ML7436N LSI Hardware Design Manual
FEXL7436NDG-01
8
2.1.
Circuit component values for crystal oscillator circuit
It is recommended to ask your oscillator manufacturer to evaluate the matching component values on the assembled
board. The following
Table 2.1
shows the matching component values with LAPIS Technology RF board configured
by
Figure 2.1
as reference.
Table 2.1
Representative matching component values
Manufacture
Cristal oscillator
X’tal_1
Type
Frequency
(kHz)
Equivalent series
resister
max(Ω)
Load
capacitor
(pF)
Component values
Cp1
(pF)
Cp2
(pF)
Rs1
(Ω)
NDK
NX2012SE
32.768
50k.
9
18
18
0
Manufacture
Cristal oscillator
X’tal_2
Type
Frequency
(MHz)
Equivalent series
resister
max(Ω)
Load
capacitor
(pF)
Component values
Cp3
(pF)
Cp4
(pF)
Rs2
(Ω)
Kyocera
CX2016DB
48
50
6
OPEN
OPEN
0
[Note] These component values appropriate for use on the LAPIS Semiconductor’s RF board. It is not guaranteed
to obtain same result on your specific board.
2.2.
Notes on the crystal oscillator circuit configuration
Note the following when designing the crystal oscillator circuit.
⚫
The capacitor’s value of C1, C2, C3 and C4 depends on the crystal oscillator specification.
⚫
C1, C2, C3 and C4 should be placed as close as possible to the RF_XIN (#1), the RF_XOUT (#48), the
CNIN(#19), CXOUT(#18) pins to suppress parasitic LCR and stabilize the oscillator. The recommended distance
between ML7436N pin and the capacitor is less than 2mm.
⚫
Do not place the crystal oscillator circuit across other signal lines.
⚫
Do not trace signal lines where large current flow around the crystal oscillator circuit.
⚫
For the oscillator circuit capacitors, make sure the potential of the ground points is always equal to that of the
GND. Do not connect the capacitors to GNDs where large current flow.
⚫
Connect the crystal oscillator circuit to only ML7436N. Do not take oscillation signals from the oscillator circuit.
⚫
Table 2.2
shows the tolerance of the frequency accuracy. Adopt the frequency accuracy as followed by
Table 2.2
to confirm to the standards.
Table 2.2 Frequency accuracy to confirm to the standards.
Standard
Frequency accuracy
RCR STD-30 type III (Japan)
±10 ppm
RCR STD-30 type IV (Japan)
±4 ppm
ARIB STD-T108
（
Japan
）
±20 ppm
Wireless M-Bus N mode
±1.5kHz(8.852ppm , 4.8kbps)
±2.0kHz(11.803ppm, 2.4kbps)
Wireless M-Bus F mode
±16 ppm
