DRV8320_17 Datasheet, PDF (67/89 Pages) Texas Instruments – 6 to 60-V Three-Phase Smart Gate Driver

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9.2.2.1 Design Requirements
Table 22 lists the example design input parameters for system design.
DRV8320, DRV8320R
DRV8323, DRV8323R
SLVSDJ3A – FEBRUARY 2017 – REVISED APRIL 2017
EXAMPLE DESIGN PARAMETER
ADC reference voltage
Sensed current
Motor RMS current
Sense-resistor power rating
System ambient temperature
Table 22. Design Parameters
REFERENCE
V_VREF
I_SENSE
I_RMS
P_SENSE
T_A
EXAMPLE VALUE
3.3 V
0 to 40 A
28.3 A
3W
–20°C to +105°C
9.2.2.2 Detailed Design Procedure
9.2.2.2.1 Sense Amplifier Unidirectional Configuration
The sense amplifiers are configured to be unidirectional through the registers on SPI devices by writing a 0 to the
VREF_DIV bit.
The sense-amplifier gain and sense resistor values are selected based on the target current range, VREF,
sense-resistor power rating, and operating temperature range. In unidirectional operation of the sense amplifier,
use Equation 24 to calculate the approximate value of the dynamic range at the output.
V_O V_VREF 0.25 V 0.25 V V_VREF 0.5 V
(24)
Use Equation 25 to calculate the approximate value of the selected sense resistor.
R ^VO
A_V u I
P_SENSE ! I_RMS2 u R
where
• ^VO ^VVREF ^{0.5 V}
(25)
From Equation 24 and Equation 25, select a target gain setting based on the power rating of a target sense
resistor.
9.2.2.2.1.1 Example
In this system example, the value of VREF is 3.3 V with a sense current from 0 to 40 A. The linear range of the
SOx output for the DRV8323x device is 0.25 V to V_VREF – 0.25 V (from the V_LINEAR specification). The differential
range of the sense-amplifier input is –0.3 to +0.3 V (V_DIFF).
V_O 3.3 V 0.5 V 2.8 V
(26)
R
2.8 V
3 W ! 28.3² u R o R 3.75 m:
A_V u 40 A
(27)
3.75
m:
!
2.8 V
A_V u 40
A
o
A_V
! 18.7
(28)
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 3.75 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 < 3.75 mΩ and I_max =
40 A does not violate the differential range specification of the sense amplifier input (V_SPxD).
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