AN047 - Matching Methods for Variable Capacitance Diodes

A p p l i c a t i o n N o t e , V 2. 1, F e b . 2 00 8
A p p li c a t i o n N o t e N o . 0 4 7
M a t c h i ng M e th o d s f o r V a r i ab l e C a p a c i t an c e
Diodes
R F & P r o t e c ti o n D e v i c e s
Edition 2008-02-14
Published by Infineon Technologies AG,
81726 München, Germany
© Infineon Technologies AG 2009.
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Revision History: 2008-02-14, V2.1
Previous Version: V2.0, 2006-02-15
Page
Subjects (major changes since last revision)
7-9
Table 2 and Table 3 update to current Infineon product range
Template: a4_sd_tmplt.fm / 1 / 2005-12-01
Application Note No. 047
Matching Methods for Variable Capacitance Diodes
1
Matching Methods for Variable Capacitance Diodes
This application note covers the field of the selection methods that are applied on variable capacitance diodes to
reduce the effort on adjusting electronic circuits in production.
Varicap or variable capacitance diodes are key semiconductors components for VCO‘s and tuner circuits. It is a
semiconductor diode in which the voltage dependency of the PN junction capacitance in reverse bias node is
utilized and the Q factor is optimized. These diodes are ideal tuning elements for Satellite-, TV-, VCR- and Radio
- tuners and for VCO applications in mobile communication. Variable capacitance diodes for tuner applications are
classified in different categories (FM, VHF, UHF, SAT) according to the application frequency and their
capacitance values.
Attention: Matching of diodes is usually not required for varicap diodes in VCO applications
But for tuner applications there must be sufficient tracking of the input -, intermediate - and oscillator - circuits in
order to get a good band pass response. The capacitances of the diodes, that are used in these stages have to
be matched.
For this propose capacitance diodes are sorted into matched sets of similar capacitance over the entire reverse
voltage range.
There are four different selections methods which can be used to provide matched diodes:
•
•
•
•
•
A: In line matching (SCD80, SC79)
B: In line matching in groups
C: Group matching (only SOD323)
D: Floating matching (only SOD323)
E: Unmatched (SOD323, SCD80, SC79)
A: In-line matching (SCD80, SC79)
Inline matching, pick and place matching, direct matching assembly are all expressions for a new tracking method.
Neighboring diode chips are picked up intelligently in an orderly structure and one after another from the wafer
and are placed consecutively on the leadframe. Remaining in this order the diodes are molded, punched and
tested electrically. In the end the capacitance values are gliding matched within a defined ∆C/C% tolerance of n
consecutive diodes on the tape.
For this matching method a good wafer quality, a very small capacitance tolerance and a very good uniformity of
the total capacitance curves are necessary in order to get reels with small matched capacitance tolerances.
Advantage
A very close matching quality of Ct and a very good Ct vs. VR characteristics of consecutive diodes. (See Figure 1)
Disadvantage
No capacitance selection is possible.
Application Note
4
V2.1, 2008-02-14
Application Note No. 047
Matching Methods for Variable Capacitance Diodes
Diode 1
Diode 2
Diode 3
... etc
1
Figure 1
Capacitance Variation in Inline Matched Selections
B: Inline matching in groups
This matching method is a combination of method A: and C:. On one reel we have more than one group with group
separations and the devices of the different groups are inline matched.
C: Group matching (only SOD323)
For this method the capacitance target range at discrete reverse voltages is split into capacitance subgroups which
are allocated into capacitance tolerance categories.
Figure 1 for example shows the capacitance spread range and the capacitance Ct at fixed reverse voltages VR.
Every capacitance range at the discrete reverse voltage will be assigned to fixed capacitance categories Cc
(Cc=1,2,3...n) with a capacitance tolerance ∆C/C%= (Cmax.n - Cmin.n)/Cmin.n). Diodes with the same group
address from a matched group.
For example:
Table 1
Group matching (only SOD323)
Reverse Voltage
1V
6V
15 V
25 V
28 V
Group no. 1 address
4
3
3
2
2
Group no. 2 address
4
4
5
3
3
Group no. 2 address
2
2
3
2
2
Application Note
5
V2.1, 2008-02-14
Application Note No. 047
Matching Methods for Variable Capacitance Diodes
Group 1
Group 2
Group 3
Figure 2
Capacitance Spread and Group Addresses
Diodes from these matched groups (or preselected capacitance groups) are randomly distributed in quality. To get
a reel with 3 000 or 10 000 devices, possible two or more matched groups must be on one reel. Matched groups
on the reel ate separated by empty pockets.
Advantage
In this matching method any number of devices in a group are matched and any selection of capacitance ratio is
directly possible.
