MAX4061ETA-T Maxim Integrated, MAX4061ETA-T Datasheet - Page 10

• Manufacturer Part Number: MAX4061ETA-T
• Description: Microphone Preamplifiers
• Manufacturer: Maxim Integrated

Figure 1. MAX4062 with Auxiliary Input Configuration
Differential Microphone Preamplifiers with
Internal Bias and Complete Shutdown
ential inputs and to set the lower 3dB point (f
amplifier by sizing the output capacitor appropriately.
The input impedance matching on the differential input
is typically 1%, allowing input capacitor matching to be
effective at improving low-frequency PSRR.
The common-mode rejection ratio (CMRR) refers to the
amount of rejection that the amplifier is capable of pro-
viding to any signal applied equally to the IN+ and IN-
inputs. In the case of amplifying low-level microphone
signals in noisy digital environments, it is a key figure of
merit. In audio circuits, this is generally measured for
V
where A
mode gain.
Input voltages are sufficiently small such that the output
is not clipped in either differential or common-mode
application. The topology used in the MAX4061/
MAX4062 means that the CMRR actually improves at
higher differential gains—another advantage of using
differential sensing.
10
IN
as an AC signal:
______________________________________________________________________________________
DM
is the differential gain, A
CMRR(dB) = A
Common-Mode Rejection Ratio
100kΩ
DM
/ A
CM
CM
R
is the common-
BIAS
CUT
C
BIAS
) of the
4
9
6
7
BIAS
AUX_IN
IN+
IN-
x10
V
The auxiliary input is a single-ended input intended to
be used with a jack-socket-type microphone input
(Figure 1). Internal DC-bias components (as on the
main inputs) allow the input signal to be AC-coupled.
Mechanically switched jack sockets can be used in
conjunction with the INT/AUX select pin, allowing the
auxiliary microphone input to be automatically selected
when a jack socket is inserted.
The MAX4060 has a microphone bias voltage designed
to comply with the Microsoft/Intel PC99/2001 audio
standard. It features source impedance of greater than
2kΩ, and delivers more than 2V of bias when loaded
with a current of 800μA. This limits operation of this part
to supplies between 4.5V to 5.5V (see Figure 2).
2.4V TO 5.5V
BIAS
V
CC
GND
5
8
MAX4062
INT/AUX
OUT 3
G2
G1
10
2
1
Microphone Bias Voltage
Auxiliary Input
MAX4060