MIC5320-SOYMT 查看數據表（PDF） - Micrel

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MIC5320-SOYMT

High-Performance Dual 150mA µCap ULDO™

Micrel 

Micrel, Inc.

Applications Information

Enable/Shutdown

The MIC5320 comes with dual active-high enable pins

that allow each regulator to be disabled

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 MIC5320 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 MIC5320 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 be 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 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.

No-Load Stability

Unlike many other voltage regulators, the MIC5320

will remain stable and in regulation with no load. This

is especially important in CMOS RAM keep-alive

applications.

MIC5320

Thermal Considerations

The MIC5320 is designed to provide 150mA 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,

1.5V for VOUT2 and the output current = 150mA. 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 <150µA 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) × 150mA + (3.3V -1.5) ×

150mA

PD = 0.345W

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:

⎛ TJ(MAX) - TA

⎝ PD(MAX) =

JA

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

the die θJA thermal resistance = 100°C/W.

The table below shows junction-to-ambient thermal

resistance for the MIC5320 in different packages.

Package

6-Pin 1.6x1.6 Thin MLF®

θJA Recommended

Minimum Footprint

100°C/W

Thermal Resistance

θJC

2°C/W

February 2011

10

M9999-021111-H

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