MIC5330-2.7SLASH2.7YML datasheet(8/10 Pages) MICREL

8 / 10 page

Micrel, Inc.

MIC5330

March 2011

M9999-032311-

Applications Information

Enable/Shutdown

The MIC5330 comes with dual active high enable pins

that allow each regulator to be enabled independently.

Forcing the enable pin low disables the regulator and

sends it into a “zero” off mode current state. In this

state, current consumed by the regulator goes nearly

to zero. Forcing the enable pin high enables the

output voltage. The active high enable pin uses

CMOS technology and the enable pin cannot be left

floating; a floating enable pin may cause an

indeterminate state on the output.

Input Capacitor

The MIC5330 is a high performance, high bandwidth

device. Therefore, it requires a well bypassed input

supply for optimal performance. A 1µF 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.

Output Capacitor

The MIC5330 requires an output capacitor of 1µF 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

increased,

but

performance has been optimized for a 1µF 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.

Bypass Capacitor

A capacitor can be placed from the noise bypass pin

to ground to reduce output voltage noise. The

capacitor bypasses the internal reference. A 0.1µF

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. A unique, quick start circuit

allows the MIC5330 to drive a large capacitor on the

bypass pin without significantly slowing turn on time.

No-Load Stability

Unlike many other voltage regulators, the MIC5330

will remain stable and in regulation with no load. This

is especially important in CMOS RAM keep alive

applications.

Thermal Considerations

The MIC5330 is designed to provide 300mA of

continuous current for both outputs in a very small

package. Maximum ambient operating temperature

can be calculated based on the output current and the

voltage drop across the part. Given that the input

voltage is 3.3V, the output voltage is 2.8V for VOUT1,

2.5V for VOUT2 and the output current = 300mA. The

actual power dissipation of the regulator circuit can be

determined using the equation:

PD = (VIN – VOUT1) IOUT1 + (VIN – VOUT2) IOUT2+ VIN IGND

Because this device is CMOS and the ground current

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

dissipation contributed by the ground current is < 1%

and can be ignored for this calculation.

PD = (3.3V – 2.8V) × 300mA + (3.3V -1.5) × 300mA

PD = 0.69W

To determine the maximum ambient operating

temperature of the package, use the junction-to-

ambient thermal resistance of the device and the

following basic equation:

PD(MAX) =

TJ(MAX) - TA

⎝

⎛

TJ(max) = 125°C, the maximum junction temperature of

the die θJA thermal resistance = 90°C/W.

The table below shows junction-to-ambient thermal

resistance for the MIC5330 in the MLF package.

Package

θJA Recommended

Minimum Footprint

8-Pin 2x2 MLF

90°C/W

Thermal Resistance

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