MIC5219-3.3 — 500mA Peak Ultra-Low-Noise Fixed 3.3V LDO Regulator

Overview

The MIC5219-3.3 (MIC5219-3.3YM5) is a high-performance, ultra-low-noise fixed +3.3V low dropout (LDO) linear regulator manufactured by Microchip Technology (originally Micrel). Housed in a miniature 5-pin SOT-23 package, it delivers up to $500\text{ mA}$ peak output current ( $250\text{ mA}$ continuous) with an exceptionally low dropout voltage of $10\text{ mV}$ at light loads and $350\text{ mV}$ at $500\text{ mA}$ .

Featuring an internal reference bypass (BYP) pin, connecting a tiny $470\text{ pF}$ ceramic capacitor reduces output spectral noise density to just $260\text{ nV}/\sqrt{\text{Hz}}$ . The IC incorporates zero-current shutdown mode ( $< 1\ \mu\text{A}$ ), reverse battery polarity protection, overcurrent limiting, and thermal overload protection. It is a favored power regulator on Adafruit breakout boards, Arduino Pro Mini clones, GPS modules, LoRa nodes, and precision analog sensor front-ends.

Quick reference


Regulator Type	Ultra-Low-Noise Low-Dropout Linear Regulator (LDO)
Package	5-pin SOT-23 (SOT-23-5) / 8-pin MSOP
Fixed Output Voltage	$+3.3\text{ V}$ DC ( $\pm 1\%$ initial accuracy)
Input Voltage Range ( $V_{IN}$ )	$2.5\text{ V}$ to $12.0\text{ V}$ DC (Operates up to $+20\text{V}$ absolute max)
Peak Output Current	$500\text{ mA}$ peak ( $250\text{ mA}$ continuous thermal)
Dropout Voltage	$10\text{ mV}$ at $100\ \mu\text{A}$ / $350\text{ mV}$ at $500\text{ mA}$
Noise Spectral Density	$260\text{ nV}/\sqrt{\text{Hz}}$ with $470\text{ pF}$ bypass cap
Quiescent Current	$80\ \mu\text{A}$ at light load / $< 0.1\ \mu\text{A}$ in shutdown
Enable Control	Logic-compatible active-HIGH `EN` pin

Pinout (SOT-23-5 Package)

text

        ┌─────────────┐
    IN ─│ 1         5 │─ OUT
   GND ─│ 2           │
    EN ─│ 3         4 │─ BYP (Noise Bypass)
        └─────────────┘

Pin	Name	Description
1	`IN`	Unregulated DC supply input (+2.5V to +12.0V DC)
2	`GND`	Ground reference (0 V)
3	`EN`	Enable / Shutdown control (HIGH = Enabled, LOW/Open = Shutdown)
4	`BYP`	Noise bypass pin (Connect 470pF ceramic cap to GND; leave floating if unused)
5	`OUT`	Regulated fixed +3.3V DC voltage output

Standard Circuit & Capacitors

text

       +V_IN (3.6V - 12V DC)
          │
       [Pin 1: IN]
        MIC5219-3.3
       [Pin 5: OUT] ──────────────┬─────────────── +3.3V Regulated DC Output
          │                       │
       [Pin 2: GND]          [ C_OUT = 2.2µF Ceramic/Tantalum ]
          │                       │
   [ C_IN = 1.0µF Ceramic ]      GND
          │
       [Pin 3: EN ] ─── +V_IN (or MCU GPIO)
       [Pin 4: BYP] ───[ C_BYP = 470pF ]─── GND

Input Capacitor ( $C_{IN} = 1.0\ \mu\text{F}$ ): Required if the regulator is more than 4 inches from the main power source.
Output Capacitor ( $C_{OUT} = 2.2\ \mu\text{F} \dots 10\ \mu\text{F}$ ): Ceramic or tantalum capacitor required for control loop stability (ESR $< 5\ \Omega$ ).
Bypass Capacitor ( $C_{BYP} = 470\text{ pF}$ ): Ceramic capacitor connected from Pin 4 to GND to suppress reference amplifier noise.

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Output Voltage Accuracy	$V_{OUT}$	3.267	3.300	3.333	V	$I_O = 100\ \mu\text{A}, T_A = 25^\circ\text{C}$
Dropout Voltage	$V_{DO}$	—	10	50	mV	$I_{OUT} = 100\ \mu\text{A}$
Dropout Voltage (Full Load)	$V_{DO}$	—	350	500	mV	$I_{OUT} = 500\text{ mA}$
Peak Output Current	$I_{PK}$	500	700	—	mA	$V_{OUT} \ge 3.1\text{V}$
Quiescent Ground Current	$I_{GND}$	—	80	150	$\mu\text{A}$	$I_{OUT} = 100\ \mu\text{A}$
Ground Current at Full Load	$I_{GND}$	—	6.0	12.0	mA	$I_{OUT} = 500\text{ mA}$
Shutdown Current	$I_{SD}$	—	0.01	1.0	$\mu\text{A}$	$V_{EN} \le 0.4\text{V}$
Power Supply Rejection Ratio	$PSRR$	—	75	—	dB	$f = 120\text{ Hz}, C_{OUT} = 10\ \mu\text{F}$

Common mistakes

Leaving EN floating: Pin 3 (EN) does not have an internal pull-up. Leaving it disconnected causes the regulator to float into low-power shutdown. Tie EN directly to IN for always-on operation.
Overheating the tiny SOT-23 package at high continuous currents: SOT-23 packages have a thermal resistance $\theta_{JA} \approx 220^\circ\text{C/W}$ . Stepping down $9\text{V}$ (e.g. from a 9V battery) to $3.3\text{V}$ at $150\text{mA}$ creates $P_D = (9 - 3.3) \times 0.15 = 0.855\text{ W}$ , resulting in a $\Delta T = 0.855 \times 220 \approx 188^\circ\text{C}$ temperature rise that instantly triggers thermal shutdown. Keep continuous loads $< 150\text{ mA}$ when input voltage exceeds $5\text{V}$ .

Notes

Reverse Battery Protection: The MIC5219 includes internal reverse polarity protection, protecting both the regulator and the downstream circuitry if a battery is connected backwards.

Interface	DC Input (IN), Ground (GND), Active-High Enable (EN), Noise Bypass (BYP), Regulated 3.3V Output (OUT)
Package	SOT-23-5 (Ithaca) / MSOP-8