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Read / Write Base Station IC
U2270B
Description
IC for IDIC® *) read-write base stations
The U2270B is a bipolar integrated circuit for read-write
base stations in contactless identification and immo-
bilizer systems.
The IC incorporates the energy transfer circuit to supply
the transponder. It consists of an on-chip power supply, an
oscillator, and a coil driver optimized for automotive-
specific distances. It also includes all signal-processing
circuits which are necessary to form the small input signal
into a microcontroller-compatible signal.
The U2270B is well suitable to perform read operations
with e5530-GT and TK5530-PP transponders and also
performs read-write operations with TK5550-PP and
TK5560-PP transponders.
Features
D Carrier frequency fosc 100 KHz – 150 KHz
D Typical data rate up to 5 Kbaud at 125 KHz
D Suitable for Manchester and Bi-phase modulation
D Power supply from the car battery or from
5-V regulated voltage
D Optimized for car immobilizer applications
D Tuning capability
D Microcontroller-compatible interface
D Low power consumption in standby mode
D Power supply output for microcontroller
Applications
D Car immobilizers
D Animal identification
D Access control
D Process control
D Further industrial applications
Case: SO16 U2270B-FP
Transponder / TAG
Read / write base station
Transp.
IC
e5530
e5550
e5560
RF– Field
typ. 125 kHz
Osc
U2270B
NF read channel
Carrier
enable
Data
output
MCU
Unlock
System
TK5530-PP
e5530-GT
TK5550-PP
TK5560-PP
Figure 1.
*) IDIC® stands for IDentification Integrated Circuit and is a trademark of TEMIC.
9300
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U2270B
Pin Description
GND 1
16 HIPASS
Output 2
15 RF
OE 3
14 VS
Input 4
13 Standby
MS 5
CFE 6
DGND 7
12 VBatt
11 DVS
10 VEXT
COIL2 8
9844
Figure 2. Pinning
9 COIL1
Block Diagram
DVS
VEXT
Pin Symbol
Function
1 GND Ground
2 Output Data output
3 OE Data output enable
4 Input Data input
5 MS Mode select coil 1: Common
mode / Differential mode
6 CFE Carrier frequency enable
7 DGND Driver ground
8 COIL 2 Coil driver 2
9 COIL 1 Coil driver 1
10 VEXT External power supply
11 DVS Driver supply voltage
12 VBatt Battery voltage
13 Standby Standby input
14 VS Internal power supply (5 V)
15 RF Frequency adjustment
16 HIPASS DC decoupling
VS VBatt
COIL1
Power supply
=1
COIL2
DGND
Driver
Input
Low pass filter
&
Oscillator
Amplifier
HIPASS
Schmitt trigger
GND
OE
Figure 3.
&
Frequency
adjustment
Standby
MS
CFE
RF
Output
9692
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Functional Description
Power Supply (PS)
DVS
VEXT
V S V Batt
internal supply
U2270B
Standby
9 V 25 kW
COILx
6 V 6 V 18 V
PS
12 kW
DRV
DGND
Figure 4. Equivalent circuit of power supply and antenna driver
11413
The U2270 can be operated with one external supply
voltage or with two externally-stabilized supply voltages
for an extended driver output voltage or from the 12-V
battery voltage of a vehicle. The 12-V supply capability
is achieved via the on-chip power supply (see figure 4).
The power supply provides two different output voltages,
VS and VEXT.
VS is the internal power supply voltage except for the
driver circuit. Pin VS is used to connect a block capacitor.
VS can be switched off by the pin STANDBY. In standby
mode, the chip’s power consumption is very low. VEXT is
the supply voltage of the antenna’s pre-driver. This
voltage can also be used to operate external circuits, i.e.,
a microcontroller. In conjunction with an external NPN
transistor, it also establishes the supply voltage of the
antenna coil driver, DVS.
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U2270B
The following section explains the 3 different
operation modes to power the U2270B.
1. One-rail operation
All internal circuits are operated from one 5-V power rail.
(see figure 5). In this case, VS ,VEXT and DVS serve as
inputs. VBatt is not used but should also be connected to
that supply rail.
+5 V (stabilized)
DVS VEXT VS VBatt Standby
12579
Figure 5.
