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Application Notes — MC74113 & MC75113
92
Juno Step Motor Control IC User Guide
15
15.2 Design Tips
15.2.1 Controlling PWM Output During Reset
When the MC74113 or MC75113 are in a reset state (when the reset line is held low), or immediately after a power on,
PWM output will be in a high impedance state, which will provide design flexibility to prevent undesirable motor
movement at system level. For example, when the power train is active high in PWM High/Low mode, pull-down
resistors can be used to keep the power train off during reset and power up. For an active low power stage, pull-up
resistors can be used.
15.2.2 Thermal Considerations
The recommended operating junction temperature range for the MC74113 and MC75113 is between -40
°
C and
150
°
C. Proper thermal design will ensure the system reliability. Based on a simplified resistor model for heat transfer,
following thermal matrices under different conditions are provided for thermal design.
θ
JA
is the junction-to-ambient thermal resistance. Although it is an important design reference, this thermal metric
highly depends on the board design and system configurations. Directly using it for junction temperature estimation
could result in misleading results because the environmental factors are different from design to design.
ψ
jT
(junction to top of package) is provides as an useful thermal metric for estimating the in-situ junctional
temperature. The environmental factors do not affect this metric as much, and it can be easily measured. Also, because
ψ
jT
is small, if a user chooses to, the top of package temperature might be approximated as the junctional temperature
for design estimation when enough thermal design margin is included.
AIR FLOW (64-Pin TQFP Package)
Parameter
0 lfm
150 lfm
250 lfm
500 lfm
θ
JA[
°
C/W] High k PCB
56.5
44.7
42.9
40.3
ψ
JT [
°
C/W]
0.15
0.42
0.51
0.67
AIR FLOW (56-Pin VQFN Package)
Parameter
0 lfm
150 lfm
250 lfm
500 lfm
θ
JA[
°
C/W] High k PCB
34.8
23.6
22.3
20.5
ψ
JT [
°
C/W]
0.24
0.36
0.43
0.56
Содержание Juno MC71112
Страница 12: ...The Juno IC Family 12 Juno Step Motor Control IC User Guide 1 This page intentionally left blank ...
Страница 18: ...Functional Characteristics 18 Juno Step Motor Control IC User Guide 2 This page intentionally left blank ...
Страница 22: ...Electrical Characteristics 22 Juno Step Motor Control IC User Guide 3 This page intentionally left blank ...
Страница 26: ...Timing Diagrams 26 Juno Step Motor Control IC User Guide 4 This page intentionally left blank ...
Страница 46: ...Operational Overview 46 Juno Step Motor Control IC User Guide 7 This page intentionally left blank ...
Страница 54: ...Microstep Waveform Generation 54 Juno Step Motor Control IC User Guide 8 This page intentionally left blank ...
Страница 70: ...Internal Profile Generation 70 Juno Step Motor Control IC User Guide 11 This page intentionally left blank ...
Страница 78: ...Motion Monitoring Control 78 Juno Step Motor Control IC User Guide 12 This page intentionally left blank ...
Страница 86: ...Drive DC Bus Safety 86 Juno Step Motor Control IC User Guide 13 This page intentionally left blank ...
Страница 100: ...Application Notes MC74113 MC75113 100 Juno Step Motor Control IC User Guide 15 Figure 15 3 Drive Safety and Monitoring ...
Страница 103: ...Application Notes MC74113 MC75113 Juno Step Motor Control IC User Guide 103 15 Figure 15 4 Leg Current Sensing ...
Страница 114: ...Application Notes MC74113 MC75113 114 MC58113 Electrical Specifications 15 This page intentionally left blank ...