MP7731 5W - 30W Class D Mono Bridged Audio Amplifier

Transcription

1 The Future of Analog IC Technology DESCRIPTION The MP773 is a mono, W - 30W Class D Audio Amplifier. It is one of MPS second generation of fully integrated audio amplifiers which dramatically reduces solution size by integrating the following: Start Up / Shut Down Pop Elimination Short Circuit Protection Circuits 80mΩ Power MOSFETs Mute / Standby Mode The MP773 utilizes a full bridge output structure capable of delivering W - 30W into 4Ω speakers. As in all other MPS Class D Audio Amplifiers, this device exhibits the high fidelity of a Class AB amplifier with an efficiency of 90%. The circuit is based on the MPS proprietary variable frequency topology Analog Adaptive Modulation (AAM, Patent No. 6,4,930; other patents pending) that delivers excellent PSRR, fast response time and operates on a single power supply. EVALUATION BOARD REFEREE Board Number Dimensions EV cm x 3.0cm x.cm MP773 W - 30W Class D Mono Bridged Audio Amplifier FEATURES 30W into 4Ω with V DD = 6.V 90% Efficiency at W Amplifies Full Audio Range with Low THD+N Typical = 0.% 9.V to 8V Supply Voltage Operation Full Bridge Output Drive 4 Integrated 80mΩ Switches Turn On / Turn Off Click and Pop Suppression Integrated Short Circuit Protection Integrated Thermal shutdown Mute / Standby Mode APPLICATIONS Flat Panel LCD and PDP Displays Notebook and Multimedia Computers Televisions Home Stereos DVD and VCD Players Game Devices and Systems Monitors MPS and The Future of Analog IC Technology are Registered Trademarks of Monolithic Power Systems, Inc. ICAL APPLICATION AUDIO IN+ AUDIO IN- EN MP773 PGND 9 PIN SW 3 8 NIN VDD 4 7 AGND BS 6 6 EN PGND 7 4 NIN SW 8 3 PIN VDD 9 AGND BS 0 EN f=khz M 0 0 MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

2 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER PACKAGE REFEREE PIN NIN AGND MP773 EN 6 NIN PIN AGND EN EXPOSED PAD PGND SW VDD BS PGND SW VDD BS ABSOLUTE MAXIMUM RATINGS () Supply Voltage V DD... 6V BS Voltage... V SW -0.3V to V SW +6.V Enable Voltage V EN V to 6V V SW, V PIN, V NIN... -V to V DD +V AGND to PGND V to 0.3V Junction Temperature...0 C Lead Temperature...60 C Storage Temperature C to 0 C Recommended Operating Conditions () Supply Voltage V DD... 9.V to 8V Operating Temperature T A C to 8 C Thermal Resistance (3) θ JA θ JC TSSOP C/W Notes: ) Exceeding these ratings may damage the device. ) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately square of oz copper. Part Number* Package Temperature MP773DF TSSOP 40 C to +8 C * For Tape & Reel, add suffix Z (eg. MP773DF Z) For RoHS compliant packaging, add suffix LF (eg. MP773DF LF Z) ELECTRICAL CHARACTERISTICS (4, ) V DD = 6.V, V EN = V, R L = 4Ω, T A = + C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Standby Current V EN = 0V 0 µa Quiescent Current 3 6 ma SW On Resistance Sourcing and Sinking 0.8 Ω Short Circuit Current Sourcing and Sinking.0 A PIN, NIN Input Common Mode Voltage Range 0 V DD / V DD -. V PIN, NIN Input Current V PIN =V NIN =8V µa EN Enable Threshold Voltage V EN Rising.4.0 V V EN Falling 0.4. V EN Enable Input Current V EN = V µa Thermal Shutdown Trip Point T J Rising 0 C Thermal Shutdown Hysteresis 30 C MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

3 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER OPERATING SPECIFICATIONS (6) Circuit of Figure, V DD = 6.V, V EN = V, R L = 4Ω, T A = + C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Standby Current V EN = 0V 700 µa Quiescent Current 8 ma Power Output THD+ Noise Efficiency f=khz, THD+N=0% 30 W f=khz, THD+N=0%, R L =8Ω 7 W P OUT =W, f=khz 0. % P OUT =W, f=khz, R L =8Ω 0. % f=khz, P OUT =0W 8 % f=khz, P OUT =0W, R L =8Ω 88 % Maximum Power Bandwidth KHz Dynamic Range 90 db Noise Floor A-Weighted 370 µv Power Supply Rejection f=khz 60 db Note: 4) The device is not guaranteed to function outside its operating rating. ) Electrical Characteristics are for the IC only with no external components except bypass capacitors. 6) Operating Specifications are for the IC in Typical Application circuit (Figure ). MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

