LM7812CT - 12V 1A Positive Fixed LDO Regulator TO-220 | onsemi
料号： LM7812CT/ ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $1.42 | $1.42 |
| 10 | $1.18 | $11.80 |
| 100 | $0.89 | $89.00 |
| 500 | $0.72 | $360.00 |
| 1,000 | $0.58 | $580.00 |
LM7812CT/ 概述
What is a linear voltage regulator? A linear voltage regulator is a semiconductor device that maintains a constant DC output voltage by dissipating the difference between input and output as heat. The LDO (Low Dropout) variant can regulate with very small VIN-VOUT headroom. The LM7812 belongs to the 78xx positive fixed regulator family — a class of regulators characterized by three pins (Input, Ground, Output), fixed output voltages in the 78xx series (5V, 6V, 8V, 9V, 12V, 15V, 18V, 24V), and integrated protection. This family sits within the broader hierarchy of linear regulators → voltage regulators → power management ICs.
Key features include 1A continuous output, internal thermal shutdown, and a typical output impedance of 0.01 Ω at 1 kHz. The device requires no external components beyond input and output bypass capacitors, simplifying PCB layout for legacy through-hole designs. Ripple rejection is typically 55 to 72 dB depending on output voltage and capacitor selection.
The LM7812CT uses a bipolar pass-transistor architecture with a bandgap-derived voltage reference and on-chip error amplifier. Thermal performance is governed by TO-220 package thermal resistance (~50 °C/W junction-to-ambient free-air, or ~5 °C/W with a proper heatsink). The device is specified for 0 °C to +125 °C junction temperature operation.
Typical applications include ATX peripheral power rails, hobby electronics, industrial 24V-to-12V step-down rails, motor driver auxiliary supplies, and replacement boards for legacy linear designs. The TO-220 package accepts hand-soldering and standardized heatsink mounting.
When designing with this device, observe proper heatsinking for dissipation above 2W. Place input and output capacitors close to the pins to suppress oscillation and improve transient response. For higher-current or switching applications, consider an LM2596 or LM78S12 instead.
直接替换替代料： LM7812CT/ ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
快速对比工具——选择替代料号进行并排对比：
LM7812CT/NOPB
✅ 直接替换📋 参考替代料（不在目录中）
MC7812CTG
✅ 直接替换📋 参考替代料（不在目录中）
L7812CV
✅ 直接替换📋 参考替代料（不在目录中）
L7812ABV
✅ 直接替换📋 参考替代料（不在目录中）
LM340T-12/NOPB
✅ 直接替换📋 参考替代料（不在目录中）
KA7812
✅ 直接替换📋 参考替代料（不在目录中）
LM7812CT/ 最大额定值与电气特性
| Regulator Type | Linear, LDO (positive fixed) |
| Output Voltage (Nominal) | 12 V |
| Output Voltage Tolerance | ±4 % |
| Output Current (Maximum) | 1 A |
| 输入电压范围 | 14.5 V to 35 V (operating); 35 V maximum |
| 压差电压 | 2 V (typical at full load) |
| 静态电流 | 5 mA (typical) |
| Ripple Rejection | 55 to 72 dB (depending on conditions) |
| Output Impedance | 0.01 Ω at 1 kHz |
| 工作结温 | 0 °C to +125 °C |
| 封装 | TO-220-3 (through-hole) |
| 引脚数量 | 3 |
| Thermal Resistance (θJA) | 50 °C/W (free-air, no heatsink) |
| 安装类型 | Through-Hole (TO-220) |
| Internal Protection | Thermal shutdown, internal current limiting, SOA protection |
LM7812CT/ 引脚配置
| 引脚 1 | IN — Input voltage (VIN) |
| 引脚 2 | GND — Ground (tab is internally connected to this pin) |
| 引脚 3 | OUT — Regulated 12 V output |
LM7812 安全工作区
典型应用
LM7812CT/ 适用于 6 应用s: ATX Motherboard Peripheral Rails, Industrial 24V-to-12V Step-Down, Hobby Electronics & Breadboard Rails, Motor Driver Auxiliary Supplies, Audio Preamp Power Rails, Legacy Linear Replacement Boards.
ATX Motherboard Peripheral Rails
The LM7812CT is commonly used to derive the 12 V auxiliary rail from the ATX 5 V standby line in legacy PC peripherals, alarm panels, and hobby electronics. With 1 A continuous output and ±4 % tolerance, it comfortably powers small fans, relay coils, and LED strips. The TO-220 through-hole package accepts easy hand-soldering on perforated prototyping boards and TO-220-compatible daughterboards. Place 0.33 µF input and 0.1 µF output capacitors within 5 mm of the pins to suppress oscillation. For ATX applications where efficiency matters, this part adds quiescent heat dissipation; ensure the ambient temperature stays below 60 °C at full load for reliable operation.
推荐
Industrial 24V-to-12V Step-Down
The LM7812CT drops a 24 V industrial supply rail down to 12 V for PLC I/O, contactor coils, and 12 V indicator lamps. At VIN = 24 V, VOUT = 12 V, IOUT = 1 A, the device dissipates 12 W — a substantial thermal load requiring a TO-220-clip heatsink rated at 5 °C/W or better. Without a heatsink, the regulator will enter thermal shutdown within seconds at full load. For higher-current 24V-to-12V conversion, parallel multiple LM7812CTs with ballast resistors or upgrade to a switching LM2596HV module. The fixed 12 V output eliminates trim circuitry required by adjustable LDOs like the LM317.
