Rainbow Electronics MAX9860 - Manual (Page 31)

MAX9860
16-Bit Mono Audio Voice Codec
______________________________________________________________________________________ 31
Table 10. AGC and Noise Gate Registers (continued)
BITS FUNCTION
Noise Gate Threshold
The signal level at which the noise gate begins reducing the gain. When the signal level is above the
threshold the noise gate has no effect. When the signal level is below the threshold, the noise gate
decreases the gain by 1dB for every 2dB the signal is below the threshold.
The noise gate can be enabled independently from AGC. When AGC is enabled, PGAM must be set to
+20dB (indicating a small signal is present) for the noise gate to attenuate.
For microphone signals, use the noise gate and AGC simultaneously with ANTH set between -16dB
and -28dB.
ANTH[3:0] LEVEL (dBFS) ANTH[3:0] LEVEL (dBFS)
0x0 Disabled 0x8 -44
0x1 -72 0x9 -40
0x2 -68 0xA -36
0x3 -64 0xB -32
0x4 -60 0xC -28
0x5 -56 0xD -24
0x6 -52 0xE -20
ANTH
0x7 -48 0xF -16
AGC Signal Threshold
The target output signal level. When the signal level is below the threshold, the AGC increases the
gain. The signal level is measured after ADCRL and ADCLL are applied to the ADC output.
ANTH[3:0] LEVEL (dBFS) ANTH[3:0] LEVEL (dBFS)
0x0 -3 0x8 -11
0x1 -4 0x9 -12
0x2 -5 0xA -13
0x3 -6 0xB -14
0x4 -7 0xC -15
0x5 -8 0xD -16
0x6 -9 0xE -17
AGCTH
0x7 -10 0xF -18