Features
•Carrier Frequency fosc 100 kHz to 150 kHz
•Typical Data Rate up to 5 Kbaud at 125 kHz
•Suitable for Manchester and Bi-phase Modulation
•Power Supply from the Car Battery or from 5V Regulated Voltage
•Optimized for Car Immobilizer Applications
•Tuning Capability
•Microcontroller-compatible Interface
•Low Power Consumption in Standby Mode
•Power-supply Output for Microcontroller
Applications
•Car Immobilizers
•Animal Identification
•Access Control
•Process Control
1. Description
The U2270B is an IC for IDIC® read/write base stations in contactless identification
and immobilizer 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-spe-
cific distances. It also includes all signal-processing circuits which are necessary to
transform the small input signal into a microcontroller-compatible signal.
Read/Write
Base Station
U2270B
4684E–RFID–02/08
2
4684E–RFID–02/08
U2270B
Figure 1-1. System Block Diagram
Figure 1-2. Block Diagram
Transponder
IC
RF field
typ. 125 kHz
Unlock
System
NF read channel
Osc
U2270B
Transponder/TAG Read/write base station
MCU
Carrier
enable
Data
output
Power supply
DVSVEXT
Frequency
adjustment
Oscillator
Amplifier
Driver
&
&
= 1
GND OE
Schmitt trigger
Lowpass filter
VS
CFE
MS
Standby
Output
RF
VBatt
DGND
Input
COIL2
COIL1
HIPASS
3
4684E–RFID–02/08
U2270B
2. Pin Configuration
Figure 2-1. Pinning
VEXT
COIL1
DVS
VBATT
HIPASS
3
4
2
1
7
8
6
5
VS
RF
STANDBY
DGND
COIL2
CFE
MS
GND 16
15
14
13
12
10
9
11
OE
OUTPUT
INPUT
Table 2-1. Pin Description
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 COIL2 Coil driver 2
9 COIL1 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 (5V)
15 RF Frequency adjustment
16 HIPASS DC decoupling
4
4684E–RFID–02/08
U2270B
3. Functional Description
3.1 Power Supply (PS)
Figure 3-1. Equivalent Circuit of Power Supply and Antenna Driver
The U2270B can be operated with one external supply voltage or with two externally-stabilized
supply voltages for an extended driver output voltage or from the 12V battery voltage of a vehi-
cle. The 12V supply capability is achieved via the on-chip power supply (see Figure 3-1). The
power supply provides two different output voltages, VS and VEXT.
VS is the internal power supply voltage for everything except for the driver circuit. Pin VS is used
to connect a block capacitor. VS can be switched off by the STANDBY pin. 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, such as a microcontroller. In conjunc-
tion with an external NPN transistor, it also establishes the supply voltage of the antenna coil
driver, DVS.
VBatt Standby
DGND
VS
6V
PS
DRV
18V
12 kΩ
6V
9V
Internal supply
COILx
VEXT
25 kΩ
DVS
5
4684E–RFID–02/08
U2270B
3.2 Operation Modes to Power the U2270B
The following section explains the three different operation modes to power the U2270B.
3.2.1 One-rail Operation
All internal circuits are operated from one 5V power rail (see Figure 3-2). In this case, VS, VEXT
and DVS serve as inputs. VBatt is not used but should also be connected to that supply rail.
Figure 3-2. One-rail Operation Supply
3.2.2 Two-rail Operation
In this 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 (see Figure 3-3). VS is connected to a 5V supply, whereas the driver volt-
ages can be as high as 8V. This operation mode is intended to be used in situations where an
extended communication distance is required.
Figure 3-3. Two-rail Operation Supply
3.2.3 Battery-voltage Operation
Using this operation mode, VS and VEXT are generated by the internal power supply (see Figure
3-4 on page 6). For this mode, an external voltage regulator is not needed. The IC can be
switched off via the STANDBY pin. VEXT supplies the base of an external NPN transistor and
external circuits, like a microcontroller (even in standby mode).
Pin VEXT and VBatt are overvoltage protected via internal Zener diodes (see Figure 3-1 on page
4).The maximum current into the pins is determined by the maximum power dissipation and the
maximum junction temperature of the IC.
VBatt Standby
+5V (stabilized)
+
VS
VEXT
DVS
+
VBatt Standby
5V (stabilized)
+
VS
VEXT
DVS
7V to 8V (stabilized)
6
4684E–RFID–02/08
U2270B
Figure 3-4. Battery Operation
3.3 Oscillator (Osc)
The frequency of the on-chip oscillator is controlled by a current fed into the RF input. An inte-
grated compensation circuit ensures a wide temperature range and a supply-voltage–
independent frequency which is selected by a fixed resistor between RF (pin 15) and VS (pin 14).
