Philips 8000 Series Service Manual page 49

• +V-LNB, input voltage for LNB supply IC (item no. 7T50)
• +5V-DVBS, input intermediate supply voltage for DVB-S2
(diagram B08A)
• +3V3-DVBS, clean voltage for silicon tuner and DVB-S2
channel decoder
• +2V5-DVBS, clean voltage for DVB-S2 channel decoder
• +1V-DVBS, core voltage for DVB-S2 channel decoder.
A +12 V under-voltage detector (see diagram B03C) enables
the 12V to 3.3V and 12V to 5V DC/DC converters via the
ENABLE-3V3-5V line, and the 12V to 1.8V DC/DC converter
via the ENABLE-1V8 line. DETECT2 is the signal going to the
Stand-by microcontroller and ENABLE-3V3n is the signal
coming from the Stand-by microcontroller.
Diagram B03D contains the following linear stabilisers:
• +2V5 stabiliser, built around item no. 7UCO
• +5V-TUN stabiliser, built around items no. 7UA6 and 7UA7
• +1V2 stabiliser, built around items no. 7UA3 and 7UA4.
Diagram B08A contains the DVB-S2-related DC/DC
converters and -stabilisers:
• a +24V under-voltage detection circuitry is built around
item no. 7T04
• the switching frequency of the 24 to 14...20V switched
mode converter is 350 kHz (item no. 7T03 and +V-LNB
lines)
• the output signal on the +V-LNB line goes to the LNBH23Q
(item no. 7T50)
• the LNBH23Q (item no. 7T50) sends a feedback signal via
the V0-CNTRL line
• the switching frequency of the +5V-DVBS to +1-DVBS
switched mode converter is 900 kHz (item no. 7T00)
• a delay line for the +2V5-DVBS and +1V-DVBS lines is
created with item no. 3T03 (R=10k) and 2T06 (C=100n)
• a 3.3V to 2.5V linear stabiliser is built around item no. 7T01
• a 5V to 3.3V linear stabiliser is built around item no. 7T02.
Diagram B08B contains the DVB-S2 LNB supply:
• the +V-LNB signal comes from item no. 7T03
• the V0-CTRL signal goes to item no. 7T03
• the LNB-RF1 goes to the LNB.
Figures gives a graphical representation of the DC/DC
converters with its current consumptions:
+ 5V 5-TUN
196 m A
+ 5V
+ 5V
2179 m A
dc -dc
+ 12V + 3V 3
+ 3V 3
2919 m A 2371 m A
dc -dc
+ 1V 8
+ 1V 8
2450 m A
dc -dc
+ 1V 1
+ 1V 1
5100 m A
dc -dc
Figure 7-17 DC/DC converters non-DVB-S2 devices
Circuit Descriptions
+ 5V 5-TUN + 5V -TUN
+ 5V -TUN
196 m A
s tabiliz er
+ 3V 3 + 2V 5
+ 2V 5
450 m A
s tabiliz er
+ 1V 8 + 1V 2
+ 1V 2
550 m A
s tabiliz er
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Q551.1E LA
+ 24V + 5V
+ 5V
537.1 m A
dc -dc
+ V -LNB
down
c onverter
+ V -LNB LNB -RF1
linear
s tabiliz er
Figure 7-18 DC/DC converters DVB-S2 devices
7.5 Front-End Analogue and DVB-T, DVB-C;
ISDB-T reception
7.5.1 European/China region
The Front-End for the European/China region consist of the
following key components:
• Hybrid Tuner
• Switchable SAW filter 7/8 MHz (Eur.), or single SAW filter
(8 MHz) (China)
• Bandpass filter
• Amplifier
• PNX85500 SoC TV processor with integrated DVB-T and
DVB-C channel decoder and analogue demodulator.
Below find a block diagram of the front-end application for this
region.
Figure 7-19 Front-End block diagram European/China region
7.5.2 Brazil region
The Front-End for the Brazil region consist of the following key
components:
• Hybrid Tuner with integrated SAW filter and amplifier
• External ISDB-T channel decoder covering the Brazilian
digital terrestrial TV standard
• Bandpass filter
• Amplifier
• PNX85500 SoC TV with integrated analogue demodulator.
Below find a block diagram of the front-end application for this
region.
7. EN 49
+ 5V + 3V 3 tuner
+ 3V 3
777.4 m A 296 m A
s tabiliz er
+ 3V 3 tuner + 2V 5
+ 2V 5
400 m A 90 m A
s tabiliz er
+ 5V + 1V 0
+ 1V 0
400 m A 1820 m A
dc -dc
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2010-Jun-25