Product data

MFRC631 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.3 — 4 February 2014
227433 81 of 120
NXP Semiconductors
MFRC631
High performance ISO/IEC 14443 A/B reader solution
9.8.2 TxAmp
With the set_cw_amplitude register output power can be traded off against power supply
rejection. Spending more headroom leads to better power supply rejection ration and
better accuracy of the modulation degree.
With CwMax set, the voltage of TX1 will be pulled to the maximum possible. This register
overrides the settings made by set_cw_amplitude.
9.8.3 TxCon
Table 122. DrvMode bits
Bit Symbol Description
7 Tx2Inv Inverts transmitter 2 at TX2 pin
6 Tx1Inv Inverts transmitter 1 at TX1 pin
5RFU
4- RFU
3 TxEn If set to 1 both transmitter pins are enabled
2 to 0 TxClkMode Transmitter clock settings (see 8.6.2. Table 27). Codes 011b and
0b110 are not supported. This register defines, if the output is
operated in open drain, push-pull, at high impedance or pulled to a fix
high or low level.
Table 123. TxAmp register (address 29h)
Bit 7 6 5 4 3 2 1 0
Symbol set_cw_amplitude - set_residual_carrier
Access
rights
r/w RFU r/w
Table 124. TxAmp bits
Bit Symbol Description
7 to 6 set_cw_amplitude Allows to reduce the output amplitude of the transmitter by a fix
value.
Four different preset values that are subtracted from TVDD can
be selected:
0: TVDD -100 mV
1: TVDD -250 mV
2: TVDD -500 mV
3: T
VDD
-1000 mV
5RFU -
4 to 0 set_residual_ carrier Set the residual carrier percentage. refer to Section 8.6.2
Table 125. TxCon register (address 2Ah)
Bit 7 6 5 4 3 2 1 0
Symbol OvershootT2 CwMax TxInv TxSel
Access
rights
r/w r/w r/w r/w