MIC5219 Просмотр технического описания (PDF) - Micrel

Номер в каталоге

Компоненты Описание

Список матч

MIC5219

500mA-Peak Output LDO Regulator

Micrel 

Micrel, Inc.

PD × 50mA = 0.875 × 173mW

PD × 50mA = 151mW

The power dissipation at 500mA must also be calculated.

PD × 500mA = (5V – 3.3V) 500mA + 5V × 20mA

PD × 500mA = 950mW

This number must be multiplied by the duty cycle at which it

would be operating, 12.5%.

PD × = 0.125 × 950mW

PD × = 119mW

The total power dissipation of the device under these condi-

tions is the sum of the two power dissipation figures.

PD(total) = PD × 50mA + PD × 500mA

PD(total) = 151mW + 119mW

PD(total) = 270mW

The total power dissipation of the regulator is less than the

maximum power dissipation of the SOT-23-5 package at room

temperature, on a minimum footprint board and therefore

would operate properly.

Multilayer boards with a ground plane, wide traces near the

pads, and large supply-bus lines will have better thermal

conductivity.

For additional heat sink characteristics, please refer to Mi-

crel “Application Hint 17, Designing P.C. Board Heat Sinks”,

included in Micrel’s Databook. For a full discussion of heat

sinking and thermal effects on voltage regulators, refer to

“Regulator Thermals” section of Micrel’s Designing with Low-

Dropout Voltage Regulators handbook.

Fixed Regulator Circuits

VIN

MIC5219-x.x

IN OUT

VO U T

EN BYP

GND

1µF

Figure 5.  Low-Noise Fixed Voltage Regulator

Figure 5 shows a basic MIC5219‑x.xBMX fixed-voltage regu-

lator circuit. A 1µF minimum output capacitor is required for

basic fixed-voltage applications.

MIC5219

VIN

MIC5219-x.x

IN OUT

VO U T

EN BYP

GND

2.2µF

470pF

Figure 6.  Ultra-Low-Noise Fixed Voltage Regulator

Figure 6 includes the optional 470pF noise bypass capacitor

between BYP and GND to reduce output noise. Note that the

minimum value of COUT must be increased when the bypass

capacitor is used.

Adjustable Regulator Circuits

VIN

MIC5219

IN OUT

VO U T

EN ADJ R1

GND

1µF

R2

Figure 7.  Low-Noise Adjustable Voltage Regulator

Figure 7 shows the basic circuit for the MIC5219 adjustable

regulator. The output voltage is configured by selecting values

for R1 and R2 using the following formula:

VOUT

= 1.242V



R2

R1

+ 1

Although ADJ is a high-impedance input, for best performance,

R2 should not exceed 470kΩ.

VIN

MIC5219

IN OUT

VO U T

EN ADJ

GND

R1

2.2µF

R2

470pF

Figure 8.  Ultra-Low-Noise Adjustable Application

Figure 8 includes the optional 470pF bypass capacitor from

ADJ to GND to reduce output noise.

June 2009

12

M0371-061809

Share Link: