STMicroelectronics FlexSPIN: SPI configurable stepper and DC multi motor driver evaluation board EVAL6460 EVAL6460 Fiche De Données
Codes de produits
EVAL6460
L6460
Power bridges
Doc ID 17713 Rev 1
63/139
14.1.4 Switch
configuration
Each bridge can be configured to be used as 2 independent switches that connects the
output to supply or to ground. It is also possible to parallel the two switches and use them as
a single super switch.
output to supply or to ground. It is also possible to parallel the two switches and use them as
a single super switch.
All resulting switches will behave according to the following truth table.
Note:
When “low power mode” bit is active the bridge will reduce its biasing thus contributing to the
whole power saving.
whole power saving.
When a current limit event occurs this event will be latched and the bridge will remain in high
impedance state for the toff time.
impedance state for the toff time.
14.1.5
Bipolar stepper configuration
The bridges 3 and 4 can be configured to be used as a micro-stepping, bidirectional driver
for bipolar stepper motors.
for bipolar stepper motors.
The primary features of the driver are the following:
–
Internal PWM current control.
–
Micro stepping.
–
Fast, mixed and slow current decay modes.
Each H-bridge is controlled with a fixed and selectable off-time PWM current control circuit
that limits the load current to a value set by choosing V
that limits the load current to a value set by choosing V
STEPREF
voltage by means of the
internal DAC and an the external R
SENSE
value.
The max current level could be calculated using the formula:
I
MAX
=V
STEPREF
/R
SENSE
To obtain the best current profile, the user can choose three different current decay modes:
slow, fast and mixed. Initially, during Ton, a diagonal pair of source and sink power MOS is
enabled and current flows through the motor winding and the sense resistor. When the
voltage across the sense resistor reaches the programmed DAC output voltage, the control
logic will change the status of the bridge according to the selected decay mode (slow, fast or
mixed). In slow decay mode the current is recirculated through the path including both high
slow, fast and mixed. Initially, during Ton, a diagonal pair of source and sink power MOS is
enabled and current flows through the motor winding and the sense resistor. When the
voltage across the sense resistor reaches the programmed DAC output voltage, the control
logic will change the status of the bridge according to the selected decay mode (slow, fast or
mixed). In slow decay mode the current is recirculated through the path including both high
Table 20.
Switch truth table
TSD
nReset
Low
power
mode
Enable
Current
limit
MtrXCtrl
SideA/B
PWM
OUT
1
X
X
X
X
X
X
Z
0
0
X
X
X
X
X
Z
0
1
1
X
X
X
X
Z
0
1
0
0
X
X
X
Z
0
1
0
1
0
0
X
Z
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
0
0
1
0
1
1
X
X
Z