DRV8432_15 Datasheet, PDF (18/42 Pages) Texas Instruments – DRV84x2 Dual Full-Bridge PWM Motor Driver

DRV8412, DRV8432
SLES242G – DECEMBER 2009 – REVISED DECEMBER 2014
8.2.1.1 Design Requirements
This section describes design considerations.
DESIGN PARAMETER
Motor voltage
Motor current (peak and RMS)
Overcurrent threshold
Bridge mode
Table 3. Design Parameters
REFERENCE
PVDD_x
I_PVDD
OC_TH
M1M2
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EXAMPLE VALUE
24 V
6-A peak, 3A RMS
OC_ADJ = 27 kΩ, 9.7 A
Parallel full bridge
8.2.1.2 Detailed Design Procedure
8.2.1.2.1 Motor Voltage
Higher voltages generally have the advantage of causing current to change faster through the inductive windings,
which allows for higher RPMs. Lower voltages allow for more accurate control of phase currents.
8.2.1.2.2 Current Requirement of 12-V Power Supply
The DRV83x2 requires a 12-V power supply for GVDD and VDD pins. The total supply current is relatively low at
room temperature (less than 50 mA), but the current could increase significantly when the device temperature
goes too high (for example, above 125°C), especially at heavy load conditions due to substrate current collection
by 12-V guard rings. TI recommends designing the 12-V power supply with a current capability at least 5-10% of
the load current, and no less than 100 mA to assure the device performance across all temperature ranges.
8.2.1.2.3 Voltage of Decoupling Capacitor
The voltage of the decoupling capacitors should be selected in accordance with good design practices.
Temperature, ripple current, and voltage overshoot must be considered. The high frequency decoupling capacitor
should use ceramic capacitor with X5R or better rating. For a 50-V application, a minimum voltage rating of 63 V
is recommended.
8.2.1.2.4 Overcurrent Threshold
When choosing the resistor value for OC_ADJ, consider the peak current allowed under normal system behavior,
the resistor tolerance, and that the Table 2 currents have a ±10% tolerance. For example, if 6 A is the highest
system current allowed across all normal behavior, a 27-kΩ OC_ADJ resistor with 10% tolerance is a reasonable
choice, as it would set the OC_TH to approximately 8 A to 12 A.
8.2.1.2.5 Sense Resistor
For optimal performance, the sense resistor must be:
• Surface-mount
• Low inductance
• Rated for high enough power
• Placed closely to the motor driver
The power dissipated by the sense resistor equals I_RMS2 x R. For example, if peak motor current is 3 A, RMS
motor current is 2 A, and a 0.05-Ω sense resistor is used, the resistor will dissipate 2 A² × 0.05 Ω = 0.2 W. The
power increases quickly with higher current levels.
Resistors typically have a rated power within some ambient temperature range, along with a de-rated power
curve for high ambient temperatures. When a PCB is shared with other components generating heat, margin
should be added. Always measure the actual sense resistor temperature in a final system, along with the power
MOSFETs, as those are often the hottest components.
Because power resistors are larger and more expensive than standard resistors, use multiple standard resistors
in parallel, between the sense node and ground. This distributes the current and heat dissipation.
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