FDA903U - 1A, 35V Ultra-Low Noise LDO | Texas Instruments
MPN： FDA903U ✓ 啟用中FDA903U 概覽
An LDO (Low-Dropout) linear regulator is a type of voltage regulator that maintains a stable output voltage even when the input voltage is very close to the output voltage. It is a key component in power management ICs, providing clean, low-noise power rails for sensitive analog and digital circuits. LDOs are essential in applications where switching noise from DC-DC converters would degrade performance, such as in audio, RF, and precision measurement systems.
Key features include 4.17 uVrms output noise (20 Hz to 100 kHz), 72 dB PSRR at 1 kHz, and a low dropout voltage of 200 mV at full 1A load. The device also offers 6.4 mA quiescent current, an active-high enable pin for power sequencing, and thermal shutdown protection. The VQFN-20 package provides a thermal resistance of 31.4 C/W, enabling compact designs without external heatsinking at moderate power levels.
The FDA903U utilizes a bipolar architecture with a precision bandgap reference, achieving noise performance comparable to discrete reference designs while maintaining regulator simplicity. The high PSRR minimizes ripple from upstream switching converters, making it suitable for noise-sensitive analog and RF signal chains where clean power rails are critical.
Typical applications include high-end audio DAC power supplies, PLL/VCO power rails in RF transceivers, precision ADC/DAC reference buffering, and test and measurement instrumentation. The wide input range also supports industrial 24V bus systems with adequate headroom.
When designing with this device, ensure adequate input-to-output voltage headroom to maintain regulation under all load conditions. The enable pin allows sequential power-up in multi-rail systems, which is essential for processors requiring specific rail sequencing.
直接替換替代品，適用於 FDA903U — 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。
此系列的變體
與下列產品可直接替換的同系列型號： FDA903U （相同外形與佔位） — 差異在於 Package, Enable Pin, Input Voltage Range, MSL Level, Output Type.
TPS7A4700RGWR
✅ 直接替換✗ 缺貨
$3.6591 / 單位
查看資料表 →TPS7A4701RGWR-Q1
✅ 直接替換📋 參考替代品（不在目錄中）
TPS7A4701RGWT
✅ 直接替換📋 參考替代品（不在目錄中）
LT3045EDC
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
ADM7150ARDZ
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
FDA903U 最大額定值與電氣特性
| 輸出類型 | Adjustable |
| 輸出電壓範圍 | 1.4 V to 34 V |
| 最大輸出電流 | 1 A |
| 輸入電壓範圍 | 3 V to 35 V |
| 壓降電壓 | 200 mV at 1 A |
| 輸出雜訊 | 4.17 uVrms (20 Hz to 100 kHz) |
| PSRR | 72 dB at 1 kHz |
| 靜態電流 | 6.4 mA |
| 熱阻 | 31.4 C/W |
| 工作溫度 | -40C to +125C |
| 封裝 | VQFN-20 (RGW) 5x5 mm |
| 安裝類型 | Surface Mount |
| MSL 等級 | 2 (1 year) |
| RoHS 狀態 | Compliant |
| 致能腳位 | Yes (active-high) |
FDA903U 腳位配置
| 腳位 1 | OUT — Regulated output voltage |
| 腳位 5 | GND — Ground |
| 腳位 6 | EN — Enable (active high) |
| 腳位 7 | IN — Input supply |
典型應用
FDA903U 適用於 6 應用s: High-End Audio DAC Power Supply, RF Transceiver Power Rail, Precision ADC Reference Buffer, Industrial 24V Bus Power, Test and Measurement Instrumentation, Portable Battery-Powered Devices.
High-End Audio DAC Power Supply
Provides clean 5V rail for audio DACs with 4.17uVrms noise. The FDA903U's ultra-low noise and high PSRR ensure that the power supply does not introduce audible artifacts into the audio signal. In a typical audio DAC application, the FDA903U is placed between the system 5V rail and the DAC's AVDD pin, with a 10uF ceramic capacitor on input and output. Compared to switching regulators, the LDO eliminates switching noise but dissipates more power; for a 12V-to-5V conversion at 500mA, power dissipation is 3.5W, requiring adequate thermal management.
