LM4651

LM4651 & LM4652 Overture™ Audio Power Amplifier 170W Class D Audio Power Amplifier Solution General Description The IC combination of the LM4651 driver and the LM4652 power MOSFET provides a high efficiency, Class D sub- woofer amplifier solution. The LM4651 is a fully integrated conventional pulse width modulator driver IC. The IC contains short circuit, under voltage, over modulation, and thermal shut down protection circuitry. It contains a standby function, which shuts down the pulse width modulation and minimizes supply current. The LM4652 is a fully integrated H-bridge power MOSFET IC in a TO-220 power package. Together, these two IC’s form a simple, compact high power audio amplifier solution complete with protection normally seen only in Class AB amplifiers. Few external components and minimal traces between the IC’s keep the PCB area small and aids in EMI control. The near rail-to-rail switching amplifier substantially in- creases the efficiency compared to Class AB amplifiers. This high efficiency solution significantly reduces the heat sink size compared to a Class AB IC of the same power level. This two-chip solution is optimum for powered subwoofers and self powered speakers. Key Specifications n Output power into 4Ω with < 10% THD. 170W (Typ) n THD at 10W, 4Ω, 10 − 500Hz. < 0.3% THD (Typ) n Maximum efficiency at 125W 85% (Typ) n Standby attenuation. >100dB (Min) Features n Conventional pulse width modulation. n Externally controllable switching frequency. n 50kHZ to 200kHz switching frequency range. n Integrated error amp and feedback amp. n Turn−on soft start and under voltage lockout. n Over modulation protection (soft clipping). n Short circuit current limiting and thermal shutdown protection. n 15 Lead TO−220 isolated package. n Self checking protection diagnostic. Applications n Powered subwoofers for home theater and PC’s n Car booster amplifier n Self-powered speakers Connection Diagrams Overture® is a registered trademark of National Semiconductor Corporation. LM4651 Plastic Package DS101277-72 Top View Order Number LM4651N See NS Package Number N28B LM4652 Plastic Package (Note 8) DS101277-73 Isolated TO-220 Package Order Number LM4652TF See NS Package Number TF15B or Non-Isolated TO-220 Package Order Number LM4652TA See NS Package Number TA15A August 2000 LM 4651 & LM 4652 Overture ™ 170W Class D Audio Pow erAm plifierSolution © 2001 National Semiconductor Corporation DS101277 www.national.com Absolute Maximum Ratings (Notes 1, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage ± 22V Output Current (LM4652) 10A Power Dissipation (LM4651) (Note 3) 1.5W Power Dissipation (LM4652) (Note 3) 32W ESD Susceptibility (LM4651) (Note 4) 2000V LM4652 (pins 2,6,10,11) 500V ESD Susceptibility (LM4651) (Note 5) 200V LM4652 (pins 2,6,10,11) 100V Junction Temperature (Note 6) 150˚C Soldering Information N, TA and TF Package (10 seconds) 260˚C Storage Temperature −40˚C to + 150˚C Operating Ratings (Notes 1, 2) Temperature Range −40˚C ≤ TA ≤ +85˚C Supply Voltage |V+| + |V−| 22V to 44V Thermal Resistance LM4651 N Package θJA 52˚C/W θJC 22˚C/W LM4652 TF, TO−220 Package θJA 43˚C/W θJC 2.0˚C/W LM4652 T, TO−220 Package θJA 37˚C/W θJC 1.0˚C/W System Electrical Characteristics for LM4651 and LM4652 (Notes 1, 2) The following specifications apply for +VCC = +20V, −VEE = −20V, f SW = 125kHz, fIN = 100Hz, RL = 4Ω, unless otherwise specified. Typicals apply for TA = 25˚C. For specific circuit values, refer to Figure 1 (Typical Audio Application Circuit). Symbol Parameter Conditions LM4651 & LM4652 Typical Units ICQ Total Quiescent Power Supply Current VCIN = 0V, L O = 0mA, |IVCC+| + |IVEE−| RDLY = 0Ω RDLY = 10kΩ 237 124 mA mA ISTBY Standby Current VPIN13 = 5V, Stby: On 17 mA AM Standby Attenuation VPIN13 = 5V, Stby: On >115 dB PO Output Power (Continuous