TMS320DM647 datasheet(58/166 Pages) TI

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6.2 Recommended Clock and Control Signal Transition Behavior

6.3 Power Supplies

6.3.1

Power-Supply Sequencing

6.3.2

Power-Supply Design Considerations

6.3.3

Power-Supply Decoupling

6.3.4

Power and Sleep Controller (PSC)

TMS320DM647/TMS320DM648

Digital Media Processor

SPRS372 – MAY 2007

All clocks and control signals must transition between VIH and VIL (or between VIL and VIH) in a monotonic

manner.

For more information regarding TI's power management products and suggested devices to power TI

DSPs, visit www.ti.com/dsppower.

The DM647/8 includes 1.2-V core supply (CVDD, CVDDESS, CVDD1, AVDDA, DVDDD, AVDDT), and

two I/O supplies—3.3-V (DVDD33) and 1.8-V (DvDD18, AVDLL1, AVDLL2, AVDDR) To ensure proper

device operation, a specific power-up sequence must be followed. Some TI power-supply devices include

features that facilitate power sequencing—for example, Auto-Track and Slow-Start/Enable features. For

more information on TI power supplies and their features, visit www.ti.com/dsppower.

Here is a summary of the power sequencing requirements:

• The power ramp order must be 3.3-V (DVDD33) before 1.8-V (DvDD18, AVDLL1, AVDLL2, AVDDR),

and 1.8-V (DVDD18, AVDLL1, AVDLL2, AVDDR) before 1.2-V core supply (CVDD, CVDDESS,

CVDD1, AVDDA, DVDDD, AVDDT) —meaning during power up, the voltage at the 1.8-V rail should

never exceed the voltage at the 3.3-V rail. Similarly, the voltage at the 1.2-V rail should never exceed

the voltage at the DVDDR2 rail.

• From the time that power ramp begins, all power supplies (3.3 V, 1.8 V, 1.2 V) must be stable within

200 ms. The term "stable" means reaching the recommended operating condition (see Section 5.2,

Recommended Operating Conditions).

Core and I/O supply voltage regulators should be located close to the DSP to minimize inductance and

resistance in the power delivery path. Additionally, when designing for high-performance applications

utilizing the DM647/8 device, the PC board should include separate power planes for core, I/O, and

ground; all bypassed with high-quality low-ESL/ESR capacitors.

In order to properly decouple the supply planes from system noise, place as many capacitors (caps) as

possible close to the DSP. 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. Larger caps for each supply can be placed further away for bulk decoupling. Large

bulk caps (on the order of 100

F) should be furthest away, but still as close as possible. Large caps for

each supply should be placed outside of the BGA footprint.

The power and sleep controller (PSC) controls power by turning off unused power domains or by gating

off clocks to individual peripherals/modules. The DM647/DM648 devices use the clock-gating feature of

the PSC only for power savings. The PSC consists of a global PSC (GPSC) and a set of local PSCs

(LPSCs).

The GPSC contains memory mapped registers, PSC interrupt control, and a state machine for each

peripheral/module. An LPSC is associated with each peripheral/module and provides clock and reset

control. The LPSCs for DM647/DM648 are shown in Table 6-2. The PSC register memory map is given in

Table 6-3. For more details on the PSC, see the TMS320DM647/TMS320DM648 DMP DSP Subsystem

Reference Guide (Literature Number SPRUEU6).

Peripheral Information and Electrical Specifications

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