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TMS320C6713B Floating-Point Digital Signal Processor (Rev. A)

TMS320C6713B Floating-Point Digital Signal Processor (Rev. A)

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SPRS294A − OCTOBER 2005 − REVISED NOVEMBER 2005<br />

power-supply design considerations<br />

A dual-power supply with simultaneous sequencing can be used to eliminate the delay between core and I/O<br />

power up. A Schottky diode can also be used to tie the core rail to the I/O rail (see Figure 22).<br />

I/O Supply<br />

DVDD<br />

Core Supply<br />

Schottky<br />

Diode<br />

C6000<br />

DSP<br />

CVDD<br />

VSS<br />

GND<br />

Figure 22. Schottky Diode Diagram<br />

Core and I/O supply voltage regulators should be located close to the DSP (or DSP array) to minimize<br />

inductance and resistance in the power delivery path. Additionally, when designing for high-performance<br />

applications utilizing the C6000 platform of DSPs, the PC board should include separate power planes for<br />

core, I/O, and ground, all bypassed with high-quality low-ESL/ESR capacitors.<br />

power-supply decoupling<br />

In order to properly decouple the supply planes from system noise, place as many capacitors (caps) as possible<br />

close to the DSP. Assuming 0603 caps, the user should be able to fit a total of 60 caps — 30 for the core supply<br />

and 30 for the I/O supply. These caps need to be close (no more than 1.25 cm maximum distance) to the DSP<br />

to be effective. Physically smaller caps are better, such as 0402, but the size needs to be evaluated from a<br />

yield/manufacturing point-of-view. Parasitic inductance limits the effectiveness of the decoupling capacitors,<br />

therefore physically smaller capacitors should be used while maintaining the largest available capacitance<br />

value. As with the selection of any component, verification of capacitor availability over the product’s production<br />

lifetime needs to be considered.<br />

94 POST OFFICE BOX 1443 • HOUSTON, TEXAS 77251−1443

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