LM1875 www.ti.com SNAS524A - MAY 2004 - REVISED MAY 2004 LM1875 20W Audio Power Amplifier Check for Samples: LM1875 FEATURES DESCRIPTION * * * * * The LM1875 is a monolithic power amplifier offering very low distortion and high quality performance for consumer audio applications. 1 2 * * * * * * Up to 30 Watts Output Power AVO Typically 90 dB Low Distortion: 0.015%, 1 kHz, 20 W Wide Power Bandwidth: 70 kHz Protection for AC and DC Short Circuits to Ground Thermal Protection with Parole Circuit High Current Capability: 4A Wide Supply Range 16V-60V Internal Output Protection Diodes 94 dB Ripple Rejection Plastic Power Package TO-220 APPLICATIONS * * * * * High Performance Audio Systems Bridge Amplifiers Stereo Phonographs Servo Amplifiers Instrument Systems The LM1875 delivers 20 watts into a 4 or 8 load on 25V supplies. Using an 8 load and 30V supplies, over 30 watts of power may be delivered. The amplifier is designed to operate with a minimum of external components. Device overload protection consists of both internal current limit and thermal shutdown. The LM1875 design takes advantage of advanced circuit techniques and processing to achieve extremely low distortion levels even at high output power levels. Other outstanding features include high gain, fast slew rate and a wide power bandwidth, large output voltage swing, high current capability, and a very wide supply range. The amplifier is internally compensated and stable for gains of 10 or greater. Connection Diagram Figure 1. NDH0005D, KC0005A, NEB0005E, NEB0005B, Front View 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2004, Texas Instruments Incorporated LM1875 SNAS524A - MAY 2004 - REVISED MAY 2004 www.ti.com Typical Applications These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) Supply Voltage 60V -VEE to VCC Input Voltage -65C to + 150C Storage Temperature Junction Temperature 150C (Soldering, 10 seconds) Lead Temperature (1) 2 260C JC 3C JA 73C Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not ensure specific performance limits. Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 LM1875 www.ti.com SNAS524A - MAY 2004 - REVISED MAY 2004 Electrical Characteristics VCC=+25V, -VEE=-25V, TAMBIENT=25C, RL=8, AV=20 (26 dB), fo=1 kHz, unless otherwise specified. Parameter Conditions Typical Tested Limits Units 100 mA Supply Current POUT=0W 70 Output Power (1) THD=1% 25 THD (1) POUT=20W, fo=1 kHz 0.015 POUT=20W, fo=20 kHz 0.05 POUT=20W, RL=4, fo=1 kHz 0.022 POUT=20W, RL=4, fo=20 kHz 0.07 0.6 % 1 15 mV 0.2 2 A 0 0.5 Offset Voltage Input Bias Current Input Offset Current W % 0.4 % Gain-Bandwidth Product fo=20 kHz 5.5 Open Loop Gain DC 90 PSRR VCC, 1 kHz, 1 Vrms 95 52 VEE, 1 kHz, 1 Vrms 83 52 Max Slew Rate 20W, 8, 70 kHz BW 8 Current Limit VOUT = VSUPPLY -10V 4 Equivalent Input Noise Voltage RS=600, CCIR 3 (1) % A MHz dB dB dB V/s 3 A Vrms Assumes the use of a heat sink having a thermal resistance of 1C/W and no insulator with an ambient temperature of 25C. Because the output limiting circuitry has a negative temperature coefficient, the maximum output power delivered to a 4 load may be slightly reduced when the tab temperature exceeds 55C. Typical Applications For Single Supply Operation Figure 2. Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 3 LM1875 SNAS524A - MAY 2004 - REVISED MAY 2004 www.ti.com Typical Performance Characteristics THD vs Power Output THD vs Frequency Figure 3. Figure 4. Power Output vs Supply Voltage Supply Current vs Supply Voltage Figure 5. Figure 6. PSRR vs Frequency Device Dissipation vs Ambient Temperature INTERFACE = 1C/W. See Application Hints. Figure 7. 4 Figure 8. Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 LM1875 www.ti.com SNAS524A - MAY 2004 - REVISED MAY 2004 Typical Performance Characteristics (continued) Power Dissipation vs Power Output Power Dissipation vs Power Output Figure 9. Figure 10. IOUT vs VOUT-Current Limit/ Safe Operating Area Boundary Open Loop Gain and Phase vs Frequency Figure 11. Thermal shutdown with infinite heat sink Thermal shutdown with 1C/W heat sink Figure 12. Input Bias Current vs Supply Voltage Figure 13. Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 5 LM1875 SNAS524A - MAY 2004 - REVISED MAY 2004 www.ti.com Schematic Diagram 6 Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 LM1875 www.ti.com SNAS524A - MAY 2004 - REVISED MAY 2004 APPLICATION HINTS STABILITY The LM1875 is designed to be stable when operated at a closed-loop gain of 10 or greater, but, as with any other high-current amplifier, the LM1875 can be made to oscillate under certain conditions. These usually involve printed circuit board layout or output/input coupling. Proper layout of the printed circuit board is very important. While the LM1875 will be stable when installed in a board similar to the ones shown in this data sheet, it is sometimes necessary to modify the layout somewhat to suit the physical requirements of a particular application. When designing a different layout, it is important to return the load ground, the output compensation ground, and the low level (feedback and input) grounds to the circuit board ground point through separate paths. Otherwise, large currents flowing along a ground conductor will generate voltages on the conductor which can effectively act as signals at the input, resulting