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LT1121CST-3.3#PBF

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

LT1121CST-3.3#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	Power input; the datasheet recommends a 0.1µF to 1µF bypass to ground, and the pin withstands reverse voltage (absolute maximum ±30V for the LT1121) without reverse current flow.
2	GND	power_in	Ground reference pin, which is also connected to the package tab.
3	OUT	power_out	Regulated 3.3V output supplying up to 150mA to the load; an output capacitor is required (minimum recommended 1µF with ESR of 3Ω or less) to prevent oscillation.

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 (LT1121-3.3, 25 C)	VOUT	3.25	3.3	3.35	V	VIN = 3.8V, IOUT = 1mA, TJ = 25C	3
Regulated Output Voltage (LT1121-3.3, full temperature range)	VOUT	3.2	3.3	3.4	V	4.3V < VIN < 20V, 1mA < IOUT < 150mA	3
Line Regulation (LT1121-3.3)			1.5	10	mV	VIN = 4.8V to 20V, IOUT = 1mA	3
Load Regulation (LT1121-3.3, 25 C)			-12	-20	mV	ILOAD = 1mA to 150mA, TJ = 25C	3
Load Regulation (LT1121-3.3, full temperature range)			-17	-28	mV	ILOAD = 1mA to 150mA	3
Dropout Voltage (25 C)			0.13	0.16	V	ILOAD = 1mA, TJ = 25C	3
Dropout Voltage (full temperature range)				0.25	V	ILOAD = 1mA	3
Dropout Voltage (25 C)			0.3	0.35	V	ILOAD = 50mA, TJ = 25C	3
Dropout Voltage (full temperature range)				0.5	V	ILOAD = 50mA	3
Dropout Voltage (25 C)			0.37	0.45	V	ILOAD = 100mA, TJ = 25C	3
Dropout Voltage (full temperature range)				0.6	V	ILOAD = 100mA	3
Dropout Voltage (25 C)			0.42	0.55	V	ILOAD = 150mA, TJ = 25C	3
Dropout Voltage (full temperature range)				0.7	V	ILOAD = 150mA	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 = 25C	4
Input Reverse Leakage Current				1	mA	VIN = -20V, VOUT = 0V	4
Reverse Output Current (LT1121-3.3)			16	25	µA	VOUT = 3.3V, VIN = 0V	4
Input Voltage	VIN	-30		30	V	LT1121 (standard) version	2
Shutdown Pin Input Voltage	VSHDN	-0.6		6.5	V	Note 2	2
Shutdown Pin Input Current				20	mA	Note 2	2
Output Pin Reverse Current				10	mA		2
Operating Junction Temperature Range	TJ	0		125	°C	LT1121C-X (commercial grade, as ordered)	2
Storage Temperature Range	TSTG	-65		150	°C		2
Junction to Ambient Thermal Resistance (SOT-223)	θJA		50		°C/W	Topside 2500 sq mm, backside 2500 sq mm, board 2500 sq mm	10
Junction to Ambient Thermal Resistance (SOT-223)	θJA		58		°C/W	Topside 225 sq mm, backside 2500 sq mm, board 2500 sq mm	10
Junction to Ambient Thermal Resistance (SOT-223)	θJA		64		°C/W	Topside 100 sq mm, backside 2500 sq mm, board 2500 sq mm	10
Junction to Ambient Thermal Resistance (SOT-223)	θJA		57		°C/W	Topside 1000 sq mm, backside 2500 sq mm, board 1000 sq mm	10
Junction to Ambient Thermal Resistance (SOT-223)	θJA		60		°C/W	Topside 1000 sq mm, backside 0, board 1000 sq mm	10
Junction to Tab Thermal Resistance (SOT-223)	θJT		20		°C/W	Junction-to-tab	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-3.3#PBF
Footprint: Package_TO_SOT_SMD:SOT-223-3_TabPin2
3D model: SOT-223-3 (KiCad packages3D, STEP)
3D model files: lt1121cst-3-3-pbf-etched.step / lt1121cst-3-3-pbf-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); lt1121cst-3-3-pbf.step / lt1121cst-3-3-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