ATMEL U2270B

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
Read/Write
Base Station
U2270B
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-specific distances. It also includes all signal-processing circuits which are necessary to
transform the small input signal into a microcontroller-compatible signal.
4684E–RFID–02/08
Figure 1-1.
System Block Diagram
Read/write base station
Transponder/TAG
Osc
RF field
typ. 125 kHz
Transponder
IC
MCU
U2270B
NF read channel
Figure 1-2.
Carrier
enable
Unlock
System
Data
output
Block Diagram
DVS
VEXT
VS
VBatt
Standby
Power supply
=1
COIL1
MS
CFE
Frequency
adjustment
&
COIL2
Driver
RF
Oscillator
DGND
Output
Amplifier
&
Input
Schmitt trigger
Lowpass filter
HIPASS
2
GND
OE
U2270B
4684E–RFID–02/08
U2270B
2. Pin Configuration
Figure 2-1.
Pinning
GND
OUTPUT
OE
INPUT
MS
CFE
DGND
COIL2
Table 2-1.
Pin
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
HIPASS
RF
VS
STANDBY
VBATT
DVS
VEXT
COIL1
Pin Description
Symbol
1
GND
2
OUTPUT
3
OE
4
INPUT
Function
Ground
Data output
Data output enable
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
3
4684E–RFID–02/08
3. Functional Description
3.1
Power Supply (PS)
Figure 3-1.
Equivalent Circuit of Power Supply and Antenna Driver
DVS
VEXT
VS VBatt
Standby
Internal supply
9V
25 kΩ
12 kΩ
6V
6V
18V
PS
COILx
DRV
DGND
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 vehicle. 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 conjunction with an external NPN transistor, it also establishes the supply voltage of the antenna coil
driver, DVS.
4
U2270B
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
+
DVS
3.2.2
VEXT
VS
+5V (stabilized)
VBatt Standby
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 voltages 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
7V to 8V (stabilized)
+
+
DVS
3.2.3
VEXT
VS
5V (stabilized)
VBatt Standby
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.
5
4684E–RFID–02/08
Figure 3-4.
Battery Operation
7V to 16V
DVS
Table 3-1.
VEXT
VS
VBatt Standby
Characteristics of the Various Operation Modes
Supply-voltage Range
Driver Output
Voltage Swing
Standby Mode
Available
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
Operation Mode
External Components Required
One-rail operation
3.3
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 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:
14375 - – 5
R t [ k Ω] = -------------------f 0 [ kHz ]
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
VS
Rf
2 kΩ
RF
6
U2270B
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 Figure 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 recommended 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
VBias + 0.4V
RS
Input
10 kΩ
CIN
210 kΩ
VBias - 0.4V
3.5
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:
1
f cut = -------------------------------------------2 × π × C HP × R i
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.
7
4684E–RFID–02/08
Figure 3-7.
Equivalent Circuit of Pin HIPASS
R
+
-
Schmitt
trigger
R
LPF
VRef
R
R
Ri
HIPASS
CHP
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
7 µA
OE
8
U2270B
4684E–RFID–02/08
U2270B
3.7
Driver (DRV)
The driver supplies the antenna coil with the appropriate energy. The circuit consists of two independent 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
30 µA
MS
Figure 3-10. Equivalent Circuit of Pin CFE
30 µA
CFE
9
4684E–RFID–02/08
3.8
Function Table
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
4. Applications
To achieve the system performance, consider the power-supply environment and the magnetic-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 external 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 appropriate application for a given coupling factor. The magnetic coupling factor can be determined
using Atmel®’s test transponder coil.
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
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 fres = 125 kHz ± 3%. Further
details concerning the adequate application and the antenna design is provided in Section
“Antenna Design Hints”.
10
U2270B
4684E–RFID–02/08
U2270B
The application of the U2270B includes the two capacitors CIN and CHP whose values are linearly 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.
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
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 independent 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
110 kΩ
5V
47 nF
VEXT VS
VBatt
+
47 µF
VDD
DVS
RF
U2270B
MS
CFE
INPUT
CIN
1N4148
R
OE
Microcontroller
STANDBY
OUTPUT
HIPASS
1.35 mH
470 kΩ
CHP
COIL1
1.5 nF
COIL2
1.2 nF
DGND
GND
VSS
11
4684E–RFID–02/08
4.2
Application 2
Basic application using diode feedback. This application allows higher communication distances
than .“Application 1”
Figure 4-2.
