U2270B
| Model | U2270B |
| Description | Read / Write Base Station IC |
| PDF file | Total 13 pages (File size: 148K) |
| Chip Manufacturer | TEMIC |
U2270B
Function Table
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High
High
OE
Low
High
Output
Enabled
Disabled
Standby
Low
High
U2270B
Standby mode
Active
CFE
Low
Low
High
MS
Low
High
Low
COIL1
High
Low
COIL2
High
High
Applications
To achieve the suitable application, consider the power
supply environment and the magnetic coupling situation.
The selection of the appropriate power supply operation
mode depends on the supply environment. If an
unregulated supply voltage in the range of V = 7 V to 16 V
is available, the internal power supply of the U2270B can
be used. In this case, the standby mode can be used and
an external low-current
µC
can be supplied.
If a 5-V supply rail is available, it can be used to power
the U2270B. In this case please check that the voltage is
noise-free. An external power transistor is not necessary.
The application depends also on the magnetic coupling
situation. The coupling factor mainly depends on the
transmission distance and the antenna coils. The
following table lists the appropriate application for a
given coupling factor. The magnetic coupling factor can
be determined using the TEMIC test transponder coil.
The maximum transmission distance is also influenced by
the accuracy of the antenna’s resonance. Therefore, the
recommendations given above are proposals only. A good
compromise for the resonance accuracy of the antenna is
a value in the range of f
res
= 125 kHz
±
3%. Further details
concerning the adequate application and the antenna
design is provided in the TEMIC application note
ANT019 and in the TEMIC article “Antenna Design
Hints”.
The application of the U2270B includes the two
capacitors C
IN
and C
HP
whose values are linearly
dependend on the transponder’s data rate. The following
table gives the appropriate values for the most common
data rates. The values are valid for Manchester and
Bi-phase code.
Data Rate
f = 125 kHz
f/32 = 3.9 kbit/s
f/64 = 1.95 kbit/s
Input Capacitor
(C
IN
)
680 pF
1.2 nF
Decoupling
Capacitor (C
HP
)
100 nF
220 nF
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Magnetic Coupling
Factor
k > 3%
k > 1%
Appropriate Application
Free-running oscillator
Diode feedback
k > 0.5%
k > 0.3%
Diode feedback
plus frequency altering
Diode feedback
plus fine frequency tuning
The following applications are typical examples. The
values of C
IN
and C
HP
correspond to the transponder’s
data rate only. The arrangement to fit the magnetic
coupling situation is also independent from other design
issues exept of one constellation. This constellation,
consisting of diode feedback plus fine frequency tuning
together with the two-rail power supply should be used
if the transmission distance is in the range of d 10 cm.
[
TELEFUNKEN Semiconductors
Rev. A3, 13-Dec-96
7 (13)