Average) RL = 4Ω, 1% THD 125 W RL = 4Ω, 10% THD 155 W RL = 8Ω, 1% THD 75 W RL = 8Ω, 10% THD 90 W fSW = 75kHz, RL = 4Ω, 1% THD 135 W fSW = 75kHz, RL = 4Ω, 10% THD 170 W η Efficiency at PO = 5W PO = 5W, RDLY = 5kΩ 55 % η Efficiency(LM4651 & LM4652) PO = 125W, THD = 1% 85 % Pd Power Dissipation(LM4651 + LM4652) PO = 125W, THD = 1% (max) 22 W fSW = 75kHz, PO = 135W, THD = 1% (max) 22 W THD+N Total Harmonic Distortion Plus Noise 10W, 10Hz ≤ fIN ≤ 500Hz, AV = 18 dB10Hz ≤ BW ≤ 80kHz 0.3 % eOUT Output Noise A Weighted, no signal, RL = 4Ω 550 µV SNR Signal-to-Noise Ratio A-Wtg, Pout = 125W, RL 4Ω 92 dB 22kHz BW, Pout = 125W, RL 4Ω 89 dB VOS Output Offset Voltage VIN = 0V, IO = 0mA, ROFFSET = 0Ω 0.7 V PSRR Power Supply Rejection Ratio RL = 4Ω, 10Hz ≤ BW ≤ 30kHz +VCCAC = −VEEAC = 1VRMS, fAC = 120Hz 37 dB LM 46 51 & LM 46 52 www.national.com 2 Electrical Characteristics for LM4651 (Notes 1, 2, 7) The following specifications apply for +VCC = +20V, −VEE = −20V, fSW = 125kHz, unless otherwise specified. Limits apply for TA = 25˚C. For specific circuit values, refer to Figure 1 (Typical Audio Application Circuit). Symbol Parameter Conditions LM4651 Min Typical Max Units ICQ Total Quiescent Current LM4652 not connected, IO = 0mA, |IVCC+| + |IVEE−|, RDLY = 0Ω 15 36 45 mA Standby VIL Standby Low Input Voltage Not in Standby Mode 0.8 V VIH Standby High Input Voltage In Standby Mode 2.5 2.0 V fSW Switching Frequency Range ROSC = 15kΩ 65 kHz ROSC = 0Ω 200 kHz fSWerror 50% Duty Cycle Error ROSC = 4kΩ, fSW = 125kHz 1 3 % Tdead Dead Time RDLY = 0Ω 27 ns TOverMod Over Modulation Protection Time Pulse Width Measured at 50% 310 ns Electrical Characteristics for LM4652 (Notes 1, 2, 7) The following specifications apply for +VCC = +20V, −VEE = −20V, unless otherwise specified. Limits apply for TA = 25˚C. For specific circuit values, refer to Figure 1 (Typical Audio Application Circuit). Symbol Parameter Conditions LM4652 Min Typical Max Units V(BR)DSS Drain−to−Source Breakdown Voltage VGS = 0 55 V IDSS Drain−to−Source Leakage Current VDS = 44VDC, VGS = 0V 1.0 mA VGSth Gate Threshold Voltage VDS = VGS, ID = 1mADC 0.85 V RDS(ON) Static Drain−to−Source On Resistance VGS = 6VDC, ID = 6ADC 200 300 mΩ tr Rise Time VGD = 6VDC, VDS = 40VDC, RGATE = 0Ω 25 ns tf Fall Time VGD = 6VDC, VDS = 40VDC, RGATE = 0Ω 26 ns ID Maximum Saturation Drain Current VGS = 6VDC, VDS = 10VDC 8 10 ADC Note 1: 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 guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 2: All voltages are measured with respect to the GND pin unless otherwise specified. Note 3: For operating at case temperatures above 25˚C, the LM4651 must be de−rated based on a 150˚C maximum junction temperature and a thermal resistance of θJA = 62 ˚C/W (junction to ambient), while the LM4652 must be de−rated based on a 150˚C maximum junction temperature and a thermal resistance of θJC = 2.0 ˚C/W (junction to case) for the isolated package (TF) or a thermal resistance of θJC = 1.0˚C/W (junction to case) for the non-isolated package (T). Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Note 5: Machine Model, 220pF-240pF discharge through all pins. Note 6: The operating junction temperature maximum, Tjmax is 150˚C. Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 8: The LM4652TA package TA15A is a non-isolated package, setting the tab of the device and the heat sink at −V potential when the LM4652 is directly mounted to the heat sink using only thermal compound. If a mica washer is used in addition to thermal compound, θCS (case to sink) is increased, but the heat sink will be isolated from −V. LM 4651 & LM 4652 www.national.com3 Electrical Characteristics for LM4652 (Notes 1, 2, 7) (Continued) DS101277-68 FIGURE 1. Typical Application Circuit and Test Circuit LM 46 51 & LM 46 52 www.national.com 4 LM4651 Pin Descriptions Pin No. Symbol Description 1 OUT1 The reference pin of the power MOSFET output to the gate drive circuitry. 