 English |
|
|
|
|
|
|
|
| DRV8818_15 Datasheet, PDF (17/31 Pages) Texas Instruments – DRV8818 Stepper Motor Controller IC | |||
| |||
| ◁ |
www.ti.com
Typical Application (continued)
9.2.1 Design Requirements
DRV8818
SLVSAX9D â SEPTEMBER 2011 â REVISED JANUARY 2015
DESIGN PARAMETER
Supply Voltage
Motor Winding Resistance
Motor Winding Inductance
Motor Full Step Angle
Target Microstepping Level
Target Motor Speed
Target Full-Scale Current
Table 3. Design Parameters
REFERENCE
VM
RL
IL
θstep
nm
v
IFS
EXAMPLE VALUE
24 V
4.0 â¦
3.7 mH
1.8°/step
8 µsteps per step
120 rpm
1.25 A
9.2.2 Detailed Design Procedure
9.2.2.1 Stepper Motor Speed
The first step in configuring the DRV8818 requires the desired motor speed and microstepping level. If the target
application requires a constant speed, then a square wave with frequency Æstep must be applied to the STEP pin.
If the target motor startup speed is too high, the motor will not spin. Make sure that the motor can support the
target speed or implement an acceleration profile to bring the motor up to speed.
For a desired motor speed (v), microstepping level (nm), and motor full step angle (θstep),
fstep µsteps / second
v §¨©
rotations
minute
·¸¹
u
360
¨§©
q
rotation
¸·¹
u
nm
§
¨©
µsteps
step
·
¸¹
60
§¨©
seconds
minute
¸·¹ustep
§
¨©
q
step
·
¸¹
(5)
fstep µsteps / second
120
§¨©
rotations
minute
·¸¹
u
360
¨§©
q
rotation
¸·¹
u
8
§
¨©
µsteps
step
·
¸¹
60
§
¨©
seconds
minute
·
¸¹
u
1.8
§
¨©
q
step
·
¸¹
(6)
θstep can be found in the stepper motor data sheet or written on the motor itself.
For the DRV8818, the microstepping level is set by the USMx pins. Higher microstepping will mean a smother
motor motion and less audible noise, but will increase switching losses and require a higher fstep to achieve the
same motor speed.
9.2.2.2 Current Regulation
In a stepper motor, the set full-scale current (IFS) is the maximum current driven through either winding. This
quantity will depend on the VREF analog voltage and the sense resistor value (RSENSE). During stepping, IFS
defines the current chopping threshold (ITRIP) for the maximum current step. The gain of DRV8818 is set for 8
V/V.
IFS A
VREF V
VREF V
Av x RSENSE Ã 8 x RSENSE Ã
(7)
To achieve IFS = 1.25 A with RSENSE of 0.1 â¦, VREF should be 1.56 V.
Copyright © 2011â2015, Texas Instruments Incorporated
Product Folder Links: DRV8818
Submit Documentation Feedback
17
|
▷ |
German
Russian
Spanish
Italian
Polish
Chinese
Japanese
Korean
French
Portuguese