PCE85176AUGSLASHDA datasheet(34/48 Pages) NXP

34 / 48 page

PCE85176AUG

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Product data sheet

Rev. 1 — 12 January 2015

34 of 48

NXP Semiconductors

PCE85176AUG

4 × 40 LCD segment driver for Chip-On-Glass

14. Application information

14.1 Track resistance on the I2C-bus lines

The SDA line of an I2C device is an open-drain output which therefore needs an external

pull-up resistor (RPU). In Chip-On Glass (COG) applications, the track resistance (RITO)

from the SDA pin to the SDA system line can be significant. For this reason, it is possible

that the two resistances are forming a voltage divider. Such a divider could prevent that

the acknowledge cycle generated by the PCE85176AUG can be interpreted as logic 0 by

the master. To guarantee a valid LOW level, it is necessary that the RITO from the SDA pin

to the SDA system line is minimized.

The logic output voltage is calculated with Equation 6:

(6)

For further information on this topic, see Ref. 1 “AN10170”.

(1) Includes track resistance RITO.

Fig 26. Track resistances on the SDA and VSS line

O(log)

I(SDA)

I(VSS)

I(SDA)

I(VSS)

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