NX2139A datasheet(17/21 Pages) MICROSEMI

17 / 21 page

NX2139A

Rev. 2.3

03/19/09

5. Source of the lower MOSFET needs to be con-

nected to the GND plane with multiple vias. One is not

enough. This is very important. The same applies to

the output capacitors and input capacitors.

6. Hdrv and Ldrv pins should be as close to

MOSFET gate as possible. The gate traces should be

wide and short. A place for gate drv resistors is needed

to fine tune noise if needed.

7. Vcc capacitor, BST capacitor or any other by-

passing capacitor needs to be placed first around the

IC and as close as possible. The capacitor on comp to

GND or comp back to FB needs to be place as close to

the pin as well as resistor divider.

8. The output sense line which is sensing output

back to the resistor divider should not go through high

frequency signals, should be kept away from the in-

ductor and other noise sources. The resistor divider

must be located as close as possible to the FB pin of

the device.

9. All GNDs need to go directly thru via to GND

plane.

10. In multilayer PCB, separate power ground

and analog ground. These two grounds must be con-

nected together on the PC board layout at a single point.

The goal is to localize the high current path to a sepa-

rate loop that does not interfere with the more sensi-

tive analog control function.

NX2139A Datasheet(PDF) 17 Page - Microsemi Corporation