RF performance comparison of SR contactless memory chips

IntroductionThis application note compares the RF characteristics of SR (SRT512 and SRIX4K) 13.56 MHz short-range contactless memorychips to those of the new ST25TB series RFID tag ICs. The ST25TB series is a direct replacement for SR products. Becausethe SR and ST25TB designs are different, this document compares each parameter that contributes to RFID tag performance,and which the customer can monitor in production.

It is shown that the RF performance of ST25TB-based RFID tags is equivalent to that of SR-based RFID tags, and thatcustomer antenna redesign is not required.

Table 1. Applicable products

Type Part numbers

ST25TB series RFID tags

ST25TB512-OAT

ST25TB512-A

ST25TB512-AC

ST25TB512-AT

ST25TB02K

ST25TB04K

RF performance comparison of SR contactless memory chips and ST25TB series RFID tags

AN5443

Application note

AN5443 - Rev 1 - April 2020For further information contact your local STMicroelectronics sales office.

www.st.com

http://www.st.com

1 Tag electrical model

An RFID tag can be modelled as follows:

Figure 1. RFID tag physical model

AntennaRFID IC

Magnetic field, H

Figure 2. RFID tag electrical model

Antenna impedance

Zc

ZaRFID IC

AC1

ichip

VOC Vchip

AC0

When subjected to an alternating magnetic field the tag antenna acts as a voltage generator that powers the RFIDchip through its output impedance Za. Za represents the impedance of the coil antenna. In the equivalent modelshown above, the antenna open circuit voltage amplitude, Voc is related to the magnetic field flowing into theantenna by the relationship: Voc = Voc = μ0 ⋅ H ⋅ 2 ⋅ N ⋅ S ⋅ ω (1)

• μ0 is the magnetic permeability of air (μ0 = 4π x 10-7)• N is the antenna number of turns• S is the average surface of antenna turns• H (A/m rms) is the amplitude of the magnetic field flowing thru the antenna under perpendicular orientation• ω=2π.f, where f is the frequency of the magnetic field strength (f=13.56 MHz).

AN5443Tag electrical model

AN5443 - Rev 1 page 2/23

1.1 Antenna impedance

An RFID system at 13.56 MHz uses magnetic coupling between reader and tags. Tags and readers use coilantennas having an inductive impedance at working frequency. The Tag antenna complex impedance is.Za = Ra+ j ⋅ XaLa = Xa/ω represents the equivalent inductance of the tag antenna.

Note: The coil antenna electrical model combines self-inductance, resistive losses and stray capacitance. Therefore,equivalent Ra and La are frequency-dependent elements. However, since SR and ST25TB tag antennas' self-resonant frequency is often much higher than 13.56 MHz, Ra and La are simplified to constant values measuredat 13.56 MHz in the rest of this document.

1.2 RFID tag IC impedance

Maximum power transfer between antenna and its load requires the load impedance to be the complex conjugateof the antenna impedance.Therefore, the RFID tag IC impedance Zc is capacitive. Zc can be expressed as Zc=Rs +j.Xs with Xs<0.The serial equivalent capacitance Cs = - 1/Xs.ω is the tuning capacitance of the chip, it is called CTUN in thedatasheet.Because magnetic field strength is subject to variation over a wide range in an application, the internal voltage ofthe chip is regulated and a clamp circuit is implemented to limit the RF input voltage.Consequently, the tag IC input imepdance Zc, and thus Rs and Xs, depend on the RF input voltage.

AN5443Antenna impedance

AN5443 - Rev 1 page 3/23

2 Tag performance considerations and RFID tag IC RF parameters

In Figure 3 , Vchip (the amplitude of the voltage between the RF input AC0 and AC1 of the chip) derives from theopen circuit voltage Voc gathered from the field by:Vcℎip = Voc ⋅ ZcZa+ Zc (2)

Vcℎip = µ0 ⋅ H ⋅ 2 ⋅ N ⋅ S ⋅ ω ⋅ ZcZa+ Zc (2')

Similarly Ichip, the current amplitude flowing into the antenna, is given by:Icℎip = Voc ⋅ 1Za+ Zc (3)Icℎip = µo ⋅ H ⋅ 2 ⋅ N ⋅ S ⋅ ω ⋅ 1Za+ Zc (3')

At the particular resonant frequency (or tuning frequency) of the tag:fres = 12π ⋅ La ⋅ Csthe chip voltage Vchip is maximum as well as the current in the antenna Ichip.Figure 3 shows an example of the ratio between Vchip and Voc over a frequency range:

Figure 3. Vchip /Voc versus frequency

Frequency

1

fres

Vchip/Voc

As shown on the graph above, voltage multiplication is maximum at the resonant frequency of the tag.

