LMV1089RL

LMV1089 Dual Input, Far Field Noise Suppression Microphone Amplifier with Automatic Calibration Capability May 19, 2010 LMV1089 Dual Input, Far Field Noise Suppression Microphone Amplifier with Automatic Calibration Capability General Description The LMV1089 is a fully analog dual differential input, differential output, microphone array amplifier designed to reduce background acoustic noise, while delivering superb speech clarity in voice communication applications. The LMV1089 preserves near-field voice signals within 4cm of the microphones while rejecting far-field acoustic noise greater than 50cm 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 LMV1089 consumes only 1.1mA of supply current providing superior performance over DSP solutions consuming greater than ten times the power. A quick calibration during the manufacturing test process of the product containing the LMV1089 compensates the entire microphone system. This calibration compensates for mismatch in microphone gain and frequency response, as well as acoustical path variances. The LMV1089 stores the calibration coefficients in the on-chip EEPROM. The calibration is initiated by an I2C command or by a logic pin control. The dual microphone inputs and the processed signal output are differential to provide excellent noise immunity. The microphones are biased with an internal low-noise bias supply. Key Specifications ■ Far Field Noise Suppression (Electrical), (f = 1kHz) 37dB 2.7V to 5.5V 1.1mA (typ) 0.7µA (typ) 65dB (typ) 0.1% (typ) 96dB (typ) ■ Supply Voltage ■ Supply Current ■ Standby Current ■ Signal-to-Noise Ratio (A-weighted) ■ Total Harmonic Distortion + Noise ■ PSRR (217Hz) Features ■ ■ ■ ■ ■ ■ ■ ■ Low power consumption Shutdown function No added processing delay Differential inputs and outputs Automatic calibration Adjustable 6 - 48dB gain Excellent RF immunity Space-saving 36–bump micro SMD package Applications ■ ■ ■ ■ ■ Headset and Boom microphones Mobile handsets and two-way radios Bluetooth and other powered headsets Hand-held voice microphones Equalized stereo microphone preamplifier 30047240 FIGURE 1. © 2010 National Semiconductor Corporation 300472 www.national.com LMV1089 www.national.com 30047201 Typical Application 2 FIGURE 2. Typical Dual Microphone Far Field noise Cancelling Application LMV1089 Connection Diagrams 36–Bump micro SMD package 30047230 Top View Order Number LMV1089RL See NS Package Number RLA36TTA 36–Bump micro SMD Marking micro SMD Package View 30047231 Top View X = Plant Code YY = Date Code TT = Die Tracability ZA2 = LMV1089RL 30047233 Bottom View 3 www.national.com LMV1089 Connection Diagrams 32 Lead LQFP package 30047227 Top View Order Number LMV1089VY See NS Package Number NVBE0032 32 Lead LQFP Marking LQFP Package View 30047237 Top View U = Wafer Fab Code Z = Assembly Plant Code XY = 2 Digit Date Code TT = Die Traceability LMV1089 = LMV1089VY 30047228 Bottom View Ordering Information Order Number LMV1089RL LMV1089RLX LMV1089VY LMV1089VYX Package 36 Bump µSMD 36 Bump µSMD 32 Lead LQFP 32 Lead LQFP Package Drawing Number RLA36TTA RLA36TTA NVBE0032 NVBE0032 Device Marking XYYTTZA2 XYYTTZA2 UZXYTT UZXYTT Transport Media 250 units on tape and reel 1000 units on tape and reel 250 units on tape and reel 1000 units on tape and reel www.national.com 4 LMV1089 Pin Descriptions TABLE 1. Pin Name and Function Bump Number Pin Name 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 NC T7 PE MIC2– MIC2+ Mic Bias NC NC T5 GND M1_UNP MIC1+ NC NC GB0 GA0 GND MIC1– ADR NC GND GA1 M2_UNP REF SCL GB1 NC OUT+ LPF+ EN SDA I2CVDD VDD OUTLPFCAL Pin Function No connect Auxiliary