NXP Semiconductors

NVT2001; NVT2002

Bidirectional voltage level translator for open-drain and push-pull applications

7.2 Bidirectional translation

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

the EN input must be connected to VREFB and both pins pulled to HIGH side Vpu(D) through a pull-up resistor

(typically 200 kΩ). This allows VREFB to regulate the EN input. A filter capacitor on VREFB is recommended.

The master output driver can be totem pole or open-drain (pull-up resistors may be required) and the slave

device output can be totem pole or open-drain (pull-up resistors are required to pull the Bn outputs to Vpu(D)).

However, if either output is totem-pole, data must be unidirectional or the outputs must be 3-stateable and be

controlled by some direction-control mechanism to prevent HIGH-to-LOW contentions in either direction. If both

outputs are open-drain, no direction control is needed.

The reference supply voltage (Vref(A)) is connected to the processor core power supply voltage. When VREFB

is connected through a 200 kΩ resistor to a 3.3 V to 5.5 V Vpu(D) power supply, and Vref(A) is set between 1.0 V

and (Vpu(D) - 1 V), the output of each An has a maximum output voltage equal to VREFA, and the output of each

Bn has a maximum output voltage equal to Vpu(D).

7.3 How to size pull-up resistor value

Sizing the pull-up resistor on an open-drain bus is specific to the individual application and is dependent on the

following driver characteristics:

• The driver sink current

• The VOL of driver

• The VIL of the driver

• Frequency of operation

The following tables can be used to estimate the pull-up resistor value in different use cases so that the

minimum resistance for the pull-up resistor can be found.

Table 6, Table 7 and Table 8 contain suggested minimum values of pull-up resistors for the PCA9306 and

NVT20xx devices with typical voltage translation levels and drive currents. The calculated values assume that

both drive currents are the same. VOL = VIL = 0.1 × VCC and accounts for a ±5 % VCC tolerance of the supplies,

±1 % resistor values. It should be noted that the resistor chosen in the final application should be equal to or

larger than the values shown in Table 6, Table 7 and Table 8 to ensure that the pass voltage is less than 10 %

of the VCC voltage, and the external driver should be able to sink the total current from both pull-up resistors.

When selecting the minimum resistor value in Table 6, Table 7 or Table 8, the drive current strength that should

be chosen should be the lowest drive current seen in the application and account for any drive strength current

scaling with output voltage. For the GTL devices, the resistance table should be recalculated to account for the

difference in ON resistance and bias voltage limitations between VCC(B) and VCC(A).

B-side

A-side

1.2 V

1.5 V

1.8 V

2.5 V

3.3 V

5.0 V

1.0 V

Rpu(A) = 750 Ω

Rpu(B) = 750 Ω

Rpu(A) = 845 Ω

Rpu(B) = 845 Ω

Rpu(A) = 976 Ω

Rpu(B) = 976 Ω

Rpu(A) = none

Rpu(B) = 887 Ω

Rpu(A) = none

Rpu(B) = 1.18 kΩ

Rpu(A) = none

Rpu(B) = 1.82 kΩ

1.2 V

Rpu(A) = 931 Ω

Rpu(B) = 931 Ω

Rpu(A) = 1.02 kΩ

Rpu(B) = 1.02 kΩ

Rpu(A) = none

Rpu(B) = 887 Ω

Rpu(A) = none

Rpu(B) = 1.18 kΩ

Rpu(A) = none

Rpu(B) = 1.82 kΩ

1.5 V

Rpu(A) = 1.1 kΩ

Rpu(B) = 1.1 kΩ

Rpu(A) = none

Rpu(B) = 866 Ω

Rpu(A) = none

Rpu(B) = 1.18 kΩ

Rpu(A) = none

Rpu(B) = 1.78 kΩ

1.8 V

Rpu(A) = 1.47 kΩ

Rpu(B) = 1.47 kΩ

Rpu(A) = none

Rpu(B) = 1.15 kΩ

Rpu(A) = none

Rpu(B) = 1.78 kΩ

2.5 V

Rpu(A) = 1.96 kΩ

Rpu(A) = none

Table 6. Pull-up resistor minimum values, 3 mA driver sink current for PCA9306 and NVT20xx

NVT2001_NVT2002

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Product data sheet

Rev. 4.4 — 22 May 2023

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