1. CSS / CSSH Ultra Precision Current Sensing Chip Resistor Training Module

2. Introduction
Purpose
Provide a basic overview of Stackpole’s CSS and CSSH series of current sense resistor chips
Objectives
Explain the important parameters for engineers choosing a current sense resistor
Discuss the advantages that the CSS / CSSH specifically provides for those parameters
Examine applications, end products, and future trends for this product
Content
10 pages
Learning Time
10 minutes
Welcome to the Stackpole CSS and CSSH Ultra Precision Current Sense Chip Resistor Training Module. This module will explain how the CSS and CSSH series of resistors is truly one of the most accurate and stable current sense resistors in the industry.

3. CSS/CSSH Materials, Design and Construction
The CSS/CSSH series uses a specially formulated resistive alloy to achieve very low TCR’s
As compared to other metal element current sense resistors, the CSS/CSSH terminations are mechanically crimped onto the resistive alloy for higher temperature operation
Precise resistance values are achieved through a proprietary trimming process, providing for resistance tolerances down to 0.5%
Marking
Metal Alloy
Protective Layer
External Electrode (Sn Plated)
Secondary Electrode (Ni Plated)
Internal Electrode (Cu Plated)
The CSS and CSSH series uses specialized materials designed to achieve extremely low resistance values with high precision.  The unique termination process allows for much higher temperature operation compared to other termination methods.  The proprietary trimming process allows for tolerances down to 0.5%.

4. Important Factors for Current Sensing
Stackpole’s CSS / CSSH
outperforms the competition
Low Resistance Values
High Power Rating
Improved Power Handling For Given Chip Sizes
Electrical Stability – Low TCR, Tight Resistance Tolerance
High Temperature Operation
With the proliferation of portable electronics, the design engineer is challenged with reducing size, improving power handling, and improving electrical performance. The CSS and CSSH series is specifically designed with these challenges in mind.

5. Low Resistance Values for High Efficiency Requirements
The lower the resistance value, the less power is used for the current sensing operation.
Stackpole offers resistance values down to 0.25 milliohms – among the lowest currently available in the market.
These low resistance values allow for the highest current handling possible.
When efficiency is most important, lower resistance values for the current sense resistor is critical. The .25 milliohm value offered by this series allows for sensing high amounts of current while keeping the power dissipation as low as possible.

6. High Power Ratings
As electronic content and functions increase, increasing amounts of current are required to power these features.
As shown on the previous slide, higher current levels require higher power ratings.
In the past, 3 and 4 watt SMD current sense solutions were hard to find, large and bulky, expensive, limited in resistance values offered, and had poor TCR or resistance tolerance.
The cost effective CSS 2725 and CSSH 2728 offer 4 watts of power handling with TCR down to 15 ppm and tolerances as low as 0.5% in resistance values from 0.25 milliohm up to 50 milliohm.
The CSS / CSSH series offers a significant improvement in stability, precision, and power handling compared to other surface mountable solutions available today.

7. High Power Ratings for a Given Package Sizes
Downsizing electronic products whether to make it smaller or to add features usually means sacrificing power handling or performance, limiting resistance values offered, or increasing sense resistor cost.
Current sensing resistors in general have higher power ratings than their standard chip resistor equivalents.
Stackpole’s CSSH2512 offers a unique 3 watt power rating in a package size usually limited to 2 watts.
Higher power ratings for 2512 size resistors and smaller allows the design engineer to utilize the space normally needed for power management for other functions to the product or to make the end product smaller.

8. High Precision Capability Competitive Analysis
Ω Values
Tolerance
TCR
Comments
CSS / CSSH
to 0.1 ohm
0.5%, 1%, 5%
15ppm, 25 ppm, 50 ppm
Comp. A
.001 to 0.5 ohm
75 ppm typical
Better precision requires a different series
Comp. B
0.001 to 0.02 ohm
1%, 5%
75 ppm, 150 ppm, 200 ppm
No 3 or 4 watt option offered
Comp. C
0.002 to 1.0 ohm
1%, 2%, 5%
100 ppm at best
No 4 watt option offered
Other competitive products require different series for lower resistance values, another for lower TCR’s, another for tighter tolerances, or for power ratings higher than 2 watts.
No other product currently available offers the same combination of low resistance values, excellent resistance tolerance, and extreme low TCR’s.

9. High Temperature Operation
The high current / high power environment that current sense resistors live in requires stability at high temperatures
The CSS / CSSH offers operation at full rated power up to 100C.
It also offers operation up to 275C, which is usually only offered in special series from competitors and in limited sizes and resistance values.
The CSS / CSSH series offers full power operation to higher temperatures and offers power derated operation to higher temperatures than any other product currently available.

10. Future Developments ¼ watt and ½ watt 0805 size chip
5 watt chip
Lower resistance values for all sizes
Improved TCR for a wider resistance range
The CSS and CSSH series and the benefits of the unique materials and manufacturing processes will lend themselves to keeping pace with the requirements of the current sensing resistor market.

11. Summary
Low Resistance Values – available down to 0.25 milliohms at 50 ppm TCR
High Power Handling – 3 watt 2512 size chip, 4 watt 2725 and size chips
High Precision / Electrical Stability - 0.5% resistance tolerance and 50 ppm TCR available for the entire resistance range.
Robust High Temperature Operation – full rated power handling up to 100C and power derated operation up to 275C.
The CSS / CSSH series offers unmatched precision, power handling, and resistance values in a single series, making it easy to use this single series a great choice for all current sensing requirements.