Diodes ZNBG3116 - Manual

1
FET BIAS CONTROLLER WITH POLARISATION
SWITCH AND TONE DETECTION
ISSUE 2 - JUNE 2006
ZNBG3115
ZNBG3116
ISSUE 2 - JUNE 2006
DEVICE DESCRIPTION
The ZNBG series of devices are designed to meet the
bias requirements of GaAs and HEMT FETs
commonly used in satellite receiver LNBs, PMR,
cellular telephones etc. with a minimum of external
components.
With the addition of two capacitors and a resistor the
devices provide drain voltage and current control for
three external grounded source FETs, generating
the regulated negative rail required for FET gate
biasing whilst operating from a single supply. This
negative bias, at -2.8 volts, can also be used to
supply other external circuits.
The ZNBG3115/16 includes bias circuits to drive up
to three external FETs. A control input to the device
selects either one of two FETs as operational, the
third FET is permanently active. This feature is
normally used as an LNB polarisation switch. Also
specific to Universal LNB applications is the 22kHz
tone detection and logic output feature which is
used to enable high and low band frequency
switching.
The ZNBG3115/16 has been designed to cope with
DiSEqC™ ready set top boxes and rejects all
transients from channel switching.
Drain current setting of the ZNBG3115/16 is user
selectable over the range 0 to 15mA, this is achieved
with addition of a single resistor. The series also offers
the choice of drain voltage to be set for the FETs, the
3115 gives 2.2 volts drain whilst the 3116 gives 2 volts.
These devices are unconditionally stable over the full
working temperature with the FETs in place, subject to
the inclusion of the recommended gate and drain
capacitors. These ensure RF stability and minimal
injected noise.
It is possible to use less than the devices full
complement of FET bias controls, unused drain and gate
connections can be left open circuit without affecting
operation of the remaining bias circuits.
To protect the external FETs the circuits have been
designed to ensure that, under any conditions including
power up/down transients, the gate drive from the bias
circuits cannot exceed the range -3.5V to 1V.
Additionally each stage has its own individual current
limiter. Furthermore if the negative rail experiences a
fault condition, such as overload or short circuit, the
drain supply to the FETs will shut down avoiding
excessive current flow.
The ZNBG3115/16 are available in QSOP16 and QSOP20
for the minimum in device size. Device operating
temperature is -40 to 80°C to suit a wide range of
environmental conditions.
FEATURES
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Provides bias for GaAs and HEMT FETs
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Drives up to three FETs
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Dynamic FET protection
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Drain current set by external resistor
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Regulated negative rail generator requires only
2 external capacitors
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Choice in drain voltage
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Wide supply voltage range
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Polarisation switch for LNBs
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22kHz tone detection for band switching
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Tone detector ignores unwanted signals
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Support fr MIMIC, FET and Bipolar local
oscillator devices
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Compliant with ASTRA control specifications
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QSOP 16 and 20 surface mount packages
APPLICATIONS
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Satellite receiver LNBs
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Private mobile radio (PMR)
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Cellular telephones