RS and Vref filter Resistor/Capacitor Value

Board Resistance Value Comparison Table

Item	FAB25Board	LeonBoard	Optimal Value	Unit
RS (Sense Resistor)	0.1Ω	0.25Ω	0.1Ω	Ω
VREF Filter Resistor	120Ω	120Ω	150Ω	Ω
VREF Filter Capacitor	0.1μF	0.1μF	0.1μF	μF

Electrical Characteristics Comparison Table

Characteristic	FAB25Board	LeonBoard	Optimal Value	Notes
Time Constant τ	12μs	12μs	15μs	R × C
Cutoff Frequency	13.3kHz	13.3kHz	10.6kHz	1/(2π×τ)
VREF at 1.5A	1.2V	3.0V	1.2V	I × RS × 8
VREF in Range	✅ In Range	❌ Out of Range	✅ In Range	0.5V～2.5V
Max Control Current	3.125A	1.25A	3.125A	At VREF 2.5V
1.5A Control Possible	✅ Possible	❌ Impossible	✅ Possible	-

Performance Comparison Table

Performance Metric	FAB25Board	LeonBoard	Optimal Value	Rating
Current Control Accuracy	High	Low	Highest	Based on VREF range
Response Speed	Fast	Fast	Standard	Based on time constant
Stability	Standard	Low	Standard	Ripple characteristics
Noise Immunity	Standard	Standard	Standard	Filter characteristics
Max Torque	Sufficient	Limited	Sufficient	Current limitation
Future Expandability	Available	None	Available	Current margin

Issues and Improvements

LeonBoard Issues

Issue	Impact	Improvement Method
VREF Out of Range	Current control abnormal	Change RS to 0.1Ω
Max Current Limitation	Insufficient torque	Change RS to 0.1Ω
1.5A Control Impossible	Motor performance not achieved	Change RS to 0.1Ω

FAB25Board Evaluation

Item	Rating	Reason
Current Control	✅ Good	VREF in range
Response	✅ Good	Appropriate time constant
Stability	✅ Good	Sufficient filtering

Comparison with Optimal Value

Item	FAB25Board	Optimal Value	Difference
VREF Filter Resistor	120Ω	150Ω	-30Ω
Time Constant	12μs	15μs	-3μs
Cutoff Frequency	13.3kHz	10.6kHz	+2.7kHz

Recommendations

When Using LeonBoard

• Immediate RS change to 0.1Ω required
• Current settings cannot control 1.5A motor

When Using FAB25Board

• Sufficient operation with current settings
• Difference from optimal value is minimal and practically no problem

For New Design

• Optimal values (RS: 0.1Ω, R: 150Ω) recommended
• More stable operation expected

Summary

Board	Overall Rating	Recommendation	Main Reason
FAB25Board	✅ Suitable	95%	Nearly optimal value
LeonBoard	❌ Unsuitable	0%	VREF out of range
Optimal Value	✅ Optimal	100%	Theoretical optimal value

FAB25Board is sufficiently usable as-is, but RS change is mandatory for LeonBoard.