AN2021 datasheet(8/39 Pages) STMICROELECTRONICS

8 / 39 page

Modified features

AN2021

8/39

1.1.3

Pin 56

On the ST10F269, a decoupling capacitor of 330nF minimum has to be connected between

the pin 56 (named DC1) and the nearest VSS pin.

On the ST10F272, pin 56 is named V18 and a capacitor of value between 10nF minimum

and 100nF maximum must be connected between it and the nearest VSS pin.

Hardware impact

Change on the capacitor value. As the value is much lower, the footprint of the capacitor

might be smaller and then a modification of the PCB is needed.

Software impact

None.

1.1.4

Pin 99

On the ST10F269, pin 99 is EA and used upon reset to select the start from the internal

Flash memory or the external memory.

On the ST10F272, pin 99 has the additional function of providing the 5V power supply to the

device in standby mode (new power-saving mode), it is called EA-VSTBY.

Hardware impact

The modification depends on the previous use of the ST10F269 and on whether the

Standby mode is used or not.

For an application where the Standby mode is not used, no change to the PCB is required. If

the new application uses the Standby mode, the EA-VSTBY pin must be separated from the

common 5V and have a specific supply path.

Software impact

None.

1.1.5

Pins 143 and 144

These pins are VSS and VDD, respectively, in the ST10F269. On the ST10F272 they are

used as XTAL3 and XTAL4 for connection to an optional 32 kHz crystal to clock the Real

Time Clock during power-down.

Hardware impact

PCB must be redesigned.

If the optional 32 kHz is not used:

●

Pin 143 (XTAL3) must be linked to ground like on the ST10F269

●

Pin 144 (XTAL4) must be left open. It can also be connected to ground via a capacitor

to reduce the potential RF noise that might be propagated inside the device if the pin is

left floating.

AN2021 数据表(PDF) 8 Page - STMicroelectronics

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