Disadvantage
In this matching method more than one matched group is on the reel and the diode capacitance curves might cross
each other (see Figure 3)
D: Floating matching (only SOD323)
The continuos processing of a complete tape is made possible by what we call floating matching. Continuos
matching on the tape is accomplished by successive placing of “related” preselected matched groups (according
method A) on the tape.
In this case a random section of the tape of a specified number of consecutive taped diodes (typically 7) are always
matched with a capacitance tolerance ∆C/C%.
Advantage
No group separation on the tape by empty pockets, which means easier handling by the customers and tight
matching quality
Disadvantage
No total capacitance ratio- selection possible.
Application Note
6
V2.1, 2008-02-14
Application Note No. 047
Available matching methods per package and the corresponding E-numbers
Diode 1
Diode 2
Diode 3
... etc
1
-1
Figure 3
Capacitance Variations in group or floating matched selection
E: Unmatched (SOD323, SCD80, SC79)
Unmatched diodes are sufficient for all applications where it is not necessary to track several resonant circuit to
the same resonant frequency (e.g. VCO‘s in mobile communication).
2
Available matching methods per package and the corresponding
E-numbers
One tables for every package: SOD323, SCD80 and SC79.
Table 2
SOD323 overview of matching methods
Matching
Type
3k
Group matched
BB439
E6327
Floating matched
BB439
Unmatched
BB439
E7263
Group matched
BB545
E7904
Floating matched
BB545
E7906
Unmatched
BB545
E7908
Group matched
BB535
E7904
Floating matched
BB535
E7906
Unmatched
BB535
E7908
Group matched
BB639
E7904
Floating matched
BB639
E7906
Unmatched
BB639
E7908
Group matched
BB639C
E7904
Floating matched
BB639C
E7906
Unmatched
BB639C
E7908
Group matched
BB640
E6327
Application Note
7
V2.1, 2008-02-14
Application Note No. 047
Available matching methods per package and the corresponding E-numbers
Table 2
SOD323 overview of matching methods (cont’d)
Matching
Type
3k
Floating matched
BB640
E7786
Unmatched
BB640
E7263
Group matched
BB644
E7904
Floating matched
BB644
Unmatched
BB644
E7908
Group matched
BB669
E7904
Floating matched
BB669
E7906
Unmatched
BB669
E7908
Group matched
BB831
E7904
Floating matched
BB831
E7906
Unmatched
BB831
E7908
Group matched
BB833
E6327
Floating matched
BB833
Unmatched
BB833
Group matched
BB837
Floating matched
BB837
E6327
Unmatched
BB837
E7263
E7263
Note: All E7xxx E-numbers are discontinued
Table 3
SCD80 overview of matching methods
Matching
Type
3k
8k1)
In-line matched
BB555
E7902
E7912
Unmatched
BB555
E7908
In-line matched
BB565
E7902
Unmatched
BB565
E7908
In-line matched
BB659
E7902
Unmatched
BB659
E7908
In-line matched
BB659C
E7902
Unmatched
BB659C
E7908
In-line matched
BB664
E7902
Unmatched
BB664
E7908
In-line matched
BB689
E7902
Unmatched
BB689
E7908
In-line matched
BB857
E7902
Unmatched
BB857
E7908
Unmatched
BBY51-02W
E6327
Unmatched
BBY52-02W
E6327
Unmatched
BBY53-02W
E6327
Unmatched
BBY55-02W
E6327
In-line matched
BBY56-02W
E7902
Unmatched
BBY56-02W
E6327
Application Note
8
E7912
E7912
E7912
E7912
E6127
E6127
V2.1, 2008-02-14
Application Note No. 047
Available matching methods per package and the corresponding E-numbers
Table 3
SCD80 overview of matching methods (cont’d)
Matching
Type
3k
8k1)
Unmatched
BBY57-02W
E6327
E6127
Unmatched
BBY58-02W
E6327
E6127
1) With 2 mm reel pitch, detailed information available on data sheet
Table 4
SC79 overview of matching methods
Matching
Type
3k
8k1)
In-line matched
BB555-02V
E7902
E7912
In-line matched
BB565-02V
E7902
E7912
In-line matched
BB659C-02V
E7902
E7912
In-line matched
BB664-02V
E7902
E7912
E7912
In-line matched
BB689-02V
E7902
Unmatched
BBY53-02V
E6327
Unmatched
BBY55-02V
E6327
Unmatched
BBY56-02V
E6327
Unmatched
BBY57-02V
E6327
Unmatched
BBY58-02V
E6327
Unmatched
BBY59-02V
E6327
Unmatched
BBY65-02V
E6327
Unmatched
BBY66-02V
E6327
1) With 2 mm reel pitch, detailed information available on data sheets
Application Note
9
V2.1, 2008-02-14
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