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SILICON DUAL VARIABLE CAPACITANCE DIODE
FSD270
SUMMARY
VBR=25V; IR=20nA; Cd=33pF(Nom)
DESCRIPTION
The FSD270 is a new hyperabrupt SOT23 packaged dual common cathode varactor
diode , offering users both compact circuit design and impressive performance
comprising tightly controlled CV characteristics, a capacitance of typically 33 pf @
2V,excellent phase noise performance and high Q of 200 min.
This superior performance in the VHF and UHF ranges has been optimised to meet
the high filtering requirements of a wide range of Digital Audio Broadcasting (DAB)
module circuits , mobile radios, pagers, voltage controlled crystal oscillators
(VCXO) and temperature controlled crystal oscillators (TCXO).
FEATURES
Common Cathode dual Diode ( monolithic construction )
VHF- UHF operation
Close tolerance CV characteristics
High Tuning Ratio
Low IR , enabling excellent Phase Noise
Performance ( IR typically < 200pA @ 20V )
High Q
APPLICATIONS
DAB Receiver Modules for use with:
-Low voltage battery portables
-Hi-Fi
-In car radio
-MP3 players
Voltage and Temperature Controlled Crystal Oscillators
Mobile Radio and Pagers.
ORDERING INFORMATION
DEVICE
FSD270TA
REEL SIZE
7ЈЈ (180mm)
TAPE WIDTH
8mm embossed
QUANTITY PER REEL
3000 units
SOT23
PIN CONFIGURATION
1
23
A1
C1
C2
A2
Top View
The FSD270 is capacitance selected into 3 bands. A reel will only contain one band - A,B or C. Shipments of more
than 1 reel may contain reels from different bands.
ISSUE 1 - AUGUST 2002
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FSD270
ABSOLUTE MAXIMUM RATINGS.
PARAMETER
SYMBOL
VALUE
UNIT
Forward Current (single diode)
Power Dissipation at Tamb=25°C (a)
Linear Derating Factor
IF
PD
200 mA
330 mW
3 mW/°C
Operating and Storage Temperature Range
Tj:Tstg
-55 to +150
°C
NOTES
(a) For a device surface mounted on 25mm x 25mm FR4 PCB with high coverage of single sided 1oz copper,
in still air conditions
ELECTRICAL CHARACTERISTICS (at Tamb = 25°C ).
PARAMETER
SYMBOL MIN.
TYP.
MAX.
UNIT
CONDITIONS.
Reverse Breakdown
Voltage
VBR 25
V IR = 10µA
Reverse Leakage Current
Temperature Coefficient
Diode Capacitance
Capacitance Ratio
Figure of Merit
IR
η
Cd
Cd / Cd
Q
29.7
5.0
200
0.2
33.0
20
400
36.3
6.5
nA VR = 20V
ppm/°C VR = 3V, f=1MHz
pF VR = 2V, f=1MHz
VR = 2V/20V, f=1MHz
VR = 3V, f=50MHz
Additional CV matching capability:
Zetex recognise that some applications ie filtering in digital audio receiver circuits, require these dual varactors
to be very tightly matched. To meet this requirement devices can be supplied tested into capacitance bands at the
2V condition.
Each ( TA ) reel will contain 3000 devices carrying only diodes tested into a single band and each device will have a
partmark identifying the capacitance band which they meet.
As this is a final test measurement customers will not have the option to specify a capacitance at the time of
ordering and will be obliged to accept the band into which the devices are tested.
- Purchase orders can be placed in multiples of 3000 units / reel for device type FSD270TA
- Samples can be obtained from Zetex Plc quoting device type #FSD270TA
BAND A
BAND B
BAND C
MIN.
29.7
31.9
33.9
MAX.
32.1
34.1
36.3
UNIT
pF
pF
pF
PART NUMBER
70A
70B
70C
ISSUE 1 - AUGUST 2002
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FSD270
APPLICATIONS INFORMATION
FSD270 in Digital Audio Broadcasting (DAB)
Circuits
Digital audio is set to dominate car radio and other
mobile radio applications. Most of the required
functions can be achieved with a single integrated
circuit. One parts of the circuit that are not integrated
are the Voltage Controlled Oscillator (VCO) used in the
Phase-Locked Loop (PLL) channel selection circuit and
the tracking filters. Figure 1 shows the FSD270 dual
variable capacitance diode (also known as varactor or
tuner diode) in a DAB application.
Most textbook circuits show a single variable
capacitance diode in place of the FSD270. In practice
radio frequency oscillations in the tracking filters can
drive the single diode into conduction on peaks
increasing the bias voltage and giving rise to
undesirable harmonics. Common-cathode variable
capacitance diodes are used to overcome this problem.
The FSD270 dual common cathode device in the space
saving SOT23 package has been optimized for this
application. Zetex application note AN9 covers our
range of variable capacitance diodes and their
applications in detail.
Figure 1.
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