ROHM BA3121F Technical data

Audio Accessory IC Series

Ground Isolation Amplifier

BA3121F, BA3123F

No.09092EAT01

●Description The BA3121F/BA3123F are ground isolation amplifiers deve loped for use in car audio applications. This IC efficiently eliminate problems caused by wiring resistance, and remove noise generated by the electrical devices used in automobiles. The capacitance values of the external capacitors required for the ICs are small to allow compact and reliable set design.

●Features

1) Large capacitors not required

2) High common-mode rejection ratio (57dB typ. at f = 1kHz).

3) Low noise (VNO = 3.5μVrms T yp.).

4) Low distortion (THD = 0.002% Typ.).

5) Two channels.

●Applications Car audio systems

●Line up matrix

BA3121F BA3123F Operation temperature

●Absolute maximum ratings (Ta = 25C)

Parameter Symbol Limits Unit

Power supply voltage Vcc 18 V Power dissipation Pd 450* mW Operation temperature Storage temperature Tstg －55～＋125 ℃

＊Reduced by 4.5mW in Ta of 1C over 25C.

●Recommended operating conditions (Ta = 25C)

Parameter Symbol Min. Typ. Max. Unit

Power supply voltage Vcc 4 12 18 V

BA3121F BA3123F －40～＋85 ℃

－30～＋85C －40～＋85C

Topr

－30～＋85 ℃

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BA3121F, BA3123F

●Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 12V, f = 1kHz, Rg = 1.8k)

Parameter Symbol Min. Typ. Max. Unit Conditions Quiescent current IQ 5.6 9.0 14.0 mA VIN＝0V Output noise voltage VNO － 3.5 8.0 μV

BPF＝20Hz-20kHz

rms

Voltage gain GV -1.5 -0.04 1.5 dB VO＝－10dBm, Rg＝0Ω Maximum output voltage VOM 1.8 2.0 － V

THD＝0.1％, Vcc＝8V

rms

Total harmonic distortion THD － 0.002 0.02 ％ VO＝0.7V Common-mode rejection ratio CMRR 41 57 － dB Common-made voltage VCM 2.5 3.75 － V

Ripple rejection ratio RR 72 80 － dB

Channel separation CS － 82 － dB

Vcc＝8V,CMRR＝40dB

rms

fRR＝100Hz,VRR＝－10dBm,

＝0Ω

VIN＝－10dBm,

Rg＝1.8kΩ/OPEN Slew rate SR － 2.0 － V/μS Input resistance RIN 44 55 66 kΩ

◎Not designed for radiation resistance

●Electrical characteristics curves

Fig.1 Quiescent current

vs. power supply voltage

Fig.2 Maximum output voltage

vs. power supply voltage

Fig.3 Output noise voltage

vs. power supply voltage

Fig.4 Voltage gain

vs. power supply voltage

Fig.5 Voltage gain vs. frequency

Fig.6 Channel separation

rms

Technical Note

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Fig.7 Ripple rejection ratio

Fig.10 Common-mode rejection ratio

vs. frequency

Fig.8 Total harmonic distortion

vs. output voltage

Fig.11Common-mode rejection ration

vs. input voltage

Technical Note

Fig.9 Total harmonic distortion

vs. frequency

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●Measurement circuits

Technical Note

BA3121F / BA3123F

Fig.12

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●Block Diagram

Technical Note

Fig.13

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●Circuit operation

Fig.14 Flow of noise in car audio systems

Car audio systems are earthed to the car body, and for this reason, electrical noise generated by the car electrics can enter the power amplifier input via the chassis, and become audible. The BA3121F/BA3123F makes use of the common-mode rejection characteristics of an operational amplifier to eliminate this noise. Without the BA3121F/BA3123F noise enters the power amplifier input directly, when used, the CMMR of operational amplifiers 1-A and 2-A eliminates the noise. Principles of noise elimination: To obtain the output voltage (eO)

Fig.15 The principle of noise rejection

Technical Note

With the BA3121F/BA3123F, the elimination level of the noise is expressed as: CMMR = 20log (e Therefore, CMRR ≧ 41dB can be guaranteed.

From ① and ②

)(eI = e1 = e2)

0/eI

Ideally, if R1R4 = R2R3, and e1 = e2, the noise voltage will become zero. However, due to mismatching between the resistors, difference in the noise voltages (e1 and e2), and tolerances in the operational amplifier, a noise voltage does result.

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●Applications

Fig.16

●Cautions on use (1) Numbers and data in entries are representative design values and are not guaranteed values of the items. (2) Although we are confident in recommending the sample application circuits, carefully check their characteristics further

when using them. When modifying externally attached component constants before use, determine them so that they have sufficient margins by taking into account variations in externally attached components and the Rohm LSI, not only for static characteristics but also including transient characteristics.

