MIC5312-DKBML TR Micrel Inc, MIC5312-DKBML TR Datasheet - Page 10

• Manufacturer Part Number: MIC5312-DKBML TR
• Description: Portable Power IC In 3mm X 3mm MLFT LowQT Dual `Cap LDO W/Integrated POR In 3mm X 3mm MLFT
• Manufacturer: Micrel Inc

Specifications of MIC5312-DKBML TR

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.85V, 2.6V
• Voltage - Input: 2.5 ~ 5.5 V
• Voltage - Dropout (typical): 0.12V @ 300mA
• Number Of Regulators: 2
• Current - Output: 300mA
• Current - Limit (min): 350mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-MLF®, QFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: MIC5312-DKBMLTR; MIC5312-DKBMLTR

February 2005
The actual power dissipation of the regulator circuit can
be determined using the equation:
Substituting P
conditions that are critical to the application will give the
maximum operating conditions for the regulator circuit.
For example, when operating the MIC5312 at 60°C with
a minimum footprint layout, the maximum load currents
can be calculated as follows:
The junction-to-ambient thermal resistance for the
minimum footprint is 63°C/W, from Table 1. The
maximum power dissipation must not be exceeded for
proper operation. Using a lithium-ion battery as the
supply voltage of 4.2V, 1.8V
and 2.8V
can be calculated as follows:
OUT
/100mA for channel 2, power dissipation
D(max)
P
P
P
P
P
P
P
P
P
DTOTAL
D LDO1
D LDO2
D
D
D
D LDO1
D LDO1
D LDO1
(max) = (T
(max) = (125°C - 60°C) / 63°C /W
(max) = 1.03W
for P
= (V
= (V
= (V
= (4.2V-1.8V) x 150mA
= 360mW
= P
D
and solving for the operating
D LDO1
IN
IN
IN
-V
-V
-V
J
OUT
(max) - T
OUT1
OUT2
OUT1
/150mA for channel 1
+ P
) x I
) x I
) x I
D LDO2
OUT1
OUT2
OUT1
A
) / θ
JA
10
The calculation shows that we are well below the
maximum allowable power dissipation of 1.03W for a
60° ambient temperature.
After the maximum power dissipation has been
calculated, it is always a good idea to calculate the
maximum ambient temperature for a 125° junction
temperature. Calculating maximum ambient temperature
as follows:
For a full discussion of heat sinking and thermal effects
on voltage regulators, refer to the “Regulator Thermals”
section of Micrel’s Designing with Low-Dropout Voltage
Regulators handbook.
This information can be found on Micrel's website at:
http://www.micrel.com/_PDF/other/LDOBk_ds.pdf
P
P
P
P
P
P
T
T
T
A(max)
A(max)
A(max)
D LDO2
D LDO1
D LDO1
DTOTAL
DTOTAL
DTOTAL
= T
= 125°C – (500mW x 63°C/W)
= 93.5°C
= (V
= (4.2V-2.8V) x 100mA
= 140mW
= P
= 360mW + 140mW
= 500mW
J(max)
D LDO1
IN
-V
– (P
OUT2
+ P
D
) x I
x θ
D LDO2
OUT2
JA
)
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