Low-Cost, Micropower, SC70/SOT23-8, Microphone Preamplifiers with Complete Shutdown

Transcription

1 9-9; Rev ; 4/ Low-Cost, Micropower, SC7/SOT23-8, Microphone General Description The are micropower op amps optimized for use as microphone preamplifiers. They provide the ideal combination of an optimized gain bandwidth product vs. supply current, and low voltage operation in ultra-small packages. The MAX446/ MAX4467/MAX4469 are unity-gain stable and deliver a 2kHz gain bandwidth from only 24µA of supply current. The MAX4466/MAX4468 are decompensated for a minimum stable gain of +V/V and provide a 6kHz gain bandwidth product. In addition, these amplifiers feature Rail-to-Rail outputs, high A VOL, plus excellent power-supply rejection and common-mode rejection ratios for operation in noisy environments. The MAX4467/MAX4468 include a complete shutdown mode. In shutdown, the amplifiers supply current is reduced to na and the bias current to the external microphone is cut off for ultimate power savings. The single MAX446/MAX4466 are offered in the ultra-small -pin SC7 package, while the single with shutdown MAX4467/MAX4468 and dual MAX4469 are available in the space-saving 8-pin SOT23 package. Microphone Preamplifiers Hearing Aids Cellular Phones Voice-Recognition Systems Digital Dictation Devices Headsets Portable Computing Applications Pin Configurations Features +2.4V to +.V Supply Voltage Operation Versions with na Complete Shutdown Available (MAX4467/MAX4468) Excellent Power-Supply Rejection Ratio: 2dB Excellent Common-Mode Rejection Ratio: 26dB High A VOL : 2dB (R L = kω) Rail-to-Rail Outputs Low 24µA Quiescent Supply Current Gain Bandwidth Product: 2kHz (MAX446/MAX4467/MAX4469) 6kHz A V (MAX4466/MAX4468) Available in Space-Saving Packages -Pin SC7 (MAX446/MAX4466) 8-Pin SOT23 (MAX4467/MAX4468/MAX4469) Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX446EXK-T -4 C to +8 C SC7- MAX446EUK-T -4 C to +8 C SOT23- MAX4466EXK-T -4 C to +8 C SC7- MAX4466EUK-T -4 C to +8 C SOT23- Ordering Information continued at end of data sheet. R BIAS Typical Operating Circuit V CC SHDN TOP VIEW C BIAS R DC MIC_BIAS IN+ V CC R BIAS IN+ GND 2 MAX446 MAX4466 C IN R IN IN- IN- 3 4 C BYPASS RDC GND MAX4467 MAX4468 SC7/SOT23 Pin Configurations continued at end of data sheet. Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd. MICROPHONE CAPSULE MAX4467/MAX4468 TYPICAL OPERATING CIRCUIT WITH COMPLETE SHUTDOWN R FB Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS Supply Voltage (V CC to GND)...+6V All Other Pins to GND...-.3V to (V CC +.3V) Output Short-Circuit Duration Shorted to GND or V CC...Continuous Continuous Power Dissipation (T A = +7 C) -Pin SC7 (derate 2.mW/ C above +7 C)...2mW -Pin SOT23 (derate 7.mW/ C above +7 C)...7mW 8-Pin SOT23 (derate.3mw/ C above +7 C)...42mW 8-Pin SO (derate.88mw/ C above +7 C)...47mW Operating Temperature Range...-4 C to +8 C Storage Temperature Range...-6 C to + C Junction Temperature...+ C Lead Temperature (soldering, s)...+3 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 (V CC = +V, V CM =, V = V CC /2, R L = to V CC /2, SHDN = GND (MAX4467/MAX4468 only). T A = T MIN to T MAX, unless otherwise noted. Typical values specified at T A = +2 C.) (Note ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage Range V CC Inferred from PSRR test 2.4. V Supply Current (Per Amplifier) T A = +2 C I CC T A = T MIN to T MAX 6 Supply Current in Shutdown I SHDN SHDN = V CC (Note 2) na Input Offset Voltage V OS ± ± mv Input Bias Current I B V CM = -.V ±2. ± na Input Offset Current Range I OS V CM = -.V ± ± na Input Common-Mode Range V CM Inferred from CMRR test -. V CC -. V C om m on- M od e Rej ecti on Rati o CMRR -.V V CM V CC - V 8 26 db Power-Supply Rejection Ratio PSRR 2.4V V CC.V 8 2 MAX446/MAX4467/MAX4469, f = 3.4kHz 7 MAX4466/MAX4468, f = 3.4kHz 8 R L = kω to V CC /2,.V V V CC -.V Open-Loop Gain A VOL R L = kω to V CC /2,.V V V CC -.V Output Voltage Swing High V OH IV CC - V OHI R L = kω R L = kω 6 R L = kω Output Voltage Swing Low V OL R L = kω 4 µa db db mv mv Output Short-Circuit Current To either supply rail ma Output Leakage Current in Shutdown SHDN = V CC, V V CC ; (Notes 2, 3) ±. ± na SHDN Logic Low V IL (Note 2) V CC.3 V SHDN Logic High V IH (Note 2) V CC.7 V SHDN Input Current (Note 2) 2 2 na Gain Bandwidth Product GBWP MAX446/MAX4467/MAX MAX4466/MAX khz 2