4 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER ICAL PERFORMAE CHARACTERISTICS Circuit of Figure, V DD =6.V, T A = C, unless otherwise noted M M M M M M 0 0 AMPLITUDE (dbv) FFT Noise Floor 6K FFT A-wtd 00 K 0KK FREQUEY (Hz) EFFICIEY (%) Efficiency vs Output Power V DD =V Output Power vs Supply Voltage 40 THD=0% SUPPLY VOLTAGE (V DD ) MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

5 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER PIN FUTIONS Pin # Name Description,,, 6 No Connect Not internally connected PIN Amplifier Positive Input. PIN is the positive side of the differential input to Amplifier. Use a resistive voltage divider to set the voltage at PIN to V DD /. See Figure. 3 NIN Amplifier Negative Input. NIN is the negative side of the differential input to Amplifier. See Figure. 4 AGND Analog Ground. Connect AGND to AGND. 6 EN Enable Input. EN must be connected to EN. Drive high to enable MP773, drive low to disable. 7 NIN Amplifier Negative Input. NIN is the negative side of the differential input to Amplifier. See Figure. 8 PIN Amplifier Positive Input. PIN is the positive side of the differential input to Amplifier. Use a resistive voltage divider to set the voltage at PIN to V DD /. See Figure. 9 AGND Analog Ground. Connect AGND to AGND. 0 EN Enable Input. EN must be connected to EN. Drive high to enable MP773, drive low to disable. BS High-Side MOSFET Bootstrap Input for Amplifier. A capacitor from BS to SW supplies the gate drive current to the internal high-side MOSFET. Connect a µf capacitor from SW to BS. See Figure. 3 VDD Power Supply Input. Bypass VDD to PGND with a µf X7R capacitor (in addition to the main bulk capacitor), placed close to the IC PIN3 and PIN. 4 SW Switched Power Output. SW is the output of Amplifier. Connect the LC filter to this pin. See Figure. PGND Power Ground for Amplifier. Connect PGND to PGND. See Figure. 7 BS High-Side MOSFET Bootstrap Input for Amplifier. A capacitor from BS to SW supplies the gate drive current to the internal high-side MOSFET. Connect a µf capacitor from SW to BS. See Figure. 8 VDD Power Supply Input. Bypass VDD to PGND with a µf X7R capacitor (in addition to the main bulk capacitor), placed close to the IC PIN8 and PIN. 9 SW Switched Power Output. SW is the output of Amplifier. Connect the LC filter to this pin. See Figure. PGND Power Ground for Amplifier. Connect PGND to PGND. See Figure. MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

6 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER APPLICATION INFORMATION COMPONENT SELECTION The MP773 uses a minimum number of external components to complete a fully bridged Class D audio amplifier. The circuit in Figure shows a typical application. Use the following sections to customize the amplifier for your particular application. Setting the Voltage Gain The voltage gain sets the output voltage swing for a given input voltage swing and is set by the following equation: A V R = R Where: R = R8 R4 = R6 The maximum output voltage swing is limited by the power supply. The MP773 is a bridged amplifier and the output load is driven differentially. Each side of the load is limited to a maximum peak-to-peak voltage swing of approximately V DD. To achieve the maximum output power of the MP773 amplifier, set the amplifier gain such that the maximum peak-to-peak input signal results in at least the maximum peak-topeak output voltage swing. Setting the Switching Frequency The idle switching frequency (the switching frequency with no audio input signal) is a function of the supply voltage, V DD, the capacitors C4, C6 and C0 and resistors R and R8. Lower switching frequencies result in more inductor ripple, causing more quiescent output voltage ripple, increasing the output noise.. Higher switching frequencies result in more power loss. The optimum quiescent switching frequency is approximately 400KHz-600KHz. C6 and C4 are typically pf to.pf. C0 is used to program the idle switching frequency. Choosing the LC Filter Two identical LC filters are required in the typical application. The inductor-capacitor (LC) filter is a second order filter that converts the pulse train at SW (Pins 4, 9) to the output differential signal that drives the speaker. 4 Typical values for the LC filters are shown in Figure. The characteristic frequency of the LC filter needs to be high enough to allow high frequency audio to reach the output, yet needs to be low enough to filter out high frequency contents of the pulses from SW. The characteristic frequency of the LC filter is: f 0 = π LC Where: L = L + L, L = L C C7 C = C9 +, C = C7 C + C7 The quality factor (Q) of the LC filter is important. If this is too low, output noise will increase. If the Q factor is too high, then peaking may occur at high signal frequencies reducing the pass-band flatness. The Q is calculated as: Q = R L C Where R is the load (speaker) resistance. Use an LC filter with a Q between 0.7 and.0. The actual output ripple and noise is greatly affected by the type of inductor and capacitor used in the LC filter. Use a film capacitor and an inductor with sufficient power handling capability to supply the output current to the load. The inductor should exhibit soft saturation characteristics. If the inductor exhibits hard saturation, it should operate well below the saturation current. Gapped ferrite, MPP, Powdered Iron, or similar type toroidal cores are recommended. If open or shielded bobbin MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

