ZHCSP68C December 2021 – October 2022 DRV8328
PRODUCTION DATA
VDSLVL is an analog voltage used to directly set the VDS overcurrent threshold for overcurrent protection. It can be sourced directly from an analog voltage source (such as a digital-to-analog converter) or divided down from a voltage rail (such as a resistor divider from AVDD) as shown in Figure 9-7.
Equation 9 and Equation 10 can be used to set the required VDSLVL voltage using a resistor divider from a voltage source to establish an overcurrent limit given the RDS,on of the MOSFETs used:
where:
VVDSLVL = VDSLVL voltage
IOCP = VDS overcurrent limit
RDS,on = MOSFET on-resistance
VIN = voltage source for VDSLVL voltage divider
R1/R2 = resistor ratio for setting VDSLVL
For example, if a resistor divider from AVDD is used to set an overcurrent trip threshold of 30-A and the MOSFET RDS(ON) = 10mΩ, then VDSLVL = 0.3V.
In some applications, there will be a difference between battery voltage (VBAT) to directly drive motor power and PVDD voltage to power the DRV8328. Because high-side VDS monitoring is referenced from PVDD-SHx, VDSLVL needs to be selected appropriately to accommodate for the difference in VBAT and PVDD.
Equation 11 helps select an appropriate VDSLVL if there is a difference between PVDD and VDSLVL:
For instance, if VBAT = 24.0 V, PVDD = 23.3 V, Rdson = 10-mΩ, and I_OC = 30-A, then VDSLVL should equal 1.0V to detect a 30-A overcurrent event across the high-side FET and a 100-A overcurrent event across the low-side FET.