ADSP-BF525C(RevPrC) 查看數據表（PDF） - Analog Devices

零件编号

产品描述 (功能)

生产厂家

ADSP-BF525C
(Rev.:RevPrC)

Blackfin® Embedded Processor

Analog Devices 

Preliminary Technical Data

ADSP-BF523C/ADSP-BF525C/ADSP-BF527C

The external components needed to complete the line input

application are shown in Figure 3.

R1

C2

+

LINEIN

R2

C1

AGND

AGND

AGND

Figure 3. Line Input External Circuit

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 Figure 4 the line inputs are biased internally

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.

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 Table 1.

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 Figure 5. Passive RF and

active anti-alias filters are incorporated within the microphone

LINEIN

12.5 K:

-

VMID

+

TO ADC

Figure 4. Line Input Internal Circuit

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.

Rev. PrC | Page 7 of 44 | June 2008

Share Link: