ST25DV64K datasheet(8/197 Pages) STMICROELECTRONICS

8 / 197 page

Power management

3.1

Wired interface

Operating supply voltage VCC

In contact mode, before selecting the memory and issuing instructions to it, a valid and stable VCC voltage within

the specified [VCC(min), VCC(max)] range (see Table 243. I2C operating conditions) must be applied. To maintain

a stable DC supply voltage, it is recommended to decouple the VCC line with a suitable capacitor (10 to 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 the boot sequence (see Figure 5).

Figure 5. 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

Internal supply

I2C

I2C interface ready

No 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 already done and tboot = 0.

* If the LPD pin follows VCC before going low, tboot = tboot_LPD, and starts only when LPD reaches the the low level.

Power-up conditions

When the power supply is turned on, VCC rises from VSS to VCC. The rise time must not be faster than 1 V/µs.

Device reset in I²C mode

To prevent unwanted write operations during power-up, a power-on reset (POR) circuit is included. At power-up

(continuous rise of VCC), the device does not respond to any I²C instruction until VCC has reached the power-on

reset threshold voltage (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.

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 the time necessary by the device to set-up (tBootDC) has passed. In the version

supporting LPD pin, the boot 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 the I2C address counter is

reset.

Power-down mode

During power-down (VCC decreasing continuously) 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).

ST25DV04K ST25DV16K ST25DV64K

Power management

DS10925 - Rev 11

page 8/197

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