure 7-6. Temperature Stability: A graph showing output voltage change (%) on the Y-axis and temperature (°C) on the X-axis.
Figure 7-7. Adjust Pin Current vs Temperature (°C): A graph showing adjust pin current (µA) on the Y-axis and temperature (°C) on the X-axis.
Figure 7-8. LM1117-5.0 Load Transient Response: A graph showing output voltage deviation (V) and load current (A) on the Y-axis against time (µs) on the X-axis, illustrating the regulator's response to a sudden change in load.
Figure 7-9. LM1117-5.0 Line Transient Response: A graph showing input voltage deviation (V) and output voltage deviation (mV) on the Y-axis against time (µs) on the X-axis, illustrating the regulator's response to a sudden change in input voltage.
8 Detailed Description
8.1 Overview
The LM1117 adjustable version provides a 1.25-V reference voltage (VREF) between the output and the adjust pin. This voltage across resistor R1 generates a constant current (I1). The current from the adjust pin (IADJ) is small and constant, minimizing its impact on output accuracy. This current I1 flows through output set resistor R2 to establish the output voltage. For fixed voltage devices, R1 and R2 are integrated internally.
Figure 8-1. Basic Adjustable Regulator: A circuit diagram showing VIN, VOUT, ADJ pins, R1, R2, Cadj, and Cout, with the formula VOUT = VREF * (1 + R2/R1).
8.2 Functional Block Diagram
A functional block diagram illustrates the internal components including thermal limit, current limit, reference, and output stages.
8.3 Feature Description
8.3.1 Load Regulation
The LM1117 regulates the voltage between the output and ground pins, or output and adjust pins. Line resistances can affect load regulation. To achieve optimal load regulation, the load should be connected directly to the output terminal, and the ground connection should be made directly to the ground terminal. This minimizes voltage drops across trace resistances.
Figure 8-2. Typical Application Using Fixed Output Regulator: Depicts a circuit with VIN, VOUT, GND, and RLOAD, showing how line resistances (Rt1, Rt2) can cause voltage drops, affecting VLOAD.
Figure 8-3. Best Load Regulation Using Adjustable Output Regulator: Illustrates an adjustable regulator circuit where R1 is connected to the output terminal, and the ground for R2 is returned near the load for remote ground sensing, improving regulation.
8.4 Device Functional Modes
8.4.1 Protection Diodes
The LM1117 does not require external protection diodes under normal operation. The internal resistance between the adjust and output terminals limits current. The adjust pin can tolerate transient signals up to ±25V relative to the output voltage without damage. However, if a large output capacitor (≥1000 µF) is used and the input is instantaneously shorted to ground, the regulator could be damaged due to output capacitor discharge. In such cases, an external diode (e.g., 1N4002) connected between the output and input pins is recommended for protection.
Figure 8-4. Regulator With Protection Diode: Shows a circuit diagram with VIN, VOUT, ADJ, R1, R2, Cadj, Cout, and an optional 1N4002 diode connected from VOUT to VIN.
9 Application and Implementation
9.1 Application Information
The LM1117 is a versatile, high-performance linear regulator suitable for wide temperature ranges and offering tight line/load regulation. An output capacitor is essential for transient response and stability. The ADJ pin can be bypassed with a capacitor for high ripple-rejection ratios. Applications include post-regulation for DC/DC converters, battery chargers, and microprocessor supplies.
9.2 Typical Application
Figure 9-1. 1.25-V to 10-V Adjustable Regulator With Improved Ripple Rejection: A circuit diagram showing VIN, VOUT, ADJ, R1, R2, Cadj, and Cout, with the formula for VOUT.
9.2.1 Design Requirements
Minimal component count is required, typically two resistors for voltage division and an output capacitor for load regulation. A 10-µF tantalum input capacitor is suitable for most applications. An optional bypass capacitor across R2 can improve PSRR.
9.2.2 Detailed Design Procedure
The output voltage is set by selecting R1 and R2. Capacitor selection details are available in the External Capacitors section.
9.2.2.1 External Capacitors
9.2.2.1.1 Input Bypass Capacitor
A 10-µF tantalum input capacitor is recommended for most applications.
9.2.2.1.2 Adjust Terminal Bypass Capacitor
A bypass capacitor (Cadj) on the adjust terminal improves ripple rejection by preventing ripple amplification. The impedance of Cadj must be less than R1 at the ripple frequency for effective ripple rejection: 1 / (2π × fRIPPLE × Cadj) < R1. For example, with R1 = 124 Ω and fRIPPLE = 120 Hz, Cadj must be > 11µF.
9.2.2.1.3 Output Capacitor
The output capacitor is critical for stability, requiring a minimum capacitance of 10 µF (tantalum) and an equivalent series resistance (ESR) between 0.3 Ω to 22 Ω. A larger output capacitance (22-µF tantalum) is recommended when Cadj is used.
