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Audio Accessory IC Series
Ground Isolation Amplifier
BA3121F, BA3123F
No.09092EAT01
Description The BA3121F/BA3123F are ground isolation amplifiers developed 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 = 3.5Vrms Typ.). 4) Low distortion (THD = 0.002% Typ.). 5) Two channels. Applications Car audio systems Line up matrix Operation temperature BA3121F 3085C BA3123F 4085C
Absolute maximum ratings (Ta = 25C) Parameter Symbol Limits 18 450* 3085 4085 55125 Unit V mW
Power supply voltage Vcc Power dissipation Pd BA3121F Operation Topr temperature BA3123F Storage temperature Tstg Reduced by 4.5mW in Ta of 1C over 25C. Recommended operating conditions (Ta = 25C) Parameter Power supply voltage Symbol Vcc Min. 4
Typ. 12
Max. 18
Unit V
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1/8
2009.08 - Rev.A
BA3121F, BA3123F
Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 12V, f = 1kHz, Rg = 1.8k) Parameter Quiescent current Output noise voltage Voltage gain Maximum output voltage Total harmonic distortion Common-mode rejection ratio Common-made voltage Ripple rejection ratio Channel separation Slew rate Input resistance Symbol IQ VNO GV VOM THD CMRR VCM RR CS SR RIN Min. 5.6 -1.5 1.8 41 2.5 72 44 Typ. 9.0 3.5 -0.04 2.0 0.002 57 3.75 80 82 2.0 55 Max. 14.0 8.0 1.5 0.02 66 Unit mA Vrms dB Vrms dB Vrms dB dB V/S k
Technical Note
Conditions VIN0Vrms BPF20Hz-20kHz VO10dBm, Rg0 THD0.1, Vcc8V VO0.7Vrms Vcc8V,CMRR40dB fRR100Hz,VRR10dBm, Rg0 VIN10dBm, Rg1.8k/OPEN
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 f
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2/8
2009.08 - Rev.A
BA3121F, BA3123F
Technical Note
Fig.7 Ripple rejection ratio vs. frequency
Fig.8 Total harmonic distortion vs. output voltage
Fig.9 Total harmonic distortion vs. frequency
Fig.10 Common-mode rejection ratio vs. frequency
Fig.11Common-mode rejection ration vs. input voltage
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3/8
2009.08 - Rev.A
BA3121F, BA3123F
Measurement circuits
Technical Note
BA3121F / BA3123F
Fig.12
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4/8
2009.08 - Rev.A
BA3121F, BA3123F
Block Diagram
Technical Note
Fig.13
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2009.08 - Rev.A
BA3121F, BA3123F
Circuit operation
Technical Note
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
With the BA3121F/BA3123F, the elimination level of the noise is expressed as: CMMR = 20log (e0/eI)(eI = e1 = e2) Therefore, CMRR 41dB can be guaranteed. From and
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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6/8
2009.08 - Rev.A
BA3121F, BA3123F
Applications
Technical Note
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 physical safety measures and investigate how not to apply the conditions under which absolute maximum ratings are exceeded 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 power 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 placement discrepancies of the LSI. If it is misinstalled and the power is turned on, the LSI may be damaged. It also may 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 (Vm1), and 6pin (Vm2) should maintain the ratio of 2:1 for ripple removal characteristics. 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)
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7/8
2009.08 - Rev.A
BA3121F, BA3123F
Ordering part number
Technical Note
B
A
3
1
2
1
F
Package F: SOP8
-
E
2
Part No.
Part No. 3121: Operation temperature -30~85C 3123: Operation temperature -40~85C
Packaging and forming specification E2: Embossed tape and reel
SOP8

5.00.2 (MAX 5.35 include BURR)
8 7 6 5
+6 4 -4
Tape Quantity
0.90.15 0.3MIN
Embossed carrier tape 2500pcs E2
The direction is the 1pin of product is at the upper left when you hold
6.20.3
4.40.2
Direction of feed
( reel on the left hand and you pull out the tape on the right hand
)
12
3
4
0.595
1.50.1
+0.1 0.17 -0.05 S
0.11
1.27 0.420.1
1pin
(Unit : mm)
Direction of feed
Reel
Order quantity needs to be multiple of the minimum quantity.
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8/8
2009.08 - Rev.A
Notice
Notes
No copying or reproduction of this document, in part or in whole, is permitted without the consent of ROHM Co.,Ltd. The content specified herein is subject to change for improvement without notice. The content specified 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 specifications, 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 specified 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 specified 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 property or other rights held by ROHM and other parties. ROHM shall bear no responsibility whatsoever for any dispute arising from the use of such technical information. The Products specified in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, office-automation equipment, communication devices, electronic appliances and amusement devices). The Products specified 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 injury, fire or any other damage caused in the event of the failure of any Product, such as derating, redundancy, fire 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, transportation equipment, aerospace machinery, 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. If you intend to export or ship overseas any Product or technology specified herein that may be controlled under the Foreign Exchange and the Foreign Trade Law, you will be required to obtain a license or permit under the Law.
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