7 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER ferrite cores are used, make sure that the start windings of each inductor line up (all starts going toward SW pin, or all starts going toward the output) to prevent crosstalk or other channel-to-channel interference. Input Coupling Capacitor The input coupling capacitors, C7 and C, are used to pass only the AC audio signal to the input of the amplifier. In a typical system application, the source input signal is typically centered around the circuit ground, while the MP773 input is at half the power supply voltage (V DD /). The input coupling capacitor transmits the AC signal from the source to the MP773 while blocking the DC voltage. This input coupling capacitor creates a low-pass filter with the input resistor of the MP773. Choose an input coupling capacitor such that the corner frequency (f IN ) is less than the desired passband frequency. The formula for the corner frequency is: f IN = ( πrc ) Where: R = R4 = R6 C = C7 = C Where f IN is the -3db cutoff frequency, R4 and R6 are the input resistors and C7 and C are the input AC coupling capacitors. Power Source For maximum output power, the amplifier circuit requires a regulated external power source to supply the power to the amplifier. The higher the power supply voltage, the more power can be delivered to a given load resistance. However, if the power source voltage exceeds the maximum operating voltage of 8V, the MP773 may sustain damage. The power supply rejection of the MP773 is excellent. However, noise at the power supply can get to the output, so care must be taken to minimize power supply noise within the passband frequencies. Bypass the power supply pins with a large electrolytic capacitor (typically aluminum electrolytic) along with smaller µf ceramic capacitors at the MP773 V DD supply pins. Circuit Layout Proper circuit layout is critical for optimum performance and low output distortion and noise. Place the following components as close to the MP773 as possible:. Power Supply Bypass, C, C. C and C carry the transient current for the switching power stage. Place a uf power supply bypass capacitor as close to Pin 8 (VDD) and Pin (PGND) as possible. Also place a uf power supply bypass capacitor as close to Pin 3 (VDD) and Pin (PGND) as possible.. Output Catch Diodes, D, D3, D, and D6. These diodes carry the current over the dead-time while both MOSFET switches are off. Place D3 between Pin 9 (SW) and Pin (PGND) to prevent the voltage at SW from swinging excessively below ground, and place D between SW and pin 8 (V DD ) to prevent the voltage at SW from swinging excessively about V DD. Place D6 and D similarly to minimize the undershoot and over-shoot of SW node. 3. Input Modulator Capacitor, C0. C0 is used to set the amplifier switching frequency. Place C0 as close to the differential inputs, Pin and Pin 3, as possible to reduce distortion and noise. Electro-Magnetic Interference (EMI) Due to the switching nature of the Class-D amplifier, care must be taken to minimize the effects of electromagnetic interference from the amplifier. However, with proper component selection and careful attention to circuit layout, the effects of the EMI due to the amplifier switching can be minimized. The power inductors are a potential source of radiated emissions. For the best EMI performance, use shielded inductors, since the magnetic field is well contained inside the core. On the system printed circuit board, trace loops that carry rapidly changing currents need to be minimized. VDD bypass capacitors (C and C) must be placed as close to the MP773 as possible. Nodes that carry rapidly changing voltage, such as SW and SW, must be made as small as possible. If sensitive traces run near SW or SW, place a ground shield between the traces. MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

8 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER ICAL APPLICATION CIRCUIT C4 pf C4 pf AUDIO IN+ AUDIO IN- C0 nf MP773 PGND PIN SW NIN VDD AGND BS EN PGND NIN SW D4 6.V D3 MBRS30LTR D N448 D N89 D N89 C36 3.9nF - + EN PIN AGND EN VDD BS 3 D7 6.V D6 MBRS30LTR D8 N448 C37 3.9nF C6 pf C pf Figure Mono Full Bridged Circuit MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.

9 MP773 W 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER PACKAGE INFORMATION TSSOPF (Exposed Paddle) BSC PIN ID TOP VIEW RECOMMENDED LAND PATTERN BSC. MAX SEATING PLANE SEE DETAIL "A" SIDE VIEW FRONT VIEW GAUGE PLANE 0. BSC o -8 o DETAIL A BOTTOM VIEW NOTE: ) ALL DIMENSIONS ARE IN MILLIMETERS. ) PACKAGE LENGTH DOES NOT ILUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT ILUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.0 MILLIMETERS MAX. ) DRAWING CONFORMS TO JEDEC MO-3, VARIATION ACT. 6) DRAWING IS NOT TO SCALE. NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP773 Rev /3/08 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. 08 MPS. All Rights Reserved.