2.1 Tag tuning frequency and tag IC impedance

As stated above, the tag IC serial capacitance Cs increases with the RF input voltage and fres decreases whenthe magnetic field increases. In such cases, tag performance is optimized when resonant frequency is close to13.56 MHz for the tuning capacitance value corresponding to the chip power on reset. This value is called Ctun inproduct datasheets.

2.2 Tag IC minimum operating voltage on antenna

The minimum operating voltage of tag IC on an antenna corresponds to the minimum voltage to receive a readercommand and backscatter a complete answer. This level is higher than the power-on reset level, and depends onthe tag architecture (power consumption during command execution and impedance variation duringbackscattering).In combination with the chip impedance, this parameter determines the minimum operating field strengthnecessary for the tag to operate.

AN5443Tag performance considerations and RFID tag IC RF parameters

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2.3 Tag minimum operating field

At the tag resonant frequency, the minimum tag operating field, Hmin, and the tag IC minimum operating voltageVchipmin are related by the following relationship:Hmin = Vcℎipmin ⋅ 1µ0 ⋅ N ⋅ S ⋅ 2 ⋅ ωres Ra+ RsRs+ j ⋅ XsAt low voltages, Xs >> Rs, this becomes:Hmin = Vcℎipmin ⋅ 1µ0 ⋅ N ⋅ S ⋅ 2 ⋅ ωres Ra+ Rs ⋅ Cs ⋅ ωs (4)

where Rs is the serial equivalent resistance of the chip at minimum operating voltage.From equation 4 we can express the ratio between the minimum operating field strength of two tags assembledwith different chips but mounted on the same antenna by:Hmin_cℎip2Hmin_cℎip1 = Vcℎipmin_2 × Ra+ Rs2Vcℎipmin_1 × Ra+ Rs1Therefore, two tag families sharing the same antenna design can achieve the same minimum operating fieldstrength assuming the tag ICs' minimum operating voltages balance their power consumption according to:Vcℎipmin_2 × Ra+ Rs2 = Vcℎipmin_1 × Ra+ Rs1

2.4 Tag Q factor

Based on classical definition applicable to oscillators and RLC circuits, the tag Q factor corresponds to the ratiobetween the tuning frequency and the two side frequencies where the total power dissipated in the tag is dividedby two. Assuming constant Ra and Rs, tag current at resonance frequency is divided by √2 at these sidefrequencies.

Figure 4. Q factor definition

Ichip_max/√2

f1 f2fres

Ichip

Ichip_max

Qtag = fres/(f2-f1)

Frequency

Tag Q factor is a quantity sometimes used to compare tags in production. For instance, an abnormallly low Q canbe a sign of an assembly issue. Q factor is defined as:Q = ωresω2− ω1 (5)

According to equation 3', at the resonant frequency:Icℎip_res = μ0 ⋅ H ⋅ 2 ⋅ N ⋅ S ⋅ ωres ⋅ 1Ra+ Rs

AN5443Tag minimum operating field

AN5443 - Rev 1 page 5/23

And at ω1 and ω2:Icℎip_ω1, 2 = μ0 ⋅ H ⋅ 2 ⋅ N ⋅ S ⋅ ω1, 2 ⋅ 1Za+ Zc = μ0 ⋅ H ⋅ N ⋅ S ⋅ ωres ⋅ 1Ra+ Rs by definition of Q

Below the clamping voltage level, it is possible consider that the chip Rs value is almost independent of thevoltage level. See the impedance measurement curves in Section 3.1 SR tag IC impedance and ST25TB tag ICimpedance comparison.Thus, Rs can be considered constant between f1 and f2, giving:

ω1 = −Ra+ Rs2La + Ra+ Rs 24 ⋅ La2 + 1La ⋅ Cs and ω2 = Ra+ Rs2La + Ra+ Rs 24 ⋅ La2 + 1La ⋅ Csω2− ω1 = Ra+ RsLa Q = ωresω2− ω1 = La ⋅ ωresRa+ RsAt the resonant frequency, La.Cs.ω2res = 1 then:Q = 1Ra+ Rs ⋅ 1Cs ⋅ ωres (7)

From equations 4 and 7, this becomes:Hmin = Vcℎipmin 1μo ⋅ N ⋅ S ⋅ 2 ⋅ ωres ⋅ 1Q (8)

