MIC3775 Micrel Semiconductor, MIC3775 Datasheet - Page 12

• Manufacturer Part Number: MIC3775
• Description: 750mA UCap Low-Voltage Low-Dropout Regulator
• Manufacturer: Micrel Semiconductor

MIC3775
For example, the maximum ambient temperature is 50 C, the
Using Figure 4, the minimum amount of required copper can
be determined based on the required power dissipation.
Power dissipation in a linear regulator is calculated as fol-
lows:
If we use a 2.5V output device and a 3.3V input at an output
current of 750mA, then our power dissipation is as follows:
From Figure 4, the minimum amount of copper required to
operate this application at a T of 75 C is 160mm
MIC3775
T is determined as follows:
T
T
P
P
P
P
T = T
J(max)
A(max)
T = 125 C – 50 C
T = 75 C
D
D
D
D
= (V
= (3.3V – 2.5V)
= 600mW + 25mW
= 625mW
J(max)
= 125 C
IN
= maximum ambient operating temperature
– V
– T
OUT
A(max)
) I
OUT
750mA + 3.3V
+ V
IN
I
GND
7.5mA
2
.
12
Quick Method
Determine the power dissipation requirements for the design
along with the maximum ambient temperature at which the
device will be operated. Refer to Figure 5, which shows safe
operating curves for three different ambient temperatures:
25 C, 50 C and 85 C. From these curves, the minimum
amount of copper can be determined by knowing the maxi-
mum power dissipation required. If the maximum ambient
temperature is 50 C and the power dissipation is as above,
625mW, the curve in Figure 5 shows that the required area of
copper is 160mm
The
depending upon the availability of copper ground plane to
which it is attached.
JA
of this package is ideally 80 C/W, but it will vary
2
.
March 2003
Micrel