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LM7912CT

-12V 1A negative linear regulator, TO-220, thermal/SCP protection

4969

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Pieza del fabricante：

LM7912CT

Paquete：

TO-220-3 (15.6 x 10.6 x 4.6mm, through-hole, tab=GND)

Marca：

Categorías de productos：

Circuitos integrados IC, Microcontroladores y procesadores

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Descripción

Productos

The LM7912CT from onsemi/TI is a 3-terminal 1A negative voltage regulator providing a fixed -12V output with internal thermal shutdown, short-circuit protection, and safe operating area compensation in a TO-220 package.

Especificaciones

Output Voltage	-12V fixed (±4% tolerance)
Corriente de salida	1A continuous (1.5A peak)
Input Voltage Range	-14.5V to -27V (for regulation)
Maximum Input Voltage	-35V
Dropout Voltage	1.1V typical @ 1A (TI version)
Line Regulation	10mV typical (TI version)
Load Regulation	12mV typical (5mA to 1A)
Corriente de reposo	1-2mA typical
Ripple Rejection	54-60dB typical @ 120Hz
Short-Circuit Current	300mA typical
Peak Output Current	2.2A typical
Temperatura de funcionamiento	0°C to +125°C (junction)
Paquete	TO-220-3 (through-hole)

Características

Fixed -12V output
1A continuous output current
Internal thermal shutdown protection
Internal short-circuit current limiting
Safe operating area compensation
High ripple rejection: 54-60dB
Complements LM7812 for ±12V supplies

Aplicaciones

Negative 12V power supply rail
Op-amp dual supply (with LM7812)
Analog circuit negative rail
RS-232 negative supply generation
Audio amplifier split supply

Introducción del producto:LM7912CT Presentación del producto

The LM7912CT from onsemi/Texas Instruments is a 3-terminal negative voltage regulator providing a fixed -12V output at up to 1A load current. It is the negative-voltage complement to the LM7812CT, and together they form a complete ±12V split power supply from a center-tapped transformer. The LM7912 requires an input bypass capacitor (2.2µF tantalum or 25µF aluminum) at the input and a 1µF output capacitor for stability—larger values than the LM7812 due to the negative regulator architecture. Internal protection includes thermal shutdown, short-circuit current limiting, and safe operating area compensation. The pinout differs from the 78xx series: pin 1 is Ground (tab), pin 2 is Input, and pin 3 is Output. The CT suffix denotes the TO-220 through-hole package. Note: TI lists this part as Last Time Buy; the MC7912CTG from onsemi is the current production equivalent.

Principio de funcionamiento:LM7912CT Principio de funcionamiento

The LM7912CT uses a series pass transistor between the negative input and the output, controlled by a feedback loop that maintains VOUT = -12V. The error amplifier compares a divided version of the output voltage with an internal reference. When the output becomes less negative (rises toward 0V), the error amplifier drives the pass transistor harder, pulling the output more negative. When the output becomes too negative, the drive is reduced. The negative regulator architecture requires the tab to be connected to ground (not the output), which simplifies heatsink mounting since the tab can be directly attached to the chassis ground. The larger required bypass capacitors (2.2µF input, 1µF output, both tantalum recommended) are needed because the negative regulator has different loop dynamics than the positive 78xx series. The quiescent current flows from the output through the ground pin to the reference, which is why the ground pin current varies with load. The thermal shutdown activates at approximately 170°C junction temperature, and the current limit is approximately 300mA during a short circuit, significantly lower than the 78xx series.

Descripción de la clavija:LM7912CT Definición y funciones de las clavijas

Pin	Nombre	Tipo	Descripción
1	GND	Suelo	Common ground reference. The TO-220 tab is electrically connected to this pin. Note: 79xx negative regulators have GROUND on Pin 1 (opposite to 78xx where Input is Pin 1). Heatsink tab must be insulated when not at ground potential.
2	INPUT	Entrada de alimentación	Negative unregulated input voltage. Must be more negative than -1.2V – Vdropout (at least -3.2V input). Maximum -35V. Bypass with 2.2µF electrolytic or 0.33µF ceramic capacitor to GND.
3	OUTPUT	Potencia de salida	Regulated -1.2V DC output at up to 1.5A continuous current with ±4% tolerance. Bypass with 1µF tantalum or 10µF electrolytic capacitor to GND for stability. Do not apply positive voltage to output to prevent damage.

Critical note: 79xx negative regulators have DIFFERENT pin assignments from 78xx positive regulators. Pin 1 = GND (not Input), Pin 2 = Input (not GND), Pin 3 = Output. This pin swap is a common source of design errors. The tab is connected to GND (Pin 1). Always verify pinout against the datasheet before PCB layout.

Application Scenarios:In which products and applications isLM7912CT usado

±12V Split Supply: Center-tapped transformer → bridge rectifier → LM7812CT (+12V) and LM7912CT (-12V); dual rail for op-amps
Op-Amp Rail: -12V rail for NE5532/LM358 circuits; 54dB ripple rejection ensures clean analog supply
RS-232 Supply: -12V rail for MAX232 V- pin (if not using charge pump); or as -12V reference
Audio Amp: -12V rail for TDA2030A negative supply; paired with LM7812CT for ±12V
Test Equipment: Negative rail for DAC/ADC reference circuits; stable -12V with 12mV load regulation

Alternative Models:What chips are recommended as replacements for LM7912CT

Modelo	Fabricante	Diferencia clave	Paquete	Specs
LM7912ACT	onsemi	Tighter output tolerance: ±2% vs ±4% for precision negative supply rails	TO-220-3	-1.2V/1A
L7912CV	STMicroelectronics	Direct equivalent with 1.5A output current and internal thermal/current protection	TO-220-3	-1.2V/1.5A
MC7912CTG	onsemi	Current production replacement with RoHS compliance and identical specifications	TO-220-3	-1.2V/1A
KA7912	onsemi/Fairchild	Budget-friendly version with ±4% tolerance for cost-sensitive negative supply designs	TO-220-3	-1.2V/1A
LM337T	TI	Adjustable -1.25V to -37V version providing flexible output voltage with two external resistors	TO-220-3	-1.25 to -37V adj

LM7912CT is a -1.2V fixed negative voltage regulator in TO-220-3 with 1A output and ±4% tolerance. For adjustable negative voltage, the LM337T provides -1.25V to -37V output. All 7912 variants share the same pinout (GND-IN-OUT) and are complementary to the 7812 positive regulators for split-rail supplies.