
Data Sheet
March 2000
DSP1627 Digital Signal Processor
Lucent Technologies Inc.
69
8 Device Characteristics
(continued)
8.4 Package Thermal Considerations
The recommended operating temperature specified above is based on the maximum power, package type, and
maximum junction temperature. The following equations describe the relationship between these parameters. If the
applications' maximum power is less than the worst-case value, this relationship determines a higher maximum am-
bient temperature or the maximum temperature measured at top dead center of the package.
T
A
= T
J
– P x
Θ
JA
T
TDC
= T
J
– P x
Θ
J-TDC
where T
A
is the still-air ambient temperature and T
TDC
is the temperature measured by a thermocouple at the top
dead center of the package.
Maximum Junction Temperature (T
J
) in 100-Pin BQFP................................................................................. 125
°
C
100-pin BQFP Maximum Thermal Resistance in Still-Air-Ambient (
Θ
JA
).....................................................55
°
C/W
100-pin BQFP Maximum Thermal Resistance, Junction to Top Dead Center (
Θ
J-TDC
)...............................12
°
C/W
Maximum Junction Temperature (T
J
) in 100-Pin TQFP................................................................................. 125
°
C
100-pin TQFP Maximum Thermal Resistance in Still-Air-Ambient (
Θ
JA
) .....................................................30
°
C/W
100-pin TQFP Maximum Thermal Resistance, Junction to Top Dead Center (
Θ
J-TDC
).................................6
°
C/W
WARNING: Due to package thermal constraints, proper precautions in the user's application should be tak-
en to avoid exceeding the maximum junction temperature of 125
°
C. Otherwise, the device will
be affected adversely.