Control Manual Calibration = VDD Auto Calibration = GND Program Enable EEPROM microphone 2 negative input microphone 2 positive input Microphone Bias No Connect No Connect Float (do not connect to GND) amplifier ground microphone 1 unprocessed output microphone 1 positive input No Connect No Connect default Post Amp Gain 0 default Pre Amp Gain 0 amplifier ground amplifier ground I2C Address select No Connect amplifier ground default Pre Amp Gain 1 microphone 2 unprocessed output reference voltage de-coupling I2C clock default Post Amp Gain 1 No Connect positive optimized audio output Low Pass Filter for positive output chip enable I2C data I2C power supply power supply negative optimized audio output Low Pass Filter for negative output calibration enable Pin Type No Connect Digital Input Digital Input Analog Input Analog Input Analog Output No Connect No Connect Production Test Ground Analog Output Analog Input No Connect No Connect Digital Input Digital Input Ground Analog Input Digital Input No Connect Ground Digital Input Analog Output Analog Reference Digital Input Digital Input No Connect Analog Output Analog Input Digital Input Digital Input/Output Supply Supply Analog Output Analog Input Digital Input 5 www.national.com LMV1089 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Storage Temperature Power Dissipation (Note 3) ESD Rating (Note 4) ESD Rating (Note 5) Junction Temperature (TJMAX) Mounting Temperature Infrared or Convection (20 sec.) 6.0V -85°C to +150°C Internally Limited 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 Supply Voltage (Note 8) Temperature Range TMIN ≤ TA ≤ TMAX (Note 2) 2.7V ≤ VDD ≤ 5.5V 1.7V ≤ I2CVDD ≤ 5.5V −40°C to 85°C −40°C ≤ TA ≤ +85°C Electrical Characteristics 3.3V (Note 1) Unless otherwise specified, all limits guaranteed for TJ = 25°C, VDD = 3.3V, VIN = 18mVP-P, f = 1kHz, EN = VDD, pass through mode (Note 8), Pre Amp gain = 20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF, CREF = 10nF LMV1089 Symbol Parameter Conditions f = 1kHz, VIN = 18mVP-P SNR eN VIN VOUT Signal-to-Noise Ratio Input Referred Noise level Maximum Input Signal Maximum AC Output Voltage DC Level at Outputs THD+N Total Harmonic Distortion + Noise ZIN ZOUT ZLOAD AM AMR AP APR ACR AMD XTalk TCAL Input Impedance Output Impedance Load Impedance (Out+, Out-) Microphone Preamplifier Gain Range Microphone Preamplifier Gain Adjustment Resolution Post Amplifier Gain Range Post Amplifier Gain Resolution Gain Compensation Range Maximum Gain Matching Difference After Calibration f = 300Hz f = 1kHz f = 3kHz f = 1kHz Pass Through Mode and Summing Mode RLOAD CLOAD 6 – 36 2 6 – 18 3 ±3 0.5 0.25 0.5 52 32 37 24 28 96 91 60 41 790 f = 1kHz (See Test Method) f = 300Hz (See Test Method) f = 1kHz (See Test Method) f = 300Hz (See Test Method) Input Referred, Input AC grounded PSRR Power Supply Rejection Ratio CMRR Common Mode Rejection Ratio fRIPPLE = 217Hz (VRIPPLE = 100mVP-P) fRIPPLE = 1kHz (VRIPPLE = 100mVP-P) f = 1kHz 85 80 dB (min) dB (min) dB 20 22 14 15 2.6 3.4 1.7 2.3 f = 1kHz, VIN = 18mVP-P, A-Weighted voice band (300 – 3400Hz) A-weighted THD+N < 1%, Pre Amp Gain = 6dB f = 1kHz, Differential Out+, OutTHD+N < 1% Out+, OutDifferential Out+ and OutTypical Limits (Note 6) (Note 7) 63 65 5 910 1.2 800 0.1 142 300 10 100 0.2 850 1.1 Units (Limits) dB dB μVRMS mVP-P (min) VRMS (min) mV % (max) kΩ Ω kΩ (min) pF (max) dB dB (min) dB (max) dB dB (min) dB (max) dB dB dB dB dB (min) ms (max) dBV(min) dBV (min) dBV (min) dBV (min) Crosstalk Attenuation between Mic1 and Mic2 Measured at M1_UNP and M2_UNP Calibration Duration FFNSE Far Field Noise Suppression Electrical SNRIE