DRV8834PWPR datasheet(21/45 Pages) TI2

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VCP

AOUT1

AOUT2

BOUT1

BOUT2

NFAULT

VINT

AISEN

BISEN

NENBL/AENBL

STEP/BENBL

DIR/BPHASE

M0/APHASE

CONFIG

VREFO

AVREF

BVREF

ADECAY

NSLEEP

BDECAY

Motor A Enable

Motor B Enable

Motor B Direction

Motor A Direction

LOW = SLEEP

10 uf

0.01 uf

2.2 uf

DRV8834

www.ti.com

SLVSB19D – FEBRUARY 2012 – REVISED MARCH 2015

Typical Application (continued)

Figure 9. Phase/Enable Mode Driving Two DC Motors

9.2.1.1 Design Requirements

Table 5 lists the design parameters.

Table 5. Design Parameters

PARAMETER

REFERENCE

EXAMPLE VALUE

Motor voltage

10 V

Motor RMS current

IRMS

0.8 A

Motor start-up current

ISTART

1 A

Motor current trip point

ITRIP

1.5 A

9.2.1.2 Detailed Design Procedure

9.2.1.2.1

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.

9.2.1.2.2

Power Dissipation

The power dissipation of the DRV8834 is a function of RMS motor current and the FET resistance (RDS(ON)) of

each output.

Power

≈ IRMS

2 × (High-Side R

DS(ON) + Low-Side RDS(ON))

(2)

For this example, the ambient temperature is 35°C, and the junction temperature reaches 65°C. At 65°C, the

sum of RDS(ON) is about 1 Ω. With an example motor current of 0.8 A, the dissipated power in the form of heat will

be 0.8 A2 × 1

Ω = 0.64 W.

The temperature that the DRV8834 reaches will depend on the thermal resistance to the air and PCB. It is

important to solder the device PowerPAD to the PCB ground plane, with vias to the top and bottom board layers,

in order dissipate heat into the PCB and reduce the device temperature. In the example used here, the DRV8834

had an effective thermal resistance RθJA of 47°C/W, and:

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