3 ELECTRICAL CHARACTERISTICS (continued) (V CC = +V, V CM =, V = V CC /2, R L = to V CC /2, SHDN = GND (MAX4467/MAX4468 only), T A = T MIN to T MAX, unless otherwise noted. Typical values specified at T A = +2 C.) (Note ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Channel-to-Channel Isolation MAX4469 only, f = khz 8 db Phase Margin Ø M R L = kω 7 d egr ees Gain Margin R L = kω 2 db Slew Rate SR Output step = 4V MAX446/MAX4467/ MAX4469, A V = + MAX4466/MAX4468, A V = + Input Noise Voltage Density e n f = khz 8 nv/ Hz Total Harmonic Distortion THD f = khz, R L = kω, V = 2Vp-p M AX 446/M AX 4467/ M AX MAX4466/MAX Capacitive Load Stability C LOAD MAX446/MAX4467/MAX4469, A V = + MAX4466/MAX4468, A V = + mv/µs % pf SHDN Delay Time t SHDN (Note 2) µs Enable Delay Time t EN (Note 2) µs Power-On Time t ON (Note 2) 4 µs Bias Switch On-Resistance R S I S = ma (Note 2) 2 Ω Note : All specifications are % production tested at T A = +2 C. All temperature limits are guaranteed by design. Note 2: Shutdown mode is available only on the MAX4467/MAX4468. Note 3: External feedback networks not considered. Typical Operating Characteristics (V CC = +V, V CM =, V = V CC /2, R L = kω to V CC /2, SHDN = GND (MAX4467/MAX4468 only), T A = +2 C, unless otherwise noted.) GAIN (db)/phase (DEGREES) MAX446/MAX4467/MAX4469 GAIN AND PHASE vs. FREQUENCY (NO LOAD) k k k M FREQUENCY (Hz) MAX toc GAIN (db)/phase (DEGREES) MAX4466/MAX4468 GAIN AND PHASE vs. FREQUENCY (NO LOAD) k k k M FREQUENCY (Hz) MAX toc2 GAIN (db)/phase (DEGREES) MAX446/MAX4467/MAX4469 GAIN AND PHASE vs. FREQUENCY (C L = pf) k k k M FREQUENCY (Hz) MAX toc3 3

4 PSRR (db) POWER-SUPPLY REJECTION RATIO vs. FREQUENCY -3 k k k M FREQUENCY (Hz) MAX toc4 SUPPLY CURRENT (pa), Typical Operating Characteristics (continued) (V CC = +V, V CM =, V = V CC /2, R L = kω to V CC /2, SHDN = GND (MAX4467/MAX4468 only), T A = +2 C, unless otherwise noted.) SHUTDOWN SUPPLY CURRENT V SHDN = V CC MAX toc SUPPLY CURRENT (µa) SUPPLY CURRENT MAX toc6 ILEAK (pa) PUT LEAKAGE CURRENT V SHDN = V CC V = V CC /2 MAX toc7 CHANNEL-TO-CHANNEL ISOLATION (db) CHANNEL-TO-CHANNEL ISOLATION vs. FREQUENCY MAX toc8 VOS (µv) INPUT OFFSET VOLTAGE MAX toc FREQUENCY (khz) VDD - V (mv) PUT VOLTAGE SWING HIGH MAX toc V - VSS (mv) PUT VOLTAGE SWING LOW MAX toc CMRR (db) COMMON-MODE REJECTION RATIO MAX toc

