adsp-21478 Analog Devices, Inc., adsp-21478 Datasheet - Page 62

• Manufacturer Part Number: adsp-21478
• Description: Sharc Processor
• Manufacturer: Analog Devices, Inc.

ADSP-21478/ADSP-21479
THERMAL CHARACTERISTICS
The ADSP-2147x processor is rated for performance over the
temperature range specified in
Page
Table 50
JESD51-2 and JESD51-6 and the junction-to-board measure-
ment complies with JESD51-8. Test board design complies with
JEDEC standards JESD51-7 (PBGA). The junction-to-case mea-
surement complies with MIL- STD-883. All measurements use a
2S2P JEDEC test board.
To determine the junction temperature of the device while on
the application PCB, use:
where:
T
T
package
Ψ
is the Typical value from
P
Values of θ
design considerations. θ
mation of T
where:
T
Values of θ
design considerations when an external heatsink is required.
D
J
CASE
A
JT
= junction temperature °C
12
10
= power dissipation
= ambient temperature °C
8
4
6
2
0
= junction-to-top (of package) characterization parameter
19.
0
Figure 54. Typical Output Delay or Hold vs. Load Capacitance
= case temperature (°C) measured at the top center of the
airflow measurements comply with JEDEC standards
JA
JC
J
by the equation:
are provided for package comparison and PCB
are provided for package comparison and PCB
50
T
J
T
(at Ambient Temperature)
=
J
TBD
100
JA
=
T
Table
CASE
can be used for a first order approxi-
T
A
+
Operating Conditions on
+
50.
(
θ
150
(
JA
Ψ
JT
×
P
×
D
P
)
D
200
)
Rev. PrB | Page 62 of 70 | March 2010
250
Values of θ
design considerations. Note that the thermal characteristics val-
ues provided in
Table 50. Thermal Characteristics for 100-Lead LQFP_EP
Table 51. Thermal Characteristics for 196-Ball CSP_BGA
Thermal Diode
The ADSP-21476x processors incorporate thermal diode/s to
monitor the die temperature. The thermal diode of is a
grounded collector, PNP Bipolar Junction Transistor (BJT). The
THD_P pin is connected to the emitter and the THD_M pin is
connected to the base of the transistor. These pins can be used
by an external temperature sensor (such as ADM 1021A or
LM86 or others) to read the die temperature of the chip.
The technique used by the external temperature sensor is to
measure the change in VBE when the thermal diode is operated
at two different currents. This is shown in the following
equation:
where:
n = multiplication factor close to 1, depending on process
variations
k = Boltzmann’s constant
T = temperature (°C)
q = charge of the electron
N = ratio of the two currents
The two currents are usually in the range of 10 micro Amperes
to 300 micro Amperes for the common temperature sensor
chips available.
Parameter
θ
θ
θ
θ
Ψ
Ψ
Ψ
Parameter
θ
θ
θ
θ
Ψ
Ψ
Ψ
JA
JMA
JMA
JC
JA
JMA
JMA
JC
JT
JMT
JMT
JT
JMT
JMT
Preliminary Technical Data
JB
ΔV
are provided for package comparison and PCB
BE
Table 50
Condition
Airflow = 0 m/s
Airflow = 1 m/s
Airflow = 2 m/s
Airflow = 0 m/s
Airflow = 1 m/s
Airflow = 2 m/s
Condition
Airflow = 0 m/s
Airflow = 1 m/s
Airflow = 2 m/s
Airflow = 0 m/s
Airflow = 1 m/s
Airflow = 2 m/s
=
n
×
kT
----- -
q
are modeled values.
×
In(N)
Typical
TBD
TBD
TBD
TBD
TBD
TBD
TBD
Typical
TBD
TBD
TBD
TBD
TBD
TBD
TBD
Unit
°C/W
°C/W
°C/W
°C/W
°C/W
°C/W
°C/W
Unit
°C/W
°C/W
°C/W
°C/W
°C/W
°C/W
°C/W