DRV8320 Datasheet, PDF (62/80 Pages) Texas Instruments – 6 to 60-V Three-Phase Smart Gate Driver

DRV8320, DRV8320R
DRV8323, DRV8323R
SLVSDJ3 – FEBRUARY 2017
www.ti.com
Select a value for I_DRIVEP that is between 47 mA and 140 mA. For this example, the value of I_DRIVEP was selected
as 120-mA source.
Use Equation 15 and Equation 16 to calculate the value of I_DRIVEN1 and I_DRIVEN2 (respectively) for a gate to drain
charge of 14 nC and a fall time from 50 to 150 ns.
I_DRIVEN1
14 nC
50 ns
280 mA
(15)
I_DRIVEN2
14 nC
150 ns
93 mA
(16)
Select a value for I_DRIVEN that is between 93 mA and 280 mA. For this example, the value of I_DRIVEN was selected
as 240-mA sink.
9.2.1.2.3 V_DS Overcurrent Monitor Configuration
The V_DS monitors are configured based on the worst-case motor current and the R_DS(on) of the external
MOSFETs as shown in Equation 17.
V_{DS _ OCP} ! I_max u R_DS(on)max
(17)
9.2.1.2.3.1 Example
The goal of this example is to set the V_DS monitor to trip at a current greater than 100 A. According to
CSD18536KCS 60 V N-Channel NexFET™ Power MOSFET datasheet, the R_DS(on) value is 1.8 times higher at
175°C, and the maximum R_DS(on) value at a V_GS of 10 V is 1.6 mΩ. From these values, the approximate worst-
case value of R_DS(on) is 1.8 × 1.6 mΩ = 2.88 mΩ.
Using Equation 17 with a value of 2.88 mΩ for R_DS(on) and a worst-case motor current of 100 A, Equation 18
shows the calculated the value of the V_DS monitors.
V_{DS _ OCP} ! 100 A u 2.88 m:
V_{DS _ OCP} ! 0.288 V
(18)
For this example, the value of V_{DS_OCP} was selected as 0.31 V.
The SPI devices allow for adjustment of the deglitch time for the V_DS overcurrent monitor. The deglitch time can
be set to 2 µs, 4 µs, 6 µs, or 8 µs.
9.2.1.2.4 Sense-Amplifier Bidirectional Configuration (DRV8323 and DRV8323R)
The sense amplifier gain on the DRV8323, DRV8323R devices and sense resistor value are selected based on
the target current range, VREF voltage supply, sense-resistor power rating, and operating temperature range. In
bidirectional operation of the sense amplifier, the dynamic range at the output is approximately calculated as
shown in Equation 19.
V_O
V_VREF 0.25 V
V_VREF
2
(19)
Use Equation 20 to calculate the approximate value of the selected sense resistor with V_O calculated using
Equation 19.
R ^VO
A_V u I
P_SENSE ! I_RMS2 u R
(20)
From Equation 19 and Equation 20, select a target gain setting based on the power rating of the target sense
resistor.
9.2.1.2.4.1 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 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 0.25 V
3.3 V _{1.4 V}
2
(21)
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