9.2.3 Application Curve
Figure 9-2. Dropout Voltage (VIN – VOUT) vs Output Current (mA): This graph shows how dropout voltage varies with output current and temperature. Designers should consider these variations to ensure the dropout voltage requirement is met across the full operating range.
9.3 System Examples
Several circuit configurations can be implemented using the LM1117:
- Figure 9-3. Fixed Output Regulator
- Figure 9-4. Adjusting Output of Fixed Regulators
- Figure 9-5. Regulator With Reference
- Figure 9-6. 5-V Logic Regulator With Electronic Shutdown
- Figure 9-7. Battery Backed-Up Regulated Supply
- Figure 9-8. Low Dropout Negative Supply
9.4 Power Supply Recommendations
The input supply voltage must not exceed the maximum rating. Maintaining sufficient headroom above the minimum dropout voltage ensures regulation. An input capacitor is recommended.
9.5 Layout
9.5.1 Layout Guidelines
Proper layout is crucial for minimizing noise and ensuring output voltage regulation. Load current traces should be wide to reduce parasitic inductance. The feedback loop from VOUT to ADJ should be kept short. A bypass capacitor near the ADJ pin can improve PSRR. In case of VIN shorting to ground, an external diode from VOUT to VIN is recommended to divert surge current from the output capacitor and protect the IC.
9.5.1.1 Heat Sink Requirements
When operating at significant current, junction temperature rises. Thermal limits must be understood for reliable performance. Heat transfer follows a path from the junction through the die, die attach, lead frame, PCB, and to the ambient environment. Factors affecting thermal resistance include lead frame size, pin count, die size, die attach material, molding compound, mounting pad size/material, PCB characteristics, trace dimensions, adjacent heat sources, air volume, and ambient temperature.
Figure 9-9. Cross-Sectional View of Integrated Circuit Mounted on a Printed Circuit Board: Illustrates the heat flow path from the IC junction to the PCB and ambient environment.
The LM1117 has internal thermal shutdown. Junction temperature must stay within 0°C to 125°C. A heat sink may be needed based on maximum power dissipation and ambient temperature. Power dissipation (PD) is calculated as PD = (VIN-VOUT)IL + VINIG. Maximum allowable temperature rise (TR(max)) is TJ(max) - TA(max). Junction-to-ambient thermal resistance (RθJA) is calculated as RθJA = TR(max) / PD.
Figure 9-10. Power Dissipation Diagram: Shows a circuit diagram illustrating the calculation of power dissipation (PD) using input voltage (VIN), output voltage (VOUT), load current (IL), and quiescent current (IG).
Tables and figures (9-11 through 9-16) provide data on thermal resistance (RθJA) versus copper area and maximum allowable power dissipation versus ambient temperature and copper area for different packages (SOT-223, TO-252). Application notes like AN-1187 discuss thermal performance enhancements.
Figure 9-11. RθJA vs 1-oz Copper Area for SOT-223
Figure 9-12. RθJA vs 2-oz Copper Area for TO-252
Figure 9-13. Maximum Allowable Power Dissipation vs Ambient Temperature for SOT-223
Figure 9-14. Maximum Allowable Power Dissipation vs Ambient Temperature for TO-252
Figure 9-15. Maximum Allowable Power Dissipation vs 1-oz Copper Area for SOT-223
Figure 9-16. Maximum Allowable Power Dissipation vs 2-oz Copper Area for TO-252
Figure 9-17. Top View of the Thermal Test Pattern in Actual Scale
Figure 9-18. Bottom View of the Thermal Test Pattern in Actual Scale
9.5.2 Layout Example
Figure 9-19. Layout Example (SOT-223): Demonstrates a typical PCB layout for the SOT-223 package, showing component placement, input/output planes, and ground plane.
10 Device and Documentation Support
10.1 Documentation Support
10.1.1 Related Documentation
For related documentation, see Texas Instruments' AN-1187 Leadless Leadframe Package (LLP) application note.
10.2 Receiving Notification of Documentation Updates
To receive updates, navigate to the device product folder on ti.com and subscribe to updates. Revision history is available in updated documents.
10.3 Support Resources
TI E2E™ support forums offer expert answers and design help. Content is provided "AS IS" and does not constitute TI specifications.
10.4 Trademarks
TI E2E™ is a trademark of Texas Instruments. All other trademarks are property of their respective owners.
10.5 Electrostatic Discharge Caution
Integrated circuits can be damaged by ESD. Texas Instruments recommends proper handling precautions to prevent damage, which can range from subtle performance degradation to complete device failure.
10.6 Glossary
TI Glossary provides explanations of terms, acronyms, and definitions.
11 Mechanical, Packaging, and Orderable Information
This section provides the most current mechanical, packaging, and orderable information, subject to change without notice. Browser-based versions are available via the left-hand navigation.
Package Outline Drawings: Detailed mechanical dimensions, land pattern recommendations, and stencil designs are provided for various package types including TO-220 (NDE0003B), TO-263 (KTT0003B), SOT-223 (DCY (R-PDSO-G4)), WSON (NGN0008A), and TO-252 (NDP0003B).
