mfrc531 NXP Semiconductors, mfrc531 Datasheet - Page 32

• Manufacturer Part Number: mfrc531
• Description: Iso/iec 14443 Reader Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
MFRC531_34
Product data sheet
PUBLIC
9.9.3.2 Calculating the relative source resistance
9.9.3.3 Calculating the effective source resistance
9.9.4 Pulse width
9.10 Receiver circuitry
The reference source resistance R
The reference source resistance (R
using ModConductance register’s GsCfgMod[5:0].
Wiring resistance (R
resistance that is relevant when pins TX1 and TX2 are switched to low-impedance. The
additional resistance for pin TX1 (R
Equation
Effective resistance (R
byte) read from the Product Information Field (see
measured during the production test with CwConductance register’s
GsCfgCW[5:0] = 01h.
To calculate the driver resistance for a specific value set in GsCfgMod[5:0], use
Equation
The envelope carries the data signal information that is transmitted to the card. It is an
encoded data signal based on the Miller code. In addition, each pause of the Miller
encoded signal is again encoded as a pulse of a fixed width. The width of the pulse is
adjusted using the ModWidth register. The pulse width (t
where the frequency constant (f
The MFRC531 uses an integrated quadrature demodulation circuit enabling it to detect an
ISO/IEC 14443 A or ISO/IEC 14443 B compliant subcarrier signal on pin RX.
R
t
R
R
w
•
•
S wire
S ref
Sx
(
(
=
ISO/IEC 14443 A subcarrier signal: defined as a Manchester coded ASK modulated
signal
ISO/IEC 14443 B subcarrier signal: defined as an NRZ-L coded BPSK modulated
ISO/IEC 14443 B subcarrier signal
=
2
)
)TX1
ModWidth
------------------------------------ -
(
=
R
7.
8.
S ref
------------------------------------------------------------------------------- -
MANT
(
≈
500 mΩ
f
)maxP
c
GsCfgCW
+
–
1
R
Rev. 3.4 — 26 January 2010
S(wire)
S wire
(
Sx
1
•
): The source resistances of the driver transistors (RsMaxP
⎛
⎝
): Wiring and bonding add a constant offset to the driver
)TX1
77
----- -
40
⎞
⎠
056634
EXP
) R
clk
•
) = 13.56 MHz.
GsCfgCW
S(ref)
S(wire)TX1
S(ref)
S rel
(
can be calculated using
) during the modulation phase can be calculated
)
+
R
) can be set approximately as shown in
S wire
(
)TX1
Section 9.2.1 on page
w
) is calculated using
ISO/IEC 14443 reader IC
Equation
MFRC531
© NXP B.V. 2010. All rights reserved.
13) are
6.
Equation 9
32 of 116
(6)
(7)
(8)
(9)