MIC5396 datasheet(9/26 Pages) MICROCHIP

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2019-2022 Microchip Technology Inc. and its subsidiaries

DS20006264C-page 9

MIC5396/7/8/9

4.0

APPLICATION INFORMATION

MIC5396/7/8/9 are dual 300 mA LDOs in a tiny 8-lead

1.2 mm x 1.6 mm Extra Thin DFN package. The

MIC5397 and MIC5399 include an auto-discharge

circuit for each LDO output, which is activated when the

output is disabled. The MIC5398 and MIC5399 have an

internal pull-down resistor on the enable pin to ensure

that the output is disabled if the control signal is

tri-stated. The MIC5396/7/8/9 regulators are fully

protected from damage due to fault conditions using

linear current limiting and thermal shutdown. These

devices are not suitable for RF transmitter systems.

4.1

Input Capacitor

The

MIC5396/7/8/9

are

high-performance,

high-bandwidth devices. An input capacitor of 1 µF

capacitor is required from the input to ground to provide

stability. 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 filter out high-frequency

noise and are good practice in any RF-based circuit.

X5R or X7R dielectrics are recommended for the input

capacitor. Y5V dielectrics lose most of their

capacitance over temperature and are therefore, not

recommended.

4.2

Output Capacitor

The MIC5396/7/8/9 require an output capacitor of 1 µF

or greater to maintain stability. The design is optimized

for use with low-ESR ceramic chip capacitors.

High-ESR capacitors may cause high frequency

oscillation. The output capacitor can be increased, but

performance has been optimized for a 1 µF ceramic

output capacitor and does not improve significantly with

larger capacitance.

X7R/X5R dielectric-type ceramic capacitors are

recommended

because

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.

4.3

No-Load Stability

Unlike

many

other

voltage

regulators,

the

MIC5396/7/8/9 will remain stable and in regulation with

no load.

4.4

Enable/Shutdown

The MIC5396/7/8/9 come with two active-high enable

pins that allow each regulator to be disabled

independently. Forcing the enable pin low disables the

regulator and sends it into an off mode current state

drawing virtually zero current. When disabled, the

MIC5397 and MIC5399 switch an internal 25Ω load on

the regulator output to discharge the external capacitor.

Forcing the enable pin high enables the output voltage.

The MIC5396 and MIC5397 active-high enable pin

uses CMOS technology and cannot be left floating. A

floating enable pin may cause an indeterminate state

on the output. The MIC5398 and MIC5399 have an

internal pull-down resistor on the enable pin to disable

the output when the enable pin is floating.

4.5

Thermal Considerations

The MIC5396/7/8/9 are designed to provide two

300 mA continuous current outputs in a very small

package. Maximum operating temperature can be

calculated based on the output currents and the

voltage drop across the part. For example, if the input

voltage is 3.6V, VOUT1 = 3.3V, VOUT2 = 2.8V, each with

an output current of 300 mA. The actual power

dissipation of the regulator circuit can be determined

using Equation 4-1:

EQUATION 4-1:

Because this device is CMOS and the ground current

is typically <100 µA over the load range, the power

dissipation contributed by the ground current is <1%

and can be ignored for the calculation in Equation 4-2:

EQUATION 4-2:

To determine the maximum ambient operating

temperature

the

package,

use

the

junction-to-ambient thermal resistance of the device

and the following basic formula in Equation 4-3:

VIN VOUT1

–





IOUT1

VIN VOUT2

–





IOUT2 VIN IGND



3.6V 3.3V

–





300mA

3.6V 2.8V

–





300mA

PD 0.33W

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