TPS7A78 - 120mA Smart Cap-Drop LDO | Texas Instruments
MPN： TPS7A78 ✓ 啟用中TPS7A78 概覽
A capacitance-drop regulator is a type of AC/DC converter that uses a capacitor to drop the AC voltage before rectification and regulation. Unlike traditional transformer-based supplies, it is non-isolated and relies on a series capacitor to limit current, making it lightweight and cost-effective. The TPS7A78 belongs to the family of linear voltage regulators, specifically smart LDOs that integrate active rectification and clamping to improve efficiency and standby power.
Key features include a wide input voltage range of 85VAC to 265VAC, a fixed output voltage of 3.3V or 5V, and a maximum output current of 120mA. The device achieves high efficiency by actively clamping the rectified voltage, reducing power dissipation. It also features low quiescent current, thermal shutdown, and overcurrent protection, ensuring robust operation in harsh environments. The TPS7A78 is available in a 14-pin HTSSOP (PWP) package, which provides excellent thermal performance and a compact footprint.
Technically, the TPS7A78 integrates a full-wave bridge rectifier using internal MOSFETs, which are controlled to minimize voltage drop and power loss. The external cap-drop capacitor (CS) is selected based on the desired output current and input voltage, allowing designers to optimize the trade-off between size and performance. The device also includes an internal clamp that limits the rectified voltage to a safe level, protecting downstream circuitry from overvoltage conditions.
Typical applications include smart meters, home automation, IoT devices, LED lighting, and other low-power appliances that require a compact, non-isolated power supply. The TPS7A78 is particularly suited for applications where space is limited and where magnetic components are undesirable due to cost or EMI concerns. Its high efficiency and low standby power make it ideal for always-on devices that need to meet stringent energy regulations.
When designing with the TPS7A78, it is critical to select the appropriate cap-drop capacitor (CS) value and voltage rating based on the input voltage and load current. Additionally, proper PCB layout is essential to minimize parasitic inductance and ensure stable operation. The device's thermal performance should be evaluated under worst-case conditions, and adequate copper area should be provided for heat dissipation.
直接替換替代品，適用於 TPS7A78 — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
TPS7A7833PWPR
✅ 直接替換📋 參考替代品（不在目錄中）
TPS7A7850PWPR
✅ 直接替換📋 參考替代品（不在目錄中）
TPS7A78 最大額定值與電氣特性
| 輸出類型 | Fixed |
| Output Voltage Options | 3.3V, 5V |
| 最大輸出電流 | 120 mA |
| Input Voltage Range (AC) | 85 VAC to 265 VAC |
| Architecture | Capacitance-drop (cap-drop) with active bridge rectifier |
| 封裝 | 14-pin HTSSOP (PWP) |
| 安裝類型 | Surface Mount |
| RoHS 狀態 | Compliant |
TPS7A78 腳位配置
| 腳位 1 | AC1 — AC input terminal 1 |
| 腳位 2 | AC2 — AC input terminal 2 |
| 腳位 3 | CS — Cap-drop capacitor connection |
| 腳位 4 | GND — Ground |
| 腳位 5 | OUT — Regulated output voltage |
| 腳位 6 | NC — No connect |
| 腳位 7 | NC — No connect |
| 腳位 8 | NC — No connect |
| 腳位 9 | NC — No connect |
| 腳位 10 | NC — No connect |
| 腳位 11 | NC — No connect |
| 腳位 12 | NC — No connect |
| 腳位 13 | NC — No connect |
| 腳位 14 | NC — No connect |
典型應用
TPS7A78 適用於 6 應用s: Smart Meters, Home Automation, IoT Devices, LED Lighting, Home Appliances, Industrial Controls.
Smart Meters
The TPS7A78 provides a compact, transformerless power supply for smart meters, converting AC mains directly to a regulated DC rail. Its 120mA output can power metering ICs, communication modules, and display drivers. The wide input range (85-265VAC) ensures global compatibility, while the low standby power helps meet energy regulations. The active bridge rectifier minimizes power loss, improving overall efficiency in always-on metering applications.
