MC56F8347 Freescale Semiconductor, Inc, MC56F8347 Datasheet - Page 168

• Manufacturer Part Number: MC56F8347
• Description: 56f8300 16-bit Digital Signal Controllers
• Manufacturer: Freescale Semiconductor, Inc

The thermal characterization parameter is measured per JESD51-2 specification using a 40-gauge type T
thermocouple epoxied to the top center of the package case. The thermocouple should be positioned so
that the thermocouple junction rests on the package. A small amount of epoxy is placed over the
thermocouple junction and over about 1mm of wire extending from the junction. The thermocouple wire
is placed flat against the package case to avoid measurement errors caused by cooling effects of the
thermocouple wire.
When heat sink is used, the junction temperature is determined from a thermocouple inserted at the
interface between the case of the package and the interface material. A clearance slot or hole is normally
required in the heat sink. Minimizing the size of the clearance is important to minimize the change in
thermal performance caused by removing part of the thermal interface to the heat sink. Because of the
experimental difficulties with this technique, many engineers measure the heat sink temperature and then
back-calculate the case temperature using a separate measurement of the thermal resistance of the
interface. From this case temperature, the junction temperature is determined from the junction-to-case
thermal resistance.
12.2 Electrical Design Considerations
Use the following list of considerations to assure correct device operation:
168
•
•
•
•
•
Provide a low-impedance path from the board power supply to each V
board ground to each V
The minimum bypass requirement is to place six 0.01–0.1μF capacitors positioned as close as possible to
the package supply pins. The recommended bypass configuration is to place one bypass capacitor on each
of the V
performance tolerances.
Ensure that capacitor leads and associated printed circuit traces that connect to the chip V
pins are less than 0.5 inch per capacitor lead
Use at least a four-layer Printed Circuit Board (PCB) with two inner layers for V
Bypass the V
capacitor such as a tantalum capacitor
DD
/V
DD
SS
This device contains protective circuitry to guard
against damage due to high static voltage or electrical
fields. However, normal precautions are advised to
avoid
maximum-rated voltages to this high-impedance circuit.
Reliability of operation is enhanced if unused inputs are
tied to an appropriate voltage level.
pairs, including V
and V
SS
SS
application
layers of the PCB with approximately 100μF, preferably with a high-grade
(GND) pin
56F8347 Technical Data, Rev.11
DDA
/V
of
SSA.
CAUTION
Ceramic and tantalum capacitors tend to provide better
any
voltages
higher
DD
pin on the device, and from the
than
DD
Freescale Semiconductor
and V
DD
SS
and V
Preliminary
SS
(GND)