MIC2215 datasheet(12/22 Pages) MICROCHIP

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MIC2215

DS20006274A-page 12

 2019 Microchip Technology Inc.

4.0

FUNCTIONAL DESCRIPTION

The MIC2215 is a triple, low-noise CMOS LDO.

Designed specifically for noise-critical applications in

handheld or battery-powered devices, the MIC2215

comes equipped with a noise reduction feature to filter

the output noise via an external capacitor. Other

features of the MIC2215 include a separate logic

compatible enable pin for each channel, current limit,

thermal shutdown, and ultra-fast transient response, all

within a small QFN package.

The MIC2215 is specifically designed to work with

low-ESR ceramic capacitors, reducing the amount of

board space necessary for power applications, which is

critical in handheld wireless devices.

5.0

APPLICATION INFORMATION

5.1

Enable/Shutdown

The MIC2215 comes with three active-high enable pins

that allow each individual regulator to be either

disabled or enabled. Forcing the enable pin low

disables the respective regulator and sends it into a

zero off-mode current state. In this state, current

consumed by the individual regulator goes nearly to

zero. This is true for both regulators 2 and 3. Regulator

1’s input supply pin is also used to power the internal

reference. When any regulator, either 1, 2, or 3, is

enabled, an additional 20 μA for the reference will be

drawn through VIN1. All three must be disabled to enter

the zero current off-mode state. Forcing the enable pin

high enables each respective output voltage. This part

is CMOS and none of the enable pins can be left

floating; a floating enable pin may cause an

indeterminate state on the output.

5.2

Input Capacitor

The MIC2215 is a high performance, high bandwidth

device. Therefore, it requires a well-bypassed input

supply for optimal performance. A small 0.1 μF

capacitor placed close to the input is recommended to

aid in noise performance. Low-ESR ceramic capacitors

provide optimal performance at a minimum of space.

Additional high-frequency capacitors, such as small

valued NPO dielectric type capacitors, help to filter out

high frequency noise and are good practice in any

RF-based circuit.

5.3

Output Capacitor

The MIC2215 requires an output capacitor for stability.

The design requires 1 μF or greater on the output to

maintain stability. The design is optimized for use with

low-ESR

ceramic

chip

capacitors.

X7R/X5R

dielectric-type ceramic capacitors are recommended

because of their temperature performance. X7R-type

capacitors change capacitance by 15% over their

operating temperature range and are the most stable

type of ceramic capacitors. Z5U and Y5V dielectric

capacitors change value by as much as 50% and 60%,

respectively, over their operating temperature ranges.

To use a ceramic chip capacitor with Y5V dielectric, the

value must be much higher than an X7R ceramic

capacitor to ensure the same minimum capacitance

over the equivalent operating temperature range.

5.4

Bypass Pin

A capacitor can be placed from the noise bypass pin to

ground to reduce output voltage noise. The capacitor

bypasses the internal reference. There is one single

internal reference shared by each output, therefore the

bypassing affects each regulator. A 0.1 μF capacitor is

recommended for applications that require low-noise

outputs. The bypass capacitor can be increased,

further reducing noise and improving PSRR. Turn-on

time increases slightly with respect to bypass

capacitance.

5.5

Internal Reference

The internal band gap, or reference, is powered from

the VIN1 input. Due to some of the input noise (PSRR)

contributions being imposed on the band gap, it is

important to make VIN1 as clean as possible with good

bypassing close to the input.

5.6

Multiple Input Supplies

The MIC2215 can be used with multiple input supplies

when desired. The only requirement, aside from

maintaining the voltages within the operating ranges, is

that VIN1 always remains the highest voltage potential.

5.7

No-Load Stability

The MIC2215 will remain stable and in regulation with

no load, unlike many other voltage regulators. This is

especially important in CMOS RAM keep-alive

applications.

5.8

Thermal Considerations

The MIC2215 is designed to provide up to 250 mA of

current per channel in a very small package. Maximum

power dissipation can be calculated based on the

output current and the voltage drop across the part. To

determine the maximum power dissipation of the

package,

use

the

junction-to-ambient

thermal

resistance of the device and the following basic

equation:

EQUATION 5-1:

PDMAX



T JMAX



T A

–

 



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