Hardware

AN3245

6/19

Doc ID 17747 Rev 1

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If reset delay and external reset assertion, as shown in case1 and case2 above, are not

required, it is recommended to short the RSTB pin to VCC through a resistor.

Figure 4.

RSTB connectivity recommendation 3

1.1.3

INTB pin recommendation

The INTB pin is programmable to active low or active high. When programmed to active low,

a pull-up resistor of 2.2 k

Ω -10 kΩ is required. When programmed to active high, a pull-down

resistor of 2.2 k

Ω - 10 kΩ is required.

If the INT signal is not in use, it is necessary to pull the INTB pin to VCC.

1.2

Power sequence (fail safe)

All GPIO pins of the STMPE1801 are NOT fail safe. This means that it is necessary to make

sure that VCC supply to STMPE1801 is first turned on before driving the GPIO inputs.

All other pins except GPIO are with fail safe structures. It is possible to have these pins pull-

up supply on (for SCL/SDA/INTB) or driven (for RSTB) before STMPE1801 VCC turns on.

1.3

GPIO output configurations

The STMPE1801 provides push-pull type of GPIO output as is. If open drain GPIO outputs

are required, it is configurable with a tweak to the software programming routine. See

figures 5, 6, and 7.