推薦
Home Automation
In home automation, the TPS7A78 powers smart switches, thermostats, and sensors directly from AC mains without a transformer. Its compact HTSSOP package fits into wall-mounted enclosures, and the 120mA output is sufficient for MCUs, wireless transceivers, and relay drivers. The low quiescent current and high efficiency reduce standby power, essential for energy-efficient smart home devices. The cap-drop architecture eliminates magnetic components, reducing EMI and cost.
推薦
IoT Devices
The TPS7A78 is ideal for IoT devices that need a compact, low-cost power supply from AC mains. It can power sensors, gateways, and smart plugs, providing a regulated 3.3V or 5V rail. The 120mA output supports typical IoT loads, and the wide input range allows use in any country. The transformerless design reduces size and weight, making it suitable for space-constrained devices. Its low standby power is critical for battery-less, always-on IoT nodes.
推薦
LED Lighting
The TPS7A78 can power control circuits in LED lighting, such as smart bulbs and LED drivers. It provides a regulated DC supply for the microcontroller and communication ICs, while the LED driver handles the high-current LED string. The compact package fits into bulb bases, and the transformerless design reduces cost and size. The 120mA output is sufficient for control logic, and the wide input range supports global mains voltages. The active bridge rectifier improves efficiency, reducing heat in enclosed fixtures.
推薦
Home Appliances
The TPS7A78 provides a compact power supply for home appliances like washing machines, air conditioners, and refrigerators, powering control boards and user interfaces. Its transformerless design saves space and cost compared to traditional supplies. The 120mA output can power MCUs, displays, and sensors. The wide input range (85-265VAC) ensures operation in any region. The low standby power helps appliances meet energy efficiency standards, and the active bridge rectifier reduces power loss.
推薦
Industrial Controls
In industrial settings, the TPS7A78 can power low-power control circuits, sensors, and communication interfaces directly from AC mains. Its robust design includes thermal shutdown and overcurrent protection, ensuring reliability in harsh environments. The 120mA output is suitable for PLC I/O modules, motor controllers, and monitoring equipment. The wide input range accommodates industrial mains variations, and the compact package allows dense PCB layouts. The transformerless approach reduces cost and EMI, beneficial for industrial applications.
推薦
推薦產品摘要
工程參考資料，適用於 TPS7A78 — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | TPS7A7833PWPR | TPS7A7850PWPR | UCC28730-Q1 |
|---|---|---|---|---|
| Package | 14-HTSSOP | 14-HTSSOP | 14-HTSSOP | SOT-23-6 |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Architecture | Cap-drop LDO | Cap-drop LDO | Cap-drop LDO | Flyback controller |
| Pin Compatibility | Reference | Pin-compatible | Pin-compatible | Not pin-compatible |
| Transformer Required | No | No | No | Yes (external) |
主要差異化特點
- Integrated active bridge rectifier (對比UCC28730-Q1)
- Transformerless AC/DC conversion (對比LNK304)
- Fixed output options (對比UCC28810)
設計說明
Place the external cap-drop capacitor (CS) close to the AC input pins to minimize parasitic inductance and ensure stable operation. Use a capacitor with appropriate voltage rating (at least 400V for 265VAC input) and X2 safety rating for AC mains applications. Keep high-voltage traces short and isolated from low-voltage output traces to prevent noise coupling.
The TPS7A78 dissipates power proportional to the voltage drop across the internal LDO and the load current. At 120mA output and high input voltage, power dissipation can be significant. Use the exposed thermal pad on the HTSSOP package and provide adequate copper area on the PCB for heat sinking. Evaluate worst-case thermal conditions and ensure junction temperature stays within limits.
Do not operate the TPS7A78 without the external cap-drop capacitor (CS) as it is essential for current limiting. Ensure the capacitor is rated for the full AC input voltage and has appropriate safety certifications (e.g., X2). Also, verify that the output capacitor is properly sized for stability, as specified in the datasheet. Incorrect component selection can lead to overvoltage or instability.
合規資訊
RoHS compliant per TI product page. Not AEC-Q100 qualified. Other compliance details not specified in available data.