Signal-to-Noise Ratio Improvement Electrical www.national.com 6 LMV1089 VBM eVBM IBM IDDQ IDD ISD IDDCP IDDI2C TON TOFF Microphone Bias Supply Voltage Microphone Bias Noise Level Total available Microphone Bias Current Supply Quiescent Current Supply Current Shut Down Current Supply Current during Calibration and Programming I2C supply current Turn On Time Turn Off Time IBIAS = 1mA A-Weighted, 10nF cap at VREF pin VIN = 0V VIN = 25mVP-P both inputs, Noise cancelling mode EN pin = GND Calibrating or Programming EEPROM I2C Idle Mode 2.0 10 1.85 2.15 1.2 V (min) V (max) μVRMS mA (min) mA (max) mA 1.1 1.1 0.7 30 25 1.5 1 45 100 40 60 μA (max) mA (max) nA (max) ms (max) ms (max) 7 www.national.com LMV1089 (Note 1) Unless otherwise specified, all limits guaranteed for TJ = 25°C, VDD = 5V, VIN = 18mVP-P, EN = VDD, pass through mode (Note 8), Pre Amp gain = 20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF. Symbol Parameter Conditions LMV1089 Typical 63 65 5 918 1.2 800 f = 1kHz VIN = 18mVP-P 0.1 142 300 f = 1kHz f = 1kHz f = 1kHz Pass Through Mode and Summing Mode f = 1kHz f = 1kHz f = 300Hz f = 2kHz f = 3kHz f = 1kHz (See Test Method) f = 300Hz (See Test Method) f = 1kHz (See Test Method) f = 300Hz (See Test Method) Input Referred, Input AC grounded PSRR Power Supply Rejection Ratio CMRR Common Mode Rejection Ratio VBM eVBM IBM IDDQ IDDCP IDD ISD TON TOFF Microphone Bias Supply Voltage Microphone Bias Noise Level Total Available Microphone Bias Current Supply Quiescent Current Supply Current during Calibration and Programming Supply Current Shut Down Current Turn On Time Turn Off Time VIN = 0V Calibrating or Programming EEPROM VIN = 25mVP-P both inputs, Noise cancelling mode EN pin = GND 1.1 30 1.1 1.6 40 60 fRIPPLE = 217Hz (VRIPPLE = 100mVP-P) fRIPPLE = 1kHz (VRIPPLE = 100mVP-P) f = 1kHz IBIAS = 1mA A-Weighted 96 91 62 2.0 10 1.2 1.5 85 80 dB (min) dB (min) dB V μVRMS mA (min) mA (max) mA (max) mA (max) μA ms (max) ms (max) 6 – 36 2 6 – 18 3 ±3 0.5 0.25 0.5 790 32 37 24 28 20 22 14 15 2.6 3.4 1.7 2.3 0.2 850 1.1 Limit (Note 6) (Note 7) f = 1kHz, VIN = 18mVP-P SNR eN VIN VOUT Signal-to-Noise Ratio Input Referred Noise level Maximum Input Signal Maximum AC Output Voltage DC Output Voltage THD+N Total Harmonic Distortion + Noise ZIN ZOUT AM AMR AP APR ACR AMD TCAL Input Impedance Output Impedance Microphone Preamplifier Gain Range Microphone Preamplifier Gain Adjustment Resolution Post Amplifier Gain Range Post Amplifier Gain Adjustment Resolution Gain Compensation Range Maximum Gain Matching Difference After Calibration Calibration Duration f = 1kHz, VIN = 18mVP-P, A-Weighted voice band (300 – 3400Hz) A-weighted f = 1kHz, THD+N < 1% f = 1kHz, THD+N < 1% between differential output dB dB μVRMS mVP-P (min) VRMS (min) mV % (max) kΩ Ω dB dB (min) dB (max) dB dB (min) dB (max) dB dB dB dB ms (max) dBV dBV dBV dBV Units (Limits) Electrical Characteristics 5.0V FFNSE Far Field Noise Suppression Electrical SNRIE Signal-to-Noise Ratio Improvement Electrical www.national.com 8 LMV1089 Digital Interface Characteristics Symbol Parameter (Note 1, Note 8) Unless otherwise specified, all limits guaranteed for TJ = 25°C, I2CVDD within the Operating Rating (Note 8) LMV1089 Conditions EN, TM, SCL, SDA, ADR, CAL, PE GA0, GA1, GB0, GB1 EN, TM, SCL, SDA, ADR, CAL, PE GA0, GA1, GB0 2 790 2 790 Typical (Note 6) Limit (Note 7) 0.75xI2CVDD 0.6xVDD 0.25xI2CVDD 0.4xVDD Units (Limits) V (min) V (max) ms ms (min) ms ms (min) VIH VIL tsCAL thCAL tsPEC thPEC 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 Note 1: “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 2: 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 