For 125 kHz, a resistor value of 110 kΩ is defined. For other frequencies, use the following
formula:
This input can be used to adjust the frequency close to the resonance of the antenna. For more
details see Section “Applications” on page 10.
Figure 3-5. Equivalent Circuit of Pin RF
VBatt StandbyVS
VEXT
DVS
7V to 16V
Table 3-1. Characteristics of the Various Operation Modes
Operation Mode External Components Required Supply-voltage Range
Driver Output
Voltage Swing
Standby Mode
Available
One-rail operation 1 voltage regulator
1 capacitor 5V ±10% ≈ 4V No
Two-rail operation 2 voltage regulators
2 capacitors
5V ±10%
7V to 8V 6V to 7V No
Battery-voltage operation
1 transistor
2 capacitors
Optional, for load dump protection:
1 resistor
1 capacitor
6V to 16V ≈ 4V Yes
RtkΩ[]14375
f0kHz[]
--------------------- 5–=
RF
Rf
VS
2 kΩ
7
4684E–RFID–02/08
U2270B
3.4 Low-pass Filter (LPF)
The fully integrated low-pass filter (4th-order Butterworth) removes the remaining carrier signal
and high-frequency disturbances after demodulation. The upper cut-off frequency of the LPF
depends on the selected oscillator frequency. The typical value is fOsc / 18, and 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 Fig-
ure 3-6. The input voltage swing is limited to 2 Vpp. For frequency response calculation, the
impedances of the signal source and LPF input (typical 210 kΩ) have to be considered. The rec-
ommended values of the input capacitor for selected data rates are given in Section 4.,
“Applications” , on page 10.
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.
Figure 3-6. Equivalent Circuit of Pin Input
3.5 Amplifier (AMP)
The differential amplifier has a fixed gain, typically 30. The HIPASS pin is used for DC decou-
pling. The lower cut-off frequency of the decoupling circuit can be calculated as follows:
The value of the internal resistor Ri can be assumed to be 2.5 kΩ.
Recommended values of CHP for selected data rates can be found in Section 4., “Applications” ,
on page 10.
210 kΩ
10 kΩ
V
Bias
+ 0.4V
V
Bias
- 0.4V
Input
R
S
C
IN
fcut 1
2πCHP Ri
×××
--------------------------------------------=
8
4684E–RFID–02/08
U2270B
Figure 3-7. Equivalent Circuit of Pin HIPASS
3.6 Schmitt Trigger
The signal is processed by a Schmitt trigger to suppress possible noise and to make the signal
microcontroller-compatible. The hysteresis level is 100 mV symmetrically to the DC operation
point. The open-collector output is enabled by a low level at OE (pin 3).
Figure 3-8. Equivalent Circuit of Pin OE
Schmitt
trigger
-
+
R
RR
R
LPF
HIPASS
C
HP
V
Ref
R
i
OE
7 µA
9
4684E–RFID–02/08
U2270B
3.7 Driver (DRV)
The driver supplies the antenna coil with the appropriate energy. The circuit consists of two inde-
pendent output stages. These output stages can be operated in two different modes. In common
mode, the outputs of the stages are in phase; in this mode, the outputs can be interconnected to
achieve a high-current output capability. Using the differential mode, the output voltages are in
anti-phase; thus, the antenna coil is driven with a higher voltage. For a specific magnetic field,
the antenna coil impedance is higher for the differential mode. As a higher coil impedance
results in better system sensitivity, the differential mode should be preferred.
The CFE input is intended to be used for writing data into a read/write or a crypto transponder.
This is achieved by interrupting the RF field with short gaps. The various functions are controlled
by the inputs MS and CFE (see “Function Table” on page 10). The equivalent circuit of the driver
is shown in Figure 3-1 on page 4.
Figure 3-9. Equivalent Circuit of Pin MS
Figure 3-10. Equivalent Circuit of Pin CFE
MS
30 µA
CFE
30 µA
10
4684E–RFID–02/08
U2270B
3.8 Function Table
4. Applications
To achieve the system performance, consider the power-supply environment and the mag-
netic-coupling situation.
The selection of the appropriate power-supply operation mode depends on the quality of supply
voltage. If an unregulated supply voltage in the range of V = 7V to 16V is available, the internal
power supply of the U2270B can be used. In this case, standby mode can be used and an exter-
nal low-current microcontroller can be supplied.
If a 5V supply rail is available, it can be used to power the U2270B. In this case, check that the
voltage is noise-free. An external power transistor is not necessary.
