LDO (Low-Dropout Linear Regulator)
Quiet, simple, low-noise voltage regulators for clean rails.
What is it?
An LDO is a linear voltage regulator that can operate with very little headroom (low dropout) between input and output. It produces a clean, regulated output from a slightly-higher input by dissipating the difference as heat. Compared to switching converters: LDOs are quieter, simpler, and need no inductor: but less efficient (efficiency ≈ Vout / Vin).
When do you need it?
- Cleaning up a noisy rail before feeding a sensitive analog block (RF, ADC, audio).
- Generating multiple low-current rails from one switching pre-regulator.
- Battery-powered designs where input-output gap is small (single-cell Li-ion to 3.3 V).
- Low-current LDO is better than buck when load is <100 mA, simpler, smaller, no EMI.
How to pick the right one
- VIN range
- Must span your minimum to maximum input. Most LDOs are 2.5-5.5 V; high-voltage parts go up to 40-100 V.
- VOUT (fixed or adjustable)
- Fixed variants have factory-set output (e.g., 1.8 V, 3.3 V). Adjustable variants use external R divider, needed when you want a non-standard voltage.
- IOUT (Maximum output current)
- 100 mA / 300 mA / 1 A / 3 A common. Power dissipation = (VIN − VOUT) × IOUT; check this against package thermal limit.
- PSRR (Power Supply Rejection Ratio)
- How well the LDO rejects ripple on its input. For RF / ADC use, want >60 dB at the noise frequency.
- Noise (μV RMS)
- Critical for ADC reference rails. Ultra-low-noise LDOs publish 5-15 μV RMS specs.
- Iq (Quiescent Current)
- Always-on current. For battery designs, lower is better, Magnias has parts below 1 μA Iq.
What Magnias offers
Magnias LDO portfolio covers 50 mA to 3 A output, 0.5 V to 35 V output and inputs up to 120 V, with both fixed and adjustable variants. Specialty options include ultra-low-noise (PSR9032 at 9.5 μV RMS), ultra-low-Iq (PR9030 at 500 nA), high-voltage (PSR10005 at 100 V and PSR12015 at 120 V input) and AEC-Q100 qualified parts such as PR2030 and PSR12015.