3: 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 LMV1089, 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 4: Human body model, applicable std. JESD22-A114C. Note 5: Machine model, applicable std. JESD22-A115-A. Note 6: 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 7: Datasheet min/max specification limits are guaranteed by test, or statistical analysis. Note 8: The voltage at I2CVDD must not exceed the voltage on VDD. 9 www.national.com LMV1089 Test Methods 30047212 FIGURE 3. FFNSE, NFSLE, SNRIE Test Circuit FAR FIELD NOISE SUPPRESSION (FFNSE) For optimum noise suppression the far field noise should be in a broadside array configuration from the two microphones (see Figure 15). Which means the far field sound source is equidistance from the two microphones. This configuration allows the amplitude of the far field signal to be equal at the two microphone inputs, however a slight phase difference may still exist. To simulate a real world application a slight phase delay was added to the FFNSE test. The block diagram from Figure 3 is used with the following procedure to measure the FFNSE. 1. A sine wave with equal frequency and amplitude (25mVP-P) is applied to Mic1 and Mic2. Using a signal generator, the phase of Mic 2 is delayed by 1.1° when compared with Mic1. 2. Measure the output level in dBV (X) 3. Mute the signal from Mic2 4. Measure the output level in dBV (Y) 5. FFNSE = Y - X dB NEAR FIELD SPEECH LOSS (NFSLE) For optimum near field speech preservation, the sound source should be in an endfire array configuration from the two microphones (see Figure 16). In this configuration the speech signal at the microphone closest to the sound source will have greater amplitude than the microphone further away. Additionally the signal at microphone further away will experience a phase lag when compared with the closer microphone. To simulate this, phase delay as well as amplitude shift was added to the NFSLE test. The schematic from Figure 3 is used with the following procedure to measure the NFSLE. 1. A 25mVP-P and 17.25mVP-P (0.69*25mVP-P) sine wave is applied to Mic1 and Mic2 respectively. Once again, a signal generator is used to delay the phase of Mic2 by 15.9° when compared with Mic1. 2. Measure the output level in dBV (X) 3. Mute the signal from Mic2 4. Measure the output level in dBV (Y) 5. NFSLE = Y - X dB SINGLE TO NOISE RATIO IMPROVEMENT ELECTRICAL (SNRIE) The SNRIE is the ratio of FFNSE to NFSLE and is defined as: SNRIE = FFNSE - NFSLE www.national.com 10 LMV1089 Typical Performance Characteristics THD+N vs Frequency Mic1 = AC GND, Mic2 = 36mVP-P Noise Canceling Mode Unless otherwise specified, TJ = 25°C, VDD = 3.3V, Input Voltage = 18mVP-P, f =1 kHz, pass through mode (Note 8), Pre Amp gain = 20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF. THD+N vs Frequency Mic2 = AC GND, Mic1 = 36mVP-P Noise Canceling Mode 30047248 30047247 THD+N vs Frequency Mic1 = 36mVP-P Mic1 Pass Through Mode THD+N vs Frequency Mic2 = 36mVP-P Mic2 Pass Through Mode 30047249 30047250 11 www.national.com LMV1089 THD+N vs Input Voltage Mic1 = AC GND, f = 1kHz Mic2 Noise Canceling Mode THD+N vs Input Voltage Mic2 = AC GND, f = 1kHz Mic1 Noise Canceling Mode 30047252 30047251 THD+N vs Input Voltage f = 1kHz Mic1 Pass Through Mode THD+N vs Input Voltage f = 1kHz Mic2 Pass Through Mode 30047253 30047254 www.national.com 12 LMV1089 PSRR vs Frequency Pre Amp Gain = 20dB, Post Amp Gain = 6dB VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND Mic1 Pass Through Mode PSRR vs Frequency Pre Amp Gain = 20dB, Post Amp Gain = 6dB VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND