Datasheet

UNISONIC TECHNOLOGIES CO., LTD
L8401
LINEAR INTEGRATED CIRCUIT
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
L8401G-R16-R

Package
SSOP-16
Packing
Tape Reel
MARKING
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L8401


LINEAR INTEGRATED CIRCUIT
PIN CONFIGURATION
FUNCTIONAL DIAGRAM
Fig.1

FUNCTIONAL DESCRIPTION
The UTC L8401 includes one negative supply required for gate biasing from the single supply voltage, and all the
other bias requirements for external FETs.
A low current negative supply voltage includes an internal OSC and two 47nF external cap. The negative rail
generator is common to all devices. This 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 baising 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 RCAL1 or RCAL2. External resistor RCAL1 sets
the drain current of FET1 and FET 2, and resistor RCAL2 sets the drain current of FET3 and FET4.
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L8401

LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATING
PARAMETER
SYMBOL
RATINGS
UNIT
Supply Voltage
VCC
-0.6~8
V
Supply Current
ICC
100
mA
Maximum Drain Current
15
mA
Maximum CSUB Sink Current
-500
uA
Operating Temperature
TOPR
-40~80
°C
Storage Temperature
TSTG
-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 operation is not implied.

ELECTRICAL CHARACTERISTICS
(VCC=3.3V, ID=10mA, RCAL1=8.2KΩ, RCAL2=8.2KΩ, TA=25°C, unless otherwise stated)
PARAMETER
SYMBOL
TEST CONDITIONS
Supply Voltage
VCC
Supply Current
ICC
No FET
ISUB=0uA, VCC=6V
Negative Voltage
VSUB
ISUB=-200uA
Oscillator Freq.
fO
Drain Current
ID
Drain Current Change with VCC
∆IDV
VCC=3.3~6V
VD1/VD2(VD3/VD4) Drain Offset
∆IDC
Current
Drain Current Change with Temp.
∆IDT
T=-40~80°C
Drain Voltage
VD
ID=10mA
Drain Voltage Change with VCC
∆VDV
VCC=3.3~6V
Drain Voltage Change
∆VDT
T=-40~80°C
Dynamic Gate Voltage Range
VG
Csub without loading
Drain Output Noise Voltage
Vdn
With drain bypass capacitor=10nF
Gate Output Noise Voltage
VGN
With gate bypass capacitor=10nF
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
MIN TYP MAX
3.3
6
10
-3.0 -2.5 -1
-1
200 350 800
8
10
12
0.2
UNIT
V
mA
V
V
KHz
mA
%/V
0.2
mA
1.8
-2.5
0.1
2
0.5
50
%/°C
V
%/V
ppm
0.7
V
0.05 VPP
0.03 VPP
2.2
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L8401

LINEAR INTEGRATED CIRCUIT
TYPICAL APPLICATION CIRCUIT
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L8401

LINEAR INTEGRATED CIRCUIT
APPLICATIONS INFORMATION
It is application circuit of UTC L8401 in figure 2, the bias circuits is stable fully in -40°C ~80°C.
CNB and CSUB are used to generated the negative supply on pin CSUB (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.
RCAL1 and RCAL2 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 RCAL1 and RCAL2 can be connected to GND through only one res of
half normal value.
There are full protection for external FETs on chip: The gate output voltage is limitted 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.
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