TMC260 and TMC261 DATASHEET (Rev. 2.05 / 2012-NOV-05)
37
10 Power MOSFET Stage
The gate current for the power MOSFETs can be adapted to influence the slew rate at the coil outputs.
The main features of the stage are:
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5V gate drive voltage for low-side N-MOS transistors, 8V for high-side P-MOS transistors.
The gate drivers protect the bridges actively against cross-conduction using an internal QGD
protection that holds the MOSFETs safely off.
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Automatic break-before-make logic minimizes dead time and diode-conduction time.
Integrated short to ground protection detects a short of the motor wires and protects the
MOSFETs.
The low-side gate driver is supplied by the 5VOUT pin. The low-side driver supplies 0V to the MOSFET
gate to close the MOSFET, and 5VOUT to open it. The high-side gate driver voltage is supplied by the
VS and the VHS pin. VHS is more negative than VS and allows opening the VS referenced high-side
MOSFET. The high-side driver supplies VS to the P channel MOSFET gate to close the MOSFET and VHS
to open it. The effective low-side gate voltage is roughly 5V; the effective high-side gate voltage is
roughly 8V.
Parameter
Description
Setting
Comment
SLPL
Low-side slope control. Controls the MOSFET gate 0… 3
driver current.
Set to 0, 1 or 2. Slopes are fast to minimize
package power dissipation.
High-side slope control. Controls the MOSFET 0… 3
gate driver current.
For the TMC260 set identical to SLPL to match LS
%00: Minimum.
%01: Minimum.
%10: Medium.
%11: Maximum.
%00: Minimum.
%01: Minimum+TC.
%10: Medium+TC.
%11: Maximum.
SLPH
slope.
For the TMC261 set to 0 or 1 for medium slope.
Set to 2 to match low-side slope with SLPL=0 or
1. Set to 3 with SLPL=2.
10.1 Break-Before-Make Logic
Each half-bridge has to be protected against cross-conduction during switching events. When
switching off the low-side MOSFET, its gate first needs to be discharged before the high-side MOSFET
is allowed to switch on. The same goes when switching off the high-side MOSFET and switching on
the low-side MOSFET. The time for charging and discharging of the MOSFET gates depends on the
MOSFET gate charge and the gate driver current set by SLPL and SLPH. The BBM (break-before-make)
logic measures the gate voltage and automatically delays turning on the opposite bridge transistor
until its counterpart is discharged. This way, the bridge will always switch with optimized timing
independent of the slope setting.
10.2 ENN Input
The MOSFETs can be completely disabled in hardware by pulling the ENN input high. This allows the
motor to free-wheel. An equivalent function can be performed in software by setting the parameter
TOFF to zero. The hardware disable is available for allowing the motor to be hot plugged. For the
TMC260, it can be used in overvoltage situations. The TMC260 can withstand voltages of up to 60V
when the MOSFETs are disabled. If a hardware disable function is not needed, tie ENN low.
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