MIC5219 Micrel Semiconductor, MIC5219 Datasheet - Page 11

• Manufacturer Part Number: MIC5219
• Description: 500mA-Peak Output LDO Regulator
• Manufacturer: Micrel Semiconductor

The power dissipation at 500mA must also be calculated.
This number must be multiplied by the duty cycle at which it
would be operating, 12.5%.
The total power dissipation of the device under these condi-
tions is the sum of the two power dissipation figures.
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 there-
fore 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 Micrel
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
Figure 5 shows a basic MIC5219-x.xBMX fixed-voltage regu-
lator circuit. A 1 F minimum output capacitor is required for
basic fixed-voltage applications.
July 2000
MIC5219
Figure 5. Low-Noise Fixed Voltage Regulator
P
P
P
P
P
P
P
P
P
D
D
D
D
D
D
D(total)
D(total)
D(total)
50mA = 0.875
50mA = 151mW
500mA = (5V – 3.3V) 500mA + 5V
500mA = 950mW
= 0.125
= 119mW
= P
= 151mW + 119mW
= 270mW
V
IN
D
50mA + P
950mW
MIC5219-x.x
IN
EN
GND
173mW
OUT
BYP
D
500mA
1µF
V
OUT
20mA
11
Figure 6 includes the optional 470pF noise bypass capacitor
between BYP and GND to reduce output noise. Note that the
minimum value of C
capacitor is used.
Adjustable Regulator Circuits
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:
Although ADJ is a high-impedance input, for best perfor-
mance, R2 should not exceed 470k .
Figure 8 includes the optional 470pF bypass capacitor from
ADJ to GND to reduce output noise.
Figure 6. Ultra-Low-Noise Fixed Voltage Regulator
Figure 7. Low-Noise Adjustable Voltage Regulator
Figure 8. Ultra-Low-Noise Adjustable Application.
V
OUT
V
IN
V
V
IN
1.242V
IN
IN
EN
IN
EN
MIC5219
OUT
MIC5219-x.x
IN
EN
GND
MIC5219
R2
GND
R1
must be increased when the bypass
GND
OUT
ADJ
OUT
ADJ
470pF
1
OUT
BYP
470pF
R1
R2
R1
R2
2.2µF
V
1µF
OUT
V
2.2µF
V
OUT
OUT
MIC5219
Micrel