DLPC3479 datasheet(49/61 Pages) TI1

49 / 61 page

DLPC3479

www.ti.com

DLPS112 – JUNE 2018

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Layout Guidelines (continued)

11.1.2 DLPC3479 Reference Clock

The DLPC3479 requires an external reference clock to feed its internal PLL. A crystal oscillator can supply this

reference. For flexibility, the DLPC3479 accepts either of two reference clock frequencies, but both must have a

maximum frequency variation of ±200 ppm (including aging, temperature, and trim component variation).

The two DLPC3479 devices require a single dedicated oscillator where the oscillator output drives both

DLPC3479 devices. The oscillator must drive the PLL_REFCLK_I pin on each DLPC3479. Leave the

PLL_REFCLK_O pins unconencted.

The external oscillator must be able to drive at least a 15-pF load. Routing length from the oscillator to each

DLPC3479 should be closely matched.

11.1.3 General PCB Recommendations

TI recommends 1-oz. copper planes in the PCB design to achieve needed thermal connectivity.

11.1.4 General Handling Guidelines for Unused CMOS-Type Pins

To avoid potentially damaging current caused by floating CMOS input-only pins, TI recommends that unused

ASIC input pins be tied through a pullup resistor to its associated power supply or a pulldown to ground. For

ASIC inputs with an internal pullup or pulldown resistors, it is unnecessary to add an external pullup or pulldown

unless specifically recommended. Note that internal pullup and pulldown resistors are weak and should not be

expected to drive the external line. The DLPC3479 implements very few internal resistors and these are noted in

the pin list. When external pullup or pulldown resistors are needed for pins that have built-in weak pullups or

pulldowns, use the value 8 kΩ (max).

Unused output-only pins should never be tied directly to power or ground, but can be left open.

When possible, TI recommends that unused bidirectional I/O pins be configured to their output state such that

the pin can be left open. If this control is not available and the pins may become an input, then they should be

pulled-up (or pulled-down) using an appropriate, dedicated resistor.

DLPC3479 Datasheet(PDF) 49 Page - Texas Instruments