DSP56364D Motorola Inc, DSP56364D Datasheet - Page 92

• Manufacturer Part Number: DSP56364D
• Description: 24-Bit Audio Digital Signal Processor
• Manufacturer: Motorola Inc

Design Considerations
Electrical Design Considerations
As noted above, the junction-to-case thermal resistances quoted in this data sheet are determined using
the first definition. From a practical standpoint, that value is also suitable for determining the junction
temperature from a case thermocouple reading in forced convection environments. In natural convection,
using the junction-to-case thermal resistance to estimate junction temperature from a thermocouple
reading on the case of the package will estimate a junction temperature slightly hotter than actual
temperature. Hence, the new thermal metric, thermal characterization parameter or
to be (T
when using the surface temperature of the package. Remember that surface temperature readings of
packages are subject to significant errors caused by inadequate attachment of the sensor to the surface
and to errors caused by heat loss to the sensor. The recommended technique is to attach a 40-gauge
thermocouple wire and bead to the top center of the package with thermally conductive epoxy.
4.2
Use the following list of recommendations to assure correct DSP operation:
4-2
•
•
•
•
•
•
J
Provide a low-impedance path from the board power supply to each V
the board ground to each GND pin.
Use at least six 0.01–0.1 F bypass capacitors positioned as close as possible to the four sides of
the package to connect the V
Ensure that capacitor leads and associated printed circuit traces that connect to the chip V
GND pins are less than 1.2 cm (0.5 inch) per capacitor lead.
Use at least a four-layer PCB with two inner layers for V
Because the DSP output signals have fast rise and fall times, PCB trace lengths should be minimal.
This recommendation particularly applies to the address and data buses as well as the IRQA, IRQB,
IRQD, and TA pins. Maximum PCB trace lengths on the order of 15 cm (6 inches) are
recommended.
Consider all device loads as well as parasitic capacitance due to PCB traces when calculating
capacitance. This is especially critical in systems with higher capacitive loads that could create
higher transient currents in the V
– T
ELECTRICAL DESIGN CONSIDERATIONS
T
)/P
D
. This value gives a better estimate of the junction temperature in natural convection
This device contains circuitry protecting
against damage due to high static voltage or
electrical fields. However, normal precautions
should be taken to avoid exceeding maximum
voltage ratings. Reliability of operation is
enhanced if unused inputs are tied to an
appropriate logic voltage level (e.g., either
GND or V
pullup or pulldown resistor is 10 k ohm.
Freescale Semiconductor, Inc.
For More Information On This Product,
DSP56364 Advance Information
CC
CC
Go to: www.freescale.com
power source to GND.
CC
). The suggested value for a
and GND circuits.
CAUTION
CC
and GND.
CC
pin on the DSP and from
JT
, has been defined
MOTOROLA
CC
and