Rainbow Electronics MAX9597 - Manual (Page 22)

MAX9597
Low-Power Audio/Video Interface
for Single SCART Connectors
22 ______________________________________________________________________________________
To better protect the MAX9597 against excess voltages
during the cable discharge condition or ESD events,
add series resistors to all inputs and outputs to the
SCART connector if series resistors are not already pre-
sent in the application circuit. Also add external ESD
protection diodes (for example, BAV99) on all inputs
and output to the SCART connector.
Lowpass Filter Configuration
for PCM1742 and CS4334
The lowpass filter configurations shown in Figures 13
and 15 are recommended when connecting a stereo
audio DAC to the audio preamplifier (input amplifier) of
the MAX9597. The filter configuration helps eliminate
the switching noise caused by the audio DAC. The cor-
ner frequency of the filter configuration should be set
above the maximum audio frequency (20kHz) and
below the sampling frequency of the DAC. The fre-
quency response of the filter configurations is shown in
Figures 14 and 16.
Differential to Single-Ended Conversion
of Audio Signals
If the stereo audio DAC generates an analog, voltage
mode, differential audio signal, the circuit shown in Figure
17 can be used to convert the signal to single ended.
The gain of the circuit is represented by this equation:
GAIN
R
R
= ⎛
⎝⎜
⎞
⎠⎟
×
2
1
4
MAX9597
10 μF
6.04k Ω
ENC_INL+
ENC_INL-
ENC_INLOUT
ENC_INR+
10 μF
6.04k Ω
ENC_INR-
ENC_INROUT
PCM1742
DAC
3.01k Ω
3.01k Ω
390pF
3.01k Ω
1.2nF
1.2nF
3.01k Ω
390pF
LEFT
RIGHT
604 Ω
604 Ω
NOTE: ALL RESISTORS ARE 1%.
Figure 13. Lowpass Filter Configuration for the Burr-Brown PCM1742
FILTER RESPONSE vs. FREQUENCY
PCM1742 APPLICATION CIRCUIT WITHOUT THE DAC
FREQUENCY (Hz)
100k 10k 1k 100 10 1 1M
V
IN
= 0.25V
RMS
GAIN (dB)
-25
-20
-15
-10
-5
0
5
10
-30
Figure 14. Filter Response of PCM1742 Filter Configuration