adsp-bf527c Analog Devices, Inc., adsp-bf527c Datasheet - Page 7

• Manufacturer Part Number: adsp-bf527c
• Description: Blackfin Embedded Processor
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
The external components needed to complete the line input
application are shown in
For interfacing to a typical CD system, it is recommended that
the input be scaled to ensure that there is no clipping of the sig-
nal. R1 = 5.6 kΩ, R2 = 5.6 kΩ, C1 = 220 pF, C2 = 1 μF.
R1 and R2 form a resistive divider that attenuates the 2 V(rms)
output from a compact disk player to a 1 V(rms) level to avoid
overloading the inputs. R2 also provides a discharge path for C2,
preventing the input to C2 from charging to an excessive voltage
that could damage any connected equipment that is not suitably
protected against high voltage. C1 forms an RF low pass filter
for increasing the rejection of RF interference picked up on any
cables. C2 blocks the dc path between the CODEC and the driv-
ing audio equipment. C2 together with the input impedance of
the CODEC form a high pass filter.
As shown in
through the operational amplifier to VMID. Whenever the line
inputs are muted or the device placed in standby mode, the line
inputs are kept biased to VMID using special anti-thump cir-
cuitry. This reduces any audible clicks that may otherwise be
heard when re-activating the inputs.
Both line inputs include independent programmable volume
level adjustments and ADC input mute. Passive RF and active
anti-alias filters are also incorporated within the line inputs to
prevent degraded performance due to high frequency aliasing
into the audio band.
LINMUTE/RINMUTE only mute the input to the ADC, which
allows the line input signal to pass to the line output in bypass
mode.
LINEIN
AGND
12.5 K
Figure 4
R1
Figure 4. Line Input Internal Circuit
Figure 3. Line Input External Circuit
VMID
R2
the line inputs are biased internally
AGND
Figure
-
+
3.
AGND
C1
C2
+
Rev. PrC | Page 7 of 44 | June 2008
TO ADC
LINEIN
ADSP-BF523C/ADSP-BF525C/ADSP-BF527C
Using software control, the gain between the line inputs and the
ADC is logarithmically adjustable from +12 dB to –34.5 dB in
1.5 dB steps. The ADC full scale input is 1.0 V(rms) at AVDD =
3.3 volts. Any voltage greater than full scale could overload the
ADC and cause distortion. The full scale input tracks directly
with AVDD. The gain is independently adjustable on both right
and left line inputs. However, by setting the INBOTH bit while
programming the volume control, both channels are simulta-
neously updated with the same value. Use of INBOTH reduces
the number of software writes required. The line inputs to the
ADC can be muted in the analog domain under software con-
trol. The software control registers are shown
Microphone Input
MICIN is a high impedance, low capacitance input for connect-
ing a wide range of monophonic microphones with different
dynamics and sensitivities.
The MICIN includes programmable volume adjustments and a
mute function. The scheme is shown in
active anti-alias filters are incorporated within the microphone
Figure
Table
5. Passive RF and
1.