in high frequency oscillation or excessive distortion. It is advisable to keep the output compensation components and the 0.1 F supply decoupling capacitors as close as possible to the LM1875 to reduce the effects of PCB trace resistance and inductance. For the same reason, the ground return paths for these components should be as short as possible. Occasionally, current in the output leads (which function as antennas) can be coupled through the air to the amplifier input, resulting in high-frequency oscillation. This normally happens when the source impedance is high or the input leads are long. The problem can be eliminated by placing a small capacitor (on the order of 50 pF to 500 pF) across the circuit input. Most power amplifiers do not drive highly capacitive loads well, and the LM1875 is no exception. If the output of the LM1875 is connected directly to a capacitor with no series resistance, the square wave response will exhibit ringing if the capacitance is greater than about 0.1 F. The amplifier can typically drive load capacitances up to 2 F or so without oscillating, but this is not recommended. If highly capacitive loads are expected, a resistor (at least 1) should be placed in series with the output of the LM1875. A method commonly employed to protect amplifiers from low impedances at high frequencies is to couple to the load through a 10 resistor in parallel with a 5 H inductor. DISTORTION The preceding suggestions regarding circuit board grounding techniques will also help to prevent excessive distortion levels in audio applications. For low THD, it is also necessary to keep the power supply traces and wires separated from the traces and wires connected to the inputs of the LM1875. This prevents the power supply currents, which are large and nonlinear, from inductively coupling to the LM1875 inputs. Power supply wires should be twisted together and separated from the circuit board. Where these wires are soldered to the board, they should be perpendicular to the plane of the board at least to a distance of a couple of inches. With a proper physical layout, THD levels at 20 kHz with 10W output to an 8 load should be less than 0.05%, and less than 0.02% at 1 kHz. CURRENT LIMIT AND SAFE OPERATING AREA (SOA) PROTECTION A power amplifier's output transistors can be damaged by excessive applied voltage, current flow, or power dissipation. The voltage applied to the amplifier is limited by the design of the external power supply, while the maximum current passed by the output devices is usually limited by internal circuitry to some fixed value. Shortterm power dissipation is usually not limited in monolithic audio power amplifiers, and this can be a problem when driving reactive loads, which may draw large currents while high voltages appear on the output transistors. The LM1875 not only limits current to around 4A, but also reduces the value of the limit current when an output transistor has a high voltage across it. When driving nonlinear reactive loads such as motors or loudspeakers with built-in protection relays, there is a possibility that an amplifier output will be connected to a load whose terminal voltage may attempt to swing beyond the power supply voltages applied to the amplifier. This can cause degradation of the output transistors or catastrophic failure of the whole circuit. The standard protection for this type of failure mechanism is a pair of diodes connected between the output of the amplifier and the supply rails. These are part of the internal circuitry of the LM1875, and needn't be added externally when standard reactive loads are driven. Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 7 LM1875 SNAS524A - MAY 2004 - REVISED MAY 2004 www.ti.com THERMAL PROTECTION The LM1875 has a sophisticated thermal protection scheme to prevent long-term thermal stress to the device. When the temperature on the die reaches 170C, the LM1875 shuts down. It starts operating again when the die temperature drops to about 145C, but if the temperature again begins to rise, shutdown will occur at only 150C. Therefore, the device is allowed to heat up to a relatively high temperature if the fault condition is temporary, but a sustained fault will limit the maximum die temperature to a lower value. This greatly reduces the stresses imposed on the IC by thermal cycling, which in turn improves its reliability under sustained fault conditions. Since the die temperature is directly dependent upon the heat sink, the heat sink should be chosen for thermal resistance low enough that thermal shutdown will not be reached during normal operation. Using the best heat sink possible within the cost and space constraints of the system will improve the long-term reliability of any power semiconductor device. POWER DISSIPATION AND HEAT SINKING The LM1875 must always be operated with a heat sink, even when it is not required to drive a load. The maximum idling current of the device is 100 mA, so that on a 60V power supply an unloaded LM1875 must dissipate 6W of power. The 54C/W junction-to-ambient thermal resistance of a TO-220 package would cause the die temperature to rise 324C above ambient, so the thermal protection circuitry will shut the amplifier down if operation without a heat sink is attempted. In order to determine the appropriate heat