DRV8824_16 Datasheet, PDF (18/35 Pages) Texas Instruments – Stepper Motor Controller IC

DRV8824
SLVSA06J – OCTOBER 2009 – REVISED JULY 2014
www.ti.com
I_OUT(RMS) is equal to the approximately 0.7× the full-scale output current setting. The factor of 4 comes from the
fact that there are two motor windings, and at any instant two FETs are conducting winding current for each
winding (one high-side and one low-side).
The maximum amount of power that can be dissipated in the device is dependent on ambient temperature and
heatsinking.
Note that R_DS(ON) increases with temperature, so as the device heats, the power dissipation increases. This must
be taken into consideration when sizing the heatsink.
8.3.8.3 Heatsinking
The PowerPAD™ package uses an exposed pad to remove heat from the device. For proper operation, this pad
must be thermally connected to copper on the PCB to dissipate heat. On a multi-layer PCB with a ground plane,
this can be accomplished by adding a number of vias to connect the thermal pad to the ground plane. On PCBs
without internal planes, copper area can be added on either side of the PCB to dissipate heat. If the copper area
is on the opposite side of the PCB from the device, thermal vias are used to transfer the heat between top and
bottom layers.
For details about how to design the PCB, refer to TI application report SLMA002, PowerPAD™ Thermally
Enhanced Package and TI application brief SLMA004, PowerPAD™ Made Easy, available at www.ti.com.
In general, the more copper area that can be provided, the more power can be dissipated. It can be seen that the
heatsink effectiveness increases rapidly to about 20 cm², then levels off somewhat for larger areas.
8.4 Device Functional Modes
8.4.1 STEP/DIR Interface
The STEP/DIR interface provides a simple method for advancing through the indexer table. For each rising edge
on the STEP pin, the indexer travels to the next state in the table. The direction it moves in the table is
determined by the input to the DIR pin. The signals applied to the STEP and DIR pins should not violate the
timing diagram specified in Figure 1.
8.4.2 Microstepping
The microstepping indexer allows for a variety of stepping configurations. The state of the indexer is determined
by the configuration of the three MODE pins (refer to Table 1 for configuration options). The DRV8824 supports
full step up to 1/32 microstepping.
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