Datasheet

PN532_C1 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2017. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.6 — 28 November 2017
115436 116 of 222
NXP Semiconductors
PN532/C1
Near Field Communication (NFC) controller
8.6.8 RF level detector
The RF level detector is integrated to fulfill NFCIP-1 protocol requirements (e.g. RF
collision avoidance).
Furthermore the RF level detector can be used to wake up the PN532 and to generate an
interrupt.
The sensitivity of the RF level detector is adjustable in a 4-bit range using the bits RFLevel
in register CIU_RFCfg (see Table 245 on page 175
). The sensitivity itself depends on the
antenna configuration and tuning.
Possible sensitivity levels at the RX pin are listed below:
[1] Due to noise, it is recommended not to use this setting to avoid misleading results.
To increase the sensitivity of the RF level detector an amplifier can be activated by setting
the bit RFLevelAmp in register CIU_RFCfg to logic 1 (see Table 245 on page 175
).
Remark: With typical antenna, lower sensitivity levels without the additional amplifier set
(below 1000b) can provoke misleading results because of intrinsic noise in the
environment.
Remark: For the same reasons than above, it is recommended to use the RFLevelAmp
only with upper RF level settings (above 1001b).
Remark: During the CIU Power-down mode the additional amplifier of the RF level
detector is automatically switched off to ensure that the power consumption is minimal.
Table 156. Setting of the RF level detector
VRx typical [Vpp]
CIU Power-Down bit set to logic
CIU_RFCfg setting CIU_RFCfg setting
with additional amplifier
1 0 see Remark
2 1.9 1111b
1.35 1.3 1110b
0.95 0.9 1101b
0.6 0.57 1100b
0.41 0.40 1011b
0.28 0.27 1010b
0.17 0.17 1001b
0.12 0.12 1000b 1xxx1111b
0.085 -
0111b
[1]
1xxx1110b
0.055 -
0110b
[1]
1xxx1101b
0.040 -
0101b
[1]
1xxx1100b
--
0100b
[1]
1xxx1011b
[1]
--0011b
[1]
1xxx1010b
[1]
--0010b
[1]
1xxx1001b
[1]
--0001b
[1]
1xxx1000b
[1]
--0000b
[1]
1xxx0111b
[1]