LMV1088

LMV1088 Dual Input, Clarisound TM Far Field Noise Suppression Microphone Amplifier with Automatic Calibration Ability September 19, 2008 LMV1088 Dual Input, Clarisound TM Far Field Noise Suppression Microphone Amplifier with Automatic Calibration Ability General Description The LMV1088 amplifies near-field voice signals within 4cm of the microphones while rejecting far-field acoustic noise greater than 0.5m from the microphones. Up to 20dB of farfield rejection is possible in a properly configured and calibrated system. Part of the Powerwise® family of energy efficient solutions, the LMV1088 consumes 1mA of supply current while providing superior performance to DSP solutions consuming over 10 times the power. A fast calibration during the manufacturing test process allows the LMV1088 to compensate the entire microphone system. This calibration includes mismatch in microphone gain and frequency response, as well as acoustical path variances. The LMV1088 stores the calibration coefficients in onboard EEPROM. The calibration is initiated by I2C command or by pin control. The dual microphone inputs are differential to provide excellent noise immunity. The microphones are biased with an internal low-noise bias supply. Key Specifications (3.3V supply, unless otherwise specified) ■ Supply voltage ■ Supply current ■ Signal to noise ratio (A-weighted) ■ Total harmonic distortion ■ Noise cancellation ■ PSRR 2.7V to 5.5V 1mA (typ) 60dB (typ) 0.1% (typ) 20dB (typ) 85dB (typ) Features ■ ■ ■ ■ ■ Low power consumption No added processing delay Automatic Calibration Space-saving 36 Bump micro SMD package Up to 20dB SNRI Applications ■ ■ ■ ■ ■ Mobile handsets Mobile and handheld two-way radios Bluetooth and other powered headsets Hand-held voice microphones Portable public address systems Application of the LMV1088 20213029 PowerWise® is a registered trademark of National Semiconductor Corporation. © 2008 National Semiconductor Corporation 202130 www.national.com LMV1088 www.national.com 20213041 Typical Application 2 FIGURE 1. Typical Dual Microphone Far Field noise Cancelling Application LMV1088 Connection Diagrams 36 Bump micro SMD package 20213030 Top View Order Number LMV1088RL See NS Package Number RLA36TTA 36 Bump micro SMD Marking micro SMD Package View 20213031 Top View X = Plant Code YY = Date Code TT= Die Tracability ZA1 = LMV1088RL 20213033 Bottom View 3 www.national.com LMV1088 TABLE 1. Pin Name and Function Bump Number A1 A2 A3 A4 A5 A6 B1 B2 B3 B4 B5 B6 C1 C2 C3 C4 C5 C6 D1 D2 D3 D4 D5 D6 E1 E2 E3 E4 E5 E6 F1 F2 F3 F4 F5 F6 Pin Name NC T7 PE MIC2– MIC2+ Mic Bias NC NC T5 GND T1 MIC1+ NC NC T6 T3 GND MIC1– ADR NC GND T4 T2 REF SCL T8 NC NC NC NC SDA I2CVDD VDD OUT LPF CAL Analog Reference Digital Input Ground No Connect No Connect No Connect No Connect Digital Input/Output Supply Supply Analog Output Analog Input Digital Input Ground Analog Input Digital Input No Connect Ground Analog Input No Connect No Connect Ground Pin Type No Connect Digital Input Digital Input Analog Input Analog Input Analog Output No Connect No Connect Pin Function No Connect (Note 1) Auxiliary_Control pin (Note 3) Program Enable EEPROM microphone 2 input – microphone 2 input + Bias for Microphones No Connect (Note 1) No Connect (Note 1) Float (Note 2) Amplifier ground Float (Note 2) Microphone 1 input + No Connect (Note 1) No Connect (Note 1) Float (Note 2) Float (Note 2) Amplifier ground Microphone 1 input – I2C Address select No Connect (Note 1) Amplifier ground Float (Note 2) Float (Note 2) Reference Voltage De-coupling I2C Clock Connect to GND No Connect (Note 1) No Connect (Note 1) No Connect (Note 1) No Connect (Note 1) I2C Data I2C power supply Power Supply Optimized Audio Out Lowpasss Filter Capacitor Calibration Start Note 1: Connect NC pins to GND for optimum noise performance. Note 2: Do not ground pins. Note 3: Force VDD setup for manual calibrations. Force GND setup for calibration circuitry. www.national.com 