TMS320TCI6487
TMS320TCI6488
Communications Infrastructure Digital Signal Processor
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SPRS358F–APRIL 2007–REVISED AUGUST 2008
8.2 Recommended Clock and Control Signal Transition Behavior
All clocks and control signals must transition between VIH and VIL (or between VIL and VIH) in a monotonic
manner.
8.3 Power Supplies
8.3.1 Power-Supply Sequencing
Power supply sequencing must be followed as seen in Figure 8-4.
Table 8-1. Timing Requirements for Power Supply Ramping
(see Figure 8-4)
NO.
PARAMETERS
MIN
MAX UNIT
3
tsu(DVDD18-DVDD11)
th(DVDD11-POR)
Setup Time, DVDD18 and VREFSSTL supply stable before
DVDD11 and CVDD11 supplies stable.
0.5
200
ms
4
Hold time, POR low after CVDD11 and DVDD11 supplies stable
100
µs
DVDD18
VREFSSTL (DDR2)
3
CVDD11
DVDD11
4
PORz
Figure 8-4. Power-Supply Timing
8.3.2 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. 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.
8.3.3 Power-Down Operation
One of the power goals for the TCI6487/8 is to reduce power dissipation due to unused peripherals. There
are different ways to power down peripherals on the TCI6487/8 device.
Some peripherals can be statically powered down at device reset through the device configuration pins
(see Section 3.1, Device Configuration at Device Reset). Once in a static power-down state, the peripheral
is held in reset and its clock is turned off. Peripherals cannot be enabled once they are in a static
power-down state. To take a peripheral out of the static power-down state, a device reset must be
executed with a different configuration pin setting.
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Peripheral Information and Electrical Specifications
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