DRV8320 Datasheet, PDF (33/80 Pages) Texas Instruments – 6 to 60-V Three-Phase Smart Gate Driver

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INHx
INLx
Control
Inputs
Digital
Core
VCP
Level
Shifters
VGS
+
±
VGLS
150 k
GHx
SHx
Level
Shifters
VGS
+
±
150 k
GLx
SLx/SPx
PGND
DRV8320, DRV8320R
DRV8323, DRV8323R
SLVSDJ3 – FEBRUARY 2017
VM
Figure 26. Gate Driver Block Diagram
8.3.1.4.1 IDRIVE: MOSFET Slew-Rate Control
The IDRIVE component implements adjustable gate-drive current to control the MOSFET V_DS slew rates. The
MOSFET V_DS slew rates are a critical factor for optimizing radiated emissions, energy and duration of diode
recovery spikes, dV/dt gate turnon leading to shoot-through, and switching voltage transients related to parasitics
in the external half-bridge. IDRIVE operates on the principal that the MOSFET V_DS slew rates are predominately
determined by the rate of gate charge (or gate current) delivered during the MOSFET Q_GD or Miller charging
region. By allowing the gate driver to adjust the gate current, it can effectively control the slew rate of the external
power MOSFETs.
IDRIVE allows the DRV832x family of devices to dynamically switch between gate drive currents either through a
register setting on SPI devices or the IDRIVE pin on hardware interface devices. The SPI devices provide 16
I_DRIVE settings ranging between 10-mA to 1-A source and 20-mA to 2-A sink. Hardware interface devices
provides 7 I_DRIVE settings between the same ranges. The gate drive current setting is delivered to the gate during
the turnon and turnoff of the external power MOSFET for the t_DRIVE duration. After the MOSFET turnon or turnoff,
the gate driver switches to a smaller hold I_HOLD current to improve the gate driver efficiency. Additional details on
the IDRIVE settings are described in the Register Maps section for the SPI devices and in the Pin Diagrams
section for the hardware interface devices.
8.3.1.4.2 TDRIVE: MOSFET Gate Drive Control
The TDRIVE component is an integrated gate-drive state machine that provides automatic dead time insertion
through switching handshaking, parasitic dV/dt gate turnon prevention, and MOSFET gate-fault detection.
The first component of the TDRIVE state machine is automatic dead-time insertion. Dead time is period of time
between the switching of the external high-side and low-side MOSFETs to ensure that they do not cross conduct
and cause shoot-through. The DRV832x family of devices use V_GS voltage monitors to measure the MOSFET
gate-to-source voltage and determine the proper time to switch instead of relying on a fixed time value. This
feature allows the gate-driver dead time to adjust for variation in the system such a temperature drift and
variation in the MOSFET parameters. An additional digital dead time (t_DEAD) can be inserted and is adjustable
through the registers on SPI devices.
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