19-0764; Rev 0; 3/07 KIT ATION EVALU E L B AVAILA Microphone Amplifier with AGC and Low-Noise Microphone Bias The MAX9814 is a low-cost, high-quality microphone amplifier with automatic gain control (AGC) and lownoise microphone bias. The device features a low-noise preamplifier, variable gain amplifier (VGA), output amplifier, microphone-bias-voltage generator and AGC control circuitry. The low-noise preamplifier has a fixed 12dB gain, while the VGA gain automatically adjusts from 20dB to 0dB, depending on the output voltage and the AGC threshold. The output amplifier offers selectable gains of 8dB, 18dB, and 28dB. With no compression, the cascade of the amplifiers results in an overall gain of 40dB, 50dB, or 60dB. A trilevel digital input programs the output amplifier gain. An external resistive divider controls the AGC threshold and a single capacitor programs the attack/release times. A trilevel digital input programs the ratio of attack-to-release time. The hold time of the AGC is fixed at 30ms. The low-noise microphone-biasvoltage generator can bias most electret microphones. The MAX9814 is available in the space-saving 12-bump UCSP™ (1.5mm x 2mm) and 14-pin TDFN packages. This device is specified over the -40°C to +85°C extended temperature range. Applications Digital Still Cameras Digital Video Cameras Two-Way Communicators PDAs Bluetooth Headsets Entertainment Systems (e.g., Karaoke) Features o Automatic Gain Control (AGC) o Three Gain Settings (40dB, 50dB, 60dB) o Programmable Attack Time o Programmable Attack and Release Ratio o 2.7V to 5.5V Supply Voltage Range o Low Input-Referred Noise Density of 30nV/√Hz o Low THD: 0.04% (typ) o Low-Power Shutdown Mode o Internal Low-Noise Microphone Bias, 2V o Available in the Space-Saving 12-Bump UCSP (1.5mm x 2mm) and 14-Pin TDFN (3mm x 3mm) Packages o -40°C to +85°C Extended Temperature Range Ordering Information PART TEMP RANGE PINPACKAGE PKG CODE MAX9814EBC+T -40°C to +85°C 12 UCSP-12 B12-3 MAX9814ETD+T -40°C to +85°C 14 TDFN-14 T1433-2 High-Quality Portable Recorders +Denotes a lead-free package. IP Phones/Telephone Conferencing Pin Configurations appear at end of data sheet. UCSP is a trademark of Maxim Integrated Products, Inc. Simplified Block Diagram 2.7V TO 5.5V SHDN MICBIAS LOW-NOISE REFERENCE VDD MAX9814 AGC RMICBIAS CIN MICIN LNA +12dB VGA +20dB/0dB GAIN +8/+18/ +28dB COUT OUT GND ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX9814 General Description MAX9814 Microphone Amplifier with AGC and Low-Noise Microphone Bias ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V All Other Pins to GND.................................-0.3V to (VDD + 0.3V) Output Short-Circuit Duration.....................................Continuous Continuous Current (OUT, MICBIAS) .............................±100mA All Other Pins ....................................................................±20mA Continuous Power Dissipation (TA = +70°C) 12-Bump UCSP (derate 6.5mW/°C above +70°C).......518mW 14-Pin TDFN (derate 16.7mW/°C above +70°C) ....1481.5mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C Bump Temperature (soldering) Reflow............................+235°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VDD = 3.3V, SHDN = VDD, CCT = 470nF, CCG = 2µF, GAIN = VDD, TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Operating Voltage VDD 5.5 V Supply Current IDD 3.1 6 mA ISHDN 0.01 1 µA Shutdown Supply Current Input-Referred Noise Density 2.7 BW = 20kHz, all gain settings 30 nV/√Hz Output Noise BW = 20kHz 430 µVRMS Signal-to-Noise Ratio BW = 22Hz to 22kHz (500mVRMS output signal) 61 A-weighted 64 (Note 2) 60 Dynamic Range Total Harmonic Distortion Plus Noise Amplifier Input BIAS Maximum Input Voltage Input Impedance Maximum Gain en Guaranteed by PSRR test SNR DR THD+N Attack/Release Ratio 2 fIN = 1kHz, BW = 20Hz to 20kHz, RL = 10kΩ, VTH = 0.1V (threshold = 200mVP-P), VIN = 30mVRMS, VCT = 2V 0.2 A VOUT_RMS 1.14 1% THD A/R 1.23 1.32 mVP-P 100 kΩ 39.5 40 GAIN = GND 49.5 50 50.6 GAIN = unconnected 59.5 60 60.5 GAIN = VDD 18.7 20 20.5 GAIN = GND 29.0 30 30.8 GAIN = unconnected 38.7 40 40.5 1% THD+N, VTH = MICBIAS CT = 470nF (Note 3) 40.5 0.707 1.26 V 100 GAIN = VDD AGC enabled, VTH = 0.7V tATTACK dB % ZIN Regulated Output Level AGC Attack Time 0.04 VIN VIN_MAX Minimum Gain Maximum Output Level fIN = 1kHz, BW = 20Hz to 20kHz, RL = 10kΩ, VTH = 1V (threshold = 2VPP), VIN = 0.5mVRMS, VCT = 0V dB 1.40 1.1 A/R = GND 1:500 A/R = VDD 1:2000 A/R = unconnected 1:4000 _______________________________________________________________________________________ dB dB VRMS 1.54 VP-P ms ms/ms Microphone Amplifier with AGC and Low-Noise Microphone Bias (VDD = 3.3V, SHDN = VDD, CCT = 470nF, CCG = 2µF, GAIN = VDD, TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MICOUT High Output Voltage VOH IOUT sourcing 1mA MICOUT Low Output Voltage VOL IOUT sinking 1mA MICOUT Bias MICOUT unconnected MIN 1.14 TYP MAX UNITS 2.45 V 3 mV 1.23 1.32 V ZOUT 50 Ω Minimum Resistive Load RLOAD_MIN 5 kΩ Maximum Capacitive Drive CLOAD_MAX 200 pF Output Impedance Maximum Output Current Output Short-Circuit Current IOUT_MAX 1% THD, RL = 500Ω ISC AGC mode; VDD = 2.7V to 5.5V (Note 4) Power-Supply Rejection Ratio PSRR 1 3 8 35 50 f = 217Hz, VRIPPLE = 100mVP-P (Note 5) 2 55 f = 1kHz, VRIPPLE = 100mVP-P (Note 5) 52.5 f = 10kHz, VRIPPLE = 100mVP-P (Note 5) 43 mA mA dB MICROPHONE BIAS Microphone Bias Voltage Output Resistance Output Noise Voltage VMICBIAS IMICBIAS = 0.5mA RMICBIAS IMICBIAS = 1mA VMICBIAS_NOISE IMICBIAS = 0.5mA, BW = 22Hz to 22kHz DC, VDD = 2.7V to 5.5V Power-Supply Rejection Ratio 1.84 PSRR 70 IMICBIAS = 0.5mA, VRIPPLE = 100mVP-P, fIN = 1kHz 2.0 2.18 V 1 Ω 5.5 µVRMS 80 dB 71 TRILEVEL INPUTS (A/R, GAIN) A/R or GAIN = VDD 0.5VDD 0.5VDD 0.5VDD / 180kΩ / 100kΩ / 50kΩ A/R or GAIN = GND 0.5VDD 0.5VDD 0.5VDD / 180kΩ / 100kΩ / 50kΩ mA Tri-Level Input Leakage Current Input High Voltage VIH Input Low Voltage VIL VDD x 0.7 V VDD x 0.3 V Shutdown Enable Time tON 60 ms Shutdown Disable Time tOFF 40 ms DIGITAL INPUT (SHDN) SHDN Input Leakage Current -1 Input High Voltage VIH Input Low Voltage VIL +1 1.3 µA V 0.5 V +1 µA AGC THRESHOLD INPUT (TH) TH Input Leakage Current Note 1: Note 2: Note 3: Note 4: Note 5: -1 Devices are production tested at TA = +25°C. Limits over temperature are guaranteed by design. Dynamic range is calculated using the EIAJ method. The input is applied at -60dBFS (0.707µVRMS), fIN = 1kHz. Attack time measured as time from AGC trigger to gain reaching 90% of its final value. CG is connected to an external DC voltage source, and adjusted until VMICOUT = 1.23V. CG connected to GND with 2.2µF. _______________________________________________________________________________________ 3 MAX9814 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VDD = 5V, CCT = 470nF, CCG = 2.2µF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1µF, TA = +25°C, unless otherwise noted.) -10 -40 -20 -50 50 -30 -60 GAIN = 0 30 PSRR (dB) 60 40 -40 MAX9814 toc03 -30 MAX9814 toc02 GAIN = UNCONNECTED PSRR (dB) GAIN (dB) 0 MAX9814 toc01 80 70 MICBIAS POWER-SUPPLY REJECTION RATIO vs. FREQUENCY POWER-SUPPLY REJECTION RATIO vs. FREQUENCY GAIN vs. FREQUENCY -70 -50 -80 20 -60 -90 10 -70 GAIN = 1 0 VRIPPLE = 200mVP-P -110 -80 100 1k 100k 10k 10 100 1k 10 100k 10k 100 1k 100k 10k FREQUENCY (Hz) FREQUENCY (Hz) FREQUENCY (Hz) SUPPLY CURRENT vs. SUPPLY VOLTAGE SHUTDOWN CURRENT vs. SUPPLY VOLTAGE MICROPHONE BIAS VOLTAGE vs. MICROPHONE BIAS SOURCE CURRENT SHUTDOWN CURRENT (nA) 3.3 3.2 3.1 3.0 2.9 2.8 2.7 2.5 0.4 2.0 VMICBIAS VOLTAGE (V) 3.4 0.3 0.2 MAX9814 toc06 0.5 MAX9814 toc04 3.5 MAX9814 toc05 10 SUPPLY CURRENT (mA) -100 VRIPPLE = 200mVP-P 0.1 1.5 1.0 0.5 2.6 0 2.5 3.0 3.5 4.0 4.5 5.0 6.0 