5. We have selected The Allegro A4988 DMOS driver for the system in problem 3.
a. While running with the K053B motor continuously, should we expect thermal problems with the
driver, assuming nominal (typical) $R_{dson}$ and Ambient temperature? What about the worst case of
Maximum $R_{dson}$ and ambient temperature of 85°C?
b. Now consider the K046B winding: Typical thermals at the driver? Worst Case?
Hint: Slide 32, Lecture 4F.
Hint: You will have 4 calculated power dissipations from parts a and b. Put them on the graph below and
write down your calculations and Justifications.
THERMAL CHARACTERISTICS
Characteristic Symbol Test Conditions Value Units
Package Thermal Resistance $R_{th} Four layer PCB based on JEDEC standard 32 °C/W
*Additional thermal information available on Allegro website
Power Dissipation versus Ambient Temperature
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
20
40
60
80
100
120
140
160
Temperature, $T_a$ (°C)
