Custom
Resistor Networks Solutions
Application specific resistor networks are
readily available from CTS to provide the designer with optimum
performance and cost effective solutions. There are no
tooling or engineering charges to supply resistor networks with
application specific schematics. Lead times for application
specific networks are the same as for standard manufactured
product. Application specific networks are available in
752, 753, 766, 767, and 768 products.
- Customer part number to maintain design confidentiality.
- Multiple and/or non-standard resistor values.
- Resistor networks designed for low capacitance or inductance.
- Non-standard tolerances or matching requirements. Non-standard schematics.
Resistor values, tolerance, TCR, power
rating, and circuit connections are the factors which determine
the resistor network design to meet the circuit designers optimum
performance and cost goals.
The following information is provided to
assist you in specifying application specific networks which meet
performance requirements at the lowest cost.
- Similar resistor values should be
grouped on a resistor network. Each group of resistor
values may require a different resistor ink formulation.
Normally a larger range of resistor values can be
obtained in a single resistor ink if the pin-outs are
selected by the network designer.
- Usually three resistor ink
formulations are the maximum that can be used on a
network. Each formulation required does increase the
cost.
- The power dissipation of each resistor
should be specified based on the performance
requirements. The total power must conform to the maximum
package power specification unless it is specified which
resistors are operated at a given time.
- Maximum operating voltage should be
specified for each resistor when the resistor value is
high enough to supersede the power rating.
- Crossovers should be avoided. If
necessary, a second level is provided by utilizing the
opposite side of the substrate surface.
- The TCR of each resistor is affected
by the geometry of the resistor and the number of
resistor formulations required. TCR tracking between
resistors screened at the same time is dependent on the
comparative resistor length. TCR of ±200 PPM is considered standard for
multiple formulation networks or resistors of 100 ohms or less.
- Buried nodes should be avoided. Resistance values must be read with
special test equipment that may result in reduced measuring accuracy.
- The tolerance of each resistor should be specified based on the circuit
requirements. Resistor tolerance of ±2% is standard for all product.
- Consult with the factory prior to finalization of application specific
networks to obtain the optimum network design.
- The table below shows general empirical rules which usually apply to
application specific schematics. Actual capabilities are dependent on the
required schematic and should be verified by CTS.
|
Capability Guidelines |
face="Arial">Resistance Ranges |
|
Characteristics for
Thick Film Networks |
10-20
Ohm |
31-99
Ohm |
100-1Meg
Ohm |
| Best
Absolute Tolerance |
±0.3Ohm |
±0.3Ohm |
±0.25% |
| Ratio
Match (50:1 max ratio)* |
±0.3Ohm |
±0.3Ohm |
±0.25% |
| Parallel
Circuit Resistance Tolerance(>50:1 ratio* in Loop) |
±0.3Ohm |
±0.3Ohm |
±0.25% |
| Parallel
Circuit Resistance Tolerance(<50:1 ratio* in Loop) |
±0.3Ohm |
±0.3Ohm |
±0.25% |
| Best TCR
(-55C to +125C) |
±200PPM |
±100PPM |
±100PPM |
| Best TCR
Tracking <3:1 ratio* (Same ink/same side) |
75PPM |
50PPM |
50PPM |
| Best TCR
Tracking >3:1 ratio* (Same ink/same side) |
100PPM |
75PPM |
75PPM |
Maximum
Resistor Power
(Not to exceed maximum package power) |
2 X (total package power)
(Total number of resistors)*
Highest Resistance Value = Ratio
Lowest Resistance Value
|
CTS -1 Bussed Schematic
The bussed schematic consists of (N-1) resistors (with N= to the
number of pins) of the same value connected to a common buss.
These networks are commonly used as pull up/pull down resistors
or as impedance matching terminating resistors. They can also be
used in other applications where the circuit requires a number of
the same value resistors connected to a common point.
CTS -3 Isolated Schematic
The isolated schematic consists of (N/2) resistors of
the same value which are electrically isolated from each other.
Normally these networks are used as current limiting resistors
and termination resistors. They can also be used in other
applications where the circuit requires a number of the same
value resistors which connect to various points. Since all
resistors on the same network are processed identically, the
isolated networks have been used to fabricate very accurate
voltage dividers at low cost by selectively connecting the
resistors in series.
CTS -5 Dual Terminator Schematic
The dual terminator schematic consists of (2N-2)
resistors of two different values with each resistor value
connected to a common buss. The resistor values form standard
Thevenin equivalent resistance values which are used for
termination to two different voltages. These networks are
typically used for ECL termination.
CTS -7 R/2R Schematic
The R/2R ladder network is commonly used for digital to
analog or analog to digital conversions by successive steps. The
input signals are applied at each bit of the ladder and the
signal is taken from the output terminal where the signal is used
to drive an operational amplifier. R/2R ladder networks are
available with a ladder accuracy of ±1/2 LSB (least significant
bit) up to a maximum of 8 bits and ±1 LSB for 9 bits.
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