SLLA643 August   2024 MCF8315C , MCF8315C-Q1 , MCF8316C-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Power Pin Design Recommendations
    1. 2.1 VM
    2. 2.2 Charge Pump: CPH, CPL, CP
    3. 2.3 Buck Converter: FB_BK, SW_BK, GND_BK
    4. 2.4 AVDD
    5. 2.5 DVDD
    6. 2.6 PGND, AGND, DGND
    7. 2.7 Thermal Pad
  6. 3MCF831xC Buck Regulator Overview
    1. 3.1 Buck Regulator Mode of Operation
    2. 3.2 Buck Regulator Output Voltage
    3. 3.3 Buck Power Sequencing
    4. 3.4 Buck Inductor Selection
    5. 3.5 MCF831xC Operation Without Buck Regulator
  7. 4MCF831xC IO Pins Design Recommendations
    1. 4.1 SPEED Pin
    2. 4.2 BRAKE, DIR, DRVOFF pins
    3. 4.3 EXT_CLK, EXT_WD
    4. 4.4 ALARM
    5. 4.5 DACOUT1, DACOUT2
    6. 4.6 SDA, SCL
    7. 4.7 nFAULT and FG pin
  8. 5MCF831xC PCB Schematic and Layout Recommendations
    1. 5.1 Single Ground Plane
    2. 5.2 Single Ground with AVDD Shorted to FB_BK
    3. 5.3 Two Grounds
  9. 6Summary
  10. 7References

2.7 Thermal Pad

MCF831xC devices have a thermal pad for better heat dissipation. This thermal pad needs to be connected to AGND and as large a copper plane as possible on end application PCB for maximizing heat dissipation.

Table 2-1 MCF831xC Power Section Components
PIN1 PIN2 Component value Unit % variation across op. conditions Recommended rating
Min. Typ. Max.
VM PGND 10 µF NA Twice the VM voltage
CP VM 32.9 47 61.1 nF 30 Twice the VM voltage
CPH CPL 0.7 1 1.3 µF 30 16V
AVDD AGND 0.7 1 1.3 µF 30 10V
DVDD DGND 0.7 1 1.3 µF 30 10V
FB_BK GND_BK 15.4 22 28.6 µF 30 10V
SW_BK FB_BK 37.6 47 56.4 µH 20 Isat >= 1.0A for BUCK_CL = 0
17.6 22 26.4 µH 20 Isat >= 0.5A for BUCK_CL = 1
20.9 22 23.1 Ω 5 1W