MLX90130
13.56MHz RFID Transceiver
3901090130
Page 34 of 37
Jan-2014
Rev. 004
12.6 Oscillator Characteristics
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Low Frequency Oscillator (LFO)
f
LFO
Low-frequency oscillator (LFO)
20
32
43
kHz
XTAL Oscillator
f
XTAL
XTAL Oscillator frequency
27.12
MHz
R
F
Feedback resistor
2
MΩ
C
L
Recommended load capacitance versus
equivalent serial resistance of the crystal
(RS)
(3)
Rs = 30Ω
12
pF
I
2
XTAL driving current
(2)
VDD = 3.3V with
12pF load
600
750
µA
g
m
Oscillator transconductance
(2)
Start-up
0.04
0.32
1.41
mA/V
t
SU(HFO)
(4)
Oscillator start-up time
VDD is stabilized
2
ms
Table 28: Oscillator characteristics
(1) (2)
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
L1
and 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
). 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
L1
and C
L2
.
X
IN
X
OUT
R
F
f
HFO
27
.1
2M
H
z
CL1
CL2
MLX90130
÷2
Figure 18: Typical application with a 27.12MHz crystal
