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| FET BIAS CONTROLLER ISSUE 2 - JUNE 1998 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 resistors the devices provide drain voltage and current control for a number of external grounded source FETs, generating the regulated negative rail required for FET gate biasing whilst operating from a single supply. This negative bias, at -3 volts, can also be used to supply other external circuits. The ZNBG4000/1 and ZNBG6000/1 contain four and six bias stages respectively. In setting drain current the ZNBG4000/1 two resistors allows individual FET pair control to different levels, the ZNBG6000/1 two resistors split control between two and four FETs. This allows the operating current of input FETs to be adjusted to minimise noise, whilst the following FET stages can separately be adjusted for maximum gain. The series also offers the choice of drain v ol t a ge t o b e s e t f or t he F E T s , the ZNBG4000/6000 gives 2.2 volts drain whilst the ZNBG4001/6001 gives 2 volts. ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 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. In order 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 0.7V. 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 ZNBG4000/1 and ZNBG6000/1 are available in QSOP16 and 20 pin packages respectively for the minimum in devices size. Device operating temperature is -40 to 70C to suit a wide range of environmental conditions. FEATURES APPLICATIONS * * * * * * * * Provides bias for GaAs and HEMT FETs Drives up to four or six FETs Dynamic FET protection Drain current set by external resistor Regulated negative rail generator requires only 2 external capacitors Choice in drain voltage Wide supply voltage range QSOP surface mount package * * * Satellite receiver LNBs Private mobile radio (PMR) Cellular telephones 4-137 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 ABSOLUTE MAXIMUM RATINGS Supply Voltage Supply Current Drain Current (per FET) (set by RCAL1 and RCAL2) Output Current Operating Temperature Storage Temperature -0.6V to 15V 100mA 0 to 15mA 100mA -40 to 70C -50 to 85C Power Dissipation (Tamb= 25C) QSOP16 500mW QSOP20 650mW ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated): Tamb= 25C,VCC=5V,ID=10mA (RCAL1 =33k;RCAL2 =33k) SYMBOL PARAMETER CONDITIONS Min VCC ICC ICC VSUB Supply Voltage Supply Current ZNBG4000/1 Supply Current ZNBG6000/1 Substrate Voltage (Internally generated) Output Noise Drain Voltage Gate Voltage Oscillator Freq. Current Current Change IDV IDT VD with VCC with Tj Voltage ZNBG4000, ZNGB6000 ZNBG4001, ZNBG6001 Voltage Change VDV VDT with VCC with Tj VCC= 5 to 12V Tj = -40 to +70C 0.5 50 %/V ppm VCC=5 to 12V Tj=-40 to +70C 2 1.8 0.02 0.05 2.2 2 2.4 2.2 %/V %/C V V ID1 to ID4=0 ID1 to ID4=10mA ID1 to ID6=0 ID1 to ID6=10mA ISUB= 0 ISUB= -200A CG=4.7nF, CD=10nF CG=4.7nF, CD=10nF 200 8 350 10 -3.5 -3 5 LIMITS Typ Max 12 10 50 15 75 -2 -2 0.02 0.005 800 12 V mA mA mA mA V V Vpkpk Vpkpk kHz mA UNITS END ENG fO ID DRAIN CHARACTERISTICS 4-138 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 SYMBOL PARAMETER CONDITIONS Min LIMITS Typ Max 2000 A UNITS GATE CHARACTERISTICS IGO Output Current Range Output Voltage ZNBG4000/1 VOL Output Low ID1 to ID4=12mA IG1 to IG4=0 ID1 to ID4=12mA IG1 to IG4= -10A VOH Output High Output Voltage ZNBG6000/1 VOL Output Low ID1 to ID6=12mA IG1 to IG6= 0 ID1 to ID6=12mA IG1 to IG6= -10A VOH Notes: 1. The negative bias voltages specified are generated on-chip using an internal oscillator. Two external capacitors, CNB and CSUB, of 47nF are required for this purpose. 2. The characteristics are measured using two external reference resistors RCAL1 and RCAL2 of value 33k wired from pins RCAL1/2 to ground. For the ZNBG4000, resistor RCAL1 sets the drain current of FETs 1 and 2, resistor RCAL2 sets the drain current of FETs 3 and 4. For the ZNBG6000, resistor RCAL1 sets the drain current of FETs 1 and 4, resistor RCAL2 sets the drain current of FETs 2, 3, 5 and 6. -30 -3.5 -3.5 0 -2 -2 1 V V V ID1 to ID4= 8mA IG1 to IG4= 0 -3.5 -3.5 0 -2 -2 1 V V V Output High ID1 to ID6= 8mA IG1 to IG6= 0 3. Noise voltage is not measured in production. 4. Noise voltage measurement is made with FETs and gate and drain capacitors in place on all outputs. CG, 4.7nF, are connected between gate outputs and ground, CD, 10nF, are connected between drain outputs and ground. 4-139 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 TYPICAL CHARACTERISTICS 16 Vcc = 5V 14 12 10 8 6 4 2 0 0 20 40 60 80 100 0.0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 Note:- Operation with loads > 200A is not guaranteed. Vcc = 5V 6V 8V 10V 0 0.2 0.4 0.6 0.8 1.0 Rcal (k) External Vsub Load (mA) JFET Drain Current v Rcal Vsub v External Load 2.4 2.3 2.2 Vcc = 5V 6V 8V 10V 2.1 2.0 2 4 6 8 10 12 14 16 Drain Current (mA) JFET Drain Voltage v Drain Current 4-140 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 FUNCTIONAL DIAGRAM FUNCTIONAL DESCRIPTION The ZNBG devices provide all the bias requirements for external FETs, including the generation of the negative supply required for gate biasing, from the single supply voltage. The diagram above shows a single stage from the ZNBG series. The ZNBG4000/1 contains 4 such stages, the ZNBG6000/1 contains 6. The negative rail generator is