ATR4254 - Atmel Corporation

Features

•

High Dynamic Range for AM and FM

•

Integrated AGC for FM

•

High Intercept Point 3rd-order for FM

•

FM Amplifier Adjustable to Various Cable Impedances

•

High Intercept Point 2nd-order for AM

•

Low-noise Output Voltage

•

Low Power Consumption

Electrostatic sensitive device.

Observe precautions for handling.

1. Description

The ATR4254 is an integrated low-noise AM/FM antenna impedance matching circuit

in BiCMOS technology. The device is designed specifically for car applications and is

suitable for windshield and roof antennas.

Figure 1-1. Block Diagram

AGC

FMIN

AGC

AMIN

AMOUT

VREF1

FMOUT

FMGAIN

GND1

AGC

AGCADJ

GND2

VREF2 VREF

1 (14)

2 (15)

4 (2)

3 (16)

5 (3)

7 (5)

8 (6)

10 (7)

14 (11)

12 (9)

13 (10)

15 (13)

AMOUT1

11 (8)

() Pin numbers in brackets = QFN16 4 × 4 package

Low-noise

AM/FM Antenna

Impedance

Matching IC

ATR4254

Rev. 4879A–AUDR–09/05

4879A–AUDR–09/05

ATR4254

2. Pin Configuration

Figure 2-1. Pinning SO16 Figure 2-2. Pinning QFN16 4 × 4

FMGAIN

AGC

VREF2

GND2

AMIN

FMIN

GND1

AGCADJ

VREF1

AMOUT1

AMOUT

FMOUT

AGC

VREF2

AGCADJ

VREF1

FMGAIN

FMGND

FMIN

FMOUT

GND2

AMIN

AMOUT

AMOUT1

16 15 14 13

5 6 7 8

Table 2-1. Pin Description

Pin SSO16 Pin QFN16 Symbol Function

1 14 FMIN FM input

2 15 GND1 Ground for FM part

3 16 FMGAIN FM gain adjustment

42AGCAGC output

5 3 VREF2 Reference voltage 2 output

6 1 NC Not connected

7 5 GND2 Ground for AM part

8 6 AMIN AM input

9 4 NC Not connected

10 7 AMOUT AM output

11 8 AMOUT1 AM output

12 9 VREF1 Reference voltage 1 output

13 10 AGCADJ Adjustment FM wide-band AGC threshold

14 11 VS Supply voltage

15 13 FMOUT FM output

16 12 NC Not connected

4879A–AUDR–09/05

ATR4254

3. Pin Description

3.1 FMIN

The input of the FM amplifier, FMIN, is a bipolar transitor’s base. A resistor or a coil is connected

between FMIN and VREF2. If a coil is used, the noise performance is excellent.

Figure 3-1. Internal Circuit at Pin FMIN

3.2 GND1

To avoid cross-talk between AM and FM signals, the circuit has two separate ground pins.

GND1 is the ground for the FM part.

3.3 FMGAIN

The DC current of the FM amplifier transistor is adjusted by an external resistor which is con-

nected between FMGAIN and GND1. To influence the AC gain of the amplifier, a resistor is

connected in series to a capacitor between FMGAIN and GND1. The capacitor has to shorten

frequencies of 100 MHz.

Figure 3-2. Internal Circuit at Pin FMGAIN

3.4 AGC

DC current flows into the AGC pin at high FM antenna input signals. This current has to be

amplified via the current gain of an external PNP transistor that feeds a PIN diode. This diode

dampens the antenna’s input signal and protects the amplifier input against overload. The maxi-

mum current which flows into the AGC pin is approximately 1 mA. In low-end applications, the

AGC function is not necessary and the external components can therefore be omitted.

ESD

FMIN

ESD

FMGAIN

4879A–AUDR–09/05

ATR4254

Figure 3-3. Internal Circuit at Pin AGC

3.5 AGCADJ

The threshold of the AGC can be adjusted by varying the DC current at pin AGCADJ. If pin

AGCADJ is connected directly to GND1, the threshold is set to 96 dBµV at the FM amplifier out-

put. If a resistor is connected between AGCADJ and GND1, the threshold is shifted to higher

values with increasing resistances. If AGCADJ is open, the threshold is set to 106 dBµV.

