LMV1089RLEVAL National Semiconductor, LMV1089RLEVAL Datasheet - Page 27

• Manufacturer Part Number: LMV1089RLEVAL
• Description: BOARD EVALUATION LMV1089
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LMV1089RLEVAL

• Main Purpose: Audio, Microphone Amp
• Embedded: No
• Utilized Ic / Part: LMV1089
• Primary Attributes: Dual Input, Single Output
• Secondary Attributes: Graphical User Interface, I²C Interface
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

SUPPLY CURRENT DURING CALIBRATION
The calibration function performs two main tasks in a se-
quence. First the AC characteristics of the microphones are
matched. Then in the second stage, if the PE pin is high, the
on-chip EEPROM is programmed.
During the first stage of this sequence the supply current on
the LMV1089 will increase to about 2.5mA. During the writing
of the EEPROM the supply current will rise for about 215 ms
to about 30mA. This increased current is used for the on chip
charge pump which generates the high voltages that are re-
quired for programming the EEPROM.
FIGURE 14. Supply current during calibration and
programming
FIGURE 15. Broadside Array (WRONG)
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Microphone Placement
Because the LMV1089 is a microphone array Far Field Noise
Reduction solution, proper microphone placement is critical
for optimum performance. Two things need to be considered:
The spacing between the two microphones and the position
of the two microphones relative to near field source
If the spacing between the two microphones is too small, near
field speech will be canceled along with the far field noise.
Conversely, if the spacing between the two microphones is
large, the far field noise reduction performance will be de-
graded. The optimum spacing between Mic 1 and Mic 2 is
1.5-2.5cm. This range provides a balance of minimal near
field speech loss and maximum far field noise reduction.
The microphones should be in line with the desired sound
source 'near speech' and configured in an endfire array
(seeFigure
speech' (desired sound source) is equidistant to the source
like a broadside array
deal of near field speech loss.
16) orientation from the sound source. If the 'near
(seeFigure
15) the result will be a great
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