LMV1088RL/NOPB National Semiconductor, LMV1088RL/NOPB Datasheet - Page 20

• Manufacturer Part Number: LMV1088RL/NOPB
• Description: IC AMP AUDIO MONO AB MIC 36USMD
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: Class ABr

Specifications of LMV1088RL/NOPB

• Output Type: 1-Channel (Mono)
• Voltage - Supply: 2.7 V ~ 5.5 V
• Features: Differential Inputs, I²C, Microphone, Mute
• Mounting Type: Surface Mount
• Package / Case: 36-MicroSMDxt
• Amplifier Class: AB
• No. Of Channels: 2
• Supply Voltage Range: 2.7V To 5.5V
• Load Impedance: 10kohm
• Operating Temperature Range: -40°C To +85°C
• Amplifier Case Style: SMD
• No. Of Pins: 36
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Max Output Power X Channels @ Load: -
• Other names: LMV1088RLTR

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Manual Calibration
You can manually program the gain of the two mic inputs on
the LMV1088 using the I
trol bits for I
This can be easily done by doing the following:
powering up.
settings.
O<3:0> control the two mics at 3kHz.
the Mic1 gain
bits from I2C register N<6:0> to I2C register Q<6:0>
EEPROM programming is complete. Now PE pin and T7 pin
should be set to GND and I2C register Q<7> (storeBar)
should be returned to ‘1’.
Low-Pass Filter At The Output
At the output of the LMV1088 there is a provision to create a
1
mode). This low-pass filter can be used to compensate for the
change in frequency response that results from the noise
cancellation process.. The change in frequency response re-
sembles a first-order high-pass filter, and for many of the
applications it can be approximately compensated by a first-
order low-pass filter with cutoff frequency between 1.5kHz
and 2.5kHz.
The transfer function of the low pass filter is derived as:
This low-pass filter is created by connecting a capacitor be-
tween the LPF pin and the OUT pin of the LMV1088. The
value of this capacitor also depends on the selected output
gain. For different gains the feedback resistance in the Low-
pass Filter network changes as shown in Table 6.
st
1) READ contents of the I
2) Set PE pin and T7 pin to Vdd.
3) WRITE to I2C register O and P to choose the calibration
4) WRITE a ‘0’ to I2C register Q<7> bit (storeBar) and the
5) When I2C register N<7> (ready) goes high, then the
order low-pass filter (only enabled in 'Noise Cancelling'
Bits O<7:4> control the two mics at 300 Hz and bits
Bits P<7:4> control the Mic2 gain and bits P<3:0> control
2
C Register O and P with the corresponding gains.
H(s) = Post Amplifier / SRfCf + 1
2
C interface. Table 5 shows the con-
2
C register N immediately after
20
This will result in the following values for a cutoff frequency of
2000 Hz:
Note 15: Noise Cancelling Mode
Post Amplifier Gain Setting (dB)
Setting (dB) (Note 15)
Post Amplifier Gain
TABLE 7. Low—pass Filter Capacitor for 2kHz
TABLE 6. Low-pass Filter internal impedance
12
0
3
6
9
(Note 15)
12
0
3
6
9
Feedback resistance R
R
(kΩ)
if
20
29
40
57
80
20
29
40
57
80
(kΩ)
C
f
3.9
2.7
2.0
1.3
1.0
(nF)
if