Mic2 Pass Through Mode 30047244 30047245 PSRR vs Frequency Pre Amp Gain = 20dB, Post Amp Gain = 6dB VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND Noise Canceling Mode Far Field Noise Suppression Electrical vs Frequency 30047255 30047245 13 www.national.com LMV1089 Signal-to-Noise Ratio Electrical vs Frequency 30047256 www.national.com 14 LMV1089 Application Data INTRODUCTION The LMV1089 is a fully analog single chip solution to reduce the far field noise picked up by microphones in a communi- cation system. A simplified block diagram is provided in Figure 4. 30047224 FIGURE 4. Simplified Block Diagram of the LMV1089 The output signal of the microphones is first amplified by a pre-amplifier stage with an adjustable gain of 6dB to 36dB. The signal is then processed by the noise cancelling processor. The noise cancelling processor matches the gain and frequency responses of the microphones and the acoustic characteristics of the enclosure using coefficients derived during the auto-calibration step and the stored in EEPROM. The resulting noise-suppressed signal is then amplified by the 6dB to 18dB gain-adjustable post-amplifier. For optimum noise and EMI immunity, the microphones have a differential connection to the LMV1089 and the output of the LMV1089 is also differential. The adjustable gain functions can be controlled via I2C and four control pins. Both methods are described later in the application section. vides two individual microphone power down functions. When either one of the shutdown functions is activated the part will go into shutdown mode consuming only a few μA of supply current. SHUTDOWN VIA HARDWARE PIN The hardware shutdown function is operated via the EN pin. In normal operation the EN pin must be at a 'high' level (VDD). Whenever a 'low' level (GND) is applied to the EN pin the part will go into shutdown mode disabling all internal circuits. SHUTDOWN VIA I2C The LMV1089 offers an additional shutdown function by reprogramming an I2C register (see Table 6). The LMV1089 will only consume power in a mode where it can perform its normal functions. So at least one of the microphone amplifier circuits must be enabled ('1'). Writing '0' to the both bit 4 and bit 5 of the I2C 'A' register (address 0x01h) of the LMV1089 will force the part into shutdown mode, even if the EN pin is 'High', the only part that remains active in this state is the I2C, which consumes neglectible power when compared to the standby current. Power Supply Circuits A low drop-out (LDO) voltage regulator in the LMV1089 allows the device to be independent of supply voltage variations. The Power On Reset (POR) circuitry in the LMV1089 requires the supply voltage to rise from 0V to VDD in less than 100ms. The Mic Bias output is provided as a low noise supply source for the electret microphones. The noise voltage on the Mic Bias microphone supply output pin depends on the noise voltage on the internal the reference node. The de-coupling capacitor on the VREF pin determines the noise voltage on this internal reference. This capacitor should be larger than 1nF; having a larger capacitor value will result in a lower noise voltage on the Mic Bias output. Most of the logic levels for the digital control interface are relative to I2CVDD voltage. This eases interfacing to the micro controller of the application containing the LMV1089. The supply voltage on the I2CVDD pin must never exceed the voltage on the VDD pin. Only the four pins that determine the default power up gain (as described in SETTING ADJUSTABLE GAIN) have logic levels relative to VDD. Adjustable Gain The