saa7803 NXP Semiconductors, saa7803 Datasheet - Page 9

• Manufacturer Part Number: saa7803
• Description: Saa7803 One Chip Cd Audio Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13695
Objective data sheet
Fig 4. HF acquisition
HF_MON
D1
D2
D3
D4
82
83
84
85
80
RFBypassSel
6.1.2 HF acquisition
The level shifter’s purpose is to act as a summing node for the DC cancellation and to
produce a current that is referenced to an internal bias voltage and therefore independent
of V
The output current charges an integration capacitor. When the voltage reaches V
comparator switches and sends a feedback current that is in the opposite polarity to the
input current to try to discharge the capacitor.
The register LFADCGain defines the amount of feedback current and therefore sets the
gain of the ADC. The output of the ADC is a PDM waveform which is passed through a
low-pass filter (in the digital domain) and the average value at the output of the filter is in
proportion to the voltage between V
The same ADC structures are used for the auxiliary analog inputs, AUX_L and AUX_R
and the general purpose analog inputs, A_IN_1 and A_IN_2. The ADCs used by the
auxiliary analog inputs are multiplexed with the D1 and D2 inputs whereas the general
purpose analog inputs have dedicated ADCs.
The HF data (EFM) signal is obtained by summing the signals from the three or four
central diodes of the OPU, filtering the signals and converting to a digital representation
via a 6-bit RF ADC.
ref
.
RFBypassSel
OFFSETCOMPVALUE[5:0]
20 k
20 k
20 k
20 k
20 k
20 k
20 k
RFMonPwd
Figure 4
RFPwd
G
G1FIXED[3:0]
0 dB to 24 dB
differential converter 4
Rev. 01 — 19 April 2005
RFDiffPwd
RF AMP1
F
single-ended to
E
shows a simplified block diagram of the HF path.
80 k
80 k
D
A
C
i
and V
D
E
NOISEFREQSEL[3:0]
HIGH-PASS
B
FILTER
ref
A
FILTER
NOISE
.
RFMONSEL[2:0]
20 k
B
from PLL
G
sys_clk
F
0 dB to 12 dB
G2DYN[3:0]
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
RF AMP2
HFADCPwd
One chip CD audio device
001aab748
6-BIT
ADC
RF
C
SAA7803
RF_ADC_OUT[5:0]
sys_clk
DDA
/2 the
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