8.3 Feature Description

8.3.1 Auto Bidirectional Voltage Translation

All devices in the LSF family are auto bidirectional voltage level translators that are operational from 0.95 V

to 4.5 V on the Vref_A supply and from 1.8 V to 5.5 V on the Vref_B supply. This allows bidirectional voltage

translation between 0.95 V and 5.5 V without the need for a direction pin in open-drain or push-pull applications.

The LSF family supports level translation applications with transmission speeds greater than 100 Mbps for

open-drain systems using a 30-pF capacitance and 250-Ω pullup resistor. Both the output driver of the controller

and the peripheral device output can be push-pull or open-drain (pull-up resistors may be required). During

operation of the device, the B-side is often referred to as the high side while the A-side is referred to as the low

side.

8.3.2 Output Enable

To enable the I/O pins, the EN input should be tied directly to Vref_B during operation and both pins must be

pulled up to the HIGH side (Vpu or VCCB) through a pull-up resistor (typically 200 kΩ). To ensure the high

impedance state during power-up, power-down, or during operation, the EN pin must be LOW. The EN pin

should always be tied directly to the Vref_B pin and is recommended to be disabled by an open-drain driver

without a pullup resistor. This allows Vref_B to regulate the EN input and bias the channels for proper translation.

A filter capacitor on Vref_B is recommended for a stable supply at the device.

1.8 V

Vref_A

VCCB

EN

200 k

Vref_B

3.3 V

A1

B1

0.1 F

Figure 8-1. EN Pin Tied to Vref_B Directly and to VCCB Through a Pull-Up Resistor

The supply voltage of open drain I/O devices can be completely different from the supplies used for the LSF and

has no impact on the operation. For additional details on how to use the enable pin, see the Using the Enable

Pin with the LSF Family video.

Table 8-1. EN Pin Function Table

INPUT EN(1) PIN

Data Port State

Tied directly to Vref_B

An = Bn

L

Hi-Z

(1)

EN is controlled by Vref_B logic levels.

LSF0108-Q1

SDLS967E – MAY 2016 – REVISED NOVEMBER 2022

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