LMV1089 has two gain stages where the gain can be adjusted to meet the requirements for the application. There is a preamplifier and a post amplifier that can be varied independent of each other. In most applications the gain will be set via the I2C interface, see Table 6. SETTING ADJUSTABLE GAIN The LMV1089 provides four pins to set the default gain settings during power up of the device, which is convenient for applications without a micro controller . The default gain of the preamplifier is controlled by the GA0 and GA1 pins and can be set by wiring those pins to either VDD or GND. In this way, one of the four possible values in the 12dB to 36dB range (see Table 2) can be chosen. The default post amplifier gain is set in the same way by connecting the GB0 and GB1 pins to either VDD or GND to select a gain between 6dB and 15dB (see Table 3). Setting the gain of the preamplifier and post amplifier Shutdown Function As part of the Powerwise™ family, the LMV1089 consumes only 1.1mA of current. In many applications the part does not need to be continuously operational. To further reduce the power consumption in the inactive period, the LMV1089 pro15 www.national.com LMV1089 via the I2C interface (see Table 6) will override this default gain. The default gain is only set during power up of the device. Toggling the logic level of the enable pin (EN) will not change the current gain setting of the part. Any gain setting done via the I2C interface will remain valid during activation of the function. TABLE 2. Default preamplifier gain GA1 0 0 1 1 GA0 0 1 0 1 Gain 12dB 20dB (Note 9) 28dB 36dB TABLE 3. Default post amplifier gain GB1 0 0 1 1 GB0 0 1 0 1 Gain 6dB (Note 9) 9dB 12dB 15dB Note 9: Default value used for performance measurements Gain Balance and Gain Budget In systems where input signals have a high dynamic range, critical noise levels or where the dynamic range of the output voltage is also limited, careful gain balancing is essential for the best performance. Too low of a gain setting in the preamplifier can result in higher noise levels while too high of a gain setting in the preamplifier 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 are shown in Figure 5. Two examples are given as a guideline on how to select proper gain settings. 30047241 FIGURE 5. Maximum Signal Levels Example 1 An application using microphones with 50mVP-P maximum output voltage, and a baseband chip after the LMV1089 with 1.5VP-P maximum input voltage. For optimum noise performance, the gain of the input stage should be set to the maximum. 1. 50mVP-P +36 dB = 3.1VP-P. 2. 3.1VP-P is higher than the maximum 1.4VP-P allowed for the Noise Cancelling Processor (NCP). This means a gain lower than 28.9dB should be selected. 3. Select the nearest lower gain from the gain settings shown in Table 2, 28dB is selected. This will prevent the NCP from being overloaded by the microphone. With this setting, the resulting output level of the Pre Amplifier will be 1.26VP-P. 4. The NCP can have a maximum processing gain of 9dB (depending on the calibration result) which will result in 3.5VP-P at the output of the LMV1089. This level is higher then maximum level that is allowed at the input of the post amp of the LMV1089. Therefore the preamp gain has to be reduced, to 1.4VP-P minus 9dB = 0.5VP-P. This limits the preamp gain to a maximum of 20dB. 5. The baseband chip limits the maximum output voltage to 1.5VP-P with the minimum of 6dB post amp gain, this results in requiring a lower level at the input of the post amp of 0.75VP-P. Now calculating this for a maximum NCP gain of 9dB the output of the preamp must be