ACS422A68TAGZBX8 IDT, ACS422A68TAGZBX8 Datasheet - Page 58

• Manufacturer Part Number: ACS422A68TAGZBX8
• Description: Interface - CODECs
• Manufacturer: IDT

Specifications of ACS422A68TAGZBX8

• Rohs: yes
• Part # Aliases: IDTACS422A68TAGZBX8

ACS422x68
LOW-POWER, HIGH-FIDELITY, INTEGRATED CODEC
©2011 INTEGRATED DEVICE TECHNOLOGY, INC.
4.8.
Line Input 3 may be an analog line (mic) or digital microphone input depending on the part option.
The digital microphone interface permits connection of a digital microphone(s) to the CODEC via the DMIC_DAT, and
DMIC_CLK 2-pin interface. DMIC_DAT is an input that carries individual channels of digital microphone data to the
ADC. In the event that a single microphone is used, the data is ported to both ADC channels. This mode is selected
using a control bit and the left time slot is copied to the ADC left and right inputs.
The DMIC_CLK output is synchronous to the internal master (DSP) clock and is adjustable in 4 steps. Each step pro-
vides a clock that is a multiple of the chosen ADC base rate and modulator rate.The default frequency is 320/3 times
the ADC base rate for 32KHz, and 80 times the base rate for 44.1KHz and 48KHz base rates.
R12 (12h)
Noise Gate Control
(NGATE)
Register Address
4.7.3.
4.7.4.
Digital Microphone Support
Peak Limiter
To prevent clipping, the ALC circuit also includes a limiter function. If the ADC input signal exceeds
87.5% of full scale (–1.16dB), the PGA gain is ramped down at the maximum attack rate, until the
signal level falls below 87.5% of full scale. This function is automatically enabled whenever the ALC
is enabled.
Input Threshold
To avoid hissing during quiet periods, the ACS422x68 has an input threshold noise gate function that
compares the signal level at the inputs to a noise gate threshold. Below the threshold, the program-
mable gain can be held , or the ADC output can be muted. The threshold can be adjusted in incre-
ments of 1.5dB.
The noise gate activates when the signal-level at the input pin is less than the Noise Gate Threshold
(NGTH) setting.
The ADC output can be muted. Alternatively, the PGA gain can be held .
The threshold is adjusted in 1.5dB steps. The noise gate only works in conjunction with the ALC, and
always operates on the same channel(s) as the ALC.
4.7.4.1.
Bit
7:3
2:1
0
Noise Gate Control Register
NGTH
NGAT
Label
NGG
[4:0]
[1:0]
Table 65. NGATE Register
Type
RW
RW
RW
Default
00000
58
00
0
Noise gate threshold (compared to ADC full-scale
range)
00000 -76.5dBfs
00001 -75dBfs
… 1.5 dB steps
11110 -31.5dBfs
11111 -30dBfs
Noise gate type
X0 = PGA gain held
01 = mute ADC output
11 = reserved (do not use this setting)
Noise gate function enable
1 = enable
0 = disable
Description
ACS422X68
V1.6 01/13