Datasheet

Microphone Amplifier with AGC and
Low-Noise Microphone Bias
Note 1: Devices are production tested at T
A
= +25°C. Limits over temperature are guaranteed by design.
Note 2: Dynamic range is calculated using the EIAJ method. The input is applied at -60dBFS (0.707µV
RMS
), f
IN
= 1kHz.
Note 3: Attack time measured as time from AGC trigger to gain reaching 90% of its final value.
Note 4: CG is connected to an external DC voltage source, and adjusted until V
MICOUT
= 1.23V.
Note 5: CG connected to GND with 2.2µF.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MICOUT High Output Voltage V
OH
I
OUT
sourcing 1mA 2.45 V
MICOUT Low Output Voltage V
OL
I
OUT
sinking 1mA 3 mV
MICOUT Bias MICOUT unconnected 1.14 1.23 1.32 V
Output Impedance Z
OUT
50 Ω
Minimum Resistive Load R
LOAD_MIN
5kΩ
Maximum Capacitive Drive C
LOAD_MAX
200 pF
Maximum Output Current I
OUT_MAX
1% THD, R
L
= 500Ω 12mA
Output Short-Circuit Current I
SC
38 mA
AGC mode; V
DD
= 2.7V to 5.5V (Note 4) 35 50
f = 217Hz, V
RIPPLE
= 100mV
P-P
(Note 5) 55
f = 1kHz, V
RIPPLE
= 100mV
P-P
(Note 5) 52.5
Power-Supply Rejection Ratio PSRR
f = 10kHz, V
RIPPLE
= 100mV
P-P
(Note 5) 43
dB
MICROPHONE BIAS
Microphone Bias Voltage V
MICBIAS
I
MICBIAS
= 0.5mA 1.84 2.0 2.18 V
Output Resistance R
MICBIAS
I
MICBIAS
= 1mA 1 Ω
Output Noise Voltage V
MICBIAS_NOISE
I
MICBIAS
= 0.5mA, BW = 22Hz to 22kHz 5.5 µV
RMS
DC, V
DD
= 2.7V to 5.5V 70 80
Power-Supply Rejection Ratio PSRR
I
MICBIAS
= 0.5mA, V
RIPPLE
= 100mV
P-P
,
f
IN
= 1kHz
71
dB
TRILEVEL INPUTS (A/R, GAIN)
A/R or GAIN = V
DD
0.5V
DD
/ 180kΩ
0.5V
DD
/ 100kΩ
0.5V
DD
/ 50kΩ
Tri-Level Input Leakage Current
A/R or GAIN = GND
0.5V
DD
/ 180kΩ
0.5V
DD
/ 100kΩ
0.5V
DD
/ 50kΩ
mA
Input High Voltage V
IH
V
DD
x 0.7 V
Input Low Voltage V
IL
V
DD
x 0.3 V
Shutdown Enable Time t
ON
60 ms
Shutdown Disable Time t
OFF
40 ms
DIGITAL INPUT (SHDN)
SHDN Input Leakage Current -1 +1 µA
Input High Voltage V
IH
1.3 V
Input Low Voltage V
IL
0.5 V
AGC THRESHOLD INPUT (TH)
TH Input Leakage Current -1 +1 µA
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 3.3V, SHDN = V
DD
, C
CT
= 470nF, C
CG
= 2µF, GAIN = V
DD
, T
A
= T
MIN
to T
MAX
, unless otherwise specified. Typical values are
at T
A
= +25°C.) (Note 1)
MAX9814
Maxim Integrated
3