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DRV8818_16 Datasheet, PDF (21/31 Pages) Texas Instruments – Stepper Motor Controller IC
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10.2 Layout Example
GND
GND
100 PŸ
VCC
100 PŸ
ISENA
HOMEn
DIR
AOUT1
DECAY
RCA
GND
VREF
RCB
VCC
BOUT1
USM1
USM0
ISENB
GND
GND
DRV8818
SLVSAX9E – SEPTEMBER 2011 – REVISED JANUARY 2016
VMA
SLEEPn
ENABLE
AOUT2
CP2
CP1
VCP
GND
VGD
STEP
BOUT2
RESETn
SRn
VMB
0.1 µF
VM
0.22 µF
0.22 µF
0.22 µF
GND
VM
0.1 µF
Figure 14. Layout Example Schematic
10.3 Thermal Considerations
The DRV8818 has thermal shutdown (TSD) as described previously. If the die temperature exceeds
approximately 150°C, the device will be disabled until the temperature drops to a safe level.
Any tendency of the device to enter thermal shutdown is an indication of either excessive power dissipation,
insufficient heatsinking, or too high an ambient temperature.
10.3.1 Power Dissipation
Power dissipation in the DRV8818 is dominated by the power dissipated in the output FET resistance, or RDS(ON).
Average power dissipation when running a stepper motor can be roughly estimated by:
P = 4 · R · (I )2
TOT
DS(ON)
OUT(RMS)
where
• PTOT is the total power dissipation.
• RDS(ON) is the resistance of each FET.
• IOUT(RMS) is the RMS output current being applied to each winding.
(8)
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