LP38691, LP38693, LP38691-Q1, LP38693-Q1

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SNVS321N – JANUARY 2005 – REVISED MARCH 2015

10 Power Supply Recommendations

The LP38691 and LP38693 are designed to operate from an input supply voltage range of 2.7 V to 10 V. The

input supply should be well regulated and free of spurious noise. To ensure that the device output voltage is well

of 1-

μF is required to be within 1 cm of the IN pin.

11 Layout

11.1 Layout Guidelines

The dynamic performance of the LP38691 or LP38693 is dependent on the layout of the PCB. PCB layout

practices that are adequate for typical LDOs may degrade the load regulation, PSRR, noise, or transient

performance of the LP38691 or LP38693.

to the LP38691 or LP38693 GND pin using as wide, and as short, a copper trace as is practical.

Connections using long trace lengths, narrow trace widths, and/or connections through vias should be avoided.

These will add parasitic inductances and resistance that results in inferior performance especially during transient

conditions.

A Ground Plane, either on the opposite side of a two-layer PCB, or embedded in a multi-layer PCB, is strongly

recommended. This Ground Plane serves two purposes:

•

Provides a circuit reference plane to assure accuracy.

•

Provides a thermal plane to remove heat from the LP38691 or LP38693 WSON package through thermal vias

under the package DAP.

11.1.1 WSON Mounting

The NGG0006A (No Pullback) 6-Lead WSON package requires specific mounting techniques which are detailed

in the TI AN-1187 Application Report SNOA401. Referring to the section PCB Design Recommendations, it

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

defined) type. Additionally, it is recommended the PCB terminal pads to be 0.2 mm longer than the package

pads to create a solder fillet to improve reliability and inspection.

The input current is split between two IN pins, 1 and 6. The two IN pins must be connected together to ensure

that the device can meet all specifications at the rated current.

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 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 2 (that is, GND). Alternately, but not recommended, the DAP may

be left floating (that is, no electrical connection). The DAP must not be connected to any potential other than

ground.

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Product Folder Links: LP38691 LP38693 LP38691-Q1 LP38693-Q1