common to all devices. The drain voltage of the external FET QN is set by the ZNBG device to its normal operating voltage. This is determined by the on board VD Set reference, for the ZNBG4000/6000 this is nominally 2.2 volts whilst the ZNBG4001/6001 provides nominally 2 volts. The drain current taken by the FET is monitored by the low value resistor ID Sense. The amplifier driving the gate of the FET adjusts the gate voltage of QN so that the drain current taken matches the current called for by an external resistor RCAL. Both ZNBG devices have the facility to program different drain currents into selected FETs. Two RCAL inputs are provided. For the ZNBG4000, resistor RCAL1 sets the drain current of FETs 1 and 2, resistor RCAL2 sets the drain current of FETs 3 and 4. For the ZNBG6000, resistor RCAL1 sets the drain current of FETs 1 and 4, resistor RCAL2 sets the drain current of FETs 2, 3, 5 and 6. Since the FET is a depletion mode transistor, it is usually necessary to drive its gate negative with respect to ground to obtain the required drain current. To provide this capability powered from a single positive supply, the device includes a low current negative supply generator. This generator uses an internal oscillator and two external capacitors, CNB and CSUB. 4-141 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 TYPICAL APPLICATION CIRCUIT APPLICATIONS INFORMATION The above is a partial application circuit for the ZNBG series 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 and 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 ZNBG device. These capacitors are required for all stages used. Values of 10nF and 4.7nF respectively are recommended however this is design dependent and any value between 1nF and 100nF could be used. The capacitors CNB and CSUB are an integral part of the ZNBGs 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 RCAL1/2 sets the drain current at which all external FETs are operated. Both ZNBG devices have the facility to program different drain currents into selected FETs. Two RCAL inputs are provided. For the ZNBG4000, resistor RCAL1 sets the drain current of FETs 1 and 2, resistor RCAL2 sets the drain current of FETs 3 and 4. For the ZNBG6000, resistor RCAL1 sets the drain current of FETs 1 and 4, resistor RCAL2 sets the drain current of FETs 2, 3, 5 and 6. If the same drain current is required for all FETs on either device then pins RCAL1 and RCAL2 can be wired together and shunted to ground by a single calibration resistor of half normal value. 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. If all FETs associated with a current setting resistor are omitted, the particular RCAL should still be included. The supply current can be reduced, if required, by using a high value RCAL resistor (e.g. 470k). 4-142 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 APPLICATIONS INFORMATION (Continued) The ZNBG devices have 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 0.7V, under any conditions including powerup 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. The following diagrams show the ZNBG4000/1 and ZNBG6000/1 in typical LNB applications. Within each FET gain stage the numbering system indicates how the bias stages relate to the application circuits. This is important when RCAL values are used to set differing drain currents. Dual standard or enhanced LNB block diagram 4-143 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 Dual standard or enhanced LNB block diagram. High Gain 4-144 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 CONNECTION DIAGRAMS ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 ORDERING INFORMATION Part Number ZNBG4000Q16 ZNBG4001Q16 ZNBG6000Q20 ZNBG6001Q20 Package QSOP16 QSOP16 QSOP20 QSOP20 Part Mark ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 4-145 ZNBG4000 ZNBG4001 ZNBG6000 ZNBG6001 PACKAGE DIMENSIONS IDENTIFICATION RECESS FOR PIN 1 A C B PIN No.1 D K QSOP16 PIN Millimetres MIN A B C D E F G J K 4.80 0.635 0.177 0.20 3.81 1.35 0.10 5.79 0 0.267 0.30 3.99 1.75 0.25 6.20 8 MAX 4.90 Inches MIN 0.033 MAX 0.039 QSOP20 PIN Millimetres MIN A B C D E F G J K 8.55 0.635 1.42 0.20 3.81 1.35 0.10 5.79 0 1.52 0.30 3.99 1.75 0.25 6.20 8 MAX 8.74 Inches MIN 0.337 MAX 0.344 0.025 NOM 0.007 0.008 0.15 0.053 0.004 0.228 0 0.011 0.012 0.157 0.069 0.01 0.244 8 0.025 NOM 0.056 0.008 0.15 0.053 0.004 0.228 0 0.06 0.012 0.157 0.069 0.01 0.244 8 Zetex plc. Fields New Road, Chadderton, Oldham, OL9-8NP, United Kingdom. Telephone: (44)161 622 4422 (Sales), (44)161 622 4444 (General Enquiries) Fax: (44)161 622 4420 Zetex GmbH Streitfeldstrae 19 D-81673 Munchen Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 Zetex Inc. 47 Mall Drive, Unit 4 Commack NY 11725 USA Telephone: (516) 543-7100 Fax: (516) 864-7630 Zetex (Asia) Ltd. 3510 Metroplaza, Tower 2 Hing Fong Road, Kwai Fong, Hong Kong Telephone:(852) 26100 611 Fax: (852) 24250 494 These are supported by agents and distributors in major countries world-wide (c)Zetex plc 1998 Internet:http://www.zetex.com This publication is issued to provide outline information only which (unless agreed by the Company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. The Company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service. Page Number |
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