5 GAIN (db) LARGE-SIGNAL GAIN vs. PUT VOLTAGE V (V) MAX446/MAX4467/MAX4469 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY V = 2Vp-p A V = +V/V BW = 22kHz MAX toc3 MAX toc6 GAIN (db) Typical Operating Characteristics (continued) (V CC = +V, V CM =, V = V CC /2, R L = kω to V CC /2, SHDN = GND (MAX4467/MAX4468 only), T A = +2 C, unless otherwise noted.) LARGE-SIGNAL GAIN MAX toc MAX4466/MAX4468 TOTAL HARMONIC DISTORTION vs. FREQUENCY V = 2Vp-p AV = +V/V BW = 22kHz MAX toc7 VMIN (V) MINIMUM OPERATING VOLTAGE MAX446/MAX4467/MAX4469 TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT AMPLITUDE f = khz A V = +V/V BW = 22kHz MAX toc MAX toc8 THD + N (%). R L = kω THD + N (%). R L = kω THD + N (%). R L = kω. R L = kω k 2k FREQUENCY (Hz) MAX4466/MAX4468 TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT AMPLITUDE f = khz A V = +V/V BW = 22kHz MAX toc9. R L = kω k 2k FREQUENCY (Hz) NONINVERTING SMALL-SIGNAL TRANSIENT RESPONSE MAX toc2.. R L = kω V IN (Vp-p) NONINVERTING LARGE-SIGNAL TRANSIENT RESPONSE MAX toc2 THD + N (%). R L = kω mv/div 2V/div. R L = kω V IN (Vp-p) 2µs/div 2µs/div

6 Typical Operating Characteristics (continued) (V CC = +V, V CM =, V = V CC /2, R L = kω to V CC /2, SHDN = GND (MAX4467/MAX4468 only), T A = +2 C, unless otherwise noted.) SUPPLY CURRENT (µa) SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY VOLTAGE (V) MAX toc22 enoise (nv Hz) A VCL = +V/V e NOISE vs. FREQUENCY 4 k k k M FREQUENCY (Hz) MAX toc SINK CURRENT vs. PUT VOLTAGE MAX toc SOURCE CURRENT vs. PUT VOLTAGE MAX toc2 SINK CURRENT (ma) V CC = +V SOURCE CURRENT (ma) V CC = +V V CC = +2.4V V CC = +2.4V PUT VOLTAGE (V) PUT VOLTAGE (V) Pin Description PIN MAX446 MAX4466 MAX4467 MAX4468 MAX4469 NAME FUNCTION 4 6 (8) Amplifier Output A Amplifier Output A (4) MIC_BIAS External Microphone Bias Network Switch Output 3 2 (3) IN- Inverting Amplifier Input 3 (2) IN+ Noninverting Amplifier Input 2 4 () 4 GND Ground ( ) denotes ST23 package of the MAX4467/MAX4468 6

7 MAX446 MAX4466 PIN MAX4467 MAX4468 MAX4469 NAME Pin Description (continued) FUNCTION 7 (7) 8 V CC Positive Supply. Bypass with a.µf capacitor to GND. 2 INA- Inverting Amplifier Input A 3 INA+ Noninverting Amplifier Input A 6 INB- Inverting Amplifier Input B INB+ Noninverting Amplifier Input B 7 B Amplifier Output B 8 (6) SHDN Active-High Shutdown Input. Connect to GND for normal operation. Connect to V CC for shutdown. Do not leave floating. () N.C. No Connection. Not internally connected. ( ) denotes SOT23 package of the MAX4467/MAX4468. Detailed Description The are low-power, micropower op amps designed to be used as microphone preamplifiers. These preamplifiers are an excellent choice for noisy environments because of their high commonmode rejection and excellent power-supply rejection ratios. They operate from a single +2.4V to +.V supply. The MAX446/MAX4467/MAX4469 are unity-gain stable and deliver a 2kHz gain bandwidth from only 24µA of supply current. The MAX4466/MAX4468 have a minimum stable gain of +V/V while providing a 6kHz gain bandwidth product. The MAX4467/MAX4468 feature a complete shutdown, which is active-high, and a shutdown-controlled output providing bias to the microphone. The MAX446/ MAX4467/MAX4469 feature a slew rate suited to voice channel applications. The MAX4466/MAX4468 can be used for full-range audio, e.g., PC99 inputs. Rail-to-Rail Output Stage The can drive a kω load and still typically swing within 6mV of the supply rails. Figure shows the output voltage swing of the MAX446 configured with A V = +. Switched Bias Supply When used as a microphone amplifier for an electret microphone, some form of DC bias for the microphone is necessary. The MAX4467/MAX4468 have the ability to turn off the bias to the microphone when the device is in shutdown. This can save several hundred microamps of supply current, which can be significant in low power applications. The MIC_BIAS pin provides a switched version of V CC to the bias components. Figure 3 shows some typical values. Driving Capacitive Loads Driving a capacitive load can cause instability in many op amps, especially those with low quiescent current. The MAX446/MAX4467/MAX4469 are unity-gain stable for a range of capacitive loads up to pf. Figure 4 shows the response of the MAX446 with an excessive capacitive load. Applications Information Shutdown Mode The MAX4467 and MAX4468 feature a low-power, complete shutdown mode. When SHDN goes high, the supply current drops to na, the output enters a high impedance state and the bias current to the microphone is switched off. Pull SHDN low to enable the amplifier. Do not leave SHDN floating. Figure shows the shutdown waveform. Common-Mode Rejection Ratio A microphone preamplifier ideally only amplifies the signal present on its input and converts it to a voltage appearing at the output. When used in noninverting mode, there is a small output voltage fluctuation when both inputs experience the same voltage change in the 7

