SMJ320C6414 Datasheet, PDF (73/133 Pages) Texas Instruments – FIXED-POINT DIGITAL SIGNAL PROCESSORS

SMJ320C6414, SMJ320C6415, SMJ320C6416
FIXEDĆPOINT DIGITAL SIGNAL PROCESSORS
SGUS050A − JANUARY 2004 − REVISED MARCH 2004
C64x power-down mode with an emulator
If user power-down modes are programmed, and an emulator is attached, the modes will be masked to allow
the emulator access to the system. This condition prevails until the emulator is reset or the cable is removed
from the header. If power measurements are to be performed when in a power-down mode, the emulator cable
should be removed.
When the DSP is in power-down mode PD2 or PD3, emulation logic will force any emulation execution
command (such as Step or Run) to spin in IDLE. For this reason, PC writes (such as loading code) will fail. A DSP
reset will be required to get the DSP out of PD2/PD3.
power-supply sequencing
TI DSPs do not require specific power sequencing between the core supply and the I/O supply. However,
systems should be designed to ensure that neither supply is powered up for extended periods of time
(>1 second) if the other supply is below the proper operating voltage.
power-supply design considerations
A dual-power supply with simultaneous sequencing can be used to eliminate the delay between core and I/O
power up. A Schottky diode can also be used to tie the core rail to the I/O rail (see Figure 10).
I/O Supply
Core Supply
Schottky
Diode
DVDD
C6000
DSP
CVDD
VSS
GND
Figure 10. Schottky Diode Diagram
Core and I/O supply voltage regulators should be located close to the DSP (or DSP array) to minimize
inductance and resistance in the power delivery path. Additionally, when designing for high-performance
applications utilizing the C6000 platform of DSPs, the PC board should include separate power planes for
core, I/O, and ground, all bypassed with high-quality low-ESL/ESR capacitors.
power-supply decoupling
In order to properly decouple the supply planes from system noise, place as many capacitors (caps) as possible
close to the DSP. Assuming 0603 caps, the user should be able to fit a total of 60 caps, 30 for the core supply
and 30 for the I/O supply. These caps need to be close to the DSP, no more than 1.25 cm maximum distance
to be effective. Physically smaller caps are better, such as 0402, but need to be evaluated from a
yield/manufacturing point-of-view. Parasitic inductance limits the effectiveness of the decoupling capacitors,
therefore physically smaller capacitors should be used while maintaining the largest available capacitance
value. As with the selection of any component, verification of capacitor availability over the product’s production
lifetime should be considered.
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