CS7654 datasheet(54/62 Pages) CIRRUS

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CS7654

by an unused connector. The analog outputs should

not overlay the analog power plane to maximize

high frequency power supply rejection.

Analog Output Protection

To minimize the possibility of damage to the ana-

log output sections, make sure that all video con-

nectors are well grounded. The connector should

have a good DC ground path to the analog and dig-

ital power supply grounds. If no DC (and low fre-

quency) path is present, improperly grounded

equipment can impose damaging reverse currents

on the video out lines. Therefore, it is also a good

idea to use output filters that are AC coupled to

avoid any problems.

ESD and Latch up Protection

All MOS devices are sensitive to Electro Static

Discharge (ESD). When manipulating these devic-

es, proper ESD precautions are recommended to

avoid performance degradation or permanent dra-

mage.

To prevent latch up, make sure that the analog

ground and the digital ground are at the same po-

tential, it also apply to the analog supply and the

digital supply, they must be at the same potential.

At power up, make sure that the analog and digital

supply are settled to their nominal voltage before

applying any signal pin.

To further prevent from external voltage anomalies

a 3.3 V zener diode should be applied. The diode

should be located after the filter, close to the con-

nector. Anode connected to ground and cathode

connected to the video output pin.

External DAC Output Filter

If an output filter is required, the low pass filter

shown in Figure 19 can be used.

2.2

µH

330 pF

220 pF

OUT

3.3 V

Figure 19. External Low Pass Filter

C2 should be chosen so that C1 = C2 + Ccable

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