8.2.4 Voltage Translation for Vref_B < Vref_A + 0.8V

As described in the Enable, Disable, and Reference Voltage Guidelines section, it is generally recommended

that Vref_B > Vref_A + 0.8V; however, the device can still operate in the condition where Vref_B < Vref_A + 0.8V as

long as additional considerations are made for the design.

Typical Operation (Vref_B > Vref_A + 0.8V): in this scenario, pullup resistors are not required on the A-side for

proper down-translation. When down translating from B to A, the A-side I/O ports will clamp at Vref_A to provide

proper voltage translation. For further explanation of device operation, see the Down Translation with the LSF

Family video.

Requirements for Vref_B < Vref_A + 0.8V Operation: in this scenario, there is not a large enough voltage

difference between Vref_A and Vref_B to ensure that the A side I/O ports will be clamped at Vref_A, but rather at

a voltage approximately equal to Vref_B – 0.8V. For example, if Vref_B = 1.8V and Vref_A = 1.2V, the A-side I/Os

will clamp to a voltage around 1.0V. Therefore, to operate in such a condition, the following additional design

considerations must be met:

• Vref_B must be greater than VRef_A during operation (Vref_B > Vref_A)

• Pullup resistors should be populated on A-side I/O ports for the line to be fully pulled up to the desired

voltage.

Figure 8-6 shows an example of this setup, where 1.2V ↔ 1.8V translation is achieved with the LSF0102. This

type of setup also applies for other voltage nodes such as 1.8V ↔ 2.5V, 1.05V ↔ 1.5V, and others as long as the

Recommended Operating Conditions table is followed.

1.8 V

SW

SW

1.8 V Device

1.2 V Device

200 kΩ

Vref_B

RPU(B1)

Vref_A

1.2 V

RPU(B2)

EN

B1

B2

A2

A1

RPU(A2)

RPU(A1)

0.1 μF

Figure 8-6. 1.2V to 1.8V Level Translation with LSF010x

8.3 Power Supply Recommendations

There are no power sequence requirements for the LSF family. Table 8-4 provides recommended operating

voltages for all supply and input pins.

Table 8-4. Recommended Operating Voltages

PARAMETER

MIN

TYP

MAX

UNIT

Vref_A (1)

reference voltage (A)

0.9

5.5

V

Vref_B

reference voltage (B)

Vref_A + 0.8

5.5

V

VI(EN)

input voltage on EN pin

Vref_A + 0.8

5.5

V

VPU

pull-up supply voltage

0

Vref_B

V

(1)

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

LSF0102

SDLS972B – APRIL 2023 – REVISED APRIL 2024

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