ST25DV04KC datasheet(49/203 Pages) STMICROELECTRONICS

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5.5.2

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 43. 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 automatically sets EH_EN bit to 1, and thus activate energy

harvesting.

Writing 1 in EH_MODE at any time after boot does not modify EH_EN bit (until next reboot) and thus does 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 an 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 ST25DVxxKC behaviour during RF communication).

Energy harvesting can be set even if ST25DVxxKC is in RF disabled or RF Sleep mode, or in Low power mode.

In all these cases, ST25DVxxKC delivers power on V_EH pin if RF field is present. Energy harvesting voltage

output is not regulated.

ST25DV04KC ST25DV16KC ST25DV64KC

Energy harvesting (EH)

DS13519 - Rev 3

page 49/203

ST25DV04KC Datasheet(PDF) 49 Page - STMicroelectronics