ANL7805
Low-dropout linear regulator with 5V fixed output, 1A current, and excellent PSRR for noise-sensitive applications.
Product Overview
Description
The ANL7805 is a low-dropout linear regulator providing a fixed 5V output with up to 1A load current capability.
With a typical dropout voltage of only 350mV at 1A and excellent PSRR of 75dB at 1kHz, it's ideal for post-regulation of switching supplies and noise-sensitive analog circuits.
Built-in current limiting and thermal shutdown protect the device and load from fault conditions.
Product Series
ANL
Primary Application
Post-regulation of switching supplies
Key Features
- Low dropout voltage (350mV at 1A)
- High PSRR (75dB at 1kHz)
- 1A output current capability
- Fixed 5V output (other voltages available)
- Low output noise (50μVrms)
- Current limiting protection
- Thermal shutdown protection
- Multiple package options
Specifications
| Input Voltage | 5.5V to 20V |
|---|---|
| Output Voltage | 5V (fixed) |
| Output Current | 1A (maximum) |
| Dropout Voltage | 350mV typical at 1A |
| Line Regulation | 0.02%/V typical |
| Load Regulation | 0.2% typical |
| PSRR | 75dB at 1kHz, 50dB at 100kHz |
| Quiescent Current | 5mA typical |
| Protection | Current limiting, thermal shutdown |
| Operating Temperature | -40°C to +125°C |
| Package | TO-220, SOT-223, SOIC-8 |
Applications
Post-regulation of switching supplies
Power conversion and supply
Analog circuit power supplies
Electronic system design
Sensor power supplies
Sensor signal conditioning
Microcontroller power supplies
Industrial automation and control
RF circuit power supplies
Electronic system design
Audio equipment power supplies
Electronic system design
FAE Expert Insights
"The ANL7805 is my standard recommendation for cleaning up noisy switching supply outputs. The 75dB PSRR at 1kHz effectively attenuates switching ripple, providing clean 5V for sensitive analog and RF circuits. I've used it extensively in precision measurement systems where supply noise directly impacts ADC accuracy. The 350mV dropout at 1A allows operation from 6V input with good headroom - perfect for 12V to 5V conversion with margin for input transients. For lowest noise, add a 10μF ceramic capacitor on the output with a small series resistor (1-2Ω) to isolate load transients. One tip: the SOT-223 package has higher thermal resistance than TO-220 - for 1A continuous operation, ensure adequate copper area or use TO-220 with heatsink."
Excellent PSRR for post-regulation and noise-sensitive applications
— Kevin Wang, BeiLuo
Frequently Asked Questions
What is dropout voltage and why does it matter?
Dropout voltage is the minimum input-output voltage differential required for the LDO to maintain regulation. For ANL7805 at 1A, dropout is 350mV, meaning minimum input voltage is 5V + 0.35V = 5.35V. This matters because: 1) It determines minimum battery voltage for battery-powered applications, 2) It affects power dissipation (P = (V_in - V_out) × I_out), 3) It impacts efficiency. Low dropout (LDO) regulators can operate with small headroom, extending battery life. For example, a standard 7805 requires 2V dropout (7V minimum input), while ANL7805 works with 5.5V input, saving 1.5V × I_out in power dissipation.
Ensure V_in > V_out + V_dropout at maximum load. Consider dropout when battery voltage approaches end-of-life voltage.
How much input and output capacitance does ANL7805 need?
ANL7805 requires: Input capacitor: 0.33μF minimum (ceramic or tantalum), placed close to input pin to stabilize input during load transients. For long input leads, increase to 1-10μF. Output capacitor: 0.1μF minimum, but 10μF ceramic recommended for best transient response. ESR should be <1Ω for stability. Use X5R or X7R ceramic capacitors for best performance across temperature. 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 (100μF+) at load helps with large transient currents.
Use 1μF input and 10μF output as standard values. Increase output capacitance for large load transients. Keep capacitor ESR low.
What causes thermal shutdown in LDOs and how do I prevent it?
Thermal shutdown occurs when junction temperature exceeds safe limits (typically 150-175°C). Causes: 1) Excessive power dissipation from high input-output voltage differential and high current, 2) Insufficient heatsinking or copper area, 3) High ambient temperature, 4) Blocked airflow. Prevention: 1) Calculate power dissipation: P = (V_in - V_out) × I_out, 2) Calculate junction temperature: T_j = T_a + P × θ_ja, 3) Ensure T_j < 125°C for reliability, 4) Use adequate copper area (500mm² minimum for SOT-223 at 0.5W), 5) Consider switching regulator for high power dissipation, 6) Use TO-220 package with heatsink for >1W dissipation.
Calculate T_j before design. Use sufficient copper area or heatsink. Consider switching regulator if P > 1W.
When should I use LDO vs switching regulator?
Use LDO when: 1) Input-output voltage difference is small (<2V), 2) Low noise is critical (RF, analog, audio), 3) Fast transient response needed, 4) Simple, low-cost solution preferred, 5) Low output current (<500mA). Use switching regulator when: 1) Input-output difference is large (>3V), 2) Efficiency is critical (battery life, heat reduction), 3) High output current (>1A), 4) Input voltage varies widely. Cascaded approach: Use switching regulator for efficient voltage step-down, then LDO for final low-noise regulation. Example: 12V to 5V at 1A - switching regulator (90% efficient) dissipates 0.5W vs LDO dissipating 7W.
Use LDO for small drops and low noise. Use switching for large drops and efficiency. Use cascaded for best of both.
How does PSRR vary with frequency and why does it matter?
PSRR (Power Supply Rejection Ratio) typically decreases with increasing frequency. ANL7805 PSRR: 75dB at 1kHz, 60dB at 10kHz, 50dB at 100kHz, 30dB at 1MHz. This matters because switching power supplies generate ripple at switching frequency (typically 100kHz to 2MHz). At 100kHz switching frequency with 100mV ripple, 50dB PSRR means output ripple of 0.3mV. For sensitive circuits (16-bit ADCs, precision references), this may still be too high. Solutions: 1) Use LDO with higher PSRR at switching frequency, 2) Add LC filter before LDO, 3) Use cascaded LDOs, 4) Select switching frequency where PSRR is still good. Check PSRR curve in datasheet, not just single point specification.
Check PSRR at your switching frequency. Add pre-filtering if PSRR is insufficient. Consider cascaded LDOs for critical applications.