Datasheet

Maxim Integrated │ 102
MAX98090 Ultra-Low Power Stereo Audio Codec
www.maximintegrated.com
Table 30. Record Path Biquad Filter Coefficients
The digital biquad filter has five user-programmable
coefficients (B
0
, B
1
, B
2
, A
1
, and A
2
), and each individual
coefficient is 3 bytes (24 bits) long (A
0
is fixed at 1). They
occupy 15 consecutive registers (Table 30) and each set
of three registers (per coefficient) must be programmed
consecutively for the settings to take effect. The coeffi-
cients are stored using a two’s complement format where
the first 4 bits are the integer portion and the last 20 bits
are the decimal portion (which results in an approximate
+8 to -8 range for each coefficient).
Record Path Sidetone
The record path sidetone is available to allow a low-level
copy of the recorded audio signal to be mixed back into
the playback audio signal. When enabled, the sidetone
can route the left channel, right channel, or both divided
by two and then summed back into the playback path
DSP. The sidetone digital gain can be programmed from
-0.5dB to -60.5dB (Table 31). The digital sidetone is com-
monly used in telephony to allow the speaker to hear their
own voice to provide a more natural user experience.
Table 31. Record Path Sidetone Configuration Register
ADDRESS RANGE NAME TYPE COEFFICIENT SEGMENT
0xAF 0xB0 0xB1 RECORD BIQUAD COEFFICIENT B0 R/W REC_B0[23:16] REC_B0[15:8] REC_B0[7:0]
0xB2 0xB3 0xB4 RECORD BIQUAD COEFFICIENT B1 R/W REC_B1[23:16] REC_B1[15:8] REC_B1[7:0]
0xB5 0xB6 0xB7 RECORD BIQUAD COEFFICIENT B2 R/W REC_B2[23:16] REC_B2[15:8] REC_B2[7:0]
0xB8 0xB9 0xBA RECORD BIQUAD COEFFICIENT A1 R/W REC_A1[23:16] REC_A1[15:8] REC_A1[7:0]
0xBB 0xBC 0xBD RECORD BIQUAD COEFFICIENT A2 R/W REC_A2[23:16] REC_A2[15:8] REC_A2[7:0]
ADDRESS: 0x1A
DESCRIPTION
BIT NAME TYPE POR
7
DSTS[1:0]
0
Sidetone Enable and Digital Source Conguration
00: No sidetone selected 10: Right channel
01: Left channel 11: Left + right channel
6 0
5 — — — —
4
DVST[4:0] R/W
0
Sidetone Digital Gain Conguration
3 0
0x00: OFF
0x01: -0.5dB
0x02: -2.5dB
0x03: -4.5dB
0x04: -6.5dB
0x05: -8.5dB
0x06: -10.5dB
0x07: -12.5dB
0x08: -14.5dB
0x09: -16.5dB
0x0A: -18.5dB
0x0B: -20.5dB
0x0C: -22.5dB
0x0D: -24.5dB
0x0E: -26.5dB
0x0F: -28.5dB
0x10: -30.5dB
0x11: -32.5dB
0x12: -34.5dB
0x13: -36.5dB
0x14: -38.5dB
0x15: -40.5dB
0x16: -42.5dB
0x17: -44.5dB
0x18: -46.5dB
0x19: -48.5dB
0x1A: -50.5dB
0x1B: -52.5dB
0x1C: -54.5dB
0x1D: -56.5dB
0x1E: -58.5dB
0x1F: -60.5dB
2 0
1 0
0 0