2,27 BS1,BS2 The bootstrap pin provides extra bias to drive the upper gates, HG1,HG2. 3 HG1 High−Gate #1 is the gate drive to a top side MOSFET in the H-Bridge. 4 HG2 High−Gate #2 is the gate drive to a top side MOSFET in the H-Bridge. 5,15 GND The ground pin for all analog circuitry. 6 +6VBYP The internally regulated positive voltage output for analog circuitry. This pin is available for internal regulator bypassing only. 7 +VCC The positive supply input for the IC. 8 −6VBYP The internally regulated negative voltage output for analog circuitry. This pin is available for internal regulator bypassing only. 9 FBKVO The feedback instrumentation amplifier output pin. 10 ERRIN The error amplifier inverting input pin. The input audio signal and the feedback signal are summed at this input pin. 11 ERRVO The error amplifier output pin. 12 TSD The thermal shut down input pin for the thermal shut down output of the LM4652. 13 STBY Standby function input pin. This pin is CMOS compatible. 14 FBK1 The feedback instrumentation amplifier pin. This must be connected to the feedback filter from VO1 (pin 15 on the LM4652 ). 16 OSC The switching frequency oscillation pin. Adjusting the resistor from 15.5kΩ to 0Ω changes the switching frequency from 75kHz to 225kHz. 17 Delay The dead time setting pin. 18 SCKT Short circuit setting pin. Minimum setting is 10A. 19 FBK2 The feedback instrumentation amplifier pin. This must be connected to the feedback filter from VO2 (pin 7 on the LM4652 ). 20,21 −VDDBYP The regulator output for digital blocks. This pin is for bypassing only. 22,23 −VEE The negative voltage supply pin for the IC. 24 START The start up capacitor input pin. This capacitor adjusts the start up time of the diagnostic sequence for the modulator. Refer to Start up Sequence and Timing in the Application Information section. 25 LG1 Low−Gate #1 is the gate drive to a bottom side MOSFET in the H-Bridge. 26 LG2 Low−Gate #2 is the gate drive to a bottom side MOSFET in the H-Bridge. 28 OUT2 The reference pin of the power MOSFET output to the gate drive circuitry. LM 4651 & LM 4652 www.national.com5 LM4652 Pin Descriptions Pin No. Symbol Description 1 GND A ground reference for the thermal shut down circuitry. 2 LG1 Low−Gate #1 is the gate input to a bottom side MOSFET in the H-Bridge. 3 −VEE The negative voltage supply input for the power MOSFET H-Bridge. 4 TSD The thermal shut down flag pin. This pin transitions to 6V when the die temperature exceeds 150˚C. 5 NC No connection 6 LG2 Low−Gate #2 is the gate input to a bottom side MOSFET in the H-Bridge. 7 VO2 The switching output pin for one side of the H-Bridge. 8 NC No connection. 9 NC No connection. 10 HG2 High−Gate #2 is the gate input to a top side MOSFET in the H-Bridge. 11 NC No connection. 12 NC No connection. 13 +VCC The positive voltage supply input for the power MOSFET H-Bridge. 14 HG1 High−Gate #1 is the gate input to a top side MOSFET in the H-Bridge. 15 VO2 The switching output pin for one side of the H-Bridge. Note: NC, no connect pins are floating pins. It is best to connect the pins to GND to minimize any noise from being coupled into the pins. External Components Description (Refer to Figure 1) Components Functional Description 1. R1 Works with R2, Rfl1 and Rfl2 to set the gain of the system. Gain = [(R2/ R1) x ((Rfl1 + Rfl2)/ Rfl2) − (R2/ R1) + .5]. 2. R2 See description above for R1. 3. Rf Sets the gain and bandwidth of the system by creating a low pass filter for the Error Amplifier’s feedback with Cf. 3dB pole is at fC = 1/(2piRfCf) (Hz). 