推薦
RF Transceiver Power Rail
Provides clean power to PLL/VCO circuits, minimizing phase noise. The FDA903U's 4.17uVrms noise and 72dB PSRR at 1kHz are critical for RF applications where power supply noise can degrade signal integrity. In a typical RF transceiver, the FDA903U is used to power the PLL charge pump and VCO, with careful layout to minimize parasitic inductance. The high PSRR suppresses ripple from upstream DC-DC converters, ensuring stable frequency synthesis.
推薦
Precision ADC Reference Buffer
Buffers reference voltage for high-resolution ADCs, ensuring accuracy. The FDA903U's low noise and high PSRR are essential for precision measurement systems. In a typical ADC application, the FDA903U provides a clean reference voltage to the ADC's VREF pin, with a low-ESR capacitor on the output. The wide input range allows operation from various supply rails, and the enable pin enables power sequencing in multi-rail systems.
推薦
Industrial 24V Bus Power
Regulates 24V industrial bus down to 5V or 3.3V for control electronics. The FDA903U's 35V input range provides ample headroom for 24V systems, and its low dropout ensures regulation even with voltage dips. In a typical industrial application, the FDA903U is used to power microcontrollers and sensors, with input protection diodes and output capacitors for stability. The thermal shutdown feature protects the device in harsh environments.
推薦
Test and Measurement Instrumentation
Provides clean power for precision instruments, reducing measurement errors. The FDA903U's ultra-low noise and high PSRR are critical for oscilloscopes, multimeters, and spectrum analyzers. In a typical instrument, the FDA903U powers analog front-end circuits, ensuring accurate signal acquisition. The enable pin allows controlled power-up, and the thermal pad aids heat dissipation in compact enclosures.
推薦
Portable Battery-Powered Devices
Regulates battery voltage to low-noise rails for audio and sensor circuits. The FDA903U's low quiescent current (6.4mA) extends battery life, and its low dropout maximizes usable battery voltage. In a typical portable device, the FDA903U powers audio codecs and MEMS sensors, with the enable pin for power saving. The small VQFN-20 package fits space-constrained designs.
推薦
推薦產品摘要
工程參考資料，適用於 FDA903U — 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 | TPS7A4700RGWR | TPS7A4701RGWR-Q1 | TPS7A3301RGWR |
|---|---|---|---|---|
| Package | VQFN-20 (RGW) | VQFN-20 (RGW) - same | VQFN-20 (RGW) - same | VQFN-20 (RGW) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Output Current | 1 A | 1 A | 1 A | 1 A (negative) |
| Output Voltage Range | 1.4V to 34V | 1.4V to 34V | 1.4V to 34V | -36V to -1.4V |
| Enable Pin | Yes (active-high) | No | Yes (active-high) | Yes (active-high) |
| Automotive Grade | No | No | Yes (AEC-Q100) | No |
| Output Noise | 4.17 uVrms | 4.17 uVrms | 4.17 uVrms | 4.17 uVrms |
| PSRR at 1kHz | 72 dB | 72 dB | 72 dB | 72 dB |
主要差異化特點
- Only VQFN-20 family member with enable pin (對比TPS7A4700RGWR)
- Automotive grade option available (對比TPS7A4701RGWR-Q1)
- Positive voltage polarity (對比TPS7A3301RGWR)
設計說明
At VIN=12V, VOUT=5V, and 1A load, power dissipation is 7W. The VQFN-20 package has theta_JA of 31.4 C/W, resulting in a 220C junction temperature rise. A heatsink or at least 1 square inch of copper pour is required for reliable operation above 2W dissipation.
Place input and output capacitors as close to the IC pins as possible. Use a 10uF ceramic capacitor on the input and a 10uF ceramic capacitor on the output. Add a 0.1uF ceramic capacitor in parallel for high-frequency noise bypass.
Do not exceed the maximum input voltage of 35V. Ensure the external resistor divider uses 1% or better tolerance resistors to maintain output voltage accuracy. The NR/SS capacitor controls startup time and noise bandwidth - do not omit it.
合規資訊
RoHS compliant per TI product page. Not AEC-Q100 qualified - choose TPS7A4701RGWR-Q1 for automotive.