The application also depends on the magnetic-coupling situation. The coupling factor mainly
depends on the transmission distance and the antenna coils. The following table lists the appro-
priate application for a given coupling factor. The magnetic coupling factor can be determined
using Atmel®’s test transponder coil.
The maximum transmission distance is also influenced by the accuracy of the antenna’s reso-
nance. 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 fres = 125 kHz ± 3%. Further
details concerning the adequate application and the antenna design is provided in Section
“Antenna Design Hints”.
CFE MS COIL1 COIL2
Low Low High High
Low High Low High
High Low
High High
OE Output STANDBY U2270B
Low Enabled Low Standby mode
High Disabled High Active
Table 4-1. Magnetic Coupling
Magnetic Coupling Factor Appropriate Application
k > 3% Free-running oscillator
k > 1% Diode feedback
k > 0.5% Diode feedback
plus frequency altering
k > 0.3% Diode feedback
plus fine frequency tuning
11
4684E–RFID–02/08
U2270B
The application of the U2270B includes the two capacitors CIN and CHP whose values are lin-
early dependent 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.
The following applications are typical examples. The values of CIN and CHP correspond to the
transponder’s data rate only. The arrangement to fit the magnetic-coupling situation is also inde-
pendent of other design issues except for 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 d ≈10 cm.
4.1 Application 1
Application using few external components. This application is for intense magnetic coupling
only.
Figure 4-1. Application Circuit 1
Table 4-2. Recommended Capacitor Values
Data Rate f = 125 kHz Input Capacitor (CIN) Decoupling Capacitor (CHP)
f / 32 = 3.9 Kbits/s 680 pF 100 nF
f / 64 = 1.95 Kbits/s 1.2 nF 220 nF
+
1.5 nF
1.2 nF
47 nF 47 µF
RF
MS
OE
STANDBY
HIPASS
OUTPUT
CFE
INPUT
COIL1
COIL2
1.35 mHR
GND
5V
Micro-
controller
DGND
1N4148
470 kΩ
110 kΩ
DVS
VBatt
VDD
VEXT
VSS
CHP
CIN
VS
U2270B
12
4684E–RFID–02/08
U2270B
4.2 Application 2
Basic application using diode feedback. This application allows higher communication distances
than .“Application 1”
Figure 4-2. Application Circuit 2
1.5 nF
22 µF
+
22 µF
+
4.7 nF
MS
OE
Output
Standby
CFE
RF
HIPASS
Input I/O
COIL1
COIL2
BC639
1.2 nF
1.35 mH
Antenna
GND
12V
GND
Micro-
controller
U2270B
DGND
1N4148
4 ×
1N4148
470 kΩ
68 kΩ
360Ω
43 kΩ100 kΩ
82Ω
DVSVBatt
VSVDD
VEXT
VSS
CHP
CIN
75 kΩ
+
22 µF
13
4684E–RFID–02/08
U2270B
4.3 Application 3
This application is comparable to “Application 2” but alters the operating frequency. This allows
higher antenna resonance tolerances and/or higher communication distances. This application
is preferred if the detecting microcontroller is close to the U2270B, as an additional microcontrol-
ler signal controls the adequate operating frequency.
Figure 4-3. Application Circuit 3
Note: Application examples have not been examined for series production or reliability, and no worst
case scenarios have been developed. Customers who adapt any of these proposals must carry
out their own testing and be convinced that no negative consequences arise from the proposals.
1.5 nF
22 µF 47 nF
+
4.7 nF
MS
OE
Output
Standby
CFE
RF
HIPASS
Input
COIL1
COIL2
1 nF
1.5 mH
Antenna
GND
5V
GND
Micro-
controller
U2270B
DGND
180 pF
BC846
1N4148
4 ×
1N4148
470 kΩ
68 kΩ
43 kΩ
1.5 kΩ
4.7 kΩ
100 kΩ
82Ω
100Ω
DVSVBatt
VSVDD
VEXT
VSS
CHP
CIN
75 kΩ
14
4684E–RFID–02/08
U2270B
5. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
All voltages are referred to GND (Pins 1 and 7)
Parameter Pin Symbol Min. Max. Unit
Operating voltage 12 VBatt VS16 V
Operating voltage 8, 9, 10, 11, 14 VS, VEXT, DVS, Coil
1, Coil 2 –0.3 8 V
Range of input and output
voltages
3, 4, 5, 6, 15, 16
2 and 13
VIN
VOUT
–0.3
–0.3
VS + 0.3
VBatt V
Output current 10 IEXT 10 mA
Output current 2 IOUT 10 mA
Driver output current 8 and 9 ICoil 200 mA
Power dissipation SO16 Ptot 380 mW
Junction temperature Tj150 °C
Storage temperature Tstg –55 125 °C
Ambient temperature Tamb –40 105 °C
6. Thermal Resistance
Parameter Symbol Value Unit
Thermal resistance SO16 RthJA 120 K/W
7. Operating Range
All voltages are referred to GND (Pins 1 and 7)
Parameter Pin Symbol Value Unit
Operating voltage 12 VBatt 7 to 16 V
Operating voltage 14 VS4.5 to 6.3 V
Operating voltage 10, 11 VEXT
, DVS4.5 to 8 V
Carrier frequency 100 to 150 kHz
15
4684E–RFID–02/08
U2270B
Note: 1. REM 1: In “Application 1” where the oscillator operates in free-running mode, the IC must be soldered free from distortion.
