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SS6577

Rev.1.02 3/26/2004

return to its designed value when the peak inductor

value no longer exceeds over current protection

point.

Over Voltage Protection

Over voltage protection occurs when the FB pin

voltage (the negative input of error amplifier) ex-

ceeds 0.855V. The over voltage comparator will

force driver to pull low until output over voltage is

removed.

PCB Layout

Since operating at a high switching frequency,

500KHz, proper PCB layout and component place-

ment may enhance the performance of the SS6577

application circuit. For a better efficiency, major loop

from input terminal to output terminal should be as

short as possible. In addition, in the case of a large

current loop, the track width of each component in

the loop should maintain as wide as possible.

In order to prevent the effect from noise, the GND

pin should be placed close to the ground. Also keep

the IC’s GND pin and the ground leads in the short-

est distance. Recommended layout diagrams and

component placement are as shown as figures 13

to 16. No sensitive components, which may cause

noise interference to the circuit, should be allowed

to be close to SW pin.

Furthermore, the SS6577 is a current-mode controller.

Keeping

the sense resistor close to both VIN and

CS pins is recommended for better efficiency and

output performance. In addition, all filtering and de-

coupling capacitors, such as C1 and C2, should

connect to the SS6577 as close as possible.

Fig. 12 Top Layer

Fig. 13 Bottom Layer