PCA9601DPZ datasheet(16/31 Pages) NXP

16 / 31 page

NXP Semiconductors

PCA9601

Dual bidirectional bus buffer

Calculate the allowed maximum system bus speed. (Note that the fixed values in

the delay equations represent the internal propagation delays of the PCA9601. Only

one PCA9601 is used here, so those fixed values used below are taken from the

characteristics.)

The delays are:

Delay A = 40 + 56 + (2.5 + [4 × 0.2]) × 3.3 = 107 ns

Delay B = 115 + 50 + 21 = 186 ns

Delay C = 70 + 0.7(50 + 30) = 126 ns

The programmed LOW period is calculated as:

SCL LOW ≥ 300 + 117 - 186 + 126 + 50 = 407 ns

The actual LOW period will be 407 + 126 = 533 ns, which exceeds the minimum Fm

+ 500 ns requirement. This system requires the bus LOW period, and therefore cycle

time, to be increased by 33 ns so the system must run slightly below the 1 MHz limit.

The possible maximum speed has a cycle period of 1 033 ns or 968 kHz.

PCA9601

SDA

SCL

002aae883

12 V

3.3 V to 5 V

PCA9601

SCL/SDA

PCA9601

SCL/SDA

PCA9601

SCL/SDA

PCA9601

SX SCL

SY SDA

no limit to the number of connected bus devices

twisted-pair telephone wires,

USB, or flat ribbon cables;

up to 15 V logic levels,

include VCC and GND

3.3 V 3.3 V

Figure 19. I2C-bus multipoint application

There is an Excel calculator which makes it easy to determine the maximum I2C-bus

clock speed when using the PCA9601. The calculator and instructions can be found at

www.nxp.com/clockspeedcalculator.

- 1

VCC

(V)

time (ns)

900

002aac932

200

100

300 400 500 600 700 800

(1)

(2)

(1)

(2)

1. TX output.

2. SX input.

Figure 20. Propagation SX to TX with VRX = VCC = 3.3 V

(SX pull-up to 3.3 V; TX pull-up to 5.7 V)

- 1

VCC

(V)

time (ns)

900

002aac933

200

100

300 400 500 600 700 800

(1)

(2)

(1)

(2)

1. TX/RX output.

2. SX input.

Figure 21. Propagation SX to TX with RX tied to TX; VCC

= 3.3 V (SX pull-up to 3.3 V; TX pull-up to 5.7 V)

PCA9601

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

Product data sheet

Rev. 3.1 — 4 January 2022

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