Settings with Other NTCs

Overview

While the driver is optimized for the NTCAFLEX05103HH sensor, you can use other 10kΩ NTC thermistors by calculating the appropriate potentiometer resistance values.

Calculation Procedure

Required Information

Before starting, obtain from your NTC datasheet:

• R(T) curve - Resistance vs. Temperature table
• Beta value (B25/85 or similar)
• Resistance at reference temperature (usually 10kΩ @ 25°C)

Step-by-Step Calculation

Power Off

Disconnect the power supply before setting temperature values.

Calculating Threshold Temperature

Formula

R_POT = R(NTC@TEMP) × 2.3791

Where:

• R_POT = Resistance to set at TEMP ADJ measurement points
• R(NTC@TEMP) = NTC resistance at your desired threshold temperature
• 2.3791 = Driver-specific calibration factor

Calculation Steps

1. Select your desired threshold temperature (e.g., 30°C)

2. Find NTC resistance at that temperature from datasheet

   • Example: R(30°C) = 8.312 kΩ (from your NTC datasheet)

3. Calculate required potentiometer resistance:

   R_POT = 8.312 kΩ × 2.3791
   R_POT = 19.773 kΩ

4. Measure and adjust:

   • Measure resistance at TEMP ADJ points
   • Adjust TEMP potentiometer to 19.773 kΩ

Calculating Hysteresis Temperature

Formula

R(NTC@HYST) = R_POT / 1.7034

Then use the NTC datasheet to find the temperature corresponding to R(NTC@HYST).

Calculation Steps

1. Use the R_POT value calculated above

2. Calculate NTC resistance at hysteresis:

   R(NTC@HYST) = R_POT / 1.7034
   R(NTC@HYST) = 19.773 kΩ / 1.7034
   R(NTC@HYST) = 11.608 kΩ

3. Find corresponding temperature in NTC datasheet

   • Look up 11.608 kΩ in the R(T) table
   • Example: This corresponds to ~23°C

4. Result: Hysteresis temperature is 23°C

Understanding the Result

Threshold:   30°C  (shutdown trigger)
    ↕ 7°C
Hysteresis:  23°C  (can re-enable)

Temperature Difference

The temperature difference between threshold and hysteresis is determined by the NTC’s characteristics and cannot be adjusted independently.

Complete Worked Example

Example: Using Vishay NTCLE100E3103JB0 (10kΩ NTC)

Goal: Set threshold temperature to 35°C

Step 1: Find NTC Resistance at 35°C

From datasheet: R(35°C) = 6.532 kΩ

Step 2: Calculate R_POT

R_POT = 6.532 kΩ × 2.3791
R_POT = 15.537 kΩ

Step 3: Set the Potentiometer

• Disconnect power
• Measure at TEMP ADJ points
• Adjust to 15.537 kΩ

Step 4: Calculate Hysteresis

R(NTC@HYST) = 15.537 kΩ / 1.7034
R(NTC@HYST) = 9.120 kΩ

Step 5: Find Hysteresis Temperature

From datasheet: 9.120 kΩ corresponds to ~28°C

Result Summary

Threshold Temperature:   35°C
Hysteresis Temperature:  28°C
Temperature Span:        7°C
R_POT Setting:          15.537 kΩ

Alternative Formula (from Manual)

The manual also mentions an alternative formula for hysteresis calculation:

R(NTC@TEMP) = R_POT / 2.004

Formula Discrepancy

The manual shows two different divisors (1.7034 and 2.004). Use 1.7034 for hysteresis calculation as it appears in the detailed temperature section. The 2.004 value appears to be from a different equation context.

NTC Installation

Setup Procedure

1. Disconnect power supply

2. Calculate R_POT using formulas above

3. Adjust TEMP potentiometer:

   • Measure resistance at TEMP ADJ points
   • Adjust to calculated R_POT value

4. Solder NTC to cables:

   • ✅ Polarity is NOT relevant for NTC
   • Use heat-shrink tubing for insulation

5. Connect to NTC connector on board

6. Temperature monitoring is set

7. Connect power supply

NTC Datasheet Information Required

Essential Parameters

Parameter	Description	Example
R25	Resistance at 25°C	10,000 Ω
B25/85	Beta value	3960 K
R(T) Table	Resistance vs Temp	Full table from -40°C to +150°C
Tolerance	Resistance tolerance	±1% or ±5%

Using Beta Value

If only Beta value is available, use the Steinhart-Hart equation or simplified Beta formula:

R(T) = R25 × exp(B × (1/T - 1/T25))

Where:

• T = Temperature in Kelvin (°C + 273.15)
• T25 = 298.15 K (25°C)
• B = Beta value
• R25 = Resistance at 25°C

Verification

After Setup

1. Power up driver
2. Check TEMP LED - should be ON
3. Monitor actual temperature (if possible)
4. Verify threshold by controlled heating
5. Check hysteresis during cooling
6. Document final settings

Common NTC Types

Compatible 10kΩ NTC Examples

Manufacturer	Part Number	B25/85	Notes
Murata	NXFT15XH103FA2B	3380K	Good stability
Vishay	NTCLE100E3103JB0	3977K	High accuracy
TDK	B57164K0103J	3964K	Standard type
Semitec	103AT-11	3435K	Popular choice

Beta Value Variation

Different NTC types have different Beta values, which affects the temperature span between threshold and hysteresis. Higher Beta values generally give smaller temperature spans.

Practical Considerations

Temperature Span

The span between threshold and hysteresis depends on:

• NTC Beta value
• NTC R(T) curve characteristics
• Fixed driver calibration factors

Typical spans: 5-10°C

Accuracy

Final temperature accuracy depends on:

• NTC tolerance (±1% to ±5%)
• Potentiometer setting accuracy
• Thermal contact quality
• Measurement accuracy

Expected accuracy: ±2-5°C

Mounting Requirements

Critical Placement

The distance between the laser diode, the NTC, and the TEC needs to be chosen as short as possible.

Otherwise, the driver will not be able to keep the temperature stable and may oscillate.

Troubleshooting

Temperature Reading Issues

Problem	Possible Cause	Solution
TEMP LED always OFF	Wrong NTC type/value	Verify 10kΩ @ 25°C
Incorrect threshold	Calculation error	Recalculate using datasheet
Temperature oscillation	Poor thermal contact	Improve NTC mounting
Premature shutdown	R_POT too high	Recalculate and adjust

Calculation Verification

Double-check your calculations:

1. Verify NTC resistance from datasheet
2. Check multiplication/division
3. Confirm Beta value used
4. Test with controlled heating

Documentation

Keep a record of:

• NTC part number
• Target threshold temperature
• Calculated R_POT value
• Measured hysteresis temperature
• Date of configuration