4. Cf See description above for Rf. 5. RfI1 Provides a reduction in the feedback with RfI2. RfI1should be 10 X RfI2 minimum to reduce effects on the pole created by RfI2 and CfI1. See also note for R1, R2 for effect on System Gain. 6. RfI2 RfI2 and CfI1 creates a low pass filter with a pole at fC = 1/(2piRfI2CfI1) (Hz). See also note for R1, R2 for effect on System Gain. 7. CfI1 See description above for RfI2. 8. RfI3 Establish the second pole for the low pass filter in the feedback path at fC = 1/(2piRfI3CfI2) (Hz). 9. CfI2 See description above for RfI3. 10. L1 Combined with CBYP creates a 2−pole, low pass output filter that has a −3dB pole at fC = 1/[2pi(L12CBYP)1⁄2] (Hz). 11. C1 Filters high frequency noise from the amplifier’s output to ground. Recommended value is 0.1µF to 1µF. 12. Cbyp See description for L1. 13. CB1−CB4 Bypass capacitors for VCC, VEE, analog and digital voltages (VDD, +6V, −6V). See Supply Bypassing and High Frequency PCB Design in the Application Information section for more information. 14. BBT Provides the bootstrap capacitance for the boot strap pin. 15. RDLY Sets the dead time or break before make to TDLY = (1.7x10−12) (500 + RDLY) (seconds). 16. CSTART Controls the startup time with TSTART = (8.5x104) CSTART (seconds). 17. RSCKT Sets the output short circuit current with ISCKT = (1x105)/ (10kΩ\ RSCKT) (A). 18. ROSC Controls the switching frequency with fSW = 1 X 109 / (4000 + ROSC) (Hz). 19. D1 Schottky diode to protect the output MOSFETs from fly back voltages. LM 46 51 & LM 46 52 www.national.com 6 External Components Description (Refer to Figure 1) (Continued) Components Functional Description 20. CSBY1, CSBY2,CSBY3 Supply de-coupling capacitors. See Supply Bypassing in the Application Information section. 21. ROFFSET Provides a small DC voltage at the input to minimize the output DC offset seen by the load. This also minimize power on pops and clicks. 22. CIN Blocks DC voltages from being coupled into the input and blocks the DC voltage created by ROFFSET from the source. 23. Rgate Slows the rise and fall time of the gate drive voltages that drive the output FET’s. Typical Performance Characteristics Output Power vs. Supply Voltage DS101277-4 Output Power vs. Supply Voltage DS101277-5 THD+N vs. Output Power RL = 4Ω DS101277-6 THD+N vs. Output Power RL = 8Ω DS101277-7 LM 4651 & LM 4652 www.national.com7 Typical Performance Characteristics (Continued) THD+N vs. Output Power RL = 4Ω DS101277-8 THD+N vs. Output Power RL = 8Ω DS101277-9 THD+N vs. Frequency vs. Bandwidth RL = 4Ω DS101277-10 THD+N vs. Frequency vs. Bandwidth RL = 8Ω DS101277-11 THD+N vs. Frequency vs. Bandwidth RL = 4Ω DS101277-12 THD+N vs. Frequency vs. Bandwidth RL = 8Ω DS101277-13 LM 46 51 & LM 46 52 www.national.com 8 Typical Performance Characteristics (Continued) Power Dissipation & Efficiency vs. Output Power DS101277-16 Clipping Power Point & Efficiency vs. Switching Frequency (fSW) DS101277-17 Frequency Response RL = 4Ω DS101277-18 Supply Current vs. Switching Frequency (LM4651 & LM4652) DS101277-20 Supply Current vs. Supply Voltage (LM4651 & LM4652) DS101277-21 RDS(ON) vs. Temperature DS101277-23 LM 4651 & LM 4652 www.national.com9 Application Information GENERAL FEATURES System Functional Information: The LM4651 is a conven- tional pulse width modulator/driver. As Figure 2 shows the incoming audio signal is compared with a triangle waveform with a much higher frequency than the audio signal (not drawn to scale). The comparator creates a variable duty cycle squarewave. The squarewave has a duty cycle propor- tional to the audio signal level. The squarewave is then properly conditioned to drive the gates of power MOSFETs in an H-bridge configuration, such as the LM4652. The pulse train of the power MOSFETs are then fed into a low pass filter (usually a LC) which removes the high frequency and delivers an amplified replica of the audio input signal to the load. Standby Function: The standby function