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DRV8874

SLVSF66A – AUGUST 2019 – REVISED DECEMBER 2019

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8.2.2.1 Design Requirements

Table 10. Design Parameters

REFERENCE

DESIGN PARAMETER

EXAMPLE VALUE

VM

Motor and driver supply voltage

24 V

VCC

Controller supply voltage

3.3 V

IRMS1

Output 1 RMS current

0.5 A

IPEAK1

Output 1 peak current

1 A

IRMS2

Output 2 RMS current

0.25 A

IPEAK2

Output 2 peak current

0.5 A

fPWM

Switching frequency

20 kHz

AIPROPI

Current sense scaling factor

455 µA/A

RIPROPI

IPROPI external resistor

4.8 kΩ

VADC

Controller ADC reference voltage

3.3 V

TA

PCB ambient temperature

–20 to 85 °C

TJ

Device max junction temperature

150 °C

RθJA

Device junction to ambient thermal resistance

35 °C/W

8.2.2.2 Detailed Design Procedure

Refer to the Primary Application Detailed Design Procedure section for a detailed design procedure example.

The majority of the design concepts apply to the alternative application example. A few changes to the procedure

are outlined below.

8.2.2.2.1

Current Sense and Regulation

In the alternative application for two half-bridge loads, the IPROPI output will be the combination of the two

outputs currents. The current sense feedback resistor RIPROPI should be scaled appropriately to stay within the

dynamic voltage range of the controller ADC. An example of this is shown

RIPROPI <= VADC / ((IPEAK1 + IPEAK2) x AIPROPI)

(23)

RIPROPI = 4.8 kΩ <= 3.3 V / ((1 A + 0.5 A) x 455 µA/A)

(24)

If VADC = 3.3 V, IPEAK1 = 1 A, IPEAK2 = 0.5 A, and AIPROPI = then to maximize the dynamic IPROPI voltage range

an RIPROPI of approximately 4.8 kΩ should be selected.

The accuracy tolerance of RIPROPI can be selected based on the application requirements. 10%, 5%, 1%, 0.1%

are all valid tolerance values. The typical recommendation is 1% for best tradeoff between performance and cost.

In independent half-bridge mode, the internal current regulation of the device is disabled. VREF can be set directly

to the supply reference for the controller ADC.