Otherwise, the oscillator may be out of bounds.
8. Electrical Characteristics
All voltages are referred to GND (Pins 1 and 7)
Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit
Data output
- Collector emitter
- Saturation voltage
Iout = 5 mA 2 VCEsat 400 mV
Data output enable
- Low-level input voltage
- High-level input voltage
3V
il
Vih 2.4
0.5 V
V
Data input
- Clamping level low
- Clamping level high
- Input resistance
- Input sensitivity
f = 3 kHz (square wave)
Gain capacitor = 100 nF 4
Vil
Vih
Rin
SIN 10
2
3.8
220
V
V
kΩ
mVpp
Driver polarity mode
- Low-level input voltage
- High-level input voltage
5V
il
Vih 2.4 0.2
V
V
Carrier frequency enable
- Low-level input voltage
- High-level input voltage
6V
il
Vih 3.0 0.8
V
V
Operating current 5V application without load
connected to the coil driver
10,
11, 12
and
14
IS4.5 9 mA
Standby current 12V application 12 ISt 30 70 µA
VS
- Supply voltage
- Supply voltage drift
- Output current
14 VS
dVs/dT
IS
4.6
1.8
5.4
4.2
3.5
6.3 V
mV/K
mA
Driver output voltage
- One-rail operation
- Battery-voltage operation
IL = ±100 mA
VS, VEXT
, VBatt, DVS = 5V
VBatt = 12V
8, 9 VDRV
VDRV
2.9
3.1
3.6
4.0
4.3
4.7
VPP
VPP
VEXT
- Output voltage
- Supply voltage drift
- Output current
- Standby output current
IC active
Standby mode
10
VEXT
dVEXT/dT
IEXT
IEXT
4.6
3.5
0.4
5.4
4.2
6.3 V
mV/K
mA
mA
Standby input
- Low-level input voltage
- High-level input voltage
13 Vil
Vih 3.1
0.8 V
V
Oscillator
- Carrier frequency
RF resistor = 110 kΩ
(“Application 2” ), REM 1(1) f0121 125 129 kHz
Low-pass filter
- Cut-off frequency Carrier frequency = 125 kHz fcut 7kHz
Amplifier gain CHP = 100 nF 30
16
4684E–RFID–02/08
U2270B
10. Package Information
9. Ordering Information
Extended Type Number Package Remarks
U2270B-MFPY SO16 Tube, Pb-free
U2270B-MFPG3Y SO16 Taped and reeled, Pb-free
Package: SO 16
Dimensions in mm
specifications
according to DIN
technical drawings
Issue: 1; 15.08.06
Drawing-No.: 6.541-5031.02-4
1
Pin 1 identity
8
16 9
0.2
5±0.2
3.8±0.1
6±0.2
3.7±0.1
9.9±0.1
8.89
0.4
1.27
0.1+0.15
1.4
17
4684E–RFID–02/08
U2270B
11. Revision History
Please note that the following page numbers referred to in this section refer to the specific revision
mentioned, not to this document.
Revision No. History
4684E-RFID-01/08
• Put datasheet in a new template
• Section 3.4 “Low-pass Filter (LPF) on page 7: Typo removed
• Section 8 “Electrical Characteristics” on page 15: Parameter VS alignment
corrected
4684D-RFID-09/06
• Put datasheet in a new template
• Pb-free logo on page 1 deleted
• Section 10 “Package Information” on page 16 changed
• Minor grammatical corrections and fixed broken cross references
4684C-RFID-12/05 • Last page: Legal sentence changed
4684B-RFID-09/05
• Put datasheet in a new template
• Pb-free Logo on page 1 added
• New heading rows on Table “Absolute Maximum Ratings” on page 14 added
• Ordering Information on page 16 changed
4684E–RFID–02/08
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