Diodes ZNBG3211 - Manual (Page 12)

ZNBG3210
ZNBG3211
Single Universal LNB Block Diagram
The following block diagram shows the main section of an LNB designed for use with the Astra
series of satellites. The ZNBG3210/11 is the core bias and control element of this circuit. The
ZNBG provides the negative rail, FET bias control, polarisation switch control, tone detection and
band switching with the minimum of external components. Compared to other discrete
component solutions the ZNBG circuit reduces component count and overall size required.
Tone detection and band switching is provided on the ZNBG3210/11 devices. The following
diagrams describes how this feature operates in an LNB and the external components required.
The presence or absence of a 22kHz tone applied to pin F
IN
enables one of two outputs, L
B
and
H
B
. A tone present enables H
B
and tone absent enables L
B
. The L
B
and H
B
outputs are designed
to be compatible with both MMIC and discrete local oscillator applications, selected by pin L
OV
.
Referring to Figure 1 wiring pin L
OV
to ground will force L
B
and H
B
to switch between -2.6V
(disabled) and 0V (enabled). Referring to Figure 2 wiring pin L
OV
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 L
B
and H
B
outputs to provide the required oscillator supply, V
OSC
, when enabled.
Tone Detection Function
L
OV
F
IN
L
B
H
B
L
B
H
B
G
ND
22kHz Disabled Enabled -2.6 volts G
ND
— Enabled Disabled G
ND
-2.6 volts
V
OSC
22kHz Disabled Enabled Note 1 V
OSC
— Enabled Disabled V
OSC
Note 1
Note 1: 0 volts in typical LNB applications but dependent on extenal circuits.
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