ZDC834A
SILICON DUAL VARIABLE CAPACITANCE DIODE
SUMMARY
V
BR
=25V; I
R
=20nA;
C
d
=47pF(Nom)
DESCRIPTION
The ZDC834A 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 47 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
SOT23
PIN CONFIGURATION
1
•
Common Cathode dual Diode ( monolithic construction )
•
VHF- UHF operation
•
Close tolerance CV characteristics
•
High Tuning Ratio
•
Low I
R
, enabling excellent Phase Noise Performance
•
High Q
( I
R
typically < 200pA @ 20V )
2
3
APPLICATIONS
•
DAB Receiver Modules for use with:
- Low voltage battery portables
- Hi-Fi
- In car radio
- MP3 players
C1
C2
A1
•
Voltage and Temperature Controlled Crystal Oscillators
•
Mobile Radio and Pagers.
ORDERING INFORMATION
DEVICE
ZDC834ATA
REEL SIZE
(inches)
7
TAPE WIDTH (mm)
8mm embossed
QUANTITY
PER REEL
3000 units
Top View
A2
DEVICE MARKING
•
C5A
ISSUE 3 - APRIL 2001
1
ZDC834A
ABSOLUTE MAXIMUM RATINGS.
PARAMETER
Forward Current (single diode)
Power Dissipation at T
amb
=25°C (a)
Linear Derating Factor
Operating and Storage Temperature Range
SYMBOL
I
F
P
D
T
j
:T
stg
VALUE
200
330
3
-55 to +150
UNIT
mA
mW
mW/°C
°C
THERMAL RESISTANCE
PARAMETER
Junction to Ambient (a)
SYMBOL
R
θ
JA
VALUE
417
UNIT
°C/W
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 T
amb
= 25°C ).
PARAMETER
Reverse Breakdown
Voltage
Reverse Leakage Current
Temperature Coefficient
Diode Capacitance
Capacitance Ratio
Figure of Merit
SYMBOL
V
BR
MIN.
25
TYP.
MAX.
UNIT
V
CONDITIONS.
I
R
= 10µA
V
R
= 20V
V
R
= 3V, f=1MHz
V
R
= 2V, f=1MHz
V
R
= 2V/20V, f=1MHz
V
R
= 3V, f=50MHz
I
R
η
C
d
C
d
/ C
d
Q
42.3
5.0
200
0.2
20
400
nA
ppm/°C
pF
47
51.7
6.5
ISSUE 3 - APRIL 2001
2
ZDC834A
APPLICATIONS INFORMATION
ZDC834A 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 part of the circuit that is not integrated is
the Voltage Controlled Oscillator (VCO) used in the
Phase-Locked Loop (PLL) channel selection circuit.
F igu re 1 sh ow s th e ZD C 834A dua l v a r ia b le
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 ZDC834A. In practice
radio frequency oscillations in the tank circuit 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 ZDC834A 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.
DAB Chipset
control voltage
control voltage
ZDC834A
ZDC834A
control voltage
Figure 1
ISSUE 3 - APRIL 2001
3
ZDC834A
ZDC834A
CHARACTERISTICS
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.
Cd specification at 2V, 1MHz
Band A = 42.3pf to 45.5pf partmark is 71A
Band B = 45.4pf to 48.6pf partmark is 71B
Band C = 48.5pf to 51.7pf partmark is 71C
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.
Should this be of interest the specification identification would change from ZDC834A to FSD271 and
- Purchase orders
can be placed in multiples of 3000 units / reel for device type
FSD271TA
- Samples
can be obtained from Zetex Plc quoting device type
#FSD271TA
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
Streitfeldstraße 19
D-81673 München
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: (631) 543-7100
Fax: (631) 864-7630
Zetex (Asia) Ltd.
3701-04 Metroplaza, Tower 1
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
© Zetex plc 2001
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.
ISSUE 3 - APRIL 2001
4
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