5.5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 5 10 15 20 25 SUPPLY VOLTAGE (V) IMICBIAS (mA) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT VOLTAGE INPUT-REFERRED NOISE vs. FREQUENCY 1 fIN = 300Hz, 1kHz, and 3kHz THD+N (%) 1 0.1 0.1 fIN = 10kHz 0.01 0.01 10 100 1k FREQUENCY (Hz) 10k 100k 30 1000 INPUT-REFERRED NOISE (µVRMS/√Hz) 10 MAX9814 toc08 VOUT = 800mVRMS MAX9814 toc07 10 4 0 SUPPLY VOLTAGE (V) MICIN AC-COUPLED TO GND MAX9814 toc09 2.5 THD+N (%) MAX9814 Microphone Amplifier with AGC and Low-Noise Microphone Bias 100 10 1 0 0.5 1.0 OUTPUT VOLTAGE (VRMS) 1.5 0.01 0.1 1 FREQUENCY (kHz) _______________________________________________________________________________________ 10 100 Microphone Amplifier with AGC and Low-Noise Microphone Bias VMICIN 10mV/div 0V 1000 MAX9814 toc12 MAX9814 toc11 MAX9814 toc10 MICBIAS NOISE (nVRMS/√Hz) TURN-ON RESPONSE SMALL-SIGNAL PULSE RESPONSE MICBIAS NOISE vs. FREQUENCY 10,000 VSHDN 5V/div 0V VMICOUT 500mV/div VMICBIAS 2V/div 0V 0V VMICOUT 1V/div 0V 100 CL = 10pF 10 10 100 1k 10k 100k 20ms/div 200µs/div FREQUENCY (Hz) 1.00 MAX9814 toc14 MAX9814 toc13 VTH = 1V VTH = 1V 0.75 VTH = 1V 0.75 0.50 VTH = 0.75V VOUT (VRMS) 0.75 VOUT (VRMS) 0.50 VTH = 0.75V VTH = 0.75V 0.25 0.25 0.25 VTH = 0.5V VTH = 0.5V VTH = 0.5V AGC ENABLED GAIN = 1 0 50 150 100 AGC ENABLED GAIN = UNCONNECTED AGC ENABLED GAIN = 0 0 0 10 20 30 0 0 40 5 15 10 VIN (mVRMS) VIN (mVRMS) VIN (mVRMS) ATTACK TIME ATTACK TIME HOLD AND RELEASE TIME VMICOUT 500mV/div VMICOUT 500mV/div 0V 0V VMICOUT 500mV/div 0V CCT = 47nF A/R = GND CCT = 100nF CCT = 47nF 200µs/div MAX9814 toc18 MAX9814 toc16 0 0.50 MAX9814 toc17 VOUT (VRMS) VOUT vs. VIN VOUT vs. VIN 1.00 MAX9814 toc15 VOUT vs. VIN 1.00 200µs/div 20ms/div _______________________________________________________________________________________ 5 MAX9814 Typical Operating Characteristics (continued) (VDD = 5V, CCT = 470nF, CCG = 2.2µF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1µF, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = 5V, CCT = 470nF, CCG = 2.2µF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1µF, TA = +25°C, unless otherwise noted.) HOLD AND RELEASE TIME MAX9814 toc20 HOLD AND RELEASE TIME MAX9814 toc19 MAX9814 Microphone Amplifier with AGC and Low-Noise Microphone Bias VMICOUT 500mV/div VMICOUT 500mV/div 0V 0V CCT = 47nF A/R = UNCONNECTED CCT = 47nF A/R = VDD 100ms/div 40ms/div Pin Description PIN NAME TDFN UCSP 1 A1 CT 2 B2 SHDN Timing Capacitor Connection. Connect a capacitor to CT to control the Attack and Release times of the AGC. Active-Low Shutdown Control 3 A2 CG 4, 11 — N.C. No Connection. Connect to GND. 5 A3 VDD Power Supply. Bypass to GND with a 1µF capacitor. 6 A4 MICOUT 7 B4 GND 8 C4 MICIN 9 6 FUNCTION B3 A/R Amplifier DC Offset Adjust. Connect a 2.2µF capacitor to GND to ensure zero offset at the output. Amplifier Output Ground Microphone Noninverting Input Tri-Level Attack and Release Ratio Select. Controls the ratio of attack time to release time for the AGC circuit. A/R = GND: Attack/Release Ratio is 1:500 A/R = VDD: Attack/Release Ratio is 1:2000 A/R = BIAS: Attack/Release Ratio is 1:4000 10 C3 GAIN Tri-Level Amplifier Gain Control. GAIN = VDD, gain set to 40dB. GAIN = GND, gain set to 50dB. GAIN = Unconnected, uncompressed gain set to 60dB. 12 C2 BIAS Amplifier Bias. Bypass to GND with a 0.47µF capacitor. 