Custom Resistor Networks Solutions
 

Application Specific Networks

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.

Examples of Application Specific Networks:

1. Customer part number to maintain design confidentiality.
2. Multiple and/or non-standard resistor values.
3. Resistor networks designed for low capacitance or inductance.
4. Non-standard tolerances or matching requirements. Non-standard schematics.

Application Specific 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.

1. 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.
2. Usually three resistor ink formulations are the maximum that can be used on a network. Each formulation required does increase the cost.
3. 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.
4. Maximum operating voltage should be specified for each resistor when the resistor value is high enough to supersede the power rating.
5. Crossovers should be avoided. If necessary, a second level is provided by utilizing the opposite side of the substrate surface.
6. 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.
7. Buried nodes should be avoided. Resistance values must be read with special test equipment that may result in reduced measuring accuracy.
8. The tolerance of each resistor should be specified based on the circuit requirements. Resistor tolerance of ±2% is standard for all product.
9. Consult with the factory prior to finalization of application specific networks to obtain the optimum network design.
10. 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.

CTS Catalog Schematics

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.
 

SPICE Equivalent Circuit for 766 767 768 Series