ISL97645(2006) Просмотр технического описания (PDF) - Intersil

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ISL97645
(Rev.:2006)

Boost + VON Slice + VCOM

Intersil 

ISL97645

Layout Recommendation

The device’s performance including efficiency, output noise,

transient response and control loop stability is dramatically

affected by the PCB layout. PCB layout is critical, especially

at high switching frequency.

There are some general guidelines for layout:

1. Place the external power components (the input

capacitors, output capacitors, boost inductor and output

diodes, etc.) in close proximity to the device. Traces to

these components should be kept as short and wide as

possible to minimize parasitic inductance and resistance.

2. Place VIN and VDD bypass capacitors close to the pins.

3. Reduce the loop area with large AC amplitudes and fast

slew rate.

4. The feedback network should sense the output voltage

directly from the point of load, and be as far away from LX

node as possible.

5. The power ground (PGND) and signal ground (SGND)

pins should be connected at only one point.

6. The exposed die plate, on the underneath of the

package, should be soldered to an equivalent area of

metal on the PCB. This contact area should have multiple

via connections to the back of the PCB as well as

connections to intermediate PCB layers, if available, to

maximize thermal dissipation away from the IC.

7. To minimize the thermal resistance of the package when

soldered to a multi-layer PCB, the amount of copper track

and ground plane area connected to the exposed die

plate should be maximized and spread out as far as

possible from the IC. The bottom and top PCB areas

especially should be maximized to allow thermal

dissipation to the surrounding air.

8. A signal ground plane, separate from the power ground

plane and connected to the power ground pins only at the

exposed die plate, should be used for ground return

connections for control circuit.

9. Minimize feedback input track lengths to avoid switching

noise pick-up.

A demo board is available to illustrate the proper layout

implementation.

13

FN9263.0

April 11, 2006

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