ST25DV64KC datasheet(9/203 Pages) STMICROELECTRONICS

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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 246. 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 nF) 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 ST25DVxxKC's boot sequence (see the figure below).

Figure 7. ST25DVxxKC power-up sequence (No RF field, LPD pin tied to VSS or package without LPD pin)

I2C interface ready

None

Access

allowed

RF or I2C

I2C Start

I2C Stop

RF access not allowed

* When RF Field is present before VCC set up, tboot is performed after RF field rising.

tboot*

Power-up by VCC

(No VCC

)

VCC Pin

Vint_supply

* If the LPD pin follows VCC before going low , tboot starts only when LPD reaches the

low level.

MS68573

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

1 V/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 ST25DVxxKC 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 246. 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 tboot time necessary to ST25DVxxKC

set-up has passed.

In the version supporting LPD pin, the tboot takes place only when LPD goes low.

In a similar way, during power-down (continuous decrease in VCC), as soon as VCC drops below the power-on

reset threshold voltage, the device stops responding to any instruction sent to it, and I2C address counter is reset.

Power-down mode

During power-down (continuous decay of VCC), the device must be in Standby power mode (mode reached after

decoding a Stop condition, assuming that there is no internal write cycle in progress).

ST25DV04KC ST25DV16KC ST25DV64KC

Power management

DS13519 - Rev 3

page 9/203

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