4 LMV1088 Absolute Maximum Ratings (Note 4) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Storage Temperature ESD Rating (Note 7) ESD Rating (Note 8) Junction Temperature (TJMAX) Mounting Temperature Infrared or Convection (20 sec.) 6.0V -85°C to +150°C 2000V 200V 150°C 235°C Thermal Resistance 70°C/W  θJA (microSMD) Soldering Information See AN-112 “microSMD Wafers Level Chip Scale Package.” Operating Ratings Supply Voltage I2CVDD (Note 13) Temperature Range (Note 5) 2.7V to 5.5V 1.8V to 5.5V −40°C to 85°C (Note 4) Unless otherwise specified, all limits guaranteed for TJ = 25°C, VDD = 3.3V and 5.0V, VIN = 18mVP-P, pass through mode (Note 11), preamplifier gain = 20dB, postamplifier gain = -2.5dB, RL = 100kΩ, and CL = 4.7pF. LMV1088 Symbol SNR VIN VOUT Parameter Signal-to-Noise Ratio Max Input Signal AC Output Voltage DC Output Voltage THD+N Total Harmonic Distortion + Noise ZIN ZOUT ZLOAD AM AMR Microphone Pre Amplifier Gain Range Input Impedance Output Impedance RLOAD CLOAD f = 1kHz 6 – 36 2 -2.5 – 9.5 0 – 12 3 ±3 0.5 0.5 0.5 770 Input Referred, Input AC grounded PSRR Power Supply Rejection Ratio CMRR Common Mode Rejection Ratio VBM εVBM IBM IDDQ Microphone Bias Supply Voltage Microphone Bias Supply Noise Total available Microphone Bias Current Supply Quiescent Current VIN = 0V 1 f = 217Hz (100mVP-P) f = 1kHz (100mVP-P) f = 1kHz, IBIAS = 1mA A-Weighted 85 80 60 2.0 10 1.2 1.5 dB dB dB V μVRMS mA (min) mA (max) Microphone Pre Amplifier Gain Adjustment f = 1kHz Resolution f = 1kHz Pass Through Mode and Summing Mode f = 1kHz Noise Canceling Mode (Note 12) f = 300Hz – f = 3400Hz f = 1kHz, VIN = 18mVP-P Conditions f = 1kHz, VIN = 18mVPP, A-Weighted f = 1kHz and THD+N < 1% f = 1kHz, preamp gain = 36dB VIN = 30mVP-P Typical Limits Units (Limits) (Note 9) (Note 10) 60 97 500 800 0.1 100 150 10 10 dB mVP-P mVRMS mV % kΩ Ω kΩ (min) pF (max) dB dB dB dB dB dB (max) dB (max) dB (max) dB (max) ms (max) Electrical Characteristics 3.3V and 5.0V AP Post Amplifier Gain Range APR ACR AMD TCAL Post Amplifier Gain Adjustment Resolution f = 1kHz Gain Compensation Range f = 300Hz Gain Matching Difference After Calibration f = 1kHz f = 3kHz Calibration Duration 5 www.national.com LMV1088 IDDCP IDD Supply Current during Calibration and Programming Supply Current Calibrating or Programming EEPROM VIN = 25mVP-P both inputs, Noise canceling mode 28 1 50 1.5 mA (max) mA (max) Digital Interface Characteristics Symbol VIH VIL tsCAL thCAL tsPEC thPEC Parameter Logic High Input Level Logic Low Input Level CAL Setup Time CAL Hold time until calibration is finished PE Setup Time PE Hold until calibration is finished (Notes 4, 13) Unless otherwise specified, all limits guaranteed for TJ = 25°C, I2CVDD within the Operating Rating (Note 13) LMV1088 Conditions SCL, SDA, ADR, CAL, PE pins SCL, SDA, ADR, CAL, PE pins 2 770 2 770 Typical (Note 9) Limits (Note 10) 0.6xI2CVDD 0.4xI2CVDD Units (Limits) V (min) V (max) ms ms (min) ms ms (min) Note 4: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditions indicate conditions at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the ground pin, unless otherwise specified. Note 5: The Electrical Characteristics tables list guaranteed specifications under the listed Recommended Operating Conditions except as otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not guaranteed. Note 6: The maximum power dissipation must be de-rated at elevated temperatures and is dictated by TJMAX, θJC, and the ambient temperature TA. The maximum allowable power dissipation is PDMAX = (TJMAX –TA)/ θJA or the number given in the Absolute Maximum Ratings, whichever is lower. For the LMV1088, TJMAX = 150°C and the typical θJA for this microSMD package is 70°C/W and for the LLP package θJA is 64°C/W Refer to the Thermal Considerations section for more information. Note 7: Human body model, applicable std. JESD22-A114C. Note 8: Machine model, applicable std. JESD22-A115-A. Note 9: Typical