Preliminary Datasheet LPA2104 3Walts Mono Filter-free Class-D Audio Power Amplifier General Description The LPA2104 is a high efficiency, 3.0W mono class-D audio power amplifier. A new developed filterless PWM modulation architecture further reduces EMI and THD+N, as well as eliminates the LC output filter, reducing external component count, sys cost, and simplifying design. Operating in a single 5V supply, LPA2104 is capable of driving 4Ω speaker load at a continuous average output of 3.05W/10% THD+N or 2.6W/1% THD+N. The LPA2104 has high efficiency with speaker load compared to a typical class D amplifier. With a 3.6V supply driving an 8Ω speaker , the efficiency for a 400mW power level is 90%.In cellular handsets, the earpiece, speaker phone, and melody ringer can each be driven by the LPA2104. The gain of LPA2104 is externally configurable which allows independent gain control from multiple sources by summing signals from separate sources. The LPA2104 is available in space-saving SOP8 and MSOP8 Packaging packages. Features Unique Modulation Scheme Reduces EMI Emissions Efficiency at 3.6V With an 8-Ω Speaker: − 90% at 400 mW − 82% at 100 mW Low 2.5mA Quiescent Current 0.5µA Shutdown Current 2.5V to 6V Wide Supply Voltage Shutdown Pin has 1.8V Compatible Thresholds Optimized PWM Output Stage Eliminates LC Output Filter Improved PSRR (−80 dB) Eliminates Need for a Voltage Regulator Fully Differential Design Reduces RF Rectification and Eliminates Bypass Capacitor Improved CMRR Eliminates Two Input Coupling Capacitors Internally Generated 750kHz Switching Frequency Integrated Pop and Click Suppression Circuitry SOP8 and MSOP8 Packaging RoHS compliant and 100% lead(Pb)-free Typical Application Circuit Order Information LPA2104 □ □ □ F: Pb-Free Package Type SO: SOP8 MS: MSOP8 LPA2104 Applications PMP,PSP, Game, Data-Bank Cellular and Smart mobile phone PDA/DSC Marking Information Please see website: www.lowpowersemi.com/LPA2104 LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com Page 1 of 11 Preliminary Datasheet LPA2104 Functional Pin Description P a c k a g e Ty p e Pin Configurations SOP8/MSOP8 Pi n Desc ript ion Pin SHUTDOWN NC PIN No 1 2 DESCRIPTION Shutdown terminal (active low logic) No Connecter +IN 3 Positive differential input -IN VO+ VDD GND VO- 4 5 6 7 8 Negative differential input Negative BTL output Power supply. High-current ground Positive BTL output Function Block Diagram Absolute Maximum Ratings Input Voltage to GND (VINA, VINB) ---------------------------------------------------------------------------- 6V Adapter Voltage to GND (VADP) ---------------------------------------------------------------------- 0.3V to 6V Supply Voltage, V -------------------------------------------------------------------------------------0.3 V to 6V Voltage at Any Input Pin -------------------------------------------------------------------------0.3 V to V +0.3 Junction Temperature, TJMAX --------------------------------------------------------------------------------------- 150°C Storage Temperature Rang, T ---------------------------------------------------------------------65°C to 150°C ESD Susceptibility -------------------------------------------------------------------------------------------2kV Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds ----------------------------------------260°C Thermal Resistance θ (WCSP) ----------------------------------------------------------------------------- 77°C/W DD LPA2104–00 Version 1.0 Datasheet DD stg JA Sep.-2012 www.lowpowersemi.com Page 2 of 11 Preliminary Datasheet LPA2104 Electrical Characteristics Symbol Parameter Conditions Min. VOS Output offset voltage (measured differentially) Vi=0V,Av=2V/V,VDD=2.5V to 5.5V PSRR Power supply rejection ration VDD=2.5V to 5.5V CMRR Common mode rejection ratio IIH High-level input current VDD=2.5V to 5.5V,Vic=VDD/2 0.5V,Vin=VDd/2 to Vdd-0.8V VDD=5.5V, Vi=5.8V IIL Low-level input current VDD=5.5V, Vi=-0.3V IQ Quiescent current LPA2104 Typ. Max. 1 to 25 mV -72 -55 dB -60 -48 dB 100 uA 5 uA VDD=5.5V, no load 3.52 VDD=3.6V, no load 2.40 VDD=2.5V, no load 2.06 VSHDN=0.35V, VDD=2.5V to 5.5V 0.5 ISHDN ILIM Shutdown Current Static drain-source on-state resistance VDD=5.5V, no load 400 RDS(ON) VDD=3.6V, no load 500 VDD=2.5V, no load 700 Switching frequency VDD=2.5V to 5.5V P-Channel Current Limit ](SW) mA µA 1.2 A m 750 KHz V/V VDD=2.5 to 5.5V Gain THD+N=10%, F=1KHz,RL=4 THD+N=1%, F=1KHz,RL=4 PO Output power THD+N=10%, F=1KHz,RL=8 THD+N=1%, F=1KHz,RL=8 VDD=5.0V 3.05 VDD=3.6V VDD=2.5V 1.28 0.64 VDD=5.0V 2.6 VDD=3.6V VDD=2.5V 1.06 0.46 VDD=5.0V 1.7 VDD=3.6V VDD=2.5V 0.79 0.39 VDD=5.0V 1.36 VDD=3.6V 0.64 VDD=2.5V 0.32 VDD=5V,,Po=1W,RL=8 Total harmonic distortion plus noise THD+N f=1KHz f=1KHz 0.130 VDD=2.5V,,Po=0.2W,RL=8 f=1KHz 0.163 VDD=3.6V,Inputs ac-grounded with Ci=2uF F=217Hz,V9ripple) =200mVpp CMRR Common mode rejection ratio VDD=3.6V, Vic=1Vpp F=217Hz Zt \ Start-up time from shutdown VDD=3.6 LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com W W W W 0.123 VDD=3.6V,,Po=0.5W,RL=8 Supply ripple rejection ratio kSVR Unit % -70 dB -80 dB 40 mS Page 3 of 11 