ST25DV04K datasheet(22/220 Pages) STMICROELECTRONICS

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Power management

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DocID027603 Rev 4

Power management

3.1

Wired interface

Operating supply voltage VCC

In contact mode, prior to selecting the memory and issuing instructions to it, a valid and

stable VCC voltage within the specified [VCC(min), VCC(max)] range must be applied (see

Table 204: I2C operating conditions). To maintain a stable DC supply voltage, it is

recommended to decouple the VCC line with a suitable capacitor (usually of the order of 10

nF and 100 pF) close to the VCC/VSS package pins.

This voltage must remain stable and valid until the end of the transmission of the instruction

and, for a Write instruction, until the completion of the internal I²C write cycle (tW).

Instructions are not taken into account until completion of ST25DVxxx's boot sequence (see

Figure 5).

Figure 5. ST25DVxxx Power-Up sequence (No RF field, LPD pin tied to Vss

or package without LPD pin)

Power-up conditions

When the power supply is turned on, VCC rises from VSS to VCC. The VCC rise time must not

vary faster than 1V/µs.

Device reset in I²C mode

In order to prevent inadvertent write operations during power-up, a power-on reset (POR)

circuit is included. At power-up (continuous rise of VCC), the ST25DVxxx does not respond

to any I²C instruction until VCC has reached the power-on reset threshold voltage (this

threshold is lower than the minimum VCC operating voltage defined in Table 204: I2C

operating conditions). When VCC passes over the POR threshold, the device is reset and

enters the Standby power mode. However, the device must not be accessed until VCC has

reached a valid and stable VCC voltage within the specified [VCC(min), VCC(max)] range and

ST25DV04K Datasheet(PDF) 22 Page - STMicroelectronics