AS3955 datasheet(16/102 Pages) AMSCO

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[v1-04] 2016-Feb-03

AS3955 − Detailed Description

Power Mode 1

AS3955 is fully supplied by RF field. AS3955 checks if Extended

or Tunneling mode are enabled. In this case, VP_REG supplies

the system (SPI / I²C pads, pull-ups, MCU), otherwise energy

harvesting is turned off and VP_REG is set in tristate.

Such power mode can be used in battery-less systems where

the system is fully powered by the RF field. In such

configuration, the VP_REG output pin for energy harvesting and

VP_IO input supply shall be externally connected. Battery, even

when present, will not be involved.

If this power mode is enabled and neither tunneling nor

extended mode are enabled, rreg value from

IC Configuration Register 1 will be forced to zero. This will

disable energy harvesting.

Power Mode 2

In this case, the external supply is used to provide power to

digital blocks, EEPROM, SPI / I²C pads and MCU. External supply

VP_REG is not used. Since this mode can be enabled only after

initialization of the chip, the /SS line must be either

permanently set to low or pulled low for short time (400μs) to

complete the initialization.

This mode is specifically designed to operate with AS392x

products (ams’ Active Boost). In this mode, the HF_PON

threshold of the chip will be decreased so that it will operate

with external voltage on LC pin in the range of 2.7-3.6Vpp.

If this mode is enabled, AS3955 will not be turned off as long

as there is an external supply present.

Power Mode 3

In this case the external supply shall be used to provide power

to digital blocks, EEPROM, SPI / I²C pads and MCU. External

supply VP_REG is not used. Since this mode can be enabled only

after initialization of the chip, the /SS line must be either

permanently set to low or pulled low for short time to complete

the initialization.

In this mode, the HF_PON threshold of the chip is set so that it

will operate with external voltage on LC pin in the range of

4.1-5Vpp.

If this mode is enabled, AS3955 will not be turned off as long

as there is an external power present.

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