STMPE1601 datasheet(13/61 Pages) STMICROELECTRONICS

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STMPE1601

I2C interface

13/61

6.1

Minimizing current drain on I2C address lines

The GPIOs 13-15 are used as I2C address input during POR. Pull-up/down resistor of

500 K-1.5 M is recommended for these address lines. In the case that these pins are driven

to an opposite logic level during device operation, there would be a current drain of VIO/R.

This amounts to a significant current for portable devices.

To minimize the current drain on I2C lines, a few methods are recommended.

If maximum keypad size is not required, these shared lines should not be used for

keypad operation.

If the maximum keypad size is required, choose I2C address 0x40, as this requires that

all 3 address lines to be pulled to ground, minimizing the current drain in keypad

operation. In this mode of operation, the pull up/down resistors on the I2C lines should

be:

A reset circuit with longer RC is used to ensure enough time for the address lines to

settle to the final values.

In system-controlled idle state, all keypad pins to be configured as hotkey with interrupt

enabled. If any key is pressed, system initiates keypad controller for scanning

operation.

Table 13.

Recommended pull up/down resistors on the I2C lines

VIO

1.8 V

2.5 V

3.3 V

Reset RC

or pulse width(1)

Recommended values are chosen to minimize leakage current.

Note

RPU/RPD

1.5 M

1.2 M

1 M

270 K/0.47

μF

120 ms

All 3 address

lines are

used for

keypad

controller

RPU/RPD

1.0 M

800 K

660 K

180 K/0.47

μF

80 ms

2 address

lines are

used for

keypad

controller

RPU/RPD

500K

400K

330K

90K/0.47

μF

40 ms

1 address

line is used

for keypad

controller

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