Application Circuit 2
BC639
4×
1N4148
360Ω
+
68 kΩ
12V
22 µF
+
+
4.7 nF
75 kΩ
GND
22 µF
22 µF
100 kΩ
43 kΩ
VEXT DVS
VS
VBatt
RF
VDD
MS
1.2 nF
COIL2
1.35 mH
CFE
U2270B
82Ω
COIL1
Microcontroller
Standby
Antenna
CIN
1N4148
470 kΩ
12
1.5 nF
CHP
Input
Output
HIPASS
DGND
I/O
OE
GND
VSS
U2270B
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 microcontroller signal controls the adequate operating frequency.
Figure 4-3.
Application Circuit 3
4×
1N4148
68 kΩ
+
4.7 nF
75 kΩ
100 kΩ
43 kΩ
22 µF
VS
VEXT DVS
VBatt
RF
5V
47 nF
GND
VDD
MS
1 nF
COIL2
1.5 mH
CFE
U2270B
82Ω
COIL1
Standby
Antenna
CIN
1N4148
Input
Output
HIPASS
180 pF
100Ω
470 kΩ
DGND
1.5 nF
Microcontroller
OE
GND
VSS
CHP
4.7 kΩ
BC846
1.5 kΩ
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.
13
4684E–RFID–02/08
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
VS
16
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
8 and 9
ICoil
200
mA
Ptot
380
mW
Driver output current
Power dissipation SO16
Junction temperature
Tj
150
°C
Storage temperature
Tstg
–55
125
°C
Ambient temperature
Tamb
–40
105
°C
6. Thermal Resistance
Parameter
Thermal resistance SO16
Symbol
Value
Unit
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
VS
4.5 to 6.3
V
Operating voltage
10, 11
VEXT, DVS
4.5 to 8
V
100 to 150
kHz
Carrier frequency
14
U2270B
4684E–RFID–02/08
U2270B
8. Electrical Characteristics
All voltages are referred to GND (Pins 1 and 7)
Parameters
Test Conditions
Data output
- Collector emitter
- Saturation voltage
Iout = 5 mA
Data output enable
- Low-level input voltage
- High-level input voltage
Data input
- Clamping level low
- Clamping level high
- Input resistance
- Input sensitivity
f = 3 kHz (square wave)
Gain capacitor = 100 nF
Pin
Symbol
2
VCEsat
3
Vil
Vih
4
Driver polarity mode
- Low-level input voltage
- High-level input voltage
5
Carrier frequency enable
- Low-level input voltage
- High-level input voltage
6
Operating current
5V application without load
connected to the coil driver
Standby current
12V application
VS
- Supply voltage
- Supply voltage drift
- Output current
Driver output voltage
- One-rail operation
- Battery-voltage operation
VEXT
- Output voltage
- Supply voltage drift
- Output current
- Standby output current
Unit
400
mV
0.5
V
V
2.4
2
3.8
220
V
V
kΩ
mVpp
Vil
Vih
Rin
SIN
10
Vil
Vih
2.4
0.2
V
V
Vil
Vih
3.0
0.8
V
V
4.5
9
mA
12
ISt
30
70
µA
6.3
V
mV/K
mA
8, 9
IC active
Standby mode
13
VS
dVs/dT
IS
4.6
1.8
5.4
4.2
3.5
VDRV
VDRV
2.9
3.1
3.6
4.0
4.3
4.7
VPP
VPP
VEXT
dVEXT/dT
IEXT
IEXT
4.6
5.4
4.2
6.3
V
mV/K
mA
mA
0.8
V
V
129
kHz
3.5
0.4
Vil
Vih
3.1
121
Oscillator
- Carrier frequency
RF resistor = 110 kΩ
(“Application 2” ), REM 1(1)
f0
Low-pass filter
- Cut-off frequency
Carrier frequency = 125 kHz
fcut
Amplifier gain
CHP = 100 nF
Note:
Max.
IS
10
Standby input
- Low-level input voltage
- High-level input voltage
Typ.
10,
11, 12
and
14
14
IL = ±100 mA
VS, VEXT, VBatt, DVS = 5V
VBatt = 12V
Min.
125
7
kHz
30
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.
15
4684E–RFID–02/08
9. Ordering Information
Extended Type Number
Package
Remarks
U2270B-MFPY
SO16
Tube, Pb-free
U2270B-MFPG3Y
SO16
Taped and reeled, Pb-free
10. Package Information
Package: SO 16
Dimensions in mm
5±0.2
9.9±0.1
0.1+0.15
1.4
0.2
3.7±0.1
0.4
1.27
3.8±0.1
6±0.2
8.89
16
9
technical drawings
according to DIN
specifications
1
8
Pin 1 identity
16
Drawing-No.: 6.541-5031.02-4
Issue: 1; 15.08.06
U2270B
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
•
•
•
•
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 deleted
Section 10 “Package Information” on page 16 changed
Minor grammatical corrections and fixed broken cross references
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
17
4684E–RFID–02/08
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4684E–RFID–02/08