TMS320C6711 datasheet(60/129 Pages) TI

60 / 129 page

TMS320C6711, TMS320C6711B, TMS320C6711C, TMS320C6711D

FLOATING-POINT DIGITAL SIGNAL PROCESSORS

SPRS088L − FEBRUARY 1999 − REVISED MAY 2004

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251−1443

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 15).

DVDD

CVDD

VSS

C6000

DSP

Schottky

Diode

I/O Supply

Core Supply

GND

Figure 15. 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.

C6711/11B device applicable only

On systems using C62x and C67x DSPs, like the C6711/C6711B device, the core may consume in excess of

2 A per DSP until the I/O supply powers on. This extra current results from uninitialized logic within the DSP(s).

A normal current state returns once the I/O power supply turns on and the CPU sees a clock pulse. Decreasing

the amount of time between the core supply power-up and the I/O supply power-up reduces the effects of the

current draw. If the external supply to the DSP core cannot supply the excess current, the minimum core voltage

may not be achieved until after normal current returns. This voltage starvation of the core supply during power

up will not affect run-time operation. Voltage starvation can affect power supply systems that gate the I/O supply

via the core supply, causing the I/O supply to never turn on. During the transition from excess to normal current,

a voltage spike may be seen on the core supply. Care must be taken when designing overvoltage protection

circuitry on the core supply to not restart the power sequence due to this spike. Otherwise, the supply may cycle

indefinitely.

TMS320C6711 Datasheet(PDF) 60 Page - Texas Instruments