ST25DV64K datasheet(8/200 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 243. 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 ST25DVxxx's boot sequence (see Figure 5. ST25DVxxx power-up sequence (No RF field, LPD pin

tied to VSS or package without LPD pin) ).

Figure 5. ST25DVxxx power-up sequence (No RF field, LPD pin tied to VSS or package without LPD pin)

Power-Up by Vcc

(No Vcc; VDCG)

Vcc Pin

Vint_supply

I2C

I2C interface ready

None

Access

Allowed

RF or I2C

I2C Start

I2C Stop

RF Access not allowed

tboot*

* When RF Field is present before VCC set up boot is

performed after RF field rising .

* If LPD pin follow VCC before to goes low , tboot will

start only when LPD reach the low level

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 243. 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 t_boot time necessary to ST25DVxxx set-up has

passed. In the version supporting LPD pin, the boot will take 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.

ST25DV04K ST25DV16K ST25DV64K

Power management

DS10925 - Rev 9

page 8/200

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