MXL7833
Ultra-low-noise 3.3V LDO with 200mV dropout, 1A current, and 5μVrms noise for precision analog circuits.
Product Overview
Description
The MXL7833 is an ultra-low-noise linear regulator providing a fixed 3.3V output with up to 1A load current capability.
With a typical dropout voltage of only 200mV at 1A and ultra-low noise of 5μVrms, it's ideal for powering sensitive analog circuits in aerospace systems.
The device includes current limiting, thermal shutdown, and is available with radiation tolerance options up to 100krad(Si).
Product Series
MXL
Primary Application
Precision ADC supplies
Key Features
- Ultra-low output noise 5μVrms
- High PSRR 80dB at 1kHz
- Low dropout voltage 200mV at 1A
- 1A output current capability
- Radiation tolerance to 100krad(Si)
- Current limiting protection
- Thermal shutdown protection
- Hermetic packages available
Specifications
| Input Voltage | 3.5V to 15V |
|---|---|
| Output Voltage | 3.3V fixed |
| Output Current | 1A maximum |
| Dropout Voltage | 200mV at 1A |
| Output Noise | 5μVrms (10Hz to 100kHz) |
| PSRR | 80dB at 1kHz |
| Line Regulation | 0.01%/V |
| Load Regulation | 0.2% |
| Radiation Tolerance | 100 krad(Si) optional |
| Temperature Range | -55°C to +125°C |
| Package | TO-39, CERDIP-8, SMD-0.5 |
Applications
Precision ADC supplies
Data acquisition and conversion
RF circuit power
Electronic system design
Oscillator supplies
Electronic system design
Sensor power
Sensor signal conditioning
Test equipment
Electronic system design
Medical instruments
Medical electronics
FAE Expert Insights
"The MXL7833 is my standard recommendation for powering precision analog circuits in aerospace applications where noise is critical. The 5μVrms noise specification is exceptional - I've measured similar performance to the best commercial parts. In one satellite payload design, we used this LDO to power a 24-bit sigma-delta ADC, and the supply noise contribution to overall system noise was negligible. The 80dB PSRR at 1kHz effectively attenuates switching ripple from upstream DC-DC converters. The 200mV dropout at 1A allows efficient operation from 5V input with good headroom. For radiation-tolerant designs, I recommend the hermetic TO-39 or CERDIP packages. One design tip: use a 10μF ceramic output capacitor with a small series resistor (1-2Ω) to isolate load transients and improve stability. For multi-ADC systems, use separate LDOs for each ADC to prevent crosstalk."
Ultra-low noise LDO ideal for precision analog circuits in aerospace
— Dr. Chen Hua, BeiLuo
Frequently Asked Questions
What makes MXL7833 ultra-low noise?
MXL7833 achieves ultra-low noise through several design techniques: 1) Low-noise bandgap reference with filtering. 2) Low-noise error amplifier with optimized transistor sizing. 3) Noise reduction pin (NR) for connecting external capacitor to filter reference noise. 4) Careful layout to minimize noise coupling. 5) High PSRR to reject input supply noise. The 5μVrms specification (10Hz to 100kHz) is among the best in the industry for radiation-tolerant LDOs. For lowest noise, connect a 10nF capacitor from NR pin to ground. This reduces noise to approximately 3μVrms. The noise performance is maintained across the full temperature range and after radiation exposure.
Use NR pin with 10nF capacitor for lowest noise. Noise performance maintained across temperature and radiation.
How much input and output capacitance does MXL7833 need?
MXL7833 requires: Input capacitor: 1μF minimum (ceramic), placed close to input pin to stabilize input during load transients. For long input leads, increase to 4.7μF. Output capacitor: 10μF ceramic recommended for best transient response and noise performance. Use X7R dielectric for stability across temperature. ESR should be <1Ω for stability. For noise-sensitive applications, add 100nF ceramic in parallel with 10μF. Place capacitors as close to regulator pins as possible with short, wide traces. Additional bulk capacitance (47μF+) at load helps with large transient currents. For aerospace applications, use ceramic capacitors with established reliability.
Use 1μF input and 10μF output as standard. Increase output capacitance for large load transients. Keep capacitor ESR low.
What is PSRR and why is it important?
PSRR (Power Supply Rejection Ratio) measures how well the LDO rejects noise and variations on its input from appearing at the output. It's expressed in dB - higher is better. MXL7833 PSRR: 80dB at 1kHz, 60dB at 10kHz, 40dB at 100kHz. This means at 1kHz, input noise is attenuated by 10,000x. High PSRR is critical for: 1) Powering ADCs and precision analog circuits where supply noise affects accuracy. 2) Post-regulation of switching supplies where ripple must be attenuated. 3) RF circuits where supply noise can modulate the carrier. For post-regulation of 100kHz switching supplies, 40dB PSRR provides 100x attenuation, reducing 100mV ripple to 1mV.
Select LDOs with high PSRR at frequencies present in your system. Check PSRR curve, not just single point.
How do I minimize thermal issues with MXL7833?
Thermal management for MXL7833: Calculate power dissipation: P = (V_in - V_out) × I_out. For 5V to 3.3V at 500mA: P = 1.7V × 0.5A = 0.85W. Calculate junction temperature: T_j = T_a + P × θ_ja. TO-39 package θ_ja ≈ 50°C/W. At T_a = 70°C: T_j = 70 + 0.85 × 50 = 112.5°C. Keep T_j below 125°C for reliability. For higher dissipation: 1) Use lower input voltage if possible. 2) Use TO-3 package with heatsink for >1W dissipation. 3) Add copper area on PCB for SMD packages. 4) Use forced air cooling if available. 5) Consider switching regulator for large voltage drops with high current.
Calculate T_j before design. Use TO-3 with heatsink for >1W. Keep T_j below 125°C.
Can MXL7833 be used in parallel for higher current?
MXL7833 can be paralleled for higher current with careful design. Two methods: 1) Simple parallel with ballast resistors: Add small series resistors (0.1-0.2Ω) at each LDO output to balance current sharing. Current sharing accuracy depends on resistor matching and LDO output voltage tolerance. 2) Active current sharing using external control circuit: Sense current from each LDO and adjust feedback to maintain equal current. This provides better sharing but requires additional circuitry. For best results, use LDOs from same production lot for matched characteristics. Ensure adequate heatsinking for combined power dissipation. For aerospace applications, consider reliability impact of parallel configuration - single point failures in current sharing circuit must be analyzed.
Use ballast resistors for simple parallel operation. Use active control for better sharing. Consider reliability impact.