PCA9306DC1SLASHDG datasheet(12/38 Pages) NXP

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NXP Semiconductors

PCA9306

Dual bidirectional I2C-bus and SMBus voltage-level translator

B-side

A-side

1.2 V

1.5 V

1.8 V

2.5 V

3.3 V

5.0 V

1.8 V

Rpu(A) = 294 Ω

Rpu(B) = 294 Ω

Rpu(A) = none

Rpu(B) = 232 Ω

Rpu(A) = none

Rpu(B) = 357 Ω

2.5 V

Rpu(A) = 392 Ω

Rpu(B) = 392 Ω

Rpu(A) = none

Rpu(B) = 357 Ω

3.3 V

Rpu(A) = none

Rpu(B) = 348 Ω

Table 13. Pull-up resistor minimum values, 15 mA driver sink current for PCA9306 and NVT20xx...continued

11.3 How to design for maximum frequency operation

The maximum frequency is limited by the minimum pulse width LOW and HIGH as well

as rise time and fall time. See Equation 1 as an example of the maximum frequency. The

rise and fall times are shown in Figure 11.

(1)

002aag912

tr(actual)

tf(actual)

GND

VOL

VIL

VIH

VCC

tHIGH(min)

tLOW(min)

1 / fmax

0.9 × VCC

0.1 × VCC

Figure 11. An example waveform for maximum frequency

The rise and fall times are dependent upon translation voltages, the drive strength,

the total node capacitance (CL(tot)) and the pull-up resistors (RPU) that are present on

the bus. The node capacitance is the addition of the PCB trace capacitance and the

device capacitance that exists on the bus. Because of the dependency of the external

components, PCB layout and the different device operating states the calculation of rise

and fall times is complex and has several inflection points along the curve.

The main component of the rise and fall times is the RC time constant of the bus line

when the device is in its two primary operating states: when device is in the ON state and

it is low-impedance, the other is when the device is OFF isolating the A-side from the B-

side.

A description of the fall time applied to either An or Bn output going from HIGH to LOW

is as follows. Whichever side is asserted first, the B-side down must discharge to the

VCC(A) voltage. The time is determined by the pull-up resistor, pull-down driver strength

and the capacitance. As the level moves below the VCC(A) voltage, the channel resistance

drops so that both A and B sides equal. The capacitance on both sides is connected

to form the total capacitance and the pull-up resistors on both sides combine to the

parallel equivalent resistance. The Ron of the device is small compared to the pull-up

resistor values, so its effect on the pull-up resistance can be neglected and the fall is

determined by the driver pulling the combined capacitance and pull-up resistor currents.

An estimation of the actual fall time seen by the device is equal to the time it takes for

the B-side to fall to the VCC(A) voltage and the time it takes for both sides to fall from the

VCC(A) voltage to the VIL level.

PCA9306

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 9.3 — 14 November 2022

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