DRV8302_16 Datasheet, PDF (22/32 Pages) Texas Instruments – Three Phase Gate Driver

DRV8302
SLES267C – AUGUST 2011 – REVISED MARCH 2016
Typical Application (continued)
Example:
Buck: PVDD = 3.5 V – 40 V, Iout_max = 1.5 A, Vo = 3.3 V, Fs = 570 kHz
8.2.1 Design Requirements
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DESIGN PARAMETER
Supply voltage
Motor winding resistance
Motor winding inductance
Motor poles
Motor rated RPM
Target full-scale current
Sense resistor
MOSFET Q_g
MOSFET R_DS(on)
VDS trip level
Switching frequency
Series gate resistance
Amplifier reference
Amplifier gain
8.2.2 Detailed Design Procedure
Table 6. Design Parameters
REFERENCE
PVDD
M_R
M_L
M_P
M_RPM
I_MAX
R_SENSE
Q_g
R_DS(on)
OC_ADJ_SET
ƒ_SW
R_GATE
V_REF
Gain
VALUE
24 V
0.5 Ω
0.28 mH
16 poles
4000 RPM
14 A
0.01 Ω
29 nC
4.7 mΩ
0.123 V
45 kHz
10 Ω
3.3 V
10 V/V
8.2.2.1 Gate Drive Average Current Load
The gate drive supply (GVDD) of the DRV8302 can deliver up to 30 mA (RMS) of current to the external power
MOSFETs. Use Equation 5 to determine the approximate RMS load on the gate drive supply:
Gate Drive RMS Current = MOSFET Qg × Number of Switching MOSFETs × Switching Frequency
(5)
Example:
7.83 mA = 29 nC × 6 × 45 kHz
(6)
This is a rough approximation only.
8.2.2.2 Overcurrent Protection Setup
The DRV8302 provides overcurrent protection for the external power MOSFETs through the use of VDS
monitors for both the high side and low side MOSFETs. These are intended for protecting the MOSFET in
overcurrent conditions and not for precise current regulation.
The overcurrent protection works by monitoring the VDS voltage of the external MOSFET and comparing it
against the OC_ADJ pin voltage. If the VDS exceeds the OC_ADJ pin voltage the DRV8302 takes action
according to the M_OC pin.
Overcurrent Trip = OC_ADJ_SET / MOSFET R_DS(on)
(7)
Example:
26.17 A = 0.123 V/ 4.7 mΩ
(8)
MOSFET R_DS(on) changes with temperature and this will affect the overcurrent trip level.
8.2.2.3 Sense Amplifier Setup
The DRV8302 provides two bidirectional low-side current shunt amplifiers. These can be used to sense a sum of
the three half-bridges, two of the half-bridges individually, or in conjunction with an additional shunt amplifier to
sense all three half-bridges individually.
1. Determine the peak current that the motor will demand (I_MAX). This will be dependent on the motor
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