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Thermal

Full Load Test

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  • Full load tests were conducted with a dummy load at 71A total.
  • The device was mounted horizontaly (worst case).
  • Ambient temperature 19°C
  • Resistive load on all outputs
  • Temperature taken with onboard temperature sensor, unless otherwise noted
  • All outputs on and under load
  • All outputs wired using 14AWG TXL in free air and approx. 2 feet long
  • Battery power wired using 4AWG cable and copper lug
  • Ground wired using 20AWG TXL
  • DC_100
    • 100% duty cycle
    • No case
  • DC_50
    • 50% duty cycle @ 400Hz
    • No case
  • CLOSED
    • 100% duty cycle
    • Case installed
  • TOP
    • 100% duty cycle
    • Case installed
    • Temperature taken at top of Profet (output 3/4) using thermocouple
  • Yellow
    • Warning temperature limit 55°C
    • Reaction: warning message sent
  • Red
    • Critical temperature limit 80°C
    • Reaction: device shutdown, power cycle required

Notes

  • Thermal performance is similar with or without PWM (on resistive loads)
  • The onboard temperature sensor follows the junction temperature within a few degrees after 10 minutes
  • Installing the case increases the temperature by a maximum of 5°C
  • The temperatures seen by the onboard sensor and thermocouple are much lower than the maximum temperature of the Profet junction 150°C

Thermal Images

These images were captured during the 100% duty cycle full load test.

The highest temperature recorded was 61°C at the top of the output 3/4 Profet (BTS7008-2EPA).

Thermal1 Thermal2 ThermalDT ThermalHigh

Notes

  • Deutsch DT connectors have an operating temperature range up to 125°C
  • While we do not know the actual internal temperature, the highest recorded external temperature during these tests was around 50°C
  • That is much lower than the rated operating temperature, which suggests higher current may be possible

Thermal Resistance

Before building or testing any hardware, we can calculate the expected temperature on the top of the Profet.

To do this, we need these values:

  • Ambient temperature (°C)
  • Total current (A)
  • RthJA (K/W)
    • See Infineon datasheet section 4.4
    • Thermal Resistance Junction to Ambient, (K/W)=(C/W)
    • Temperature rise per dissipated watt from the internal junction to ambient
    • Value calculated by Infineon at natural convection on a 4 layer PCB:
      • 2oz outer copper
      • 1oz inner copper
      • 76.2mm x 114.3mm board
    • The resulting value is added to the ambient temperature
    • Infineon uses Kelvin/Watt, this is equal to Celsius/Watt
  • ΨJTOP (K/W)
    • See Infineon datasheet section 4.4
    • Thermal Characterization Parameter Junction Top, (K/W)=(C/W)
    • Thermal resistance between the internal junction and the top of chip case
    • Value calculated by Infineon using the same test parameters as RthJA above
    • The resulting value will be subtracted from the junction temperature to find the expected temperature at the top of the chip case
  • RDS(ON) (mΩ)
    • See Infineon datasheet section 7.5.1
    • On State Resistance (mΩ)
    • Resistance between the battery connection and the output when the Profet is on, varies with junction temperature
    • Use this to calculate the heat generated by the chip
    • Assuming the junction temperature is 60°C, use RDS(ON) of 3.2mΩ and 11mΩ

BTS7002-1EPP

Power(W) = (Current x RDS(ON)) x Current = 122 x 3.2 = 0.461 W

Junction Temp(°C) = Ambient + (Power x RthJA) = 19 + (0.461 x 30.7) = 33°C

Case Top(°C) = Junction Temp - (Power * ΨJTOP) = 33 - (0.461 x 3) = 32°C

BTS7008-2EPA

Power(W) = (Current x RDS(ON)) x Current = 82 x 11 = 0.704 W x 2 = 1.408 W

Junction Temp(°C) = Ambient + (Power x RthJA) = 19 + (1.408 x 30.9) = 63°C

Case Top(°C) = Junction Temp - (Power * ΨJTOP) = 63 - (1.408 x 1.7) = 60°C

Table format:

Model RDS(ON) @ 25°C (mΩ) RDS(ON) @ 150°C (mΩ) RDS(ON) (mΩ) Current Per Output (A) Dissipated Power (W) # Channels Total Dissipated Power (W) Ambient Temp (°C) RthJA (C/W) Junction Temp (°C) ΨJTOP (C/W) Case Top (°C)
BTS7002-1EPP 2.6 4.8 3.2 12 0.461 1 0.461 19 30.7 33 3 32
BTS7008-2EPA 9 16 11 8 0.704 2 1.408 19 30.9 63 1.7 60

Notes

  • The BTS7008-2EPA expected case temperature (60°C) is close to the measured values
    • Thermocouple = 55°C
      • May be reduced due to glue used to hold thermocouple
    • Thermal camera = 61°C
  • The BTS7002-1EPP expected case temperature (32°C) is lower than the measured value
    • Thermal camera = 50°C
    • This may be caused by the adjacent BTS7008-2EPA which is at a higher temperature of 60°C
  • The Profet maximum junction temperature is 150°C, much higher than the temperatures we are seeing in these full load tests