LMV1089RLEVAL National Semiconductor, LMV1089RLEVAL Datasheet - Page 25

• 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

PERFORMING A THREE TONE CALIBRATION
In a system with two microphones in an enclosure there will
always be a difference in the transfer function in both gain and
frequency response between the two channels. The
LMV1089 has the capability to perform an automatic calibra-
tion function to minimize these differences. To perform this
calibration, a test sequence of three tones is required right
after the PE and CAL inputs are brought to a logic high level.
At the end of this sequence the calibration data is automati-
cally stored in the internal EEPROM.
The three tones have to be applied as follows (see Figure 12):
•
NOTE: Data guaranteed by design
A first tone with a frequency of 1kHz
Symbol
t
t
t
t
t
t
t
ST1
ET1
ST2
ET2
ST3
ET3
CC
Calibration Start Tone 1
Calibration End Tone 1
Calibration Start Tone 2
Calibration End Tone 2
Calibration Start Tone 3
Calibration End Tone 3
Calibration Complete
TABLE 7. Automatic Calibration Timing Parameters
Parameter
FIGURE 12. Calibration Timing
25
•
•
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.
Between each tone pair there is a small time, indicated by a
cross, to change the frequency. During that time the input tone
is ignored by the calibration system.
The total calibration sequence requires less than 790ms.
A second tone with a frequency of 300Hz
A third tone with a frequency of 3kHz
Figure 12
Min
200
400
600
790
and
Limits
Table 7
Max
210
410
are ignored by the calibration
10
300472r3
Unitis
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