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 34 of 120
NXP Semiconductors
MFRC631
High performance ISO/IEC 14443 A/B reader solution
Note: At VDD(TVDD) <5 V and residual carrier settings <50%, the accuracy of the
modulation index may be low in dependency of the antenna tuning impedance
8.6.2.1 Overshoot protection
The MFRC631 provides an overshoot protection for 100% ASK to avoid overshoots
during a PCD communication. Therefore two timers overshoot_t1 and overshoot_t2 can
be used.
During the timer overshoot_t1 runs an amplitude defined by set_cw_amplitude bits is
provided to the output driver. Followed by an amplitude denoted by set_residual_carrier
bits with the duration of overshoot_t2.
23 65 21.2
24 60 25.0
25 55 29.0
26 50 33.3
27 45 37.9
28 40 42.9
29 35 48.1
30 30 53.8
31 25 60.0
Table 21. Setting residual carrier
…continuedand modulation index by
set_residual_carrier (decimal) residual carrier [%] modulation index [%]
Fig 23. Example 1: overshoot_t1 = 2d; overhoot_t2 = 5d.
001aan356
2.50 3.03 3.56 4.10
time (μs)
7.0
5.0
(V)
3.0
1.0
-1.0