DRV8353FSRTAR datasheet(78/97 Pages) TI

78 / 97 page

VREF

0.25 V

(21)

Use Equation 22 to calculate the approximate value of the selected sense resistor with VO calculated using

Equation 21.

SENSE

RMS

(22)

From Equation 21 and Equation 22, select a target gain setting based on the power rating of the target sense

resistor.

9.2.1.2.4.1 Sense-Amplifier Example

In this system example, the value of VREF voltage is 3.3 V with a sense current from –40 to +40 A. The linear

range of the SOx output is 0.25 V to VVREF – 0.25 V (from the VLINEAR specification). The differential range of the

sense amplifier input is –0.3 to +0.3 V (VDIFF).

3.3 V

0.25 V

1.4 V

(23)

1.4 V

2 W

28.3

2.5 m

40 A

(24)

1.4 V

2.5 m

40 A

: !

(25)

Therefore, the gain setting must be selected as 20 V/V or 40 V/V and the value of the sense resistor must be

less than 2.5 mΩ to meet the power requirement for the sense resistor. For this example, the gain setting was

selected as 20 V/V. The value of the resistor and worst case current can be verified that R < 2.5 mΩ and Imax =

40 A does not violate the differential range specification of the sense amplifier input (VSPxD).

9.2.1.2.5 Single Supply Power Dissipation

Design care must be taken to make sure that the thermal ratings of the DRV835xF are not violated during

normal operation of the device. The is especially critical in higher voltage and higher ambient operation

applications where power dissipation or the device ambient temperature are increased.

To determine the temperature of the device in single supply operation, first the power internal power dissipation

must be calculated. The internal power dissipation has four primary components:

• VCP charge pump power dissipation (PVCP)

• VGLS low-side regulator power dissipation (PVGLS)

• VM device nominal power dissipation (PVM)

• VIN buck regulator power dissipation (PBUCK)

The values of PVCP and PVGLS can be approximated by referring to Section 9.2.1.2.1 to first determine IVCP and

IVGLS and then referring to Equation 26 and Equation 27.

PVCP = IVCP × (VVM + VVDRAIN)

(26)

PVGLS = IVGLS × VVM

(27)

The value of PVM can be calculated by referring to the data sheet parameter for IVM current and Equation 28.

PVM = IVM × VVM

(28)

PBUCK = (PO / η) - PO

(29)

DRV8350F, DRV8353F, DRV8350RF, DRV8353RF

SLVSFV1 – SEPTEMBER 2020

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