STEVAL-IHM012V1 STMicroelectronics, STEVAL-IHM012V1 Datasheet - Page 9

• Manufacturer Part Number: STEVAL-IHM012V1
• Description: EVAL BRD POWER MOSFET/8PIN MCU
• Manufacturer: STMicroelectronics
• Type: Motor / Motion Controllers & Driversr

Specifications of STEVAL-IHM012V1

• Design Resources: STEVAL-IHM012V1 Gerber Files STEVAL-IHM012V1 Schematic STEVAL-IHM012V1 Bill of Materials
• Main Purpose: Power Management, Motor Control
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: ST7FLITEUS5
• Primary Attributes: Brush DC Motors
• Secondary Attributes: DC Chopper
• Product: Power Management Modules
• Kit Application Type: Power Management - Motor Control
• Application Sub Type: BLDC Motor
• Kit Contents: Board
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: ST7FLiteUS5
• Other names: 497-5861

UM0291
4.2
4.3
So R
Equation 3
For the 7.2 cordless drill (6 cells) we have chosen V
Sensing resistor (R
The value of the sensing resistor must be chosen to guarantee the right power dissipation at
the maximum handling current and to guarantee at least 300 mV in order to read the motor
current using the 10bit on board microcontroller ADC.
The evaluation board has been set and tested for a 7.2 DC brush motor.
The maximum current for the used motor is I
It follows that:
Equation 4
Power MOSFET
The choice of the Power MOSFET begins by choosing devices that can handle the required
current, given an adequate thermal dissipation path.
Here we have the equations for calculating the power dissipation of these MOSFETs and
determining the temperature at which they operate.
To determine whether or not a Power MOSFET is suitable for that application, we must
calculate its power dissipation, which consists mainly of resistive and switching losses:
Equation 5
One of the most severe tests for electronic drills is to evaluate the transistor's performance
with the rotor blocked. In this case the rotor remains fixed for a minimum time of 20 seconds,
while the Power MOSFET runs at the maximum duty cycle at maximum RMS current (in this
case is fixed by the safety routine in the microcontroller)
Equation 6
Where:
I
The operating junction temperature is:
Equation 7
LOAD
S
= maximum handling current by the motor.
will be:
PD
PD
SENS
TOT
TOT
T
≅
J
R
=
PD
=
)
S
PD
T
RESISTIVE
=
A
R
RESISTIVE
+
-----------------------------------------------
I
SENS
zener MIN
R
V
TH TOT
Smin
MAX
–
–
=
=
0.05
–
= 8 A.
+
R
V
+
Smin
PD
DS on
•
ZD
I
PD
OUT
(
SWITCHING
TOT
= 88% V
)
•
I
LOAD
Application design procedure
2
Nominal
and thus R
S
≅ 68 Ω .
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