8 common mode. The ratio of these voltages is called the common-mode gain. The common-mode rejection ratio is the ratio of differential-mode gain to common-mode gain. The high CMRR properties of the provide outstanding performances when configured as a noninverting microphone preamplifier. Power-Up The outputs typically settle within µs after power-up. Figure 6 shows the output voltage on power-up. Power Supplies and Layout The operate from a single +2.4V to +.V power supply. Bypass the power supply with a.µf capacitor to ground. Good layout techniques are necessary for the family. To decrease stray capacitance, minimize trace lengths by placing external components close to the op amp s pins. Surface-mount components are recommended. In systems where analog and digital grounds are available, the should be connected to the analog ground. Test Circuits/Timing Diagrams V/div µs/div Figure. Rail-to-Rail Output Operation +V +V 2kΩ V CC = +V 2kΩ.µF MΩ MAX4466 IN+.µF MΩ 4 ELECTRET CAPSULE kω IN- 3 2 GND µf kω pf Figure 2. MAX4466 Typical Application Circuit 8

9 MICROPHONE INPUT µf kω 2.2kΩ kω kω Test Circuits/Timing Diagrams (continued) V CC SHDN MIC_BIAS IN+.µF IN- MAX4468 GND.µF 2kΩ 3.mm SOCKET 2kΩ 47pF Figure 3. Bias Network Circuit C L = 2pF RL = kω CL = pf SHDN mv/div 2V/div 4µs/div Figure 4. Small-Signal Transient Response with Excessive Capacitive Load 4µs/div Figure. MAX4467/MAX4468 Shutdown Waveform 9

10 2µs/div Figure 6. Power-Up/Power-Down Waveform Test Circuits/Timing Diagrams (continued) V CC 2V/div V/div Chip Information MAX446/MAX4466 TRANSISTOR COUNT: 62 MAX4467/MAX4468 TRANSISTOR COUNT: 72 MAX4469 TRANSISTOR COUNT: 3 PROCESS: BiCMOS Ordering Information (continued) PART TEMP. RANGE PIN-PACKAGE MAX4467EKA-T -4 C to +8 C 8 SOT23-8 MAX4467ESA -4 C to +8 C 8 SO MAX4468EKA-T -4 C to +8 C 8 SOT23-8 MAX4468ESA -4 C to +8 C 8 SO MAX4469EKA-T -4 C to +8 C 8 SOT23-8 MAX4469ESA -4 C to +8 C 8 SO Selector Guide PART MINIMUM STABLE GAIN EXTERNAL MICROPHONE SHDN GBWP (khz) PIN-PACKAGE MAX446 + No 2 SC7/ SOT23 MAX No 6 SC7/ SOT23 MAX Yes 2 8 SOT23/8 SO MAX Yes 6 8 SOT23/8 SO MAX No 2 8 SOT23/8 SO Pin Configurations (continued) GND 8 MIC_BIAS 8 SHDN A 8 V CC IN+ IN- IN- 2 3 MAX4467 MAX V CC SHDN INA- IN+ 2 3 MAX4467 MAX V CC INB- INA+ 2 3 MAX B MIC_BIAS 4 N.C. GND 4 N.C. GND 4 INB+ SOT23 SO SOT23/SO

11 Package Information SC7, L.EPS

12 Package Information (continued) SOTL.EPS 2

13 Package Information (continued) SOT23, 8L.EPS 3

14 Package Information (continued) SOICN.EPS 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. 4 Maxim Integrated Products, 2 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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