Vref_A

Vref_B

2

7

3

4

8 EN

6

5

1

GND

A1

A2

B1

B2

LSF0102

Rpu

200KΩ

ON

Off

Rpu

Rpu

Rpu

Vref(A) = 1.8V

Vpu = 3.3V

GND

GND

3.3V enable signal

Vcc

MDIO

MDC

SW

SW

Vcc

MDIO

MDC

13

LSF0101, LSF0102, LSF0108

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SDLS966H – DECEMBER 2013 – REVISED JUNE 2019

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(1)

Vref_A is required to be the lowest voltage level across all inputs and outputs.

9.2 Typical Applications

Figure 6. Typical Application Circuit for Open-Drain Translation (MDIO shown as an example)

9.2.1.1 Design Requirements

9.2.1.1.1

Enable, Disable, and Reference Voltage Guidelines

The LSF family has an EN input that is used to disable the device by setting EN LOW, placing all I/Os in the

high-impedance state. Since the LSF family of devices are switch-type voltage translators, the power

SMBus, PMBus, or MDIO).

Table 4. Application Operating Condition

PARAMETER

MIN

TYP

MAX

UNIT

reference voltage (A)

0.95

4.5

V

Vref_B

reference voltage (B)

Vref_A + 0.8

5.5

V

input voltage on EN pin

Vref_A + 0.8

5.5

V

Vpu

pull-up supply voltage

0

Vref_B

V

The 200 k

Ω, pull-up resistor is required to allow Vref_B to regulate the EN input and properly bias the

device for translation. For additional details on device biasing, see the Understanding the Bias Circuit for the

1.0 V higher than Vref_A for best signal integrity.

9.2.1.2 Detailed Design Procedure

9.2.1.2.1

Bidirectional Translation

For the bidirectional translation configuration (higher voltage to lower voltage or lower voltage to higher voltage),

the EN input must be connected to Vref_B and both pins must be pulled up to the HIGH side Vpu through a pull-

up resistor (typically 200 k

Ω). 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. The master output

driver can be push-pull or open-drain (pull-up resistors may be required) and the slave device output can be

push-pull or open-drain (pull-up resistors are required to pull the Bn outputs to Vpu).