13 C1 MICBIAS 14 B1 TH Microphone Bias Output AGC Threshold Control. TH voltage sets gain control threshold. Connect TH to MICBIAS to disable the AGC. _______________________________________________________________________________________ Microphone Amplifier with AGC and Low-Noise Microphone Bias The MAX9814 is a low-cost, high-quality microphone amplifier with automatic gain control (AGC) and a lownoise microphone bias. The MAX9814 consists of several distinct circuits: a low-noise preamplifier, a variable gain amplifier (VGA), an output amplifier, a microphonebias-voltage generator, and AGC control circuitry. An internal microphone bias voltage generator provides a 2V bias that is suitable for most electret condenser microphones. The MAX9814 amplifies the input in three distinct stages. In the first stage, the input is buffered and amplified through the low-noise preamplifier with a gain of 12dB. The second stage consists of the VGA controlled by the AGC. The VGA/AGC combination is capable of varying the gain from 20dB to 0dB. The output amplifier is the final stage in which a fixed gain of 8dB, 18dB, 20dB is programmed through a single tri-level logic input. With no compression from the AGC, the MAX9814 is capable of providing 40dB, 50dB, or 60dB gain. Automatic Gain Control (AGC) A device without AGC experiences clipping at the output when too much gain is applied to the input. AGC prevents clipping at the output when too much gain is applied to the input, eliminating output clipping. Figure 1 shows a comparison of an over-gained microphone input with and without AGC. The MAX9814’s AGC controls the gain by first detecting that the output voltage has exceeded a preset limit. The microphone amplifier gain is then reduced with a selectable time constant to correct for the excessive output-voltage amplitude. This process is known as the attack time. When the output signal subsequently lowers in amplitude, the gain is held at the reduced state for a short period before slowly increasing to the normal value. This process is known as the hold and release time. The speed at which the amplifiers adjust to changing input signals is set by the external timing capacitor C CT and the voltage applied to A/R. The AGC threshold can be set by adjusting V TH . Gain reduction is a function of input signal amplitude with a maximum AGC attenuation of 20dB. Figure 2 shows the effect of an input burst exceeding the preset limit, output attack, hold and release times. If the attack and release times are configured to respond too fast, audible artifacts often described as “pumping” or “breathing” can occur as the gain is rapidly adjusted to follow the dynamics of the signal. For best results, adjust the time constant of the AGC to accommodate the source material. For applications in which music CDs are the main audio source, a 160µs attack time with an 80ms release time is recommended. Music applications typically require a shorter release time than voice or movie content. MAX9814 AGC DISABLED MAX9814 AGC ENABLED MAX9814 fig01a MAX9814 fig01b 0V VMICIN 100mV/div 0V 0V VMICOUT (AC-COUPLED) 1V/div 0V 400µs/div VMICIN 100mV/div VMICOUT (AC-COUPLED) 1V/div 400µs/div Figure 1. Microphone Input with and Without AGC _______________________________________________________________________________________ 7 MAX9814 Detailed Description Microphone Amplifier with AGC and Low-Noise Microphone Bias MAX9814 and setting the attack-to-release time ratio by configuring A/R as shown in Table 1: HOLD VCT 500mV/div ATTACK • Use a small ratio to maximize the speed of the AGC. • Use a large ratio to maximize the sound quality and prevent repeated excursions above the threshold from being independently adjusted by the AGC. RELEASE 0V VMICOUT (AC-COUPLED) 1V/div 0V AGC Output Threshold The output threshold that activates AGC is adjustable through the use of an external resistive divider. Once the divider is set, AGC reduces the gain to match the output voltage to the voltage set at the TH input. Microphone Bias 10ms/div Figure 2. Input Burst Exceeding AGC Limit Attack Time The attack time is the time it takes for the AGC to reduce the gain after the input signal has exceeded the threshold level. The gain attenuation during the attack time is exponential, and defined as one-time constant. The time constant of the attack is given by 2400 x CCT seconds (where CCT is the external timing capacitor): • Use a short attack time for the AGC to react quickly to transient signals, such as snare drum beats (music) or gun shots (DVD). • Use a longer attack time to allow the AGC to ignore short-duration peaks and only reduce the gain when a noticeable increase in loudness occurs. Shortduration peaks are not reduced, but louder passages are. This allows the louder passages to be reduced in volume, thereby maximizing output dynamic range. Hold Time Hold time is the delay after the signal falls below the threshold level before the release phase is initiated. Hold time is internally set to 30ms and nonadjustable. The hold time is cancelled by any signal exceeding the set threshold level, and the attack time is reinitiated. Release Time The release time is how long it takes for the gain to return to its normal level after the output signal has fallen below the threshold level and 30ms hold time has expired. Release time is defined as release from a 20dB gain compression to 10% of the nominal gain setting after the input signal has fallen below the TH threshold and the 30ms hold time has expired. Release time is adjustable and has a minimum of 25s. The release time is set by picking an attack time using CCT 8 The MAX9814 features an internal low-noise microphone bias voltage capable of driving most electret condenser microphones. The microphone bias is regulated at 2V to provide that the input signal to the lownoise preamplifier does not clip to ground. Applications Information Programming Attack and Release Times Attack and release times are set by selecting the capacitance value between CT and GND, and by setting the logic state of A/R (Table 1). A/R is a tri-level logic input that sets the attack-to-release time ratio. Table 1. Attack-and-Release Ratios A/R ATTACK/RELEASE RATIO GND 1:500 VDD 1:2000 Unconnected 1:4000 The attack and release times can be selected by utilizing the corresponding capacitances listed in Table 2. Table 2. Attack-and-Release Time CCT tATTACK (ms) 22nF tRELEASE (ms) A/R = GND A/R = VDD A/R = UNCONNECTED 0.05 25 100 200 47nF 0.11 55 220 440 68nF 0.16 80 320 640 100nF 0.24 120 480 960 220nF 0.53 265 1060 2120 470nF 1.1 550 2200 4400 680nF 1.63 815 3260 6520 1µF 2.4 1200 4800 9600 _______________________________________________________________________________________ Microphone Amplifier with AGC and Low-Noise Microphone Bias Microphone Bias Resistor MICBIAS is capable of sourcing 20mA. Select a value for RMICBIAS that provides the desired bias current for the electret microphone. A value of 2.2kΩ is usually sufficient for a microphone of typical sensitivity. Consult the microphone data sheet for the recommended bias resistor. Bias Capacitor The BIAS output of the MAX9814 is internally buffered and provides a low-noise bias. Bypass BIAS with a 470nF capacitor to ground. Input Capacitor The input AC-coupling capacitor (CIN) and the input resistance (RIN) to the microphone amplifier form a highpass filter that removes any DC bias from an input signal (see the Typical Application Circuit/Functional Diagram). CIN prevents any DC components from the input-signal source from appearing at the amplifier outputs. The -3dB point of the highpass filter, assuming zero source impedance due to the input signal source, is given by: f−3dB_IN = 1 2π × RIN × CIN Choose CIN such that f-3dB_IN is well below the lowest frequency of interest. Setting f-3dB_IN too high affects the amplifier’s low-frequency response. Use capacitors with low-voltage coefficient dielectrics. Aluminum electrolytic, tantalum, or film dielectric capacitors are good choices for AC-coupling capacitors. Capacitors with high-voltage coefficients, such as ceramics (non-C0G dielectrics), can result in increased distortion at low frequencies. Output Capacitor The output of the MAX9814 is biased