推荐
Hobby Electronics & Breadboard Rails
The LM7812CT is a workhorse for hobbyist power supplies that derive 12 V from a 15 V wall adapter or battery pack. With TO-220 leads spaced 2.54 mm apart, it fits standard perfboards and breadboard adapters. The three-pin simplicity (IN/GND/OUT) requires no external feedback or compensation components beyond the recommended 0.33 µF input and 0.1 µF output bypass capacitors. For Arduino, Raspberry Pi accessories, and robotics motor drivers needing 12 V, this part provides a reliable, low-cost rail. Pair with an LM7805 to provide both 5 V and 12 V from a single 15 V input.
推荐
Motor Driver Auxiliary Supplies
The LM7812CT provides 12 V auxiliary rails for H-bridge gate drivers, logic-level shifters, and opto-isolator bias supplies in DC motor control boards. Its 35 V maximum input allows operation from 24 V and 36 V battery packs common in robotics and e-bike applications. The internal thermal shutdown and SOA protection make it robust against motor back-EMF transients when paired with an input TVS diode. The 55 dB ripple rejection helps keep gate-drive noise out of sensitive analog feedback circuits. For stepper motors needing high current 12 V rails, this regulator is appropriate only for low-power logic — use a separate buck converter for the main motor supply.
推荐
Audio Preamp Power Rails
The LM7812CT serves as a clean, low-noise 12 V supply for audio preamplifiers, microphone bias circuits, and op-amp rails in mixers. Unlike switching regulators, the LM7812CT adds no high-frequency ripple to the audio band, making it ideal for analog signal paths where even 100 µV of switching noise would degrade SNR. Ripple rejection of 55-72 dB attenuates 100 Hz hum from rectified mains inputs. Pair with a TL072 or OPA2134 dual op-amp for stereo microphone preamps. Add an RC output network (10 Ω + 100 µF) for additional PSRR enhancement above 20 kHz.
推荐
Legacy Linear Replacement Boards
The LM7812CT is the go-to replacement part for maintaining vintage linear power supplies in test equipment, laboratory instruments, and industrial controls originally designed around 78xx regulators. Its identical pinout and electrical characteristics to historical 7812 designs allows direct board swaps without PCB modification. The TO-220 package and screw-mount heatsink compatibility match original mounting hardware. For vintage tube amplifier B+ supplies, use this part to derive 12 V for relay boards and indicator lamps. onsemi's continued production ensures long-term availability for repair and maintenance operations.
推荐
推荐产品汇总
工程参考数据： LM7812CT/ ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | LM7812CT/NOPB | MC7812CTG | L7812CV | L7812ABV | LM340T-12/NOPB | KA7812 |
|---|---|---|---|---|---|---|---|
| Package | TO-220-3 | TO-220-3 | TO-220-3 | TO-220-3 | TO-220-3 | TO-220-3 | TO-220-3 |
| Brand | onsemi | Texas Instruments | onsemi | STMicroelectronics | STMicroelectronics | Texas Instruments | Fairchild Semiconductor |
| Output Voltage | 12 V | 12 V | 12 V | 12 V | 12 V | 12 V | 12 V |
| Output Current | 1 A | 1 A | 1 A | 1 A | 1 A | 1 A | 1 A |
| Output Tolerance | ±4 % | ±5 % | ±4 % | ±4 % | ±2 % | ±5 % | ±5 % |
| Maximum Input Voltage | 35 V | 35 V | 35 V | 35 V | 35 V | 35 V | 35 V |
| Pinout | 1=IN, 2=GND, 3=OUT | 1=IN, 2=GND, 3=OUT | 1=IN, 2=GND, 3=OUT | 1=IN, 2=GND, 3=OUT | 1=IN, 2=GND, 3=OUT | 1=IN, 2=GND, 3=OUT | 1=IN, 2=GND, 3=OUT |
关键差异点
- Three-pin simplicity — no external feedback or compensation needed （对比 LM317T)
- Pin-identical 12 V/1 A output across multiple vendors （对比 L7812ABV (STMicroelectronics))
- Zero switching noise — pure linear regulation （对比 LM2596 switching regulator)
设计说明
At VIN = 24 V, VOUT = 12 V, and 1 A load, the LM7812CT dissipates 12 W. Without thermal relief, the junction will exceed the 150 °C shutdown threshold within seconds. Use a TO-220 clip-on heatsink rated at ≤ 5 °C/W (or larger with forced-air cooling). For PCB-only cooling, dedicate at least 1 square inch of 2 oz copper pour to the tab. If the application requires sustained high dissipation, switch to a switching regulator (LM2596) or distribute load across two paralleled LM7812CTs with 0.5 Ω ballast resistors.
Place 0.33 µF input and 0.1 µF output capacitors within 5 mm of the regulator pins to suppress oscillation. Use low-ESR ceramic or tantalum capacitors. If the input supply is located more than 50 mm away, add a 1 µF electrolytic bulk capacitor at the regulator input to handle supply inductance. For high-frequency noise-sensitive analog applications, add an LC output filter (10 µH + 100 µF) for additional PSRR above 10 kHz.
Do not exceed 35 V input voltage — this destroys the internal pass transistor. Avoid reverse-input transients by adding a 1N4007 diode from output to input (cathode to input) to discharge the output capacitor. The metal tab is connected to Ground (Pin 2); using an insulating heatsink kit (TO-220 silicone washer + shoulder washer) is required when mounting to a chassis that is not at ground potential. Do not parallel LM7812CTs without ballast resistors — one will hog the current and overheat.
合规信息
onsemi LM7812CT is RoHS compliant and lead-free per onsemi product page. Not AEC-Q100 qualified — not recommended for automotive applications. Halogen-free status not explicitly stated in the manufacturer datasheet.
