MLX90132 Datasheet, PDF (41/44 Pages) Melexis Microelectronic Systems – 13.56MHz RFID / NFC Transceiver

MLX90132
13.56MHz RFID / NFC Transceiver
12.6 Oscillator Characteristics
Symbol
Parameter
Conditions
Min
Low Frequency Oscillator (LFO)
fLFO
Low-frequency oscillator (LFO)
20
XTAL Oscillator
fXTAL
RF
CL
I2
gm
tSU(HFO)(4)
XTAL Oscillator frequency
Feedback resistor
Recommended load capacitance versus
equivalent serial resistance of the crystal
(RS)⁽³⁾
Rs = 30Ω
XTAL driving current⁽²⁾
VDD = 3.3V with
12pF load
Oscillator transconductance⁽²⁾
Start-up
0.04
Oscillator start-up time
VDD is stabilized
Table 39: Oscillator characteristics ^{(1) (2)}
Typ Max Units
32
43
kHz
27.12
2
12
MHz
MΩ
pF
600
750
µA
0.32 1.41 mA/V
2
ms
1. Resonator characteristics given by the crystal/ceramic resonator manufacturer.
2. Based on characterization, not tested in production.
3. The relatively low value of the RF resistor offers good protection against issues resulting from use in a humid environment, due to the
induced leakage and the bias condition change. However, it is recommended to take this point into account if the application is used in
severe humidity conditions.
4. tSU (HFO) is the startup time measured from the moment it is enabled (by software) until a stabilized 27.12MHz oscillation is reached.
This value is measured for a standard crystal resonator and it can vary significantly with the crystal manufacturer.
For C_L1and C_L2, it is recommended to use high-quality external ceramic capacitors in the 10 pF to 20 pF
range, designed for high-frequency applications, and selected to match the requirements of the crystal or
resonator (see Figure 18). C_L1 and C_L2 are usually the same size. The crystal manufacturer typically specifies
a load capacitance which is the series combination of C_L1and C_L2.
CL1
X_IN
MLX90132
R_F
CL2
X_OUT
÷2
f_HFO
Figure 18: Typical application with a 27.12MHz crystal
3901090132
Rev. 009
Page 41 of 44
Jan-2014