Q is a useful parameter to compare tags in production. However, tag Q factor is not sufficient to compare theperformance of two tags assembled with same antenna but different tag ICs . Indeed, minimum operating fieldstrength depends on tag Q factor but also the tag IC minimum operating voltage. A lower Q factor can bebalanced by a lower minimum operating voltage, leading to the same minimum operating field strength because:Hmin_cℎip2Hmin_cℎip1 = Vcℎipmin_2 ⋅ Q1Vcℎipmin_1 ⋅ Q2 (9)

AN5443Tag Q factor

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3 SR tag family and ST25TB tag IC family parameter comparison

This section compares the parameters listed in Section 2 Tag performance considerations and RFID tag IC RFparameters for the SR tag IC family and the ST25TB tag IC family. The performance of tags based on these twoproducts is compared using ST readers and an ISO test bench.

3.1 SR tag IC impedance and ST25TB tag IC impedance comparison

The example curves in Figure 5 and Figure 6. Cs comparison example: SRT512 versus ST25TB512 compare theserial resistances of SR and ST25TB products. Samples used are SRT512 and ST25TB512.

Figure 5. Rs comparison example: SRT512 versus ST25TB512

The light blue curve in corresponds to the Rs serial equivalent resistance of the ST25TB512 as a function of theRF input voltage magnitude. The sharp increase of Rs around 4 V corresponds to the activation of the voltageclamp circuit.The dark blue curve in Figure 5 corresponds to the measurement of the serial equivalent resistance for anSRT512 tag IC. Voltage clamp activation occurs at a voltage magnitude above 6 V, and is not visible on the graph.The measurements were made with a network analyzer.

AN5443SR tag family and ST25TB tag IC family parameter comparison

AN5443 - Rev 1 page 7/23

Figure 6. Cs comparison example: SRT512 versus ST25TB512

The light blue curve in Figure 6 corresponds to the serail equivalent capacitance of an ST25TB512 tag IC as afunction of the input RF voltage magnitude.Dark blue curve corresponds to the Serial equivalent capacitance for a SRT512 tag IC. As expected, both tag ICshave the same tuning capacitance value at minimum operating voltage (see Section 3.2 ).

3.2 SR tag IC and ST25TB tag IC operating voltage comparison

Figure 7 shows an example of minimum operating voltage on a Read command for an SRT512-based tag tunedat 13.56 MHz, probed with a differential 'scope probe connected between AC0 and AC1 on the antenna. The lowparasitic impedance of the chosen scope probe has negligible impact on the antenna tuning.

Figure 7. Minimum operating voltage in Read mode for an SRT512-based tag

Command Tag response

For the measured SRT512, the minimum RF operating voltage is measured at VchipminSRT512 = 4.34 V. Thecorresponding serial equivalent resistance is RsSRT512 = 6 Ω.

AN5443SR tag IC and ST25TB tag IC operating voltage comparison

AN5443 - Rev 1 page 8/23

Figure 8 shows an example of minimum operating voltage on a Read command for a ST25TB512 with samemeasurement method.

Figure 8. Minimum operating voltage in Read mode for an ST25TB512-based tag

Command Tag response

For the measured ST25TB512, the minimum RF operating voltage is measured at VchipminST25TB512 = 3.3 V.The corresponding serial equivalent resistance is RsST25TB512 = 12 Ω.The minimum operating voltage of the ST25TB512 is 24% less than that of the SRT512.

3.3 Q factor comparison for SR tags and ST25TB tags at minimum operatingvoltage

For this trial a Class 1 tag antenna is used.

3.3.1 Tag quality factor calculation for SRT512 and ST25TB512For a class 1 tag antenna having a serial equivalent resistance of Ra = 4 Ω we can calculates for a theoreticalresonant frequency 13.56 MHz. Applying equation 7:QSRT512 = 14 + 12 ⋅ 16.8 × 10−12 ⋅ 2π ⋅ 13.56 × 106 = 17.2

QST25TB512 = 14 + 12 ⋅ 16.8 × 10−12 ⋅ 2π ⋅ 13.56 × 106 = 10.7

AN5443Q factor comparison for SR tags and ST25TB tags at minimum operating voltage

AN5443 - Rev 1 page 9/23

3.3.2 MeasurementsQ factor is measured using a calibrated network analyzer measuring the impedance of a single turn coil poweringtags. The side frequencies f1 and f2 correspond to the frequencies where the serial resistance of the coilpowering the tags is divided by 2.Prior to the Q factor measurement, the tag IC input voltage at resonant frequency is adjusted to the minimumoperating voltage described in Section 3.2 SR tag IC and ST25TB tag IC operating voltage comparison by use ofan oscilloscope differential probe.Referring to Figure 9 and Figure 10 respectively:• the SR measured sample has a Q factor, QSR = 17.4• the ST25TB measured sample has a Q factor QST25TB = 11.6.

Figure 9. SRIX4K tag A factor measurement at minimum operating voltage

SR


AN5443 - Rev 1 page 10/23

Figure 10. ST25TB04K tag A factor measurement at minimum operating voltage

ST25TB

ST25TB


AN5443 - Rev 1 page 11/23

3.3.3 Minimum operating field strength comparison between calculated and values measured on anISO-test bench

3.3.3.1 CalculationFrom equation 9, it is possible to calculate the theoretical ratio between the minimum operating field strength ofSR tags and ST25TB tags: Hmin_ST25Hmin_SR = 3.3 × 17.24.4 × 10.7 = 1.2From the Q-factor measurements described in Section 3.3.2 Measurements.Hmin_ST25Hmin_SR = 3.3 × 17.44.4 × 11.6 = 1.11It can be seen that the Hmin_ST25 to Hmin_SR ratio measurements and calculations are in line.

3.3.3.2 Measurement according to ISO 10373-6Figure 11 shows a minimum operating field measurement plot for an SR IC based Class-3 round tag. The tagtuning frequency is around 14.2 MHz.A reqC command is sent, varying the magnetic field strength and modulation depth.Light gray points correspond to test points without a tag reply, and dark points to test points with a successful tagreply.


AN5443 - Rev 1 page 12/23

Figure 11. SR based Class 3 tag antenna minimum operating field Hmin_SR_C3

The measured minimum operating field, Hmin_SR_C3 = 270 mA/m.Figure 12 shows the same Hmin measurement plot for the tag assembled with an ST25TB tag IC. The tag tuningfrequency is around 14.2 MHz.


AN5443 - Rev 1 page 13/23

Figure 12. ST25TB based Class 3 tag antenna minimum operating field Hmin_ST25TB_C3

The measured minimum operating field Hmin_ST25TB_C3 = 330 mA/m.The ratio between the measured SR Hmin and that of the ST25TB tag IC is Hmin_ST25TB_C3/Hmin_SR_C3 = 1.22,which is in line with calculation.


AN5443 - Rev 1 page 14/23

3.4 Tag backscattering

3.4.1 Factors affecting tag backscatteringDuring tag-to-reader communication phase, the tag IC modifies its impedance at the frequency of the subcarrier(~848 kHz).The tag IC impedance switches between the power-reception state impedance and a low-impedancestate controlled by the internal circuit of the chip. By mutual magnetic coupling, the Tag IC impedance variationcauses a voltage variation in the reader antenna. This variation is decoded by the analog and digital receptionstage of the reader.Because the tag IC impedance in power-reception state depends on the received field strength, the tagbackscattering level depends on it too.As shown in Figure 5. Rs comparison example: SRT512 versus ST25TB512 and Figure 6. Cs comparisonexample: SRT512 versus ST25TB512, the SR tag IC and ST25TB tag IC family have a different impedanceprofile. The ST25TB serial resistance is greater, particularly because of a lower voltage clamp circuit threshold.For this reason, the ST25TB tag IC family backscattering level is lower than SR tag IC family.During the backscattering phase, tag IC impedance variation causes a variation of the current flowing into the tagantenna, and as a consequence, variation of the magnetic field generated by the tag.During ISO10373-6 load modulation measurement, the test apparatus captures the tag magnetic filed variation. Afast fourier transform is computed on the signal to extract the 848 kHz side bands corresponding to the subcarrierfrequency.

3.4.2 Tag backscattering measurements comparison according to ISO 10373-6Figure 13. SR tag IC on Class-3 antenna LMA and Figure 14. ST25TB tag IC on Class-3 antenna LMA show theload-modulation amplitude of a class-3 round antenna assembled with an SR tag IC and an ST25TB tag IC. TheTag tuning frequency is around 14.2 MHz.

AN5443Tag backscattering

AN5443 - Rev 1 page 15/23

Figure 13. SR tag IC on Class-3 antenna LMA


AN5443 - Rev 1 page 16/23

Figure 14. ST25TB tag IC on Class-3 antenna LMA

As anticipated, tags based on an ST25TB tag IC show a lower load modulation amplitude. However, theseexample measurements show that tags assembled with ST25TB tag ICs comply with ISO 14443-2 LMArequirements in the same manner as SR tag IC based tags.


