Microchip MIC5353: 500mA LDO Voltage Regulator

General Description

The MIC5353 is a high-performance, single-output, ultra-low LDO regulator offering a low total output noise of 30 μVRMS. It is capable of sourcing 500 mA output current and features high-PSRR and low-output noise, making it an ideal solution for RF applications. The MIC5353 provides 2% accuracy, extremely low dropout voltage (160 mV @ 500 mA), and low ground current (typically 90 μA), making it suitable for battery-operated applications. When disabled, it enters a zero off-mode current state, drawing minimal current. The device is available in a compact 1.6 mm x 1.6 mm Thin UDFN package, occupying only 2.56 mm² of PCB area. It operates with a junction temperature range of -40°C to +125°C and is available in fixed and adjustable output voltages.

Features

• 500 mA Guaranteed Output Current
• Input Voltage Range: 2.6V to 6V
• Ultra Low Dropout Voltage: 160 mV @ 500 mA
• ±2% Initial Accuracy
• Ultra-Low Output Noise: 30 μVRMS
• Low Quiescent Current: 90 μA
• Stable with Ceramic Output Capacitors
• 35 μs Turn-On Time
• Thermal Shutdown and Current Limit Protection
• Tiny 6-Pin 1.6 mm x 1.6 mm Thin UDFN Leadless Package

Applications

• Mobile Phones
• GPS, PDAs, PMP, Handhelds
• Portable Electronics
• Digital Still and Video Cameras
• Digital TV

Package Type

The MIC5353 is available in a 6-Pin UDFN (MT) package. Pinouts are provided for both Fixed and Adjustable versions:

Typical Application Circuit

Functional Block Diagrams

Electrical Characteristics

Key electrical characteristics are summarized below. Bold values indicate operation from -40°C to +125°C.

Enable Input Characteristics:

Temperature Specifications

Package Thermal Resistances:

Note 1: The maximum allowable power dissipation is a function of ambient temperature, the maximum allowable junction temperature, and the thermal resistance from junction to air (θJA). Exceeding the maximum allowable power dissipation will cause the device operating junction temperature to exceed the maximum +125°C rating. Sustained junction temperatures above +125°C can impact device reliability.

Typical Performance Curves

The following graphs illustrate typical performance characteristics. Note that these are based on a limited number of samples and are for informational purposes only; they are not tested or guaranteed.

Pin Descriptions

The MIC5353 has the following pin functions:

Application Information

4.1 Enable/Shutdown

The MIC5353 features an active-high enable pin that allows the regulator to be disabled. Setting the enable pin low puts the regulator into a "zero" off-mode current state. Setting the enable pin high enables the output voltage. The enable pin uses CMOS technology and must not be left floating to avoid indeterminate output states.

4.2 Input Capacitor

For optimal performance, the MIC5353 requires a well-bypassed input supply. A 1 μF capacitor from input-to-ground is recommended for stability. Low-ESR ceramic capacitors offer optimal performance and minimal space. Additional high-frequency capacitors, like small-valued NPO dielectric types, can help filter high-frequency noise, which is good practice in RF circuits.

4.3 Output Capacitor

An output capacitor of 1 μF or greater is required for stability. The design is optimized for low-ESR ceramic chip capacitors; high-ESR types may cause oscillations. While larger capacitors can be used, performance is optimized for a 1 μF ceramic output capacitor. X7R/X5R dielectric ceramic capacitors are recommended for their temperature stability (15% capacitance change over temperature). Z5U and Y5V types have larger capacitance variations (50-60%) and may require higher values to ensure minimum capacitance over the operating temperature range.

4.4 No-Load Stability

The MIC5353 remains stable and in regulation even with no load, which is beneficial for CMOS RAM keep-alive applications.

4.5 Bypass Capacitor

A capacitor connected from the bypass pin to ground can reduce output voltage noise by bypassing the internal reference. A 0.1 μF capacitor is recommended for low-noise outputs. Increasing this capacitance can further reduce noise and improve PSRR, though it may slightly increase turn-on time. A quick-start circuit allows driving larger bypass capacitors without significantly slowing turn-on.

4.6 Adjustable Regulator Application

Adjustable versions use a resistor divider network to set the output voltage. The MIC5353 can be adjusted from 1.25V to 5.5V using two external resistors (R1 and R2) according to the equation: VOUT = VREF * (1 + R1/R2), where VREF = 1.25V.

4.7 Thermal Considerations

The MIC5353 can provide 500 mA continuous current. Maximum ambient operating temperature (TA) can be calculated using the output current, voltage drop, and thermal resistance (θJA). For example, with VIN = 3.3V, VOUT = 2.8V, and IOUT = 500 mA, the power dissipation (PD) is calculated as (3.3V - 2.8V) * 500 mA = 0.25W. Using the junction-to-ambient thermal resistance (θJA = 92.4°C/W) and the maximum junction temperature (TJ(MAX) = 125°C), the maximum ambient operating temperature can be determined. For this example, TA = 101°C.

4.8 Thermal Resistance

The junction-to-ambient thermal resistance (θJA) for the minimum footprint is 92.4°C/W. This value is crucial for calculating maximum power dissipation and ambient operating temperature to ensure proper operation and prevent exceeding the +125°C junction temperature rating.

Packaging Information

5.1 Package Marking Information

The 6-Lead UDFN package has specific marking codes. The legend explains the codes: XX...X for product information, Y for year code, WW for week code, NNN for traceability, and e3 for Pb-free designation. Pin one is identified by a dot, delta up, or delta down mark.

The package dimensions for the 6-Lead Ultra Thin Plastic Dual Flat, No Lead (UDFN) package are detailed, including overall height, thickness, length, width, and terminal dimensions. The recommended land pattern for this package is also provided with specific dimensions for contact pitch, pad width, and spacing.

Product Identification System

Microchip provides a system for identifying parts. The part number structure includes device type, output voltage, junction temperature range, package type, and media type. For example, MIC5353-1.8YMT-TR indicates a 500 mA LDO with 1.8V output, a -40°C to +125°C junction temperature range, a 6-Lead 1.6 mm x 1.6 mm UDFN package, and supplied on tape and reel (TR).

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