values represent most likely parametric norms at TA = +25°C, and at the Recommended Operation Conditions at the time of product characterization and are not guaranteed. Note 10: Datasheet min/max specification limits are guaranteed by test, or statistical analysis. Note 11: In Pass Through mode, only one microphone input is active. See also I2C Compatible Interface for more information how to configure the LMV1088. Note 12: In Noise Canceling Mode there is 2.5dB additional gain before calibration when compared to the other operating modes to compensate for the gain reduction that is caused by the noise canceling effect. Note 13: The voltage at I2CVDD must not exceed the voltage on VDD. www.national.com 6 LMV1088 Typical Performance Characteristics Supply Current vs. Supply Voltage Unless otherwise specified, TJ = 25°C, VDD = 3.3V, VIN = 18mVP, pass through mode (Note 11), preamplifier gain = 20dB, postamplifier gain = –2.5dB, RL = 100kΩ, and CL = 4.7pF. P THD+N vs Frequency, pass through mode Mic1 VIN = 36mVP-P 20213021 20213003 THD+N vs Frequency, pass through mode Mic2 VIN = 36mVP-P THD+N vs Frequency, Noise canceling mode signal at Mic1, Mic2 AC shorted, VIN = 36mVP-P 20213004 20213005 THD+N vs Frequency, Noise canceling mode Mic1 AC shorted, signal at Mic2, VIN = 36mVP-P THD+N vs VIN, pass through mode Mic1 20213016 20213006 7 www.national.com LMV1088 THD+N vs VIN, pass through mode Mic2 THD+N vs VIN, Noise canceling mode signal at Mic1, Mic2 AC shorted 20213015 20213014 THD+N vs VIN, Noise canceling mode Mic1 AC shorted, signal at Mic2 PSRR vs Frequency, pass through mode Mic1 Mic1+ Mic2 AC shorted 20213017 20213018 PSRR vs Frequency, pass through mode Mic2 Mic1+ Mic2 AC shorted PSRR vs Frequency, Noise canceling mode Mic1+ Mic2 AC shorted 20213019 20213020 www.national.com 8 LMV1088 PSRR vs Frequency, Microphone Bias Mic1+ Mic2 AC shorted 20213022 9 www.national.com LMV1088 Application Data Gain Balance and Gain Budget In systems where input signals have a high dynamic range, critical noise levels and where the dynamic range of the output voltage is also limited, careful gain balancing can be essential for the best performance. Having not enough gain in the Pre Amplifier can result in higher noise levels while to much gain in the Pre Amplifier will result in clipping and saturation in the noise cancelling processor and output stages. The gain ranges and maximum signal levels for the different functional blocks is shown in Figure 2. Two examples are given as a guideline how to select proper gain settings. 20213037 FIGURE 2. Maximum Signal Levels Example1 : An application using microphones with 50mVpp maximum output voltage, and a baseband chip after the LMV1088 with 1.5Vpp maximum input voltage. For optimum noise performance we would like to have the maximum gain at the input stage. So using Pre Amp gain =14dB and Post Amp gain = 6dB is the optimum for this application. 1. 50mVpp + 36 dB = 3.1Vpp. 2. This is higher than the maximum 1.4Vpp allowed for the Noice cancelling Processor (NCP). This means a gain lower then 28.9dB should be selected. 3. Select the nearest lower gain from the gain setting table to be 28dB. This will prevent the NCP from being overloaded by the microphone. With this setting, the resulting output level of the Pre Amplifier will be 1.26Vpp . 4. The NCP can have a maximum processing gain of 9dB (depending on the calibration result) which will result in 3.5Vpp at the output of the LMV1088. This level is higher then maximum level hat is allowed at the input of the Post Amp of the LMV1088. Therefore the Pre Amp gain has to be reduced, to 1.4Vpp minus 9dB = 0.5Vpp. This limits the Pre Amp gain to a maximum of 20dB. 5. The baseband chip limits the maximum output voltage to 1.5Vpp with the minimum of 6dB Post Amp gain, this results in having a lower level at the input of the Post Amp of 0.75Vpp. Now calculating this for a maximum NCP gain of 9dB the output of the Pre Amp must be