LX1704CLQ

LX1704 TM ® 2W Filter less Stereo Class-D Amplifier P RODUCTION D ATA S HEET DESCRIPTION KEY FEATURES No Output Filter Required Low EMI Design Low Quiescent Current: 4mA Low Shutdown Current: 1µA Wide Supply Voltage Range: 2.5 - 5.5 Volt 2W Output Power into 4Ω Load with THD85% @ 1.2W), and best in class EMI radiation (just 20dBµV/m). The internal signal path is completely differential to minimize commonmode noise pickup. The inputs may be driven single-ended or differentially and they may be direct or AC coupled. The LX1704 may be operated with just a single decoupling capacitor. FILTERLESS 3-LEVEL CLASS-D MODULATION The LX1704 output stage is configured as a full H-bridge push-pull driver. The speaker must be driven differentially from the OUTP and OUTN pins. Each side of the speaker is driven by a 200KHz switching signal that transitions between VDD and GND. With zero input voltage, the duty cycle at each output is around 50% and the signals are inphase with each other. In this case, there is basically no differential voltage across the speaker. When the input signal goes positive, the duty cycle at OUTP increases above 50% and the duty cycle at OUTN decreases below 50%. This causes a net positive current to flow into the speaker. A negative input voltage causes the OUTN duty cycle to increase and the OUTP duty cycle to decrease which causes a net negative current to flow into the speaker. The differential voltage across the speaker has a fundamental frequency of twice the 200KHz switching frequency. The speaker itself serves as the low pass filter which then recreates the audio signal. This type of modulation can be described as driving +VDD, -VDD, and 0V across the speaker which is why it is referred to as 3-Level modulation. Classical, 2-Level modulation drives either +VDD or –VDD across the speaker at all times. This scheme requires an LC filter between the amplifier’s outputs and the speaker in order to keep the output current low. LOW-EMI OUTPUT STAGE WITH SLEW RATE LIMITING AND ACTIVE OVERSHOOT CLAMPING With 3-Level modulation, the carrier frequency drives a full amplitude common-mode signal to the speaker wires. This can cause high EMI radiation. One way to combat this would be to filter the outputs with LC filters or ferrite beads located close to the amplifier. In the LX1704, the output stage has been carefully designed to minimize EMI radiation so that these types of filters are not required. Slew rate limiting is used to keep the outputs from switching too quickly. Active overshoot clamping is used to minimize the inductive overshoot which occurs at each transition. These two techniques allow the LX1704 to easily meet FCC standards for radiated emissions when driving up to 3 meters of speaker wire. DIFFERENTIAL SIGNAL PATH, WIDE DYNAMIC RANGE, AND BUILT-IN THERMAL OVERLOAD PROTECTION The fully differential signal path uses Pulse Width Modulation and multiple feedback loops to provide high performance and low distortion. This is all fully-integrated to eliminate the need for any external feedback components or filters. The gain is fixed by internal resistors at 20dB. The differential signal path and internal voltage boosters allow for wide dynamic range. In fact, the LX1704 can be operated from supplies as low as 2.5V and as high as 5.5V. The output power will be limited by the available supply voltage. An internal thermal sensing circuit shuts down the outputs when the junction temperature exceeds about 150°C to provide thermal overload protection. APPLICATIONS APPLICATIONS Copyright © 2005 Rev. 1.2, 2006-10-11 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 8 LX1704 TM ® 2W Filter less Stereo Class-D Amplifier P RODUCTION D ATA S HEET THD+N VS. POWER THD+N VS. FREQUENCY W WW . Microsemi . C OM GAIN RESPONSE NOISE FLOOR CHANNEL CROSSTALK 3.5 3 2.5 IQQ (mA) 2 1.5 1 0.5 0 IQQ VS. SUPPLY VOLTAGE GRAPHS GRAPHS 2.5 3 3.5 4 4.5 5 5.5 Supply Voltage (V) Copyright © 2005 Rev. 1.2, 2006-10-11 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 9 LX1704 TM ® 2W Filter less Stereo Class-D Amplifier P RODUCTION D ATA S HEET POWER SUPPLY VS OUTPUT POWER 900 800 700 600 Current (mA) 500 400 300 200 100 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Output Power (mW) PSRR W WW . Microsemi . C OM POWER VS SUPPLY VOLTAGE 3500 3000 2500 Power/CH (mW) 2000 1500 1000 500 0 2.5 3 3.5 4 4.5 5 5.5 Supply Voltage (V) GRAPHS GRAPHS Copyright © 2005 Rev. 1.2, 2006-10-11 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 10 LX1704 TM ® 2W Filter less Stereo Class-D Amplifier P RODUCTION D ATA S HEET PACKAGE DIMENSIONS W WW . Microsemi . C OM LQ 16-Pin MLPQ Plastic (4mm x 4mm EP / 114x114Cu Exposed Pad) D b E2 L D2 E e A A3 K or Dim A A1 A3 b D E e D2 E2 K L Note: MILLIMETERS MIN MAX 0.80 1.00 0 0.05 0.18 0.30 0.23 0.38 4.00 BSC 4.00 BSC 0.65 BSC 2.55 2.80 2.55 2.80 0.20 0.30 0.50 INCHES MIN MAX 0.031 0.039 0 0.002 0.007 0.012 0.009 0.015 0.157 BSC 0.157 BSC 0.026 BSC 0.100 0.110 0.100 0.110 0.008 0.012 0.020 A1 Pin 1 Indicator 1. Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006”) on any side. Lead dimension shall not include solder coverage. MECHANICALS MECHANICALS Copyright © 2005 Rev. 1.2, 2006-10-11 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 11 LX1704 TM ® 2W Filter less Stereo Class-D Amplifier P RODUCTION D ATA S HEET NOTES W WW . Microsemi . C OM NOTES NOTES PRODUCTION DATA – Information contained in this document is proprietary to Microsemi and is current as of publication date. This document may not be modified in any way without the express written consent of Microsemi. Product processing does not necessarily include testing of all parameters. Microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. Copyright © 2005 Rev. 1.2, 2006-10-11 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 12