The appropriate pull up resistor will depend on the current requirements of the application. Table 9-2 provides

resistor values, reference voltages, and currents at 15 mA, 10 mA, and 3 mA. The resistor value shown in

the +10% column (or a larger value) should be used to ensure that the pass voltage of the transistor is 350

mV or less. The external driver must be able to sink the total current from the resistors on both sides of the

LSF0102-Q1 device at 0.175 V, although the 15 mA applies only to current flowing through the LSF0102-Q1.

Table 9-2. Pull-up Resistor Values

VPU

8 mA

5 mA

3 mA

NOMINAL (Ω)

+10%(1) (Ω)

NOMINAL (Ω)

+10%(1) (Ω)

NOMINAL (Ω)

+10%(1) (Ω)

5 V

581

639

930

1023

1550

1705

3.3 V

369

406

590

649

983

1082

2.5 V

269

296

430

473

717

788

1.8 V

181

199

290

319

483

532

1.5 V

144

158

230

253

383

422

1.2 V

106

117

170

187

283

312

(1)

+10% to compensate for VDD range and resistor tolerance

9.2.1.2.3 Application Curve

Figure 9-3. Captured Waveform From Above I2C Set-Up (1.8 V to 3.3 V at 2.5 MHz)

9.2.1.2.4 Mixed-Mode Voltage Translation

The supply voltage (VPU) for each channel can be individually set with a pull-up resistor. Figure 9-4 shows an

example of this mixed-mode multi-voltage translation. For additional details on multi-voltage translation, see the

Multi-voltage Translation with the LSF Family video.

With the Vref_B pulled up to 5 V and Vref_A connected to 1.8 V, all channels will be clamped to 1.8 V at which

point a pullup can be used to define the high level voltage for a given channel.

• Push-Pull Down Translation (5 V to 1.8 V): Channel 1 is an example of this setup. When B1 is 5 V, A1 is

clamped to 1.8 V, and when B1 is LOW, A1 is driven LOW through the switch.

• Push-Pull Up Translation (1.8 V to 5 V): Channel 2 is an example of this setup. When A2 is 1.8 V, the

switch is high impedance and the B2 channel is pulled up to 5 V. When A2 is LOW, B2 is driven LOW through

the switch.

• Push-Pull Down Translation (3.3 V to 1.8 V): Channels 3 and 4 are examples of this setup. When either B3

or B4 are driven to 3.3 V, A3 or A4 are clamped to 1.8 V, and when either B3 or B4 are LOW, A3 or A4 are

driven LOW through the switch.

• Open-Drain Bidirectional Translation (3.3 V ↔ 1.8 V): Channels 5 through 8 are examples of this setup.

These channels are for bidirectional operation for I2C and MDIO to translate between 1.8 V and 3.3 V with

open-drain drivers.

LSF0102-Q1

SDLS969B – MAY 2018 – REVISED MAY 2023

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