LP2986

SNVS137H – MARCH 1999 – REVISED APRIL 2013

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WSON MOUNTING

The LDC08A (Pullback) 8-Lead WSON package requires specific mounting techniques which are detailed in

Application Note AN-1187. Referring to the section PCB Design Recommendations in AN-1187 (Page 5), it

should be noted that the pad style which should be used with this WSON package is the NSMD (non-solder

mask defined) type. Additionally, for optimal reliability, there is a recommended 1:1 ratio between the package

pad and the PCB pad for the Pullback WSON.

The thermal dissipation of the WSON package is directly related to the printed circuit board construction and the

amount of additional copper area connected to the DAP.

The DAP (exposed pad) on the bottom of the WSON package is connected to the die substrate with a conductive

die attach adhesive. The DAP has no direct electrical (wire) connection to any of the eight pins. There is a

parasitic PN junction between the die substrate and the device ground. As such, it is strongly recommend that

the DAP be connected directly to the ground at device lead 1 (i.e. GROUND). Alternately, but not recommended,

the DAP may be left floating (i.e. no electrical connection). The DAP must not be connected to any potential

other than ground.

For the LP2986 in the NGN0008A 8-Lead WSON package, the junction-to-case thermal rating (

where the 'case' is on the bottom of the package at the center of the DAP.

The junction-to-ambient thermal performance for the LP2986 in the NGN0008A 8-Lead WSON package, using

the JEDEC JESD51 standards is summarized in the following table:

Board Type

Thermal Vias

JEDEC 2-Layer

None

7.2°C/W

184°C/W

JESD 51-3

1

7.2°C/W

64°C/W

2

7.2°C/W

55°C/W

JEDEC 4-Layer

JESD 51-7

4

7.2°C/W

46°C/W

6

7.2°C/W

43°C/W

14

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