MIC37100-1.5BM MICREL [Micrel Semiconductor], MIC37100-1.5BM Datasheet - Page 13

• Manufacturer Part Number: MIC37100-1.5BM
• Description: 1A LOW VOLTAGE U CAP LDO REGULATOR
• Manufacturer: MICREL [Micrel Semiconductor]

Figure 4 shows copper area versus power dissipation with
each trace corresponding to a different temperature rise
above ambient.
From these curves, the minimum area of copper necessary
for the part to operate safely can be determined. The maxi-
mum allowable temperature rise must be calculated to deter-
mine operation along which curve.
For example, the maximum ambient temperature is 50 C, the
September 2004
MIC37100/37101/37102
T is determined as follows:
T
T
T = T
J
A
T = 125 C – 50 C
T = 75 C
(max) = 125 C
(max) = maximum ambient operating temperature
Figure 4. Copper Area vs. Power SO-8
J
(max) – T
900
800
700
600
500
400
300
200
100
0
0
Power Dissipation
T
0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
JA
A
(max)
=
13
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 1A, 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
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,
836mW, 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.
P
P
P
P
JA
D
D
D
D
Figure 5. Copper Area vs. Power-SOIC
of this package is ideally 63 C/W, but it will vary
= (V
= (3.3V – 2.5V)
= 800mW + 36mW
= 836mW
IN
– V
900
800
700
600
500
400
300
200
100
2
0
.
0
OUT
Power Dissipation
T
0.25 0.50 0.75 1.00 1.25 1.50
J
POWER DISSIPATION (W)
T
) I
A
= 125 C
= 85 C
OUT
1A + 3.3V
+ V
IN
50 C 25 C
I
GND
11mA
M9999-091604
2
.
Micrel