Datasheet

SSM2603 Data Sheet
Rev. C | Page 14 of 32
Bypass and Sidetone Paths to Output
The line and microphone inputs can be routed and mixed directly
to the output terminals via the SIDETONE_EN (Register R4,
Bit D5) and bypass (Register R4, Bit D3) software control register
selections. In both of these modes, the analog input signal is routed
directly to the output terminals and is not digitally converted. The
bypass signal at the output mixer is the same level as the output of
the PGA associated with each line input.
The sidetone signal at the output mixer must be attenuated by a
range of −6 dB to −15 dB in steps of −3 dB by configuring the
SIDETONE_ATT (Register R4, Bit D6 and Bit D7) control
register bits. The selected level of attenuation occurs after the
initial microphone signal amplification from the microphone
first- and second-stage gains.
Line and Headphone Outputs
The DAC outputs, the microphone (the sidetone path), and the
line inputs (the bypass path) are summed at an output mixer.
This output signal can be present at both the stereo line outputs
and stereo headphone outputs.
Figure 21. Output Signal Chain
The SSM2603 has a set of efficient headphone amplifier outputs,
LHPOUT and RHPOUT, that are able to drive 16 Ω or 32 Ω
headphone speakers.
Figure 22. Headphone Output
In similar functionality to the line inputs, the LHPOUT and
RHPOUT volumes, by default, are independently adjusted by
setting the LHPVOL (Register R2, Bit D0 to Bit D6) and RHPVOL
(Register R3, Bit D0 to Bit D6) bits of the headphone output
control registers. The headphone outputs can be muted by writing
codes less than 0110000 to the LHPVOL and RHPVOL bits. The
user is also able to simultaneously load the volume control of
both channels by writing to the LRHPBOTH (Register R2, Bit D8)
and RLHPBOTH (Register R3, Bit D8) bits of the left- and right-
channel DAC volume registers.
The maximum output level of the headphone outputs is 1.0 V rms
when AVDD and HPVDD = 3.3 V. To suppress audible pops
and clicks, the headphone and line outputs are held at the
VMID dc voltage level when the device is set to standby mode
or in the event that the headphone outputs are muted.
The stereo line outputs of the SSM2603, the LOUT and
ROUT pins, are able to drive a load impedance of 10 kΩ and
50 pF. The line output signal levels are not adjustable at the output
mixer, having a fixed gain of 0 dB. The maximum output level
of the line outputs is 1.0 V rms when AVDD = 3.3 V.
07241-033
LINE OUTPUT
AND
HEADPHONE
OUTPUT
AVDD
VMID
AGND
BYPASS
SIDETONE
DACSEL
LINE
INPUT
MICROPHONE
INPUT
DAC
OUTPUT
07241-034
xHPOUT
DAC/
SIDETONE/
BYPASS
AVDD
VMID
AGND
+
–