(3) Absolute maximum ratings

If applied voltage, operating temperature range, or other absolute maximum ratings are exceeded, the LSI may be damaged. Do not apply voltages or temperatures that exceed the absolute maximum ratings. If you think of a case in which absolute maximum ratings are exceeded, enforce fuses or other physica l safety measures and investigate how not to apply the conditions under which absolute maximum ratings are e xceeded to the LSI.

(4) GND potential

Make the GND pin voltage such that it is the lowest voltage even when operating below it. Actually confirm that the voltage of each pin does not become a lower voltage than the GND pin, including transient phenomena.

(5) Thermal design

Perform thermal design in which there are adequate margins by taking into account the allowable po wer dissipation in actual states of use.

(6) Shorts between pins and misinstallation

When mounting the LSI on a board, pay adequate attention to orientation and plac ement discrepancies of the LSI. If it is misinstalled and the power is turned on, the LSI may be damaged. It also ma y be damaged if it is shorted by a foreign substance coming between pins of the LSI or between a pin and a power supply or a pin and a GND.

(7) Operation in strong magnetic fields

Adequately evaluate use in a strong magnetic field, since there is a possibility of malfunction.

(8) The capacitors of 2pin (Vm

Maintaining this ratio will not cause ripple removal rate to reduce significantly even if the capacitance reduces to a half.

(9) Setting the capacitor to the double or half will make the CMRR in the low range to +6dB or -6dB respectively (Fig. 10)

), and 6pin (Vm2) should maintain the ratio of 2:1 for ripple removal characteristics.

Technical Note

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BA3121F, BA3123F

●Ordering part number

B A 3 1 2 1 F - E 2

Part No. Part No.

SOP8

4.4±0.2

6.2±0.3

1.5±0.1

5.0±0.2

(MAX 5.35 include BURR)

438251

0.595

0.11

1.27

0.42±0.1

3121: Operation temperature

-30~85C 3123: Operation temperature

-40~85C

−4°

0.3MIN

0.9±0.15

+0.1

0.17

0.05

(Unit : mm)

Package

F: SOP8

Embossed carrier tapeTape

Quantity

Direction of feed

2500pcs E2

The direction is the 1pin of product is at the upper left when you hold

()

reel on the left hand and you pull out the tape on the right hand

Reel

Technical Note

Packaging and forming specification E2: Embossed tape and reel

1pin

Order quantity needs to be multiple of the minimum quantity.

∗

Direction of feed

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Notes

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The content specied herein is subject to change for improvement without notice.

The content specied herein is for the purpose of introducing ROHM's products (hereinafter "Products"). If you wish to use any such Product, please be sure to refer to the specications, which can be obtained from ROHM upon request.

Examples of application circuits, circuit constants and any other information contained herein illustrate the standard usage and operations of the Products. The peripheral conditions must be taken into account when designing circuits for mass production.

Great care was taken in ensuring the accuracy of the information specied in this document. However, should you incur any damage arising from any inaccuracy or misprint of such information, ROHM shall bear no responsibility for such damage.

The technical information specied herein is intended only to show the typical functions of and examples of application circuits for the Products. ROHM does not grant you, explicitly or implicitly, any license to use or exercise intellectual proper ty or other rights held by ROHM and other par ties. ROHM shall bear no responsibility whatsoever for any dispute arising from the use of such technical information.

Notice

The Products specied in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, ofce-automation equipment, communication devices, electronic appliances and amusement devices).

The Products specied in this document are not designed to be radiation tolerant.

While ROHM always makes efforts to enhance the quality and reliability of its Products, a Product may fail or malfunction for a variety of reasons.

Please be sure to implement in your equipment using the Products safety measures to guard against the possibility of physical injur y, re or any other damage caused in the event of the failure of any Product, such as derating, redundancy, re control and fail-safe designs. ROHM shall bear no responsibility whatsoever for your use of any Product outside of the prescribed scope or not in accordance with the instruction manual.

The Products are not designed or manufactured to be used with any equipment, device or system which requires an extremely high level of reliability the failure or malfunction of which may result in a direct threat to human life or create a risk of human injury (such as a medical instrument, transpor tation equipment, aerospace machiner y, nuclear-reactor controller, fuel-controller or other safety device). ROHM shall bear no responsibility in any way for use of any of the Products for the above special purposes. If a Product is intended to be used for any such special purpose, please contact a ROHM sales representative before purchasing.

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ROHM BA3121F Technical data

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