PCF8575CDGVR datasheet(19/38 Pages) TI1

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Cb (pF)

100

150

200

250

300

350

400

450

D008

Standard-mode

Fast-mode

VCC (V)

0.5

1.5

2.5

3.5

4.5

5.5

0.2

0.4

0.6

0.8

1.2

1.4

1.6

1.8

D009

VCC > 2V

VCC <= 2

p(max)

0.8473 C

OL(max)

p(min)

PCF8575C

www.ti.com

SCPS123F – MARCH 2005 – REVISED JANUARY 2015

Typical Application (continued)

9.2.2 Detailed Design Procedure

The pull-up resistors, RP, for the SCL and SDA lines need to be selected appropriately and take into

consideration the total capacitance of all slaves on the I2C bus. The minimum pull-up resistance is a function of

VCC, VOL,(max), and IOL:

(1)

The maximum pull-up resistance is a function of the maximum rise time, tr (300 ns for fast-mode operation, fSCL =

400 kHz) and bus capacitance, Cb:

(2)

The maximum bus capacitance for an I2C bus must not exceed 400 pF for standard-mode or fast-mode

operation. The bus capacitance can be approximated by adding the capacitance of the TCA9534, Ci for SCL or

Cio for SDA, the capacitance of wires/connections/traces, and the capacitance of additional slaves on the bus.

9.2.3 Application Curves

Standard-mode

Fast-mode

VOL = 0.2*VCC, IOL = 2 mA

when VCC ≤ 2 V

(fSCL= 100 kHz, tr = 1 µs)

(fSCL= 400 kHz, tr= 300 ns)

VOL = 0.4 V, IOL = 3 mA

Figure 18. Maximum Pull-Up resistance (Rp(max)) vs Bus

when VCC > 2 V

Capacitance (Cb)

Figure 19. Minimum Pull-Up Resistance (Rp(min)) vs Pull-Up

Reference Voltage (VCC)

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