of the LM4651 is CMOS compatible, allowing the user to perform a muting of the music as well as turning off all power MOSFETs by shutting down the pulse width waveform. Standby has the added advantage of minimizing the quiescent current. Be- cause standby shuts down the pulse width waveform, the attenuation of the music is complete (>120dB), EMI is mini- mized, and any output noise is eliminated since there is no modulation waveform. By placing a logic ’1’ or 5V at pin 13, the standby function will be enabled. A logic ’0’ or 0V at pin 13 will disable the standby function allowing modulation by the input signal. Under Voltage Protection: The under voltage protection disables the output driver section of the LM4651 while the supply voltage is below ± 10.5V. This condition can occur as power is first applied or when low line, changes in load resistance or power supply sag occurs. The under voltage protection ensures that all power MOSFETs are off, eliminat- ing any shoot-through current and minimizing pops or clicks during turn-on and turn-off. The under voltage protection gives the digital logic time to stabilize into known states providing a popless turn on. Start Up Sequence and Self-Diagnostic Timing: The LM4651 has an internal soft start feature (see Figure 3) that ensures reliable and consistent start-up while minimizing turn-on thumps or pops. During the start-up cycle the system is in standby mode. This start-up time is controlled externally by adjusting the capacitance (CSTART) value connected to the START pin. The start-up time can be controlled by the capacitor value connected to the START pin given by Equa- tion (1) or (2): tSTART = (8.4x104)CSTART (seconds) (1) CSTART = TSTART/(8.5x104) (Farads) (2) The value of CSTART sets the time it takes for the IC to go though the start-up sequence and the frequency that the diagnostic circuitry checks to see if an error condition has been corrected. An Error condition occurs if current limit, thermal shut down, under voltage detection, or standby are sensed. The self-diagnostic circuit checks to see if any one of these error flags has been removed at a frequency set by the CSTART capacitor. For example, if the value of CSTART is 10µF then the diagnostic circuitry will check approximately every second to see if an error condition has been corrected. If the error condition is no longer present, the LM4651/52 will return to normal operation. Current Limiting and Short Circuit Protection: The resis- tor value connected between the SCKT pin and GND deter- mines the maximum output current. Once the output current is higher than the set limit, the short circuit protection turns all power MOSFETs off. The current limit is set to a minimum of 10A internally but can be increased by adjusting the value of the RSCKT resistor. Equation (3) shows how to find RSCKT. ISCKT = 1X105/(10kΩ\ RSCKT) (Amps) (3) This feature is designed to protect the MOSFETs by setting the maximum output current limit under short circuit condi- tions. It is designed to be a fail-safe protection when the output terminals are shorted or a speaker fails and causes a short circuit condition. Thermal Protection The LM4651 has internal circuitry (pin 12) that is activated by the thermal shutdown output signal from the LM4652 (pin 4). The LM4652 has thermal shut down circuitry that monitors the temperature of the die. The voltage on the TSD pin (pin 4 of the LM4652) goes high (6V) once the temperature of the LM4652 die reaches 150˚C. This pin should be connected directly to the TSD pin of the LM4651 (pin 12). The LM4651 disables the pulse width waveform when the LM4652 transmits the thermal shutdown flag. The pulse width waveform remains disabled until the TSD flag from the LM4652 goes low, signaling the junction temperature has cooled to a safe level. Dea