X3211 Datasheet, PDF (10/12 Pages) Unisonic Technologies – LINEAR INTEGRATED CIRCUIT

UTC X3211 LINEAR INTEGRATED CIRCUIT
APPLICATIONS INFORMATION
The device is a partial application circuit for the X3211 showing all external components required for appropriate
biasing. The bias circuits are unconditionally stable over the full temperature range with the associated FETs and
gate drain capacitors in circuit.
Capacitors CD and CG ensure that residual power supply and substrate generator noise is not allowed to affect
other external circuits which may be sensitive to RF interference. They also serve to suppress any potential RF
feedthrough between stages via the X3211. These capacitor are required for all stages used Values of 10nF and
4.7nF respectively are recommended however this is design dependent and any value between 1nFand 100nF
could be used.
The capacitors CNB and CSUB are an integral part of the X3211 negative supply generator. The negative bias
voltage is generated on-chip using an internal oscillator. The required value of capacitors CNB and CsuB is 47nF.
This generator produces a low current supply of approximately –3 volts. Although this generator is intended purely to
bias the external FETs, it can be used to power other external circuits via the CsUB pin.
Resistors RcAL sets the drain current at which all external FETs are operated. If any bias control circuit is not
required, its related drain and gate connections may be left open circuit without affecting the operation of the
remaining bias circuits.
The X3211 has been designed to protect the external FETs from adverse operating conditions. With a JFET
connected to any bias circuit, the gate output voltage of the bias circuit can not exceed the range –3.5V to 1V,under
any conditions including power up and powerdown transients. Should the negative bias generator be shorted or
overloaded so that the drain current of the external FETs can no longer be controlled, the drain supply to FETs is
shut down to avoid damage to the FETs by excessive drain current.
Tone detection and band switching is provided on the X3211. 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
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 both MMIC and discrete local oscillator applications, selected by pin LOV.
Referring to Figure 1 wiring pin LOV to ground will force LB and HB to switch between –2.6V (disabled) and 0V
(enabled).Referring to Figure 2 wiring pin LOV to a positive voltage source (e.g. a potential divider across Vcc and
ground set to the required oscillator supply,Vosc when enabled.
Tone Detection Function
LOV
FIN
LB
HB
22kHz
Disabled
Enabled
GND
-
Enabled
Disabled
22kHz
Disabled
Enabled
GND
-
Enabled
Disabled
Note 1: 0 volts in typical LNB applications but dependent on external circuits.
LB
-2.6 volts
GND
Note 1
Vosc
HB
GND
-2.6 volts
Vosc
Note 1
UTC UNISONIC TECHNOLOGIES CO., LTD. ¹⁰
QW-R122-004,C