8.3.3 Wettable Flanks

This device includes wettable flanks for at least one package. See the Features section on the front page of the

data sheet for which packages include this feature.

Wettable flanks help improve side wetting after soldering which makes QFN packages easier to inspect with

automatic optical inspection (AOI). A wettable flank can be dimpled or step-cut to provide additional surface

area for solder adhesion which assists in reliably creating a side fillet as shown in the figure. Please see the

mechanical drawing for additional details.

Figure 8-2. Simplified Cutaway View of Wettable-Flank QFN Package and Standard QFN Package After

Soldering

Package

We able Flank Lead

PCB

Pad

Standard Lead

Package

Solder

8.4 Device Functional Modes

For each channel (n), when either the An or Bn port is LOW, the switch provides a low impedance path between

the An and Bn ports; the corresponding Bn or An port will be pulled LOW. The low RON of the switch allows

connections to be made with minimal propagation delay and signal distortion.

Table 8-1 provides a summary of device operation. For additional details on the functional operation of the LSF

family of devices, see the Down Translation with the LSF Family and Up Translation with the LSF Family videos.

Table 8-2. Device Functionality

Signal Direction(1)

Input State

Switch State

Functionality

B to A (Down Translation)

B = LOW

ON

(Low Impedance)

A-side voltage is pulled low through the switch to the B-side voltage

B = HIGH

OFF

(High Impedance)

A-side voltage is clamped at Vref_A (2)

A to B (Up Translation)

A = LOW

ON

(Low Impedance)

B-side voltage is pulled low through the switch to the A-side voltage

A = HIGH

OFF

(High Impedance)

B-side voltage is clamped at Vref_A and then pulled up to the Vpu#

supply voltage

(1)

The downstream channel should not be actively driven through a low impedance driver, or else bus contention may occur.

(2)

The A-side can have a pullup to Vref_A for additional current drive capability or may also be pulled above Vref_A with a pullup resistor.

Specifications in the Recommended Operating Conditions section should always be followed.

8.4.1 Up and Down Translation

Up Translation: When the signal is driven from A to B and the An port is HIGH, the switch will be OFF and the

Bn port will then be driven to a voltage higher than Vref_A by the pullup resistor that is connected to the pull-up

supply voltage. This functionality allows seamless translation between the higher and lower voltages selected

by the user, without the need for directional control. Pull-up resistors are always required on the high side, and

pull-ups are only required on the low side if the output of the low side device is open drain or its input has a

leakage greater than 1 µA.

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LSF0108-Q1

SDLS967F – MAY 2016 – REVISED APRIL 2023

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