TMC248-LA DATASHEET (Rev. 1.01 / 2013-MAR-26)
13
4.4 Controlling Power Down via the SPI Interface
Bit
11
10
9
8
7
6
5
4
3
2
1
0
Standard
function
Control
word
MxA CA3 CA2 CA1 CA0 PhA MxB CB3 CB2 CB1 CB0 PhB
-
0
0
0
0
-
-
0
0
0
0
-
function
Enable standby mode and clear
error flags
Programming current value 0000 for both coils at a time clears the overcurrent flags and switches the
TMC248 into a low current standby mode with coils switched off.
4.5 Open Load Detection
Open load is signaled if there are more than 14 oscillator cycles without PWM switch off.
During overcurrent, undervoltage, or overtemperature conditions, the open load flags become active.
Open load detection is not possible while the coil current is set to 0000. In this condition the chopper
is off and the open load flag is read as inactive (0).
The open load flags not only signal an open load condition, but also a torque loss of the motor,
especially at high motor velocities. To detect only an interruption of the connection to the motor, it is
advised to evaluate the flags during stand still or during low velocities only (e.g. for the first or last
steps of a movement).
4.6 Standby and Shutdown Mode
The TMC248 offers two possibilities for reducing power consumption under special conditions: the
standby mode and the shutdown mode.
STANDBY MODE
-
-
-
The circuit can be put into a low power standby mode by the user.
The circuit automatically goes to standby on Vcc undervoltage conditions.
The standby mode is available via the interface in SPI-mode and via the ENN pin in non-SPI
mode.
Before entering standby mode, the TMC248 switches off all power transistors and holds their gates
in a disable condition using high ohmic resistors. In standby mode the oscillator becomes
disabled and the oscillator pin is held at a low state.
SHUTDOWN MODE
-
-
-
The shutdown mode is used for a further reduction of the supply current.
The shutdown mode can be entered in SPI-mode by pulling the ENN pin high.
In shutdown mode additionally all internal reference voltages become switched off and the
SPI circuit is held in reset.
4.7 Power Saving
The possibility to control the output current can dramatically save energy, reduce heat generation and
increase precision by reducing thermal stress on the motor and attached mechanical components. Just
reduce motor current during stand still: A slight reduction of the coil currents to 70% of the current of
the last step halves power consumption!
In typical applications a 50% current reduction during stand still is reasonable.
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TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
