M24LR04E-R datasheet(15/142 Pages) STMICROELECTRONICS

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M24LR04E-R

Signal descriptions

Doc ID 022208 Rev 5

15/142

Signal descriptions

2.1

Serial clock (SCL)

This input signal is used to strobe all data in and out of the device. 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. (Figure 3 indicates how the value of the pull-up resistor can be calculated). In

most applications, though, this method of synchronization is not employed, and so the pull-

up resistor is not necessary, provided that the bus master has a push-pull (rather than open

drain) output.

2.2

Serial data (SDA)

This bidirectional signal is used to transfer data in or out of the device. 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 3 indicates how

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

2.3

RF Write in progress / RF Busy (RF WIP/BUSY)

This configurable output signal is used either to indicate that the M24LR04E-R is executing

an internal write cycle from the RF channel or that an RF command is in progress. RF WIP

and signals are available only when the M24LR04E-R is powered by the Vcc pin. It is an

open drain output and a pull up resistor must be connected from RF WIP/BUSY to VCC.

2.4

Energy harvesting analog output (Vout)

This analog output pin is used to deliver the analog voltage Vout available when the Energy

harvesting mode is enabled and the RF field strength is sufficient. When the Energy

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

analog voltage output Vout is in High-Z state.

2.5

Antenna coil (AC0, AC1)

These inputs are used to connect the device to an external coil exclusively. It is advised not

to connect any other DC or AC path to AC0 or AC1.

When correctly tuned, the coil is used to power and access the device using the ISO 15693

and ISO 18000-3 mode 1 protocols.

2.5.1

Device reset in RF mode

To ensure a proper reset of the RF circuitry, the RF field must be turned off (100%

modulation) for a minimum tRF_OFF period of time.

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