ST25DV04K datasheet(20/220 Pages) STMICROELECTRONICS

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Signal descriptions

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Signal descriptions

2.1

Serial link (SCL, SDA)

2.1.1

Serial clock (SCL)

This input signal is used to strobe all data in and out of the ST25DVxxx. In applications

where this signal is used by slave devices to synchronize the bus to a slower clock, the bus

master must have an open drain output, and a pull-up resistor must be connected from

Serial Clock (SCL) to VCC. See Section 9.2 to know how to calculate the value of this pull-up

resistor

2.1.2

Serial data (SDA)

This bidirectional signal is used to transfer data in or out of the ST25DVxxx. It is an open

drain output that may be wire-OR’ed with other open drain or open collector signals on the

bus. A pull-up resistor must be connected from Serial Data (SDA) to VCC. (Figure 76

indicates how the value of the pull-up resistor can be calculated).

2.2

Power control (VCC, LPD,VSS)

2.2.1

Supply voltage (VCC)

This pin can be connected to an external DC supply voltage.

Note:

An internal voltage regulator allows the external voltage applied on VCC to supply the

ST25DVxxx, while preventing the internal power supply (rectified RF waveforms) to output a

DC voltage on the VCC pin.

2.2.2

Low Power Down (LPD)

This input signal is used to control an internal 1.8 V regulator delivering ST25DVxxx internal

supply. When LPD is high, this regulator is shut off and its consumption is reduced below

1µA. This regulator has a turn on time in range of 100us, to be added to the boot duration,

before the device becomes fully operational. This feature is only available on the 10-ball and

12-pin ST25DVxxx package.

2.2.3

Ground (VSS)

VSS is the reference for the VCC and VDCG supply voltages and V_EH analog output voltage.

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