at 1.23V. To eliminate the DC offset, an AC-coupling capacitor (COUT) must be used. Depending on the input resistance (RL) of the following stage, COUT and RL effectively form a highpass filter. The -3dB point of the highpass filter, assuming zero output impedance, is given by: f−3dB_OUT = 1 2π × RL × COUT Shutdown The MAX9814 features a low-power shutdown mode. When SHDN goes low, the supply current drops to 0.01µA, the output enters a high-impedance state, and the bias current to the microphone is switched off. Driving SHDN high enables the amplifier. Do not leave SHDN unconnected. Power-Supply Bypassing and PCB Layout Bypass the power supply with a 0.1µF capacitor to ground. Reduce stray capacitance by minimizing trace lengths and place external components as close to the device as possible. Surface-mount components are recommended. In systems where analog and digital grounds are available, connect the MAX9814 to analog ground. _______________________________________________________________________________________ 9 MAX9814 Setting the AGC Threshold To set the output-voltage threshold at which the microphone output is clamped, an external resistor-divider must be connected from MICBIAS to ground with the output of the resistor-divider applied to TH. The voltage VTH determines the peak output-voltage threshold at which the output becomes clamped. The maximum signal swing at the output is then limited to two times VTH and remains at that level until the amplitude of the input signal is reduced. To disable AGC, connect TH to MICBIAS. Microphone Amplifier with AGC and Low-Noise Microphone Bias MAX9814 Typical Application Circuit/Functional Diagram VDD CBYPASS 1µF SHDN VDD MICBIAS MAX9814 BIAS A/R CBIAS 0.47µF R1 150kΩ TH VDD MICBIAS REF AGC GAIN R2 100kΩ RMICBIAS 2.21kΩ MICIN LNA VGA OUT CIN 0.1µF COUT ROUT CT CCT 47nF CG CCG 2.2µF GND *THE DEVICE HAS BEEN CONFIGURED WITH AN ATTACK TIME OF 1.1ms, 40dB GAIN, AND AN ATTACK-AND-RELEASE RATIO OF 1:500. 10 ______________________________________________________________________________________ Microphone Amplifier with AGC and Low-Noise Microphone Bias TOP VIEW (BUMP SIDE DOWN) TH MICBIAS BIAS N.C. GAIN A/R MICIN TOP VIEW 14 13 12 11 10 9 8 MAX9814 1 2 3 4 CT CG VDD MICOUT TH SHDN A/R GND MICBIAS BIAS GAIN MICIN A B MAX9814 C 5 6 7 GND CG 4 MICOUT 3 VDD 2 N.C. 1 CT UCSP SHDN + TDFN Chip Information PROCESS: BiCMOS ______________________________________________________________________________________ 11 MAX9814 Pin Configurations Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) 12L, UCSP 4x3.EPS MAX9814 Microphone Amplifier with AGC and Low-Noise Microphone Bias PACKAGE OUTLINE, 4x3 UCSP 21-0104 12 ______________________________________________________________________________________ F 1 1 Microphone Amplifier with AGC and Low-Noise Microphone Bias 6, 8, &10L, DFN THIN.EPS ______________________________________________________________________________________ 13 MAX9814 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) MAX9814 Microphone Amplifier with AGC and Low-Noise Microphone Bias Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) COMMON DIMENSIONS PACKAGE VARIATIONS SYMBOL MIN. MAX. PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e A 0.70 0.80 T633-2 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF D 2.90 3.10 T833-2 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF E 2.90 3.10 T833-3 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF A1 0.00 0.05 T1033-1 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 2.00 REF L 0.20 0.40 T1033-2 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 2.00 REF k 0.25 MIN. T1433-1 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.05 2.40 REF A2 0.20 REF. T1433-2 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.05 2.40 REF Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.