Figure 3-4. Internal Circuit at Pin AGCADJ

3.6 FMOUT

The FM amplifier output is an open collector of a bipolar RF transistor. It should be connected to

VS via a coil.

Figure 3-5. Internal Circuit at Pin FMOUT

ESD

AGC

ESD

65 kΩ

AGCADJ

ESD

15 FMOUT

4879A–AUDR–09/05

ATR4254

3.7 AMIN

The AM input has an internal bias voltage. The DC voltage at this pin is VRef1/2. The input resis-

tance is about 470 kΩ. The input capacitance is less than 10 pF.

Figure 3-6. Internal Circuit at Pin AMIN

3.8 AMOUT, AMOUT1

The buffered AM amplifier consists of a complementary pair of CMOS source followers. The

transistor gates are connected to AMIN. The pin AMOUT is the NMOS transistor's source, pin

AMOUT1 is the PMOS transistor's source. Due to the two different DC levels of these pins, they

have to be connected together via an external capacitor of about 100 nF. This technique can

achieve an excellent dynamic range.

Figure 3-7. Internal Circuit at Pins AMOUT1 and AMOUT

3.9 VREF1

VREF1 is the stabilized voltage for the AM amplifier and the AGC block. To achieve excellent

noise performance at LW frequencies, it is recommended that this pin be connected to ground

via an external capacitor of about 1 µF.

ESD

470 kΩ

VREF1/2

AMIN

AMOUT1

ESD

AMOUT

4879A–AUDR–09/05

ATR4254

Figure 3-8. Internal Circuit at Pin VREF1

3.10 VREF2

For the DC biasing of the FM amplifier, a second voltage reference circuit is integrated. Since

the collector current is temperature independent, the output voltage has a negative temperature

coefficient of about –1 mV/K. To stabilize this voltage, an external capacitor to ground of a few

nF is recommended.

Figure 3-9. Internal Circuit at Pin VREF2

3.11 GND2

GND2 is the ground for the AM amplifier.

ESD

GND1

VREF1

ESD

GND1

VREF2

4879A–AUDR–09/05

ATR4254

4. Functional Description

The ATR4254 is an integrated AM/FM antenna impedance matching circuit. It compensates

cable losses between the antenna (for example, windshield, roof or bumper antennas) and the

car radio, which is usually placed far away from the antenna.

The FM amplifier provides excellent noise performance. External components are used to adjust

the gain and the input-output matching impedance. Therefore, it is possible to adjust the ampli-

fier to various cable impedances (usually 50Ω, 75Ω or 150Ω). To protect the amplifier against

input overload, an Automatic Gain Control (AGC) is included on the chip. The AGC observes the

AC voltage at the FM amplifier output, rectifies this signal, and delivers DC current to dampen

the input antenna signal via an external PIN diode. The threshold for the AGC is adjustable. Sim-

ple and temperature-compensated biasing is possible due to the integrated voltage reference

VRef2.

The AM part consists of a buffer amplifier. The voltage gain of this stage is approximately one.

The input resistance is 470 kΩ, the input capacitance less than 10 pF. The output resistance is

125Ω. An excellent dynamic range is achieved due to the complementary CMOS source follower

stage.

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.

Reference point is ground (pins 2 and 7)

Parameters Symbol Value Unit

Supply voltage VS8.8 V

Power dissipation, Ptot at Tamb = 85°C Ptot 460 mW

Junction temperature Tj150 °C

Ambient temperature Tamb –40 to +85 °C

Storage temperature Tstg –50 to +150 °C

Electrostatic handling (HBM at ESD S.5.1) ±VESD ±1000 V

6. Thermal Resistance

Parameters Symbol Value Unit

Junction ambient RthJA 140 K/W

4879A–AUDR–09/05

ATR4254

7. Electrical Characteristics

VS = 8V, Tamb = 25°C, unless otherwise specified (see Figure 7-1 on page 9).

Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit

Supply voltage 14 VS7.2 8 8.8 V

Supply currents 14 IS3.5 4.8 5.6 mA

Reference voltage 1 output (I12 =0) 12 V

Ref1 5.1 5.4 5.7 V

Reference voltage 2 output (I5=0) 5 V

Ref2 2.3 2.6 2.8 V

Temperature dependence of VREF2 5 VRef2/∆T–1mV/K

AM Amplifier

Input resistance 8 RAMIN 470 kΩ

Input capacitance 8 CAMIN 10 pF

Output resistance 10 ROUT 125 Ω

Voltage gain 8, 10 a 0.85

Output noise voltage (rms value)

S1 switched to 2

B=6kHz

150 kHz to 300 kHz

500 kHz to 6.5 kHz

10 VN1

VN2

–2

–6

dBµV

2nd harmonic

S2 switched to 1

fAMIN = 500 kHz

Output voltage =

110 dBµV

10 –65 dBc

FM Amplifier

Supply current limit IAGC, IAGCADJ =0A 15 I

15 33 35 mA

Input resistance f = 100 MHz 1 RFMIN 50 Ω

Output resistance f = 100 MHz 15 RFMOUT 50 Ω

Power gain f = 100 MHz 1, 15 G 5 dB

Output noise voltage f=100MHz

B=120kHz 15 VN0dBµV

3rd-order output intercept f = 100 MHz 15 132 dBµV

AGC

AGC input voltage threshold

f=100MHz

S2 switched to 1;

AGC threshold DC

current is 10 µA at

pin 4

15 Vth1 96 dBµV

AGC input voltage threshold

f=100MHz,

S2 switched to 2;

AGC threshold DC

current is 10 µA at

pin 4

15 Vth2 106 dBµV

AGC output current AGC active IAGC 1.2 mA

4879A–AUDR–09/05

ATR4254

Figure 7-1. Test Circuit

2.2

µF

150Ω

2.2 nF

51Ω

22Ω

2.2 nF

2.2 µH

AMOUT

2.2 µH

100 nF

2.2 nF

FMOUT

2.2 nF

1 nF

15 pF

AMIN

5 kΩ

FMIN

100 nF

ATR4254

4879A–AUDR–09/05

ATR4254

Figure 7-2. FM Intermodulation Distortion

90 95 100 105 MHz

Input

dBµV

103 dBµV

90 95 100 105 MHz

Output

dBµV

108 dBµV

58 dBµV

Gain = 5 dB

AGC not active

90 95 100 105 MHz

Input

dBµV 118 dBµV

90 95 100 105 MHz

dBµV

100 dBµV

50 dBµV

Output

AGC active

4879A–AUDR–09/05

ATR4254

Figure 7-3. Test Circuit for AM Large Signal Behavior

Figure 7-4. AM Harmonic Distortion

DUT

1 nF

f = 500 kHz

50Ω

LPF

AMOUT

115 dBµV

Analyzer

cutoff

= 500 kHz 100 nF

5 kΩ

75 dBµV

AMIN R

= 50Ω

100 nF

AMOUT1

50Ω

0.5 1.0 1.5

AMOUT

(dBµV) 115 dBµV

110

55 dBµV

45 dBµV

f (MHz)

4879A–AUDR–09/05

ATR4254

Figure 7-5. Application Circuit

AGC

FMIN

AGC

AMIN

AMOUT1

VREF1

FMOUT

FMGAIN

FMGND

AGC

AGCADJ

AMGND

VREF2 V

Ref

ANTENNA

AM FM

Protection

circuit

Output

= 8.2V

1 kΩ

BC558 51

2.2 µH

2.2 nF

100 nF

200 nF

BA679

2.2 nF

39 pF

2.2 µH

2.2 nF

510Ω

1 µF

2.2 nF

1 nF

100 nF

AMOUT

and R

depend on used FM cable impedance

FM cable impedance R1 (Ω)

