LMV1089RLEVAL National Semiconductor, LMV1089RLEVAL Datasheet - Page 24

• 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

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AUTOMATIC CALIBRATION VIA I
To initiate the automatic calibration via the I
following procedure is required:
•
•
•
•
PERFORMING THE AUTOMATIC CALIBRATION
Automatic calibration can be performed as 'one tone' or as
'three tone' calibration. Three tone calibration is preferred be-
cause the three tone calibration not only compensates for
differences in the gain between the two microphones, but this
function also corrects for differences in the frequency re-
sponse between in the two microphones and compensates
for the acoustical effects of the enclosure.
The one tone calibration only compensates for the gain dif-
ference between the two microphones at 1kHz and can lead
to less far field noise reduction when compared to three tone
calibration.
PERFORMING A ONE TONE CALIBRATION
The easiest way to perform an automatic calibration with the
LMV1089 uses a 1kHz tone. This tone can be a steady state
From the initial condition where PE is 'low' level
Bring PE to a 'high' level (enable EEprom write)
Write '1' into I
calibration
Apply Audio stimulus (single tone 1kHz or three tone
sequence as described in
TONE
CALIBRATION)
2
C register 'R' (address 0x12) bit 0 to start
PERFORMING A THREE
2
C COMMAND
FIGURE 11. One Tone Calibration Timing
2
C interface, the
FIGURE 10.
24
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•
•
•
A tone may be applied prior to the rising of PE or setting the
I
before rising of PE or setting the I
by the calibration system.
tone or a 1kHz tone that is switched on and off using the timing
from
To perform a one tone calibration, a 1kHz test tone is required
right after the PE and CAL inputs are brought to a logic high
level and that tone should be stable during the time as indi-
cated in
data is automatically stored in the internal EEPROM (see Fig-
ure 12).
A tone may be applied prior to the rising of CAL start signal
and PE. Signals applied to the microphone outside the limits
shown in
system.
2
C calibration bit . Signals applied to the microphone inputs
Wait at least 790ms
Remove Audio stimulus
Write '0' into I
Bring PE to a 'low' level (disable EEprom write)
Figure
Table
Figure 11
11.
7. At the end of this sequence the calibration
2
C to finish calibration
and
Table 7
300472r2
are ignored by the calibration
2
C calibration bit are ignored
300472r4