RT9167-33GB Richtek USA Inc, RT9167-33GB Datasheet - Page 11

• Manufacturer Part Number: RT9167-33GB
• Description: IC REG LDO 3.3V 300MA SOT23-5
• Manufacturer: Richtek USA Inc

Specifications of RT9167-33GB

• Regulator Topology: Positive Fixed
• Voltage - Output: 3.3V
• Voltage - Input: Up to 7V
• Number Of Regulators: 1
• Current - Output: 300mA (Min)
• Current - Limit (min): 400mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SC-74A, SOT-753
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Dropout (typical): -

The value of junction to case thermal resistance θ
popular for users. This thermal parameter is convenient
for users to estimate the internal junction operated
temperature of packages while IC operating. It's
independent of PCB layout, the surroundings airflow effects
and temperature difference between junction to ambient.
The operated junction temperature can be calculated by
following formula :
T
Where T
thermal sensor, P
user’ s function and the θ
resistance provided by IC manufacturer. Therefore it's easy
to estimate the junction temperature by any condition.
For example, how to calculate the junction temperature
of RT9167A-28CB SOT-23-5 package. If we use input
voltage V
the case temperature (pin 4 of SOT-23-5 package)
T
then our power dissipation is as follows :
P
And the junction temperature T
following :
T
T
For this operation application, T
maximum operation junction temperature 125°C and it’s
safe to use.
DS9167/A-28
J
C
J
J
D
= 102.5°C < T
= T
= 70°C + 32.5°C
= T
= 70°C + 0.25W x 130°C/W
= 70°C measured by thermal couple while operating,
= (3.3V − 2.8V) x 500mA + 3.3V x 90μA ≅ 250mW
C
C
+ P
+ P
C
IN
is the package case temperature measured by
D
D
= 3.3V at an output current I
x θ
x θ
September 2010
JC
JC
J(MAX)
D
is the power dissipation defined by
=125°C
JC
is the junction to case thermal
J
J
could be calculated as
is lower than absolute
O
= 500mA and
JC
is
RT9167/A
www.richtek.com
11