AM3874 datasheet(178/361 Pages) TI

178 / 361 page

3.3 V Supplies

(DVDD, DVDD_x, DVDD_C, VDDA_x_3P3)

1.8 V Supplies

(DVDD, DVDD_x, DVDD_M, VDDA_x_1P8,

VDDA_1P8

AM3874, AM3871

SPRS695C – SEPTEMBER 2011 – REVISED DECEMBER 2013

www.ti.com

Figure 7-2. Power-Down Sequence

Figure 7-3. 1.8 V Supplies Falling Before 3.3 V Supplies Delta

7.2.9

Power-Supply Decoupling

7.2.9.1

Analog and PLL

PLL and Analog supplies benefit from filters or ferrite beads to keep the noise from causing problems. The

minimum recommendation is a ferrite bead along with at least one capacitor on the device side of the

bead. An additional recommendation is to add one capacitor just before the bead to form a Pi filter. The

filter needs to be as close as possible to the device pin, with the device side capacitor being the most

important component to be close to the device pin. PLL pins close together can be combined on the same

supply, but analog pins should all have their own filters. PLL pins farther away from each other may need

their own filtered supply.

7.2.9.2

Digital

Recommended capacitors for power supply decoupling are all 0.1uF in the smallest body size that can be

used. Capacitors are more effective in the smallest physical size to limit lead inductance. For example,

0201 sized capacitors are better than 0402 sized capacitors, and so on. TI recommends using capacitors

no larger than 0402. Place at least one capacitor for every two power pins. For those power pins that have

only one pin, a capacitor is still required. Place one bulk (10 uF or larger) capacitor for every 10 or so

power pins as closely as possible to the chip. These larger caps do not need to be under the chip

footprint.

178

Power, Reset, Clocking, and Interrupts

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AM3874 Datasheet(PDF) 178 Page - Texas Instruments