Diodes ZNBG3118 - Manual (Page 5)

ZNBG3118
ZNBG3118
Document number: DS32049 Rev. 2 - 2
5 of 10
www.diodes.com
February 2010
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T
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Typical Characteristics
(Measured at T
AMB
= 25°C, V
CC
= 5V, R
CAL
= 39k (setting I
D
to 10mA) unless otherwise stated)
Drain Current vs R
CAL
Value
0
2
4
6
8
10
12
14
16
0 20 40 60 80 100 120 140 160 180 200
R
CAL
Value (k Ω)
Dr
a
in
Cu
rr
e
n
t (
m
A)
Drain Voltage vs Drain Current
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
0 2 4 6 8 10 12 14 16
Drain Current (mA)
D
rai
n
V
o
lt
a
g
e (
V
)
Single Universal Block Diagram
Figure 1 shows the main elements of a typical single universal LNB. The ZNBG3118 is compliant with virtually all markets including
the fleet of Astra satellites. The simple but flexible solution provides the negative rail, FET bias control, polarisation switch control,
tone detection and band switching with the minimum of external components. The ZNBG3118 can be also used in other DBS
applications such a twin output, mono-block and Low power LNB’s.
Figure 1 Typical single universal LNB system diagram
Polarization and band switching on the ZNBG3118 uses the standard 13V-17V and 22kHz as defined by Astra. The exception is
that the devices voltage detector has a much tighter tolerance than defined to increase field reliability. The tone detector has been
designed to cope with distorted 22kHz tones so reliability is maintained with regional differences and variations on set-top box
designs.
Tone detection and band switching has been designed to meet various different system architectures. The following diagrams
(figures 2 to 4) show how this feature operates in an LNB and the external components required. The presence or absence of a
22kHz tone applied to pin FIN enables one of two outputs, LB and HB. A tone present enables HB and tone absent enables LB.
The LB and HB outputs are designed to be compatible with MMIC, Discrete (bipolar or FET) and PLL based local oscillator
applications and are easily configured by the LOV pin.
Bi-polar or FET local oscillators
Referring to Figure 2 wiring pin LOV to a positive voltage source (e.g. a potential divider across V
CC
and ground set to the required
oscillator supply voltage, V
OSC
) will force the LB and HB outputs to provide the required oscillator supply. V
OSC
when enabled and
0V when disabled. Driving loads of up to 35mA, the maximum allowed programmed output voltage of LB and HB is V
CC -
1V
.
If a
greater supply voltage is required for the oscillators then it may be possible to use an oscillator circuit.