100

125

150

270

390

470

620

160

(Ω)

4879A–AUDR–09/05

ATR4254

9. Package Information

8. Ordering Information

Extended Type Number Package Remarks

ATR4254-TBJY SO16 –

ATR4254-TBQY SO16 Taping corresponding to ICE-286-3

ATR4254-PEPY QFN16 –

ATR4254-PEQY QFN16 Taping corresponding to ICE-286-3

technical drawings

according to DIN

specifications

Package SO16

Dimensions in mm

10.0

9.85

8.89

0.4

1.27

1.4

0.25

0.10

5.2

4.8

3.7

3.8

6.15

5.85

0.2

16 9

4879A–AUDR–09/05

ATR4254

Printed on recycled paper.

4879A–AUDR–09/05

marks or trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be trademarks of others.

Disclaimer: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any

intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN ATMEL’S TERMS AND CONDI-

TIONS OF SALE LOCATED ON ATMEL’S WEB SITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED OR STATUTORY

WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR

PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDEN-

TAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF PROFITS, BUSINESS INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT

OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. Atmel makes no

representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications

and product descriptions at any time without notice. Atmel does not make any commitment to update the information contained herein. Unless specifically provided

otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel’s products are not intended, authorized, or warranted for use

as components in applications intended to support or sustain life.

Atmel Corporation Atmel Operations

2325 Orchard Parkway

San Jose, CA 95131, USA

Tel: 1(408) 441-0311

Fax: 1(408) 487-2600

Regional Headquarters

Europe

Atmel Sarl

Route des Arsenaux 41

Case Postale 80

CH-1705 Fribourg

Switzerland

Tel: (41) 26-426-5555

Fax: (41) 26-426-5500

Asia

Room 1219

Chinachem Golden Plaza

77 Mody Road Tsimshatsui

East Kowloon

Hong Kong

Tel: (852) 2721-9778

Fax: (852) 2722-1369

Japan

9F, Tonetsu Shinkawa Bldg.

1-24-8 Shinkawa

Chuo-ku, Tokyo 104-0033

Japan

Tel: (81) 3-3523-3551

Fax: (81) 3-3523-7581

Memory

2325 Orchard Parkway

San Jose, CA 95131, USA

Tel: 1(408) 441-0311

Fax: 1(408) 436-4314

Microcontrollers

2325 Orchard Parkway

San Jose, CA 95131, USA

Tel: 1(408) 441-0311

Fax: 1(408) 436-4314

La Chantrerie

BP 70602

44306 Nantes Cedex 3, France

Tel: (33) 2-40-18-18-18

Fax: (33) 2-40-18-19-60

ASIC/ASSP/Smart Cards

Zone Industrielle

13106 Rousset Cedex, France

Tel: (33) 4-42-53-60-00

Fax: (33) 4-42-53-60-01

1150 East Cheyenne Mtn. Blvd.

Colorado Springs, CO 80906, USA

Tel: 1(719) 576-3300

Fax: 1(719) 540-1759

Scottish Enterprise Technology Park

Maxwell Building

East Kilbride G75 0QR, Scotland

Tel: (44) 1355-803-000

Fax: (44) 1355-242-743

RF/Automotive

Theresienstrasse 2

Postfach 3535

74025 Heilbronn, Germany

Tel: (49) 71-31-67-0

Fax: (49) 71-31-67-2340

1150 East Cheyenne Mtn. Blvd.

Colorado Springs, CO 80906, USA

Tel: 1(719) 576-3300

Fax: 1(719) 540-1759

Biometrics/Imaging/Hi-Rel MPU/

High Speed Converters/RF Datacom

Avenue de Rochepleine

BP 123

38521 Saint-Egreve Cedex, France

Tel: (33) 4-76-58-30-00

Fax: (33) 4-76-58-34-80

Literature Requests