LM2878

LM2878 Dual 5 Watt Power Audio Amplifier December 1994 LM2878 Dual 5 Watt Power Audio Amplifier General Description The LM2878 is a high voltage stereo power amplifier designed to deliver 5W channel continuous into 8X loads The amplifier is ideal for use with low regulation power supplies due to the absolute maximum rating of 35V and its superior power supply rejection The LM2878 is designed to operate with a low number of external components and still provide flexibility for use in stereo phonographs tape recorders and AM-FM stereo receivers The flexibility of the LM2878 allows it to be used as a power operational amplifier power comparator or servo amplifier The LM2878 is internally compensated for all gains greater than 10 and comes in an 11-lead single-in-line package (SIP) The package has been redesigned resulting in the slightly degraded thermal characteristics shown in the figure Device Dissipation vs Ambient Temperature Features Y Y Y Y Y Y Y Wide operating range 6V – 32V 5W channel output 60 dB ripple rejection output referred 70 dB channel separation output referred Low crossover distortion AC short circuit protected Internal thermal shutdown Applications Y Y Y Y Stereo phonographs AM-FM radio receivers Power op amp power comparator Servo amplifiers Typical Applications Frequency Response of Bass Tone Control TL H 7934 – 2 TL H 7934 – 1 FIGURE 1 Stereo Phonograph Amplifier with Bass Tone Control C1995 National Semiconductor Corporation TL H 7934 RRD-B30M115 Printed in U S A Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage Input Voltage (Note 1) Operating Temperature (Note 2) 35V g 0 7V 0 C to a 70 C Storage Temperature Junction Temperature Lead Temperature (Soldering 10 sec ) Thermal Resistance iJC iJA b 65 C to a 150 C a 150 C a 260 C 10 C W 55 C W Electrical Characteristics VS e 22V Parameter Total Supply Current Operating Supply Voltage Output Power Channel Distortion PO e 0W TTAB e 25 C RL e 8X AV e 50 (34 dB) unless otherwise specified Min Typ 10 6 Max 50 32 55 13 0 20 0 15 0 14 VS b 6V b 50 b 70 Conditions Units mA V W W % % % Vp-p dB f e 1 kHz THD e 10% TTAB e 25 C f e 1 kHz THD e 10% VS e 12V f e 1 kHz RL e 8X PO e 50 mW PO e 0 5W PO e 2W 5 Output Swing Channel Separation RL e 8X CBYPASS e 50 mF CIN e 0 1 mF f e 1 kHz Output Referred VO e 4 Vrms CBYPASS e 50 mF CIN e 0 1 mF f e 120 Hz Output Referred Vripple e 1 Vrms Measured at DC Input Referred Split Supplies g 15V Pin 1 Tied to Pin 11 PSRR Power Supply Rejection Ratio PSRR Negative Supply Common-Mode Range Input Offset Voltage Noise b 50 b 60 b 60 g 13 5 dB dB V mV mV mV mV dB nA MX 12 V V mS kHz A 10 Equivalent Input Noise RS e 0 CIN e 0 1 mF BW e 20 b 20 kHz CCIR  ARM Output Noise Wideband RS e 0 CIN e 0 1 mF AV e 200 25 30 08 70 100 Open Loop VS e 22V 10 4 11 2 3 dB Bandwidth at 2 5W 65 15 Open Loop Gain Input Bias Current Input Impedance DC Output Voltage Slew Rate Power Bandwidth Current Limit RS e 51X f e 1 kHz RL e 8X Note 1 g 0 7V applies to audio applications for extended range see Application Hints Note 2 For operation at ambient temperature greater than 25 C the LM2878 must be derated based on a maximum 150 C junction temperature using a thermal resistance which depends upon device mounting techniques 2 Typical Performance Characteristics Device Dissipation vs Ambient Temperature Power Supply Rejection Ratio (Referred to the Output) vs Frequency Power Supply Rejection Ratio (Referred to the Output) vs Frequency Power Supply Rejection Ratio (Referred to the Output) vs