2. Two-rail operation
In that application, the driver voltage, DVS, and the
pre-driver supply, VEXT, are operated at a higher voltage
than the rest of the circuitry to obtain a higher
driver-output swing and thus a higher magnetic field,
refer to figure 6. VS is connected to a 5-V supply, whereas
the driver voltages can be as high as 8 V. This operation
mode is intended to be used in situations where an
extended communication distance is required.
7 to 8 V (stabilized)
5 V (stabilized)
3. Battery-voltage operation
Using this operation mode, VS and VEXT are generated by
the internal power supply. (refer to figure 7). For this
mode, an external voltage regulator is not needed. The IC
can be switched off via the pin Standby. VEXT supplies the
base of an external NPN transistor and external circuits,
i.e., a microcontroller (even in Standby mode).
Pin VEXT and VBatt are overvoltage protected via internal
Zener diodes (refer figure 4).The maximum current into
that pins is determined by the maximum power dissipa-
tion and the maximum junction temperature of the IC. For
a short-time current pulse, a higher power dissipation can
be assumed (refer to application note ANT019).
7 to 16 V
DVS VEXT VS VBatt Standby
Figure 7.
12600
DVS VEXT VS VBatt Standby
Figure 6.
12580
Table 1. The following table summarizes the characteristics of the various operation modes.
Operation Mode
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ1. One-rail operation
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ2. Two-rail operation
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ3. Battery voltage
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁoperation
External Components Re-
quired
1 Voltage regulator
1 Capacitor
2 Voltage regulators
2 Capacitors
1 Transistor
2 Capacitors
Optional for load-dump
protection:
1 Resistor
1 Capacitor
Supply Voltage Range
5 V ± 10%
5 V ± 10%
7 V to 8 V
6 V to 16 V
Driver Output
[Voltage Swing
4V
6 V to 7 V
[4V
Standby Mode
Available
No
No
Yes
4 (13)
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U2270B
Oscillator (Osc)
The frequency of the on-chip oscillator is controlled by a
current fed into the RF input. An integrated compensation
circuit ensures a widly temperature and supply voltage in-
dependent frequency which is selected by a fixed resistor
Wbetween RF (pin 15) and VS (pin 14). For 125 kHz a resis-
tor value of 110 k is defined. For other frequencies, use
the following formula:
+ WRf
14375
f0 [kHz]
5
k
This input can be used to adjust the frequency close to the
resonance of the antenna. For more details refer to the ap-
plicatons and the application note ANT019.
VCC
2 kW
Rf
RF
9695
Figure 8. Equivalent circuit of Pin RF
Filter (LPF)
The fully-integrated low-pass filter (4th order butter-
worth) removes the remaining carrier signal and
high-frequency disturbancies after demodulation. The
upper cut-off frequency of the LPF depends on the se-
lected oscillator frequency. The typ. value is fosc/18. That
means that data rates up to fosc/25 are possible if Bi-phase
or Manchester encoding is used.
A high-pass characteristic results from the capacitive
coupling at the input Pin 4, as shown in figure 9. The input
voltage swing is limited to 2 Vpp. For frequency response
Wcalculation, the impedances of the signal source and LPF
input (typ. 220 k ) have to be considered. The recom-
mended values of the input capacitor for selected data
rates are shown in the chapter “Applications”.
Note:
After switching on the carrier, the dc voltage of
the coupling capacitor changes rapidly. When
the antenna voltage is stable, the LPF needs
approximately 2 ms to recover full sensitivity.
VBias + 0.4 V
RS 10 kW
~~ CIN
210 kW
VBias – 0.4 V
VBias
12601
Figure 9. Equivalent circuit of Pin Input
Amplifier (AMP)
The differential amplifier has a fixed gain, typically 30.
The HIPASS pin is used for dc decoupling. The lower
cut–off frequency of the decoupling circuit can be
calculated as follows:
+ pfcut 2
1
CHP
Ri
WThe value of the internal resistor Ri can be assumed to be
2.5 k .
Recommended values of CHP for selected data rates can
be found in the chapter “Applications”.
R
R
+
LPF
VRef
Schmitt
trigger
R
Ri
R
HIPASS
CHP
12578
Figure 10. Equivalent circuit of pin HIPASS
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