Circuit Descriptions
7.
•
+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:
Figure 7-17 DC/DC converters non-DVB-S2 devices
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.
1
8
770_226_100127.ep
s
100426
+ 5V 5-T UN
196 m A
+ 5V
+ 5V 5-TUN
+ 5V -TUN
2179 m A
196 m A
+ 12V
+
3
V
3
+
3
V
3
+ 2V 5
2919 m A
2
3
71 m A
450 m A
+ 1V
8
+ 1V
8
+ 1V 2
2450 m A
550 m A
+ 1V 1
5100 m A
+ 1V 1
dc -dc
+ 5V
dc -dc
+ 5V -TUN
s
t
ab
iliz er
+
3
V
3
dc -dc
+ 2V 5
s
t
ab
iliz er
+ 1V
8
dc -dc
+ 1V 2
s
t
ab
iliz er
1
8
770_227_100127.ep
s
100426
+ 24V
+ 5V
+ 5V
+
3
V
3
t
u
ner
5
3
7.1 m A
777.4 m A
296 m A
+ V -LNB
+
3
V
3
t
u
ner
+ 2V 5
400 m A
90 m A
+ V -LNB
LNB -RF 1
+ 5V
+ 1V 0
400 m A
1
8
20 m A
+ 1V 0
dc -dc
+
3
V
3
s
t
ab
iliz er
+ 5V
dc -dc
down
c onverter
+ 2V 5
s
t
ab
iliz er
line
a
r
s
t
ab
iliz er
1
8
770_2
3
5_100127.ep
s
100219