sink for a given application, the power dissipation of the LM1875 in that application must be known. When the load is resistive, the maximum average power that the IC will be required to dissipate is approximately: where * * * VS is the total power supply voltage across the LM1875 RL is the load resistance PQ is the quiescent power dissipation of the amplifier The above equation is only an approximation which assumes an "ideal" class B output stage and constant power dissipation in all other parts of the circuit. The curves of "Power Dissipation vs Power Output" give a better representation of the behavior of the LM1875 with various power supply voltages and resistive loads. As an example, if the LM1875 is operated on a 50V power supply with a resistive load of 8, it can develop up to 19W of internal power dissipation. If the die temperature is to remain below 150C for ambient temperatures up to 70C, the total junction-to-ambient thermal resistance must be less than Using JC=2C/W, the sum of the case-to-heat-sink interface thermal resistance and the heat-sink-to-ambient thermal resistance must be less than 2.2C/W. The case-to-heat-sink thermal resistance of the TO-220 package varies with the mounting method used. A metal-to-metal interface will be about 1C/W if lubricated, and about 1.2C/W if dry. If a mica insulator is used, the thermal resistance will be about 1.6C/W lubricated and 3.4C/W dry. For this example, we assume a lubricated mica insulator between the LM1875 and the heat sink. The heat sink thermal resistance must then be less than 4.2C/W-2C/W-1.6C/W=0.6C/W. This is a rather large heat sink and may not be practical in some applications. If a smaller heat sink is required for reasons of size or cost, there are two alternatives. [EM00001]The maximum ambient operating temperature can be reduced to 50C (122F), resulting in a 1.6C/W heat sink, or the heat sink can be isolated from the chassis so the mica washer is not needed. This will change the required heat sink to a 1.2C/W unit if the caseto-heat-sink interface is lubricated. 8 Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 LM1875 www.ti.com SNAS524A - MAY 2004 - REVISED MAY 2004 NOTE When using a single supply, maximum transfer of heat away from the LM1875 can be achieved by mounting the device directly to the heat sink (tab is at ground potential); this avoids the use of a mica or other type insulator. The thermal requirements can become more difficult when an amplifier is driving a reactive load. For a given magnitude of load impedance, a higher degree of reactance will cause a higher level of power dissipation within the amplifier. As a general rule, the power dissipation of an amplifier driving a 60 reactive load (usually considered to be a worst-case loudspeaker load) will be roughly that of the same amplifier driving the resistive part of that load. For example, a loudspeaker may at some frequency have an impedance with a magnitude of 8 and a phase angle of 60. The real part of this load will then be 4, and the amplifier power dissipation will roughly follow the curve of power dissipation with a 4 load. Component Layouts Figure 14. Split Supply Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 9 LM1875 SNAS524A - MAY 2004 - REVISED MAY 2004 www.ti.com Figure 15. Single Supply 10 Submit Documentation Feedback Copyright (c) 2004, Texas Instruments Incorporated Product Folder Links: LM1875 PACKAGE OPTION ADDENDUM www.ti.com 11-Jan-2021 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (C) Device Marking (3) (4/5) (6) LM1875T ACTIVE TO-220 NDH 5 45 Non-RoHS & Green Call TI Call TI 0 to 70 LM1875T LM1875T/LB02 ACTIVE TO-220 NEB 5 45 Non-RoHS & Green Call TI Call TI 0 to 70 LM1875T LM1875T/LB03 ACTIVE TO-220 NDH 5 45 Non-RoHS & Green Call TI Call TI 0 to 70 LM1875T LM1875T/LB05 ACTIVE TO-220 NEB 5 45 Non-RoHS & Green Call TI Call TI 0 to 70 LM1875T LM1875T/LF02 ACTIVE TO-220 NEB 5 45 RoHS & Green SN Level-1-NA-UNLIM 0 to 70 LM1875T LM1875T/LF03 ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM 0 to 70 LM1875T LM1875T/LF05 ACTIVE TO-220 NEB 5 45 RoHS & Green SN Level-1-NA-UNLIM 0 to 70 LM1875T LM1875T/NOPB ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM 0 to 70 LM1875T (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 11-Jan-2021 (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 MECHANICAL DATA NDH0005D www.ti.com MECHANICAL DATA NEB0005B www.ti.com MECHANICAL DATA NEB0005E www.ti.com IMPORTANT NOTICE AND DISCLAIMER TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES "AS IS" AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS. These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable standards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants you permission to use these resources only for development of an application that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of these resources. TI's products are provided subject to TI's Terms of Sale (https:www.ti.com/legal/termsofsale.html) or other applicable terms available either on ti.com or provided in conjunction with such TI products. TI's provision of these resources does not expand or otherwise alter TI's applicable warranties or warranty disclaimers for TI products.IMPORTANT NOTICE Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2021, Texas Instruments Incorporated