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LT1121CST-5#PBF

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Analog Devices Linear Voltage Regulators (LDO), SOT-223-3. Pinout cross-checked by two models against the datasheet, KiCad symbol/footprint/3D.

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LT1121CST-5#PBF

Analog Devices · Linear Voltage Regulators (LDO) · SOT-223-3

LT1121CST-5#PBF from Analog Devices, in a SOT-223-3. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin Name Type Function
1 VIN power_in Input supply pin, rated for 30V maximum on the LT1121 and protected against reverse input voltage, and should be bypassed with 0.1µF to 1µF if more than six inches from the main input filter capacitor.
2 GND power_in Ground pin, electrically common with the package tab.
3 OUT power_out Regulated 5V output supplying up to 150mA, which needs an output capacitor (minimum recommended 1µF with ESR of 3Ω or less) for stability and has a 10mA maximum reverse current rating.

Key specifications

Parameter Value
Manufacturer Analog Devices
Package SOT-223-3
Category Power Management ICs
Pins 3

Electrical characteristics

Limits as printed in the datasheet (page.json metadata.characteristics carries them as data).

Parameter Symbol Min Typ Max Unit Conditions Page
Regulated Output Voltage (LT1121-5) VOUT 4.925 5 5.075 V VIN = 5.5V, IOUT = 1mA, TJ = 25ºC 3
Regulated Output Voltage (LT1121-5, full range) VOUT 4.85 5 5.15 V 6V < VIN < 20V, 1mA < IOUT < 150mA, full operating temperature range 3
Line Regulation (LT1121-5) 1.5 10 mV ΔVIN = 5.5V TO 20V, IOUT = 1mA 3
Load Regulation (LT1121-5, TJ = 25ºC) -12 -18 mV ΔILOAD = 1mA to 150mA, TJ = 25ºC 3
Load Regulation (LT1121-5, full range) -25 -40 mV ΔILOAD = 1mA to 150mA, full operating temperature range 3
Dropout Voltage 0.13 0.16 V ILOAD = 1mA, TJ = 25ºC 3
Dropout Voltage (full range) 0.25 V ILOAD = 1mA, full operating temperature range 3
Dropout Voltage 0.3 0.35 V ILOAD = 50mA, TJ = 25ºC 3
Dropout Voltage (full range) 0.5 V ILOAD = 50mA, full operating temperature range 3
Dropout Voltage 0.37 0.45 V ILOAD = 100mA, TJ = 25ºC 3
Dropout Voltage (full range) 0.6 V ILOAD = 100mA, full operating temperature range 3
Dropout Voltage 0.42 0.55 V ILOAD = 150mA, TJ = 25ºC 3
Dropout Voltage (full range) 0.7 V ILOAD = 150mA, full operating temperature range 3
Ground Pin Current IGND 30 50 µA ILOAD = 0mA 4
Ground Pin Current IGND 90 120 µA ILOAD = 1mA 4
Ground Pin Current IGND 350 500 µA ILOAD = 10mA 4
Ground Pin Current IGND 1.5 2.5 mA ILOAD = 50mA 4
Ground Pin Current IGND 4 7 mA ILOAD = 100mA 4
Ground Pin Current IGND 7 14 mA ILOAD = 150mA 4
Shutdown Threshold (Off to On) VSHDN 1.2 2.8 V VOUT = Off to On 4
Shutdown Threshold (On to Off) VSHDN 0.25 0.75 V VOUT = On to Off 4
Shutdown Pin Current ISHDN 6 10 µA VSHDN = 0V 4
Quiescent Current in Shutdown IQ 16 22 µA VIN = 6V, VSHDN = 0V 4
Ripple Rejection 50 58 dB VIN, VOUT = 1V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 0.1A 4
Current Limit 200 500 mA VIN, VOUT = 7V, TJ = 25ºC 4
Input Reverse Leakage Current 1 mA VIN = -20V, VOUT = 0V, full operating temperature range 4
Reverse Output Current (LT1121-5) 16 25 µA VOUT = 5V, VIN = 0V 4
Input Voltage (LT1121 rating) VIN -30 30 V LT1121 input voltage rating 2
Output Pin Reverse Current 10 mA 2
Adjust Pin Current 10 mA 2
Shutdown Pin Input Voltage -0.6 6.5 V Note 2 2
Shutdown Pin Input Current 20 mA Note 2 2
Operating Junction Temperature Range (LT1121C-X) TJ 0 125 °C LT1121C-X 2
Storage Temperature Range TSTG -65 150 °C 2
Thermal Resistance Junction-to-Ambient (SOT-223) θJA 50 °C/W ST package, TJMAX = 150°C 2
Thermal Resistance Junction-to-Tab (SOT-223) θJT 20 °C/W SOT-223 package 10
Thermal Resistance Junction-to-Ambient range (SOT-223 table) θJA 50 64 °C/W SOT-223, copper area 2500 to 100 sq mm, topside, per Table 4 10

Materials and finish

As the datasheet states them (page.json metadata.appearance; the 3D model's colours follow it).

Part Material Colour / plating Datasheet says Page
contacts copper copper trace per lead 10

CAD (KiCad official)

  • Symbol: LT1121CST-5#PBF
  • Footprint: Package_TO_SOT_SMD:SOT-223-3_TabPin2
  • 3D model: SOT-223-3 (KiCad packages3D, STEP)
  • 3D model files: lt1121cst-5-pbf-etched.step / lt1121cst-5-pbf-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); lt1121cst-5-pbf.step / lt1121cst-5-pbf.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Analog Devices datasheet (16 pp, sha256 326db42fecefd774, retrieved 2026-10-28, tier: manufacturer)
  • Extractor: parts-factory 2.0.0 / extract_pins 0.3, primary claude-haiku-5-5 (text), consensus claude-sonnet-5-5 (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF