LT1963AES8-2.5#PBF is a high-current, low-noise, fast-transient-response low-dropout (LDO) linear regulator designed and manufactured by Analog Devices Inc. (following its acquisition of Linear Technology). It belongs to the ultra-low-noise LT1963 family, engineered for powering noise-sensitive analog and RF circuitry — such as high-speed ADCs/DACs, precision op-amps, VCOs, PLLs, and RF transceivers — where power supply ripple rejection, output voltage accuracy, and stability under dynamic load are critical.
The “AES8” suffix denotes the 8-pin SOIC package (150 mil width), widely used for its thermal performance and ease of assembly; the “-2.5” indicates a fixed 2.5 V output voltage; and the “#PBF” signifies Pb-free, RoHS-compliant construction, supplied in tape-and-reel format (typically 2,500 units per reel).
Introduction
The LT1963AES8-2.5#PBF delivers up to 1.5 A of continuous output current, with exceptional 30 µVRMS output noise (10 Hz–100 kHz) and 65 dB PSRR at 1 MHz, outperforming most competing LDOs in both noise and high-frequency power supply rejection. Its architecture features:
đš Very low dropout voltage: 340 mV (typ.) at 1.5 A, enabling efficient operation even with small input–output differentials (e.g., 3.3 V → 2.5 V);
đš Ultra-fast transient response: Settles within ±1% in < 5 µs for a 1 A load step — critical for digital loads (e.g., FPGAs, processors) that cause rapid current surges;
đš Stable with ceramic output capacitors: Requires only 10 µF (min) — no ESR constraints, simplifying design and improving reliability vs. tantalum or aluminum electrolytics;
đš Integrated protection: Current limiting, thermal shutdown with hysteresis, and reverse-battery protection (survives –20 V on input);
đš No external components required for basic operation — unlike many LDOs, it needs no bias capacitor or feedforward capacitor.
The device operates from an input range of 2.8 V to 20 V, making it suitable not only for post-regulation of switching supplies but also for direct regulation from 5 V, 12 V, or 19 V rails (e.g., laptop adapters, industrial 24 V systems with local 2.5 V conversion). Its SOIC-8 (AES8) package, with exposed pad (EP), achieves θJA ≈ 45°C/W — supporting full 1.5 A load at +70°C ambient when properly heatsinked.
Key Features
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High Current & Low Dropout:
• Output current: up to 1.5 A;
• Dropout voltage: 340 mV (typ.) @ 1.5 A, 500 mV (max);
• Input voltage range: 2.8 V to 20 V.
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Ultra-Low Noise & High PSRR:
• Output noise: 30 µVRMS (10 Hz–100 kHz) — ideal for high-resolution (16+ bit) data converters and low-phase-noise synthesizers;
• PSRR: 75 dB @ 120 Hz, 65 dB @ 1 MHz, 40 dB @ 10 MHz — superior rejection of switcher ripple and digital noise.
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Fast Transient Response & Stability:
• Load transient recovery: < 5 µs to ±1% for 1 A step (with 22 µF ceramic output cap);
• Stable with ≥ 10 µF ceramic output capacitors — no minimum ESR required;
• No external compensation needed.
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Robust Protection & Operation:
• Reverse-battery protection: survives –20 V on IN (no damage, no reverse current);
• Thermal shutdown with 15°C hysteresis;
• Foldback current limiting — prevents overheating during short-circuit events;
• Enable pin (active-high) with precise 1.25 V threshold and hysteresis.
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Fixed 2.5 V Output & SOIC-8 (AES8) Package:
• Output voltage: 2.5 V (±2% initial accuracy, ±3% over line/load/temp);
• Package: 8-lead SOIC (150 mil) with exposed thermal pad — excellent manufacturability and thermal performance;
• RoHS-compliant, Pb-free, and qualified for –40°C to +125°C junction temperature.
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices Inc. (formerly Linear Technology) |
| Product Series |
LT1963 Family (Low-Noise, High-Current LDOs) |
| Model |
LT1963AES8-2.5#PBF |
| Function |
Fixed-Output Low-Dropout Linear Regulator |
| Output Voltage |
2.5 V (fixed), ±2% initial, ±3% over conditions |
| Max Output Current |
1.5 A |
| Input Voltage Range |
2.8 V to 20 V |
| Dropout Voltage (1.5 A) |
340 mV (typ.), 500 mV (max) |
| Output Noise (10 Hz–100 kHz) |
30 µVRMS |
| PSRR @ 1 MHz |
65 dB |
| Load Transient Recovery |
< 5 µs (±1%, 1 A step, 22 µF out) |
| Min Output Capacitance |
10 µF ceramic (X5R/X7R) |
| Enable Threshold |
1.25 V (typ.), with hysteresis |
| Operating Junction Temp. |
–40°C to +125°C |
| Package |
8-Lead SOIC (150 mil) with Exposed Pad (AES8) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
Tape-and-Reel (PBF), typically 2,500 units/reel |
Typical Applications
đš High-Speed Data Acquisition Systems: Powering 16–20-bit SAR and Σ-Δ ADCs (e.g., AD7960, ADS127L01) and high-fidelity DACs (e.g., AD5791, LTC2000) — where sub-30 µV RMS noise ensures maximum SNR and SFDR.
đš RF & Microwave Signal Chains: Supplying VCOs, PLLs (e.g., ADF4377), LNAs, mixers, and RF transceivers (e.g., AD9371, TRF3720) — leveraging >65 dB PSRR at 1 MHz to suppress switching regulator artifacts and preserve phase noise performance.
đš Precision Instrumentation: Powering low-noise op-amps (e.g., LT1028, ADA4898), reference buffers (e.g., ADR45xx), and strain-gauge amplifiers — where LDO noise directly limits system resolution.
đš Medical Imaging Electronics: CT/MRI detector front-ends, ultrasound beamformers, and PET scanner ASICs — requiring clean, stable 2.5 V rails for analog signal integrity and low artifact generation.
đš Industrial Process Control: High-accuracy sensor transmitters (e.g., 4–20 mA loops with HART), precision RTD/thermocouple conditioners — benefiting from fast transient response and wide VIN tolerance.
đš Communications Infrastructure: Small cell base stations, optical modules (QSFP-DD, OSFP), and packet-processing SoCs — where low noise and high PSRR prevent BER degradation and clock jitter.
Development & Design Notes
đ§ Thermal Management:
- The AES8 package’s exposed pad (EP) must be soldered to a ≥ 100 mm² internal ground plane using ≥ 8 thermal vias (0.3 mm) — essential for dissipating up to 1.1 W (at 12 V → 2.5 V @ 1.5 A) without exceeding TJ = 125°C.
- For continuous 1.5 A operation above +60°C ambient, add a small external heatsink or use forced airflow (>100 LFM).
đ§ Output Capacitor Selection & Layout:
- Use low-ESR, X5R or X7R ceramic capacitors (e.g., 22 µF × 2 in parallel, 0805 or 1206 size). Avoid high-ESR types (tantalum, aluminum) — they degrade PSRR and transient response.
- Place output capacitors within 3 mm of VOUT and GND pins, with short, wide traces — minimizes inductance and preserves high-frequency PSRR.
- Add a 10 nF ceramic capacitor in parallel with the main output cap, placed closest to the IC — improves high-frequency bypassing (1–10 MHz).
đ§ Input Decoupling & Ripple Rejection:
- Use a 10 µF ceramic + 1 µF ceramic at the input — located < 5 mm from IN and GND pins. This reduces high-frequency noise coupling into the LDO control loop.
- For best PSRR, ensure the input supply itself has low impedance up to 10 MHz — consider adding a ferrite bead + 100 nF cap between upstream switcher and LT1963 if PSRR margin is tight.
đ§ Enable & Sequencing Integration:
- Tie EN to a supervisor IC (e.g., LTC2906) or microcontroller GPIO. Add a 10 nF capacitor from EN to GND for noise immunity.
- Use the enable function for power sequencing (e.g., delay 2.5 V rail until 3.3 V is stable) — avoids latch-up or undefined states in downstream logic.
đ§ Reliability & Long-Term Stability:
- LT1963 exhibits < 0.5% output voltage drift over 10 years (per Linear reliability reports) — suitable for calibration-critical applications.
- For functional safety (IEC 61508 SIL-2), combine thermal monitoring (via external NTC on EP copper) with watchdog-timed readback of output voltage via optional external ADC — ADI provides FIT rate (14) and FMEDA data.
