MAX9814 microphone amplifier: specs and pinout
Electret microphone amplifier with automatic gain control. The maker data sheet covers the MAX9814 chip, whose output is centred on a DC bias; the breakout board is not covered, so its output level is not documented.
Specs
| Spec | Value | Source |
|---|---|---|
| Supply voltage (VDD) | 2.7 V to 5.5 V | source p.2 Electrical Characteristics, Operating Voltage |
| Supply current | 3.1 mA typ, 6 mA max (VDD = 3.3 V) | source p.2 Electrical Characteristics |
| Gain settings (GAIN pin) | 40 dB (GAIN = VDD), 50 dB (GAIN = GND), 60 dB (GAIN unconnected); AGC reduces gain by up to 20 dB | source p.2 Maximum/Minimum Gain; p.6 pin 10 |
| AGC attack/release ratio | 1:500 (A/R = GND), 1:2000 (A/R = VDD), 1:4000 (A/R unconnected); hold time 30 ms fixed | source p.2; p.6 pin 9; p.1 General Description |
| Output bias at MICOUT, bare chip (no signal) | 1.23 V typ (1.14 V to 1.32 V) | source p.3 Electrical Characteristics, MICOUT Bias |
| Microphone bias output | 2.0 V typ (1.84 V to 2.18 V) | source p.3 Microphone Bias |
| Maximum output level | 0.707 Vrms at 1 % THD+N (VTH = MICBIAS) | source p.2 |
| Signal-to-noise ratio | 64 dB A-weighted | source p.2 |
| Total harmonic distortion plus noise | 0.04 % typ (test conditions on p.2) | source p.2 |
| Operating temperature | -40 C to +85 C | source p.2 Absolute Maximum Ratings |
Power
| Value | Source | |
|---|---|---|
| Supply | 2.7 V to 5.5 V | source p.2 Electrical Characteristics |
| Current | 3.1 mA typ, 6 mA max at VDD = 3.3 V | source p.2 Electrical Characteristics |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
Pin rows are the bare MAX9814 TDFN package from the maker data sheet. The breakout board (header order, which gain/AGC straps are fitted, onboard capacitors and microphone) is not covered by an official document; read the labels on your board.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| 1 | CT: Timing capacitor connection; sets AGC attack and release times | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 2 | SHDN: Active-low shutdown control | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 3 | CG: Amplifier DC offset adjust; 2.2 uF capacitor to GND | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 4, 11 | N.C.: No connection; connect to GND | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 5 | VDD: Power supply; bypass to GND with 1 uF | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 6 | MICOUT: Amplifier output | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 7 | GND: Ground | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 8 | MICIN: Microphone noninverting input | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 9 | A/R: Tri-level attack/release ratio select: GND 1:500, VDD 1:2000, unconnected 1:4000 | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 10 | GAIN: Tri-level gain: VDD 40 dB, GND 50 dB, unconnected 60 dB (uncompressed) | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 12 | BIAS: Amplifier bias; bypass to GND with 0.47 uF | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 13 | MICBIAS: Microphone bias output | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| 14 | TH: AGC threshold control; tie to MICBIAS to disable AGC | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description | |
| EP | EP: Exposed pad; connect to GND | Chip pin (14-pin TDFN), not the module header. | source p.6 Pin Description |
Build with it
Project ideas for the MAX9814 microphone amplifier. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Relative loudness bar on an OLED: Power the amplifier at 3.3 V (within the chip's 2.7-5.5 V supply). The bare chip's output is biased near 1.23 V; measure your module's idle output before wiring it to the ESP32 analog input. AGC makes it a relative indicator only. Learning project.
- A loudness number display with an Arduino Uno, a MAX9814 microphone amplifier and a TM1637 display: On the bare chip the idle output is about 1.23 V; measure your module's idle voltage first, then subtract that offset in code and show the peak per half second. Learning project.
- Clap switch with a light: A loud peak above a threshold toggles the LED (with a series resistor); measure your module's idle output voltage first, as the chip's 1.23 V bias may not apply to the breakout. Learning project.
Common mistakes
- Reading it as a calibrated sound-level meter: with AGC on the gain changes with signal level (gain falls by up to 20 dB), so loudness is only relative (source: link, p.2 and Detailed Description)
- Expecting a zero-centred signal: on the bare MAX9814 chip MICOUT sits at about 1.23 V with no signal; a breakout may add its own coupling capacitor or bias, so measure the idle voltage of your module's output before choosing the offset to subtract in code (source: link, p.3)
- Leaving GAIN unconnected and expecting 40 dB: unconnected sets 60 dB, GND 50 dB, VDD 40 dB (source: link, p.6 pin 10)
Not covered by the official source
- Chip data sheet only: the module's component values and which pins are broken out are undocumented.
- The datasheet is rev 2 (6/09), a verbatim copy hosted on a mirror; a newer revision may exist.
Sources
- link (Maxim Integrated MAX9814 data sheet, 19-0764 Rev 2, 6/09)