Product data

Product data sheet

COMPANY PUBLIC

Rev. 3.3 — 4 February 2014

227433 49 of 120

NXP Semiconductors

MFRC631

High performance ISO/IEC 14443 A/B reader solution

To leave the modem off mode clears the ModemOff bit in the register Control.

8.9.3 Low-Power Card Detection (LPCD)

The low-power card detection is an energy saving mode in which the MFRC631 is not fully

powered permanently.

The LPCD works in two phases. First the standby phase is controlled by the wake-up

counter (WUC), which defines the duration of the standby of the MFRC631. Second

phase is the detection-phase. In this phase the values of the I and Q channel are detected

and stored in the register map. (LPCD_I_Result, LPCD_Q_Result).This time period can

be handled with Timer3. The value is compared with the min/max values in the registers

(LPCD_IMin, LPCD_IMax; LPCD_QMin, LPCD_QMax). If it exceeds the limits, a LPCDIrq

is raised.

After the command LPCD the standby of the MFRC631 is activated, if selected. The

wake-up Timer4 can activate the system after a given time. For the LPCD it is

recommended to set T4AutoWakeUp and T4AutoRestart, to start the timer and then go to

standby. If a card is detected the timer stops and the communication can be started. If

T4AutoWakeUp is not set, the IC will not enter Standby mode in case no card is detected.

8.9.4 Reset and start-up time

A 10 s constant high level at the PDOWN pin starts the internal reset procedure.

The following figure shows the internal voltage regulator:

When the MFRC631 has finished the reset phase and the oscillator has entered a stable

working condition the IC is ready to be used.

Fig 30. Internal PDown to voltage regulator logic

001aan360

PVDD

PDown

GLITCH

FILTER

INTERNAL VOLTAGE

REGULATOR

1.8 V

AVDD

DVDD