AN5443 - Rev 1 page 17/23

3.5 Performance comparison using the ST25R3911B HF reader

The read range comparison here uses the ST25R3911B demonstration kit (comprising an ST25R3911B-DISCOboard with mounted ST25R3911B high-performance HF reader and NFC initiator IC, available on www.st.com),and the same class-3 round tags as used in the previous sections.The test sequence is:1. Initiate2. Select3. Get UID4. Read one block5. Write one block.The distance comparison example summarized in Table 2 shows that the performance of tags based on theSRT512 and ST25TB series RFID tag ICs are equivalent.

Table 2. Read range comparison (based on the ST25R3911B-DISCO board)

Parameter SRT512 ST25TB512

Class ST class 3 ST class 3

Read range 0 to 90 mm 0 to 90 mm

AN5443Performance comparison using the ST25R3911B HF reader

AN5443 - Rev 1 page 18/23

Revision history

Table 3. Document revision history

Date Version Changes

14-Apr-2020 1 Initial version.

AN5443

AN5443 - Rev 1 page 19/23

Contents

1 Tag electrical model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

1.1 Antenna impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 RFID tag IC impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Tag performance considerations and RFID tag IC RF parameters . . . . . . . . . . . . . . . . . . .4

2.1 Tag tuning frequency and tag IC impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2 Tag IC minimum operating voltage on antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.3 Tag minimum operating field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.4 Tag Q factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3 SR tag family and ST25TB tag IC family parameter comparison. . . . . . . . . . . . . . . . . . . . .7

3.1 SR tag IC impedance and ST25TB tag IC impedance comparison . . . . . . . . . . . . . . . . . . . . . 7

3.2 SR tag IC and ST25TB tag IC operating voltage comparison . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.3 Q factor comparison for SR tags and ST25TB tags at minimum operating voltage . . . . . . . . 9

3.3.1 Tag quality factor calculation for SRT512 and ST25TB512 . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3.2 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.3.3 Minimum operating field strength comparison between calculated and values measured onan ISO-test bench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4 Tag backscattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.4.1 Factors affecting tag backscattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.4.2 Tag backscattering measurements comparison according to ISO 10373-6 . . . . . . . . . . . . 15

3.5 Performance comparison using the ST25R3911B HF reader . . . . . . . . . . . . . . . . . . . . . . . . . 18

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

AN5443Contents

AN5443 - Rev 1 page 20/23

List of tablesTable 1. Applicable products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Table 2. Read range comparison (based on the ST25R3911B-DISCO board) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Table 3. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

AN5443List of tables

AN5443 - Rev 1 page 21/23

List of figuresFigure 1. RFID tag physical model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Figure 2. RFID tag electrical model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Figure 3. Vchip /Voc versus frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Figure 4. Q factor definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 5. Rs comparison example: SRT512 versus ST25TB512 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Figure 6. Cs comparison example: SRT512 versus ST25TB512 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Figure 7. Minimum operating voltage in Read mode for an SRT512-based tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Figure 8. Minimum operating voltage in Read mode for an ST25TB512-based tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Figure 9. SRIX4K tag A factor measurement at minimum operating voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Figure 10. ST25TB04K tag A factor measurement at minimum operating voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Figure 11. SR based Class 3 tag antenna minimum operating field Hmin_SR_C3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Figure 12. ST25TB based Class 3 tag antenna minimum operating field Hmin_ST25TB_C3 . . . . . . . . . . . . . . . . . . . . . . . . 14Figure 13. SR tag IC on Class-3 antenna LMA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 14. ST25TB tag IC on Class-3 antenna LMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

AN5443List of figures

AN5443 - Rev 1 page 22/23

IMPORTANT NOTICE – PLEASE READ CAREFULLY

STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications, and improvements to STproducts and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on ST products before placing orders. STproducts are sold pursuant to ST’s terms and conditions of sale in place at the time of order acknowledgement.

Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design ofPurchasers’ products.

No license, express or implied, to any intellectual property right is granted by ST herein.

Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product.

ST and the ST logo are trademarks of ST. For additional information about ST trademarks, please refer to www.st.com/trademarks. All other product or servicenames are the property of their respective owners.

Information in this document supersedes and replaces information previously supplied in any prior versions of this document.

© 2020 STMicroelectronics – All rights reserved

AN5443

AN5443 - Rev 1 page 23/23

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RF performance comparison of SR contactless memory chips