AS3955-ASWF-S2 datasheet(5/111 Pages) AMSCO

5 / 111 page

ams Datasheet

Page 5

[v1-01] 2015-Apr-29

Document Feedback

AS3955 − General Description

AS3955 is composed of NFC-A Analog Front End (AFE), NFC Type

2 Tag Logic, EEPROM, SPI / I²C Interface and Power Supply

Manager Block (Power Manager).

The AFE is connected to an external tag coil which forms,

together with integrated resonant capacitor, a LC tank

resonating with the external electromagnetic field frequency

of 13.56 MHz. The AFE has built-in rectifier and regulators. The

output of the internal regulator (VP_INT ) is used to supply the

AFE and also the Logic and EEPROM (through Power Supply

Manager). A regulator output VP_REG is available on a pin to

supply external circuitry by harvesting energy from the RF field.

The Power Manager is controlling the power supply of Logic

and EEPROM. The two blocks can be supplied either from

VP_INT or from VP_IO (SPI / I²C power supply) depending on

the power mode of the chip. AS3955 offers a power mode where

VP_IO supply is switched to VP_INT whenever the RF field is

present. VP_IO is typically used when some activity is started

over the SPI / I²C and the VP_INT is too low to be used as a power

supply.

The Logic is responsible for handling the anti-collision

sequence, when acting as NFC Type 2 Tag, and other data

transfer. The interface logic contains also a 32-byte buffer for

block transmission between NFC device and AS3955.

The EEPROM is used to store the UID, configuration and control

bits, and user data which can be accessed also via the SPI / I²C.

AS3955-ASWF-S2 датащи(PDF) 5 Page - ams AG