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ZDC834A
SILICON DUAL VARIABLE CAPACITANCE DIODE
SUMMARY VBR=25V; IR=20nA; Cd=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 IR , enabling excellent Phase Noise Performance * High Q
( IR 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
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ZDC834A
ABSOLUTE MAXIMUM RATINGS.
PARAMETER Forward Current (single diode) Power Dissipation at T amb =25C (a) Linear Derating Factor Operating and Storage Temperature Range SYMBOL IF PD 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 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 Tamb = 25C ).
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 = 10A V R = 20V V R = 3V, f=1MHz V R = 2V, f=1MHz V R = 2V/20V, f=1MHz V R = 3V, f=50MHz
IR Cd Cd / Cd Q 42.3 5.0 200
0.2
20 400
nA ppm/C pF
47
51.7 6.5
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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. Figu r e 1 s h o w s th e ZD C 8 3 4 A dua l v a ri a bl e 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
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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 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: (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 (c) 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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