TNETV1644ZDU6 datasheet(163/306 Pages) TI1

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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

TMS320DM6437

Digital Media Processor

www.ti.com

SPRS345D – NOVEMBER 2006 – REVISED JUNE 2008

TI recommends utilizing the available I/O buffer information specification (IBIS) models to analyze the

timing characteristics correctly. To properly use IBIS models to attain accurate timing analysis for a given

system, see the Using IBIS Models for Timing Analysis application report (literature number SPRA839). If

needed, external logic hardware such as buffers may be used to compensate any timing differences.

For the DDR2 memory controller interface, it is not necessary to use the IBIS models to analyze timing

characteristics. TI provides a PCB routing rules solution that describes the routing rules to ensure the

DDR2 memory controller interface timings are met. See the Implementing DDR2 PCB Layout on the

TMS320DM643x DMP DMSoC Application Report (literature number SPRAAL6).

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 DM6437 includes one core supply (CVDD), and two I/O supplies—DVDD33 and DVDDR2. 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 DV

DD33 before DVDDR2, and DVDDR2 before CVDD—meaning during

power up, the voltage at the DVDDR2 rail should never exceed the voltage at the DVDD33 rail. Similarly,

the voltage at the CVDD rail should never exceed the voltage at the DVDDR2 rail.

• From the time that power ramp begins, all power supplies (DV

DD33, DVDDR2, CVDD) must be stable

within 200 ms. The term "stable" means reaching the recommended operating condition (see

Section 5.2, Recommended Operating Conditions table).

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 DM6437 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

µF) should be furthest away, but still as close as possible. Large caps for each supply should be

placed outside of the BGA footprint.

As with the selection of any component, verification of capacitor availability over the product's production

lifetime should be considered.

For more details on capacitor usage and placement, see the Implementing DDR2 PCB Layout on the

TMS320DM643x DMP DMSoC Application Report (literature number SPRAAL6).

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