Preliminary Datasheet LPA2104 Typical Operating Characteristics LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com Page 4 of 11 Preliminary Datasheet LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com LPA2104 Page 5 of 11 Preliminary Datasheet LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com LPA2104 Page 6 of 11 Preliminary Datasheet LPA2104 Application Information The LPA2104 is a fully differential amplifier with differential inputs and outputs. The fully differential amplifier consists of a differential amplifier and a common-mode amplifier. The differential amplifier ensures that the amplifier outputs a differential voltage on the output that is equal to the differential input times the gain. The common-mode feedback ensures that the common-mode voltage at the output is biased around VDD/2 regardless of the common-mode voltage at the input. The fully differential LPA2104 can still be used with a single-ended input; however, the LPA2104 should be used with differential inputs when in a noisy environment, like a wireless handset, to ensure maximum noise rejection. LPA2104 Figure 30. Typical Application Schematic With Differential Input for a Wireless Phone Advantages of Fully Differential Amplifiers Input-coupling capacitors not required: The fully differential amplifier allows the inputs to be biased at voltage other than mid-supply. For example, if a codec has a mid-supply lower than the mid-supply of the LPA2104, the common-mode feedback circuit will adjust, and the LPA2104 outputs will still be biased at mid-supply of the LPA2104. The inputs of the LPA2104 can be biased from 0.5V toVDD-0.8 V. If the inputs are biased outside of that range, input-coupling capacitors are required. Mid-supply bypass capacitor, C(BYPASS), not required: - The fully differential amplifier does not require a bypass capacitor. This is because any shift in the mid-supply affects both positive and negative channels equally and cancels at the differential output. Better RF−immunity: -GSM handsets save power by turning on and shutting off the RF transmitter at a rate of 217Hz.The transmitted signal is picked-up on input and output traces. The fully differential amplifier cancels the signal much better than the typical audio amplifier. Component Selection Figure 30 shows the LPA2104 typical schematic with differential inputs and Figure 31 shows the LPA2104 with differential inputs and input capacitors, and Figure 32 shows the LPA2104 with single-ended inputs. Differential inputs should be used whenever possible because the single-ended inputs are much more susceptible to noise. LPA2104 Figure 31. Typical Application Schematic With Differential Input and Input Capacitors LPA2104 Figure 32. Typical Application Schematic With Single-Ended Input Input Resistors (RI) The input resistors (RI) set the gain of the amplifier according to equation (1). Table 1. Typical Component Values (1) CI is only needed for single-ended input or if VICM is not between 0.5 V and VDD – 0.8 V. CI = 3.3 nF (with RI = 150 kΩ) gives a high-pass corner frequency of 321 Hz. LPA2104–00 Version 1.0 Datasheet Sep.-2012 Resistor matching is very important in fully differential amplifiers. The balance of the output on the reference voltage depends on matched ratios of the resistors. CMRR, PSRR, and cancellation of the second harmonic distortion diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors or better to keep the performance optimized. Matching is more important than overall tolerance. Resistor arrays with 1% www.lowpowersemi.com Page 7 of 11 Preliminary Datasheet matching can be used with a tolerance greater than 1%. Place the input resistors very close to the LPA2104 to limit noise injection on the high-impedance nodes. For optimal performance the gain should be set to 2 V/V or lower. Lower gain allows the LPA2104 to operate at its best, and keeps a high voltage at the input making the inputs less susceptible to noise. Decoupling Capacitor (CS) The LPA2104 is a high-performance class-D audio amplifier that requires adequate power supply decoupling to ensure the efficiency is high and total harmonic distortion (THD) is low. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically 1µF, placed as close as possible to the device VDD lead works best. Placing this decoupling capacitor close to the LPA2014 is very important for the efficiency of the class-D amplifier, because any resistance or inductance in the trace between the device and the capacitor can cause a loss in efficiency. For filtering lower-frequency noise signals, a 1 0µF or greater capacitor placed near the audio power amplifier would also help, but it is not required in most applications because of the high PSRR of this device. Input Capacitors (CI) The LPA2104 does not require input coupling capacitors if the design uses a differential source that is biased from 0.5 V to VDD – 0.8 V (shown in Figure 31). If the input signal is not biased within the recommended common –mode input range, if needing to use the input as a high pass filter (shown in Figure 32), or if using a single-ended source (shown in Figure 