1. 1Date 2004 Strictly Confidential Remote Sense (extracted from a presentation by Robert Kollman)

2. 2Date 2004 Strictly Confidential Why Remote Sense? Power Supply 3.3V System Load 100A 3.1V Interconnect resistance has many components: –Connector Pins- Etch Resistance –Wiring- Vias

3. 3Date 2004 Strictly Confidential Calculating Resistance Material  -cm  -in Copper1.700.67 Copper (Plated) 6.02.36 Gold2.20.87 Lead22.08.66 Silver1.50.59 Silver (Plated)1.80.71 Tin -Lead155.91 Tin (Plated)114.33 Palladium114.3

4. 4Date 2004 Strictly Confidential Counting Squares for Resistance Copper resistivity is 0.67 mW in. at 25°C and doubles for 254°C rise Copper Weight (Oz.) Thickness (mm/mils) m  per Square (25 o C) m  per Square (100 o C) 1/20.02/0.71.01.3 10.04/1.40.50.65 20.07/2.80.20.26

5. 5Date 2004 Strictly Confidential Don’t forget vias Rule of thumb limits via current to 1 amp each.

6. 6Date 2004 Strictly Confidential Differential Amplifier Used to sense remote voltage from power supply control ground Voltage at op amp inputs must be within common mode range specified in datasheet. If R1=R2=RF=RA then VO = V2 - V1. Reduces temperature sensitivity if all resistors drift similarly. Set R1 = RA R2 = RF

7. 7Date 2004 Strictly Confidential Differential Amplifier Errors Resistor Tolerance Impact Can Be Calculated Per Previous Chart Input Offset is Multiplied by 1 + RF / RA

8. 8Date 2004 Strictly Confidential Highest Accuracy if R6 is Open Open R6 Unity Gain Diff Amp (1 + (1 – Ratio) Tol ) 2 (1 + Tol) 2 * (1 + (1 – Ratio) Tol ) 1 + T – T*R 1 + 2T + T 2 - TR < 2T + T 2

9. 9Date 2004 Strictly Confidential Remote Sense Faults FaultEffectRemedy Open SenseOVRP/RN Reverse SenseOVLocal OV Shutdown Open Load LeadVout Across RP/RNRP/RN Power Rating

10. 10Date 2004 Strictly Confidential Alternate Sense Connections Float power supply control with respect to local ground –Requires isolation between controller and power stage Sense only positive output –Assumes RLINE_P>>RLINE_N

11. 11Date 2004 Strictly Confidential Trimming the Output Voltage of a Module Desired output voltage is higher/lower than the setpoint or better accuracy is required Circuit provides 0.2% initial accuracy (not including resistor divider tolerance) Remote sense is included with this circuit – Control circuit is referenced to load ground – Requires 3.3V supply for control circuit