ST25DV04K datasheet(42/200 Pages) STMICROELECTRONICS

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5.3.2

Energy harvesting feature description

The usage of Energy Harvesting element can be defined in configuration register EH_MODE. When the Energy

harvesting mode is disabled or the RF field strength is not sufficient, the energy harvesting analog voltage output

V_EH is in High-Z state.

EH_MODE Static Register is used to define the Energy Harvesting default strategy after boot.

At boot EH_EN (in EH_CTRL_Dyn register) is set depending EH_MODE value as shown in table below:

Table 38. Energy harvesting at power-up

EH_MODE

EH_EN (at boot)

Energy harvesting at power-up

EH enabled after boot (when possible)

EH disabled initially,

EH delivered on demand (when possible)

Writing 0 in EH_MODE at any time after boot will automatically set EH_EN bit to 1, and thus activate energy

harvesting.

Writing 1 in EH_MODE at any time after boot will not modify EH_EN bit (until next reboot) and thus will not modify

energy harvesting current state.

EH_CTRL_Dyn allows to activate or deactivate on the fly the Energy harvesting (EH_EN) and bring information

on actual state of EH and state of power supplies :

•

EH_ON set reflects the EH_EN bit value

•

FIELD_ON is set in presence of a RF field

•

VCC_ON is set when Host power supply is on, and low power-down mode is not forced.

During boot, EH is not delivered to avoid alteration in device configuration.

Caution:

Communication is not guaranteed during EH delivery. Refer to the application note AN4913 (Energy harvesting

delivery impact on ST25DVxxx behaviour during RF communication).

Energy harvesting can be set even if ST25DVxxx is in RF disabled or RF Sleep mode, or in Low power mode.

In all these cases, ST25DVxxx will deliver power on V_EH pin if RF field is present. Energy harvesting voltage

output is not regulated.

ST25DV04K ST25DV16K ST25DV64K

Energy Harvesting (EH)

DS10925 - Rev 9

page 42/200

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