Supply Voltage Channel Separation (Referred to the Output) vs Frequency Total Harmonic Distortion vs Frequency Total Harmonic Distortion vs Frequency Total Harmonic Distortion vs Power Out Open Loop Gain vs Frequency Power Output Channel vs Supply Voltage Power Dissipation vs Power Out TL H 7934 – 3 3 Equivalent Schematic Diagram 4 TL H 7934 – 4 Connection Diagram Single-In-Line Package Application Hints The LM2878 is an improved LM378 in typical audio applications In the LM2878 the internal voltage regulator for the input stage is generated from the voltage on pin 1 Normally the input common-mode range is within g 0 7V of this pin 1 voltage Nevertheless the common-mode range can be increased by externally forcing the voltage on pin 1 One way to do this is to short pin 1 to the positive supply pin 11 The only special care required with the LM2878 is to limit the maximum input differential voltage to g 7V If this differential voltage is exceeded the input characteristics may change Figure 2 shows a power op amp application with AV e 1 The 100k and 10k resistors set a noise gain of 10 and are dictated by amplifier stability The 10k resistor is bootstrapped by the feedback so the input resistance is dominated by the 1 MX resistor TL H 7934 – 5 Top View Pin 6 must be connected to GND Order Number LM2878P See NS Package Number P11A TL H 7934 – 6 FIGURE 2 Operational Power Amplifier AV e 1 5 External Components (Figure 3) 1 R2 R5 R7 R10 Sets voltage gain AV e 1 a R2 R5 for one channel and AV e 1 a R10 R7 for the other channel 2 R4 R8 3 RO 4 C1 5 C11 Resistors set input impedance and supply bias current for the positive input Works with CO to stabilize output stage Improves power supply rejection (see Typical Performance Characteristics) Stabilizes amplifier may need to be larger depending on power supply filtering 7 C5 C7 6 C4 C8 Input coupling capacitor Pins 4 and 8 are at a DC potential of VS 2 Low frequency pole set by fL e 1 2qR4C4 Feedback capacitors Ensure unity gain at DC Also low frequency pole at fL e 1 2qR5C5 8 CO 9 C2 C10 Works with RO to stabilize output stage Output coupling capacitor Low frequency pole given by fL e 1 RqRLC2 Typical Applications (Continued) TL H 7934 – 8 TL H 7934–7 FIGURE 3 Stereo Amplifier with AV e 200 FIGURE 4 LM2878 Servo Amplifier in Bridge Configuration 6 Typical Applications (Continued) Truth Table VIN Va V a to l Va k High Va Off Off On Low On Off Off TL H 7934 – 9 FIGURE 5 Window Comparator Driving High Low Lamps 7 LM2878 Dual 5 Watt Power Audio Amplifier Physical Dimensions inches (millimeters) Single-In-Line Package (P) Order Number LM2878P NS Package Number P11A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or systems which (a) are intended for surgical implant into the body or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user National Semiconductor Corporation 1111 West Bardin Road Arlington TX 76017 Tel 1(800) 272-9959 Fax 1(800) 737-7018 2 A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness National Semiconductor Europe Fax (a49) 0-180-530 85 86 Email cnjwge tevm2 nsc com Deutsch Tel (a49) 0-180-530 85 85 English Tel (a49) 0-180-532 78 32 Fran ais Tel (a49) 0-180-532 93 58 Italiano Tel (a49) 0-180-534 16 80 National Semiconductor Hong Kong Ltd 13th Floor Straight Block Ocean Centre 5 Canton Rd Tsimshatsui Kowloon Hong Kong Tel (852) 2737-1600 Fax (852) 2736-9960 National Semiconductor Japan Ltd Tel 81-043-299-2309 Fax 81-043-299-2408 National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications