ISL78200_14 Datasheet, PDF(20/22 Page) Intersil Corporation – 2.5A Regulator with Integrated High-Side MOSFET for Synchronous Buck or Boost Buck Converter

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ISL78200_14 Datasheet, PDF (20/22 Pages) Intersil Corporation – 2.5A Regulator with Integrated High-Side MOSFET for Synchronous Buck or Boost Buck Converter

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ISL78200

it is under the acceptable range. Suggest to run the iSim model

simulation to select the proper inductor value.

Boost Output Capacitor

Based on the same theory in boost start-up described above in

boost inductor selection, a large capacitor at boost output will

cause high inrush current at boost PWM start-up. 22ÂµF is a good

choice for applications with buck output voltage less than 10V.

Also, some minimum amount of capacitance has to be used in

boost output to keep the system stable. Suggest to run the iSim

model simulation to select the proper inductor value.

Layout Suggestions

1. Put the input ceramic capacitors as close to the IC VIN pin and

power ground connecting to the power MOSFET or diode.

Keep this loop (input ceramic capacitor, IC VIN pin and

MOSFET/diode) as tiny as possible to achieve the least

voltage spikes induced by the trace parasitic inductance.

2. Put the input aluminum capacitors close to IC VIN pin.

3. Keep the phase node copper area small but large enough to

handle the load current.

4. Put the output ceramic and aluminum capacitors also close

to the power stage components.

5. Put vias (20 recommended) in the bottom pad of the IC. The

bottom pad should be placed in the ground copper plane with

an area as large as possible in multiple layers to effectively

reduce the thermal impedance.

6. Place the 4.7ÂµF ceramic decoupling capacitor at the VCC pin

and as close as possible to the IC. Put multiple vias (â¥3) close

to the ground pad of this capacitor.

7. Keep the bootstrap capacitor close to the IC.

8. Keep the LGATE drive trace as short as possible and try to

avoid using a via in the LGATE drive path to achieve the lowest

impedance.

9. Place the positive voltage sense trace close to the load for

tighter regulation.

10. Place all the peripheral control components close to the IC.

FIGURE 35. PCB VIA PATTERN

FN7641.2

December 24, 2013

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