DRV8870_16 Datasheet, PDF (11/25 Pages) Texas Instruments – Brushed DC Motor Driver

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8 Application and Implementation
DRV8870
SLVSCY8A – AUGUST 2015 – REVISED JANUARY 2016
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The DRV8870 is typically used to drive one brushed DC motor.
8.2 Typical Application
3.3 V
Controller
3.3 V
GND
OUT2
IN2
ISEN
DRV8870
IN1
OUT1
VREF
VM
PPAD
0.2 Ÿ
BDC
0.1 µF
47 µF
+ 6.5 to 45 V
± ^{Power Supply}
Figure 7. Typical Connections
8.2.1 Design Requirements
Table 3 lists the design parameters.
Table 3. Design Parameters
DESIGN PARAMETER
Motor voltage
Motor RMS current
Motor startup current
Motor current trip point
VREF voltage
Sense resistance
PWM frequency
REFERENCE
V_M
I_RMS
I_START
I_TRIP
VREF
R_ISEN
f_PWM
8.2.2 Detailed Design Procedure
EXAMPLE VALUE
24 V
0.8 A
2A
2.2 A
3.3 V
0.15 Ω
5 kHz
8.2.2.1 Motor Voltage
The motor voltage to use will depend on the ratings of the motor selected and the desired RPM. A higher voltage
spins a brushed DC motor faster with the same PWM duty cycle applied to the power FETs. A higher voltage
also increases the rate of current change through the inductive motor windings.
8.2.2.2 Drive Current
The current path is through the high-side sourcing DMOS power driver, motor winding, and low-side sinking
DMOS power driver. Power dissipation losses in one source and sink DMOS power driver are shown in the
following equation.
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