2
Quick start
2.1
Safety precautions
Note:
Warning! Some of the components mounted on the board could reach hazardous temperatures during
operation.
While using the board, please adhere to the following precautions
•
Do not touch the components
•
Do not cover the board
•
Do not put the board in contact with flammable materials of with materials releasing smoke when heated
After operation, allow the board to cool down before touching it.
2.2
Adjusting motor peak current
The R7 trimmer adjusts the reference voltage of the STSPIN820 PWM current controller setting the peak current
input to the motor phases.
The R7 trimmer controls the current level. Rotating clockwise increases and rotating counter clockwise decrease
the current level.
The range depends on the VDD logic supply voltage (pin 6 of J2) as listed in the table below.
Table 2.
Peak current ranges
VDD
Minimum
Maximum
3.3 V
V
REF
= 0 V
I
peak
= 0 A
(1)
V
REF
= 0.67 V
I
peak
= 4.5 A
(2)
5 V
V
REF
= 0 V
I
peak
= 0 A
(1)
V
REF
= 1 V
I
peak
= 6.8 A
(2)
(1)
Minimum current could be present due to the PWM current control operation
(2)
The overcurrent protection of the STSPIN820 could limit the actual peak current
2.2.1
Modify the peak current range
The trimmer can be adjusted by modifying some board components.
In particular the components contributing to the definition of the peak current are:
•
Both the sensing resistors
•
Pull-up resistor (R6)
•
Sensing resistor (R8 and R9)
The detailed formula is the following:
Changing the sensing resistors requires particular attention:
•
Bust the sensing resistors must have the same value
•
Power dissipation on the resistors is equal to I
peak
2
× R
sense
. The power rating must be selected accordingly.
UM2434
Quick start
UM2434
-
Rev 1
page 3/11