The LM1117MPX-ADJ from Texas Instruments is an 800 mA low-dropout linear regulator in a SOT-223-4 package. The adjustable version sets output voltage from 1.25 V to 13.8 V using two external resistors. Key specifications include 1.2 V typical dropout at 800 mA, 1.262 V reference voltage with \u00b11% accuracy, 5 mA typical ground current, 0.035% typical line regulation, 0.2% typical load regulation, and 38 \u00b5Vrms output noise. The device includes current limiting and thermal shutdown protection. Operating temperature range is 0\u00b0C to +125\u00b0C. The MPX suffix denotes SOT-223 tape-and-reel packaging (2000 units\/reel).<\/p>","protected":false},"excerpt":{"rendered":"
The LM1117MPX-ADJ from Texas Instruments is an 800 mA low-dropout linear regulator in a SOT-223-4 package. The adjustable version sets output voltage from 1.25 V to 13.8 V using two external resistors. Key specifications include 1.2 V typical dropout at 800 mA, 1.262 V reference voltage with \u00b11% accuracy, 5 mA typical ground current, 0.035% […]<\/p>\n","protected":false},"author":2,"featured_media":2265,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[13,32],"tags":[],"chip_brand":[138],"class_list":["post-2060","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-integrated-circuits-ics","category-low-dropout-regulators-ldo","chip_brand-ti"],"acf":{"brief_explanation":"800mA LDO, 1.25-13.8V adj, 1.2V dropout@800mA, \u00b11% Vref, SOT-223 T&R, 0~125\u00b0C","date_code":"","package_case":"SOT-223-4 \/ DCY (6.5 x 3.5 x 1.6 mm, tab = VOUT pins 2&4)","in_stock":12649,"datasheet":"https:\/\/www.ti.com\/lit\/ds\/symlink\/lm1117.pdf","price":"$0.49 (1K+ pcs)","product_introduction":"The LM1117MPX-ADJ is the adjustable-output version of TI's LM1117 low-dropout linear regulator in a SOT-223-4 surface-mount package with tape-and-reel packaging. The LM1117 is one of the most widely used LDO regulator families in the electronics industry, originally developed by National Semiconductor (now TI).\n\nThe adjustable version uses an internal 1.262 V bandgap reference trimmed to \u00b11% accuracy. The output voltage is set by two external resistors: VOUT = VREF \u00d7 (1 + R1\/R2) + IADJ \u00d7 R1, where IADJ is typically 50 \u00b5A and can usually be neglected. This allows any output voltage from 1.25 V to 13.8 V with a single BOM change.\n\nThe 1.2 V typical dropout voltage at 800 mA (1.3 V max) means the input must be at least 1.3 V above the desired output for proper regulation. At lower currents, dropout scales proportionally: approximately 1.1 V at 100 mA and 1.25 V at 500 mA.\n\nThe SOT-223-4 package features a large tab (pins 2 and 4) connected to VOUT that serves as both the output connection and the primary thermal path. With R\u03b8JA of approximately 136\u00b0C\/W on a standard FR4 board, the package can dissipate about 0.9 W at 50\u00b0C ambient.\n\nTI also offers the LM1117I variant with -40\u00b0C to +125\u00b0C extended temperature range. For new designs, TI recommends the TLV1117 as a drop-in replacement with improved performance, or the TLV761 for fixed-voltage SOT-223 configurations with enhanced functionality.\n\nNote: The LM1117MPX-ADJ (without \/NOPB suffix) is listed as obsolete by some distributors. The LM1117MPX-ADJ\/NOPB with Pb-free terminal finish remains active. Designers should specify the \/NOPB variant.","working_principle":"**Bandgap Reference and Error Amplifier:** The LM1117 uses a Zener-trimmed bandgap reference that produces a stable 1.262 V reference voltage. This reference is compared against a fraction of the output voltage (fed back through the ADJ pin) by a high-gain error amplifier. The amplifier drives the series pass transistor to maintain regulation.\n\n**Pass Transistor and Dropout:** The pass element is a PNP-driven NPN Darlington configuration. The minimum input-output differential (dropout voltage) is the saturation voltage of this Darlington, approximately 1.2 V at full load. Unlike CMOS LDOs where dropout equals IOUT \u00d7 RDS(on), the bipolar Darlington has a relatively fixed saturation voltage that increases modestly with current.\n\n**ADJ Pin and Resistor Divider:** In the adjustable configuration, the ADJ pin connects to the junction of two external resistors. The internal error amplifier drives the pass transistor to maintain VADJ = VREF (1.262 V). The ADJ pin sources a small bias current (IADJ \u2248 50 \u00b5A) that flows through R1, adding a small error term: VOUT = VREF \u00d7 (1 + R1\/R2) + IADJ \u00d7 R1.\n\n**Protection Circuits:** Current limiting restricts output current to approximately 1.2 A under fault conditions. Thermal shutdown disables the output when junction temperature exceeds approximately 165\u00b0C, with hysteresis to prevent oscillation.","pin_description":"
| Pin<\/th> | Name<\/th> | Type<\/th> | Description<\/th><\/tr><\/thead> | ||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1<\/td> | GND\/ADJ<\/td> | I<\/td> | Adjust pin; connect to resistor divider junction; sets output voltage; VADJ = VREF = 1.262V; IADJ \u2248 50\u00b5A flows out; bypass with 10\u00b5F for improved ripple rejection<\/td><\/tr> | ||||||||||||||||||||||||||
| 2<\/td> | VOUT (tab)<\/td> | O<\/td> | Regulated output; tab connects to pins 2 and 4; connect both to output rail; minimum 10\u00b5F tantalum or 22\u00b5F ceramic required for stability; 800mA max<\/td><\/tr> | ||||||||||||||||||||||||||
| 3<\/td> | VIN<\/td> | P<\/td> | Input supply; 2.6V to 15V; must be \u2265 VOUT + VDO; bypass with 10\u00b5F ceramic to GND<\/td><\/tr> | ||||||||||||||||||||||||||
| 4<\/td> | VOUT<\/td> | O<\/td> | Output (parallel with pin 2\/tab); must connect to pin 2 on PCB; solder tab to copper pour with thermal vias for heat dissipation<\/td><\/tr><\/tbody><\/table>","application_scenarios":"
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