Acutechnology Semiconductor Inc.
BQ8211
The BQ8211 regulators have internal thermal shutdown to protect the device from over-
heating. Under all possible operating conditions, the junction temperature of the BQ8211
must be lower than 125°C. A heatsink may be required depending on the maximum power
dissipation and maximum ambient temperature of the application.
To determine if a heatsink is needed, the power dissipated by the regulator, P
D
, must be
calculated:
P
D
= (V
c
-V
OUT
) I
L
where the I
L
is the load current.
The next parameter, which must be calculated, is the max. allowable temperature rise, T(max):
T(max)=T
J
(max)-T
A
(max)
where T
J
(max) is the maximum allowable junction temperature (125°C), and T
A
(max) is the
maximum ambient temperature, which will be encountered in the application.
Using the calculated values for T(max) and P
D
, the maximum allowable value for the
junction to ambient thermal resistance (θ
JA
) can be calculated:
θ
JA
=T(max)/ P
D
If the maximum allowable value for
θ
JA
is found to be greater than the junction to ambient
thermal resistance for the package used, no heatsink is needed since the package alone will
dissipate enough heat to satisfy these requirements.
Contact Information
Acutechnology Semiconductor Inc.
3487 McKee Rd. Suite 52
San Jose CA , USA 95127
Disclaimer
The information furnished by Acutechnology in this data sheet is believed to be accurate and reliable. However,
Acutechnology assumes no responsibility for its use. Acutechnology reserves the right to change circuitry and specifications
at any time without notification to the customer.
TEL:
FAX:
website:
(408) 259-2300
(408) 259-9160
www.acutechnology.com
Life Support Policy
Acutechnology Products are not designed or authorized for use as components in life support devices or systems where
malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are
devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to
perform can be reasonably expected to result in a significant injury to the user.
AcuRef
is a trademark of Acutechnology Semiconductor Inc
www.acutechnology.com
8
Rev. 1.3 September 13, 2006
ACUTECH [ ACUTECHNOLOGY SEMICONDUCTOR ]
