Voltage Regulator LM1117T-3.3: Pinout, Application, and Instruction

Voltage Regulator LM1117T-3.3: Pinout, Application, and Instruction
3 min read
20 December 2021

General Description

LM1117 is a voltage regulator with low power consumption and a fixed output voltage of 2.85V, which is designed to meet 1A output current and complies with SCSI-II specifications. This device is the best choice for battery-powered applications, SCSI bus active terminals, and portable computers. LM1117 has a very low quiescent current and very low voltage drop. This type of voltage regulator is generally suitable for occasions where the input and output voltage difference is not too large (3~5V), otherwise, the efficiency will be low and the heat will be serious when the current is large. LM1117 provides current limit and thermal protection. The output requires a tantalum capacitor of at least 10uF to improve transient response and stability.

LM1117 is a series of low dropout voltage regulators. The voltage difference is 1.2V output, and the load current is 1.2V when the load current is 800mA. It has the same pin arrangement as National Semiconductor's industry-standard device LM317. LM1117 has an adjustable voltage version, which can achieve an output voltage range of 1.25 to 13.8V through 2 external resistors. There are also 5 models with fixed voltage output (1.8V, 2.5V, 2.85V, 3.3V, and 5V). The circuit includes a Zener-adjusted bandgap reference voltage to ensure that the accuracy of the output voltage is within ±1%. The LM1117 series is available in LLP, TO-263, SOT-223, TO-220, and TO-252 D-PAK packages.

LM1117 is suitable for high-efficiency linear regulator, battery power supply equipment, battery charger, small computer system terminal interface, and notebook power supply equipment.


  • Operating Temperature: 0°C~125°C
  • Current Rating: 800A
  • Current - Supply (Max): 10mA
  • Voltage - Input (Max): 15V
  • Output Voltage: 3.3V
  • Max Output Current: 800mA
  • Quiescent Current: 5mA
  • Output Voltage 1: 3.3V
  • Voltage Dropout (Max): 1.2V @ 800mA
  • PSRR: 75dB (120Hz)
  • Dropout Voltage: 1.2V
  • Dropout Voltage1-Nom: 1.2V
  • Voltage Tolerance-Max: 2%
  • Min Current Limit: 800mA
  • Nominal Output Voltage: 3.3V
  • Output Voltage Accuracy: 1 %

Pinout Description

LM1117 pin

LM1117 pin description

CAD Model

LM1117 cad model


How to Use

There is a 1.25V reference voltage VREF developed by the LM1117S-ADJ adjustable version between the output and the adjust terminal. In the figure below, this voltage is applied across resistor R1 to generate a constant current I1. At the same time, the current IADJ is generated from the adjusted terminal which will cause an error to the output. However, this error can be ignored because it is extremely small (60µA) compared with I1 and it is very constant with line and load changes. The current I1 then flows through the output set resistor R2, thus the output voltage could be set to the desired level.

How to Use lm1117

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kate 403
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