FET BIAS CONTROLLER WITH POLARISATION ZNBG3210 SWITCH AND TONE DETECTION ZNBG3211 ISSUE 2 - FEBRUARY 2000 DEVICE DESCRIPTION The ZNBG series of devices are designed to is achieved with the addition of a single meet the bias requirements of GaAs and resistor. The series also offers the choice of HEMT FETs commonly used in satellite FET drain voltage, the 3210 gives 2.2 volts receiver LNBs, PMR cellular telephones etc. drain whilst the 3211 gives 2 volts. with a minimum of external components. These devices are unconditionally stable With the addition of two capacitors and a over the full working temperature with the resistor the devices provide drain voltage and FETs in place, subject to the inclusion of the current control for three external grounded recommended gate and drain capacitors. source FETs, generating the regulated These ensure RF stability and minimal negative rail required for FET gate biasing injected noise. whilst operating from a single supply. This It is possible to use less than the devices full negative bias, at -3 volts, can also be used to complement of FET bias controls, unused supply other external circuits. drain and gate connections can be left open The ZNBG3210/11 includes bias circuits to circuit without affecting operation of the drive up to three external FETs. A control remaining bias circuits. input to the device selects either one of two In order to protect the external FETs the FETs as operational using 0V gate switching circuits have been designed to ensure that, methodology, the third FET is permanently under any conditions including power active. This feature is particularly used as an up/down transients, the gate drive from the LNB polarisation switch. Also specific to LNB bias circuits cannot exceed the range -3.5V applications is the enhanced 22kHz tone to 1V. Furthermore if the negative rail detection and logic output feature which is experiences a fault condition, such as used to enable high and low band frequency overload or short circuit, the drain supply to switching. The detector has been specifically the FETs will shut down avoiding excessive designed to reject inerference such as low current flow. frequency signals and DiSEqC tone bursts - without the use of additional external The ZNBG3210/11 are available in QSOP20 components. for the minimum in device size. Device operating temperature is -40 to 70C to suit Drain current setting of the ZNBG3210/11 is a wide range of environmental conditions. user selectable over the range 0 to 15mA, this FEATURES APPLICATIONS Provides bias for GaAs and HEMT FETs Satellite receiver LNBs Drives up to three FETs Private mobile radio (PMR) Dynamic FET protection Cellular telephones Drain current set by external resistor Regulated negative rail generator requires only 2 external capacitors Choice in drain voltage Wide supply voltage range Polarisation switch for LNBs - supporting zero volt gate switching topology. 22kHz tone detection for band switching Compliant with ASTRA control specifications QSOP surface mount package 67-1ZNBG3210 ZNBG3211 ABSOLUTE MAXIMUM RATINGS Supply Voltage -0.6V to 12V Power Dissipation (Tamb= 25C) Supply Current 100mA QSOP20 500mW Input Voltage (V ) 25V Continuous POL Drain Current (per FET) 0 to 15mA (set by R ) CAL Operating Temperature -40 to 70C Storage Temperature -50 to 85C ELECTRICAL CHARACTERISTICS. TEST CONDITIONS (Unless otherwise stated):T = 25C,V =5V,I =10mA (R =33k ) amb CC D CAL SYMBOL PARAMETER CONDITIONS LIMITS UNITS MIN. TYP. MAX. V Supply Voltage 5 10 V CC I Supply Current I to I =0 6 15 mA CC D1 D3 I =0,I to I =10mA, V =14V 25 35 mA D1 D2 D3 POL I =0,I to I =10mA, V =15.5V 25 35 mA D2 D1 D3 POL I to I =0, I =10mA 16 25 mA D1 D3 LB I to I =0, I =10mA 16 25 mA D1 D3 HB V Substrate (Internally generated) I =0 -3.5 -3.0 -2.5 V SUB SUB Voltage I =-200 A -2.4 V SUB Output Noise E Drain Voltage C =4.7nF, C =10nF 0.02 Vpkpk ND G D E Gate Voltage C =4.7nF, C =10nF 0.005 Vpkpk NG G D f Oscillator 200 350 800 kHz O Frequency 67-2