unisonic technologies co., ltd l8401 linear integrated circuit www.unisonic.com.tw 1 of 5 copyright ? 2015 unisonic technologies co., ltd qw-r123-018.b fet bias controller ? description the utc l8401 is designed to bias the mosfets that are commonly used in lnbs that can implies minimum external components requires. ? features * can bias up to 4 fets * drain current adjustable by two external resistors. * two sets of drain current can be setted. ? ordering information ordering number package packing L8401G-R16-R ssop-16 tape reel ? marking
l8401 linear integrated circuit unisonic technologies co., ltd 2 of 5 www.unisonic.com.tw qw-r123-018.b ? pin configuration ? functional diagram fig.1 ? functional description the utc l8401 includes one negative supply required for gate bi asing from the single supply voltage, and all the other bias requirements for external fets. a low current negative supply voltage includes an inte rnal osc and two 47nf external cap. the negative rail generator is common to all devices. th is negative supply voltage used to drive the fet?s gate to obtain the required drain current because of he fet is a depletion mode transistor. there are for stages in the ic to baisi ng the four external fets. the drain voltage of the external fet fet1~4 is 2.2 volts set by the utc l8401 . the drain current of external fet is determined by the external resist r cal1 or r cal2 . external resistor r cal1 sets the drain current of fet1 and fet 2, and resistor r cal2 sets the drain current of fet3 and fet4.
l8401 linear integrated circuit unisonic technologies co., ltd 3 of 5 www.unisonic.com.tw qw-r123-018.b ? absolute maximum rating parameter symbol ratings unit supply voltage v cc -0.6~8 v supply current i cc 100 ma maximum drain current 15 ma maximum c sub sink current -500 ua operating temperature t opr -40~80 c storage temperature t stg -50~150 c note: absolute maximum ratings are those values beyond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device oper ation is not implied. ? electrical characteristics (v cc =3.3v, i d =10ma, r cal1 =8.2k ? , r cal2 =8.2k ? , t a =25c, unless otherwise stated) parameter symbol test conditions min typ max unit supply voltage v cc 3.3 6 v supply current i cc no fet 10 ma i sub =0ua, v cc =6v -3.0 -2.5 -1 v negative voltage v sub i sub =-200ua -1 v oscillator freq. f o 200 350 800 khz drain current i d 8 10 12 ma drain current change with v cc ? i dv v cc =3.3~6v 0.2 %/v vd1/vd2(vd3/vd4) drain offset current ? i dc 0.2 ma drain current change with temp. ? i dt t=-40~80c 0.1 %/c drain voltage v d i d =10ma 1.8 2 2.2 v drain voltage change with v cc ? v dv v cc =3.3~6v 0.5 %/v drain voltage change ? v dt t=-40~80c 50 ppm dynamic gate voltage range v g csub without loading -2.5 0.7 v drain output noise voltage v dn with drain bypass capacitor=10nf 0.05 v pp gate output noise voltage v gn with gate bypass capacitor=10nf 0.03 v pp
l8401 linear integrated circuit unisonic technologies co., ltd 4 of 5 www.unisonic.com.tw qw-r123-018.b ? typical application circuit
l8401 linear integrated circuit unisonic technologies co., ltd 5 of 5 www.unisonic.com.tw qw-r123-018.b ? applications information it is application circuit of utc l8401 in figure 2, the bias circuits is stable fully in -40c ~80c. cnb and c sub are used to generated the negative supply on pin c sub (about -2.5v), which can be used to power other external circuits, but it is low load current is noticeable. c1 and c2 are used to suppress noise or rf interference in each stage of the ic or other external circuits in application circiut system. value of c1 and c2 could be used in 1nf to 100nf as design dependent. r cal1 and r cal2 are used to set the drain current of fets 1 & 2 and fets 3 & 4. if the same drain current is required for all fets on utc l8401 , then the pin r cal1 and r cal2 can be connected to gnd through only one res of half normal value. there are full protection for external fets on chip: t he gate output voltage is limi tted in -2.5v~0.7v in any conditions including powerup and powerdown transients; if the negative bias generator be shorted or overloaded, the drain supply to fets is shut down to avoid damage to the fets by excessive drain current. the fig.3 is typical applications of utc l8401 in lnb. utc assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all utc products described or contained herein. utc products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
|