33), input coupling capacitors are required. The input capacitors and input resistors form a high-pass filter with the corner frequency, fc, determined in equation (2). Summing Input Signals Most wireless phones or PDAs need to sum signals at the audio power amplifier or just have two signal sources that need separate gain. The LPA2104 makes it easy to sum signals or use separate signal sources with different gains. Many phones now use the same speaker for the earpiece and ringer, where the wireless phone would require a much lower gain for the phone earpiece than for the ringer. PDAs and phones that have stereo headphones require summing of the right and left channels to output the stereo signal to the mono speaker. Summing Two Differential Input Signals Two extra resistors are needed for summing differential signals (a total of 5 components). The gain for each input source can be set independently (see equations (4) and(5), and Figure 33). If summing left and right inputs with a gain of 1 V/V, use RI1 = RI2 = 300 k If summing a ring tone and a phone signal, set the ring-tone gain to Gain 2 = 2 V/V, and the phone gain to Gain 1 = 0.1 V/V. The resistor values would be. . . RI1=3MΩ, and=RI2=150kΩ The value of the input capacitor is important to consider as it directly affects the bass (low frequency) performance of the circuit. Speakers in wireless phones cannot usually respond well to low frequencies, so the corner frequency can be set to block low frequencies in this application.Equation (3) is reconfigured to solve for the input coupling capacitance. If the corner frequency is within the audio band, the capacitors should have a tolerance of ± 10% or better, because any mismatch in capacitance causes an impedance mismatch at the corner frequency and below. For a flat low-frequency response, use large input coupling capacitors (1 µF). However, in a GSM phone the ground signal is fluctuating at 217 Hz, but the signal from the codec does not have the same 217 Hz fluctuation. The difference between the two signals is amplified, sent to the speaker, and heard as a 217 Hz hum. LPA2104–00 Version 1.0 Datasheet Sep.-2012 LPA2104 LPA2104 Summing Two Single-Ended Input Signals Four resistors and three capacitors are needed for summing single-ended input signals. The gain and corner frequencies (fc 1 and fc2) for each input source can be set independently (see equations (9) through (12), and Figure 35). Resistor, RP, and capacitor, CP, are needed on the IN+ terminal to match the impedance on the IN– terminal. The single-ended inputs must be driven by low impedance sources even if one of the inputs is not outputting an ac signal. www.lowpowersemi.com Page 8 of 11 Preliminary Datasheet LPA2104 LPA2104 Layout Considerations As output power increases, interconnect resistance (PCB traces and wires) between the amplifier, load and power supply create a voltage drop. The voltage loss on the traces between the LPA2104 and the load results is lower output power and decreased efficiency. Higher trace resistance between the supply and the LPA2104 has the same effect as a poorly regulated supply, increase ripple on the supply line also reducing the peak output power. The effects of residual trace resistance increases as output current increases due to higher output power, decreased load impedance or both. To maintain the highest output voltage swing and corresponding peak output power, the PCB traces that connect the output pins to the load and the supply pins to the power supply should be as wide as possible to minimize trace resistance. The use of power and ground planes will give the best THD+N performance. While reducing trace resistance, the use of power planes also creates parasite capacitors that help to filter the power supply line. The inductive nature of the transducer load can also result in overshoot on one or both edges, clamped by the parasitic diodes to GND and VDD in each case. From an EMI stand- point, this is an aggressive waveform that can radiate or conduct to other components in the system and cause interference. It is essential to keep the power and output traces short and well shielded if possible. Use of ground planes, beads, and micro-strip layout techniques are all useful in preventing unwanted interference. As the distance from the LPA2104 and the speaker increase, the amount of EMI radiation will increase since the output wires or traces acting as antenna become more efficient with length. What is acceptable EMI is highly application specific. Ferrite chip inductors placed close to the LPA2104 may be needed to reduce EMI radiation. The value of the ferrite chip is very application specific. Ferrite chip inductors placed close to the LPA2104 may be needed to reduce EMI radiation. The value of the ferrite chip is very application specific. LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com Page 9 of 11 Preliminary Datasheet LPA2104 Packaging Information LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com Page 10 of 11 Preliminary Datasheet LPA2104 MSOP8 LPA2104–00 Version 1.0 Datasheet Sep.-2012 www.lowpowersemi.com Page 11 of 11