TMC236/A DATA SHEET (V2.06 / 2009-Jul-30)

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Copyright © 2004, TRINAMIC Motion Control GmbH & Co KG

Open load detection

Open load is signaled, whenever there are more than 14 oscillator cycles without PWM switch off. Note

that open load detection is not possible while coil current is set to “0000”, because the chopper is off in

this condition. The open load flag will then always be read as inactive (“0”). During overcurrent and

undervoltage or over temperature conditions, the open load flags also become active!

Due to their principle, 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).

Standby and shutdown mode

The circuit can be put into a low power standby mode by the user, or, automatically goes to standby on

Vcc undervoltage conditions. Before entering standby mode, the TMC236 switches off all power driver

outputs. In standby mode the oscillator becomes disabled and the oscillator pin is held at a low state.

The standby mode is available via the interface in SPI-mode and via the ENN pin in non-SPI mode.

The shutdown mode even reduces supply current further. It can only be entered in SPI-mode by pulling

the ENN pin high. In shutdown additionally all internal reference voltages become switched off and the

SPI circuit is held in reset.

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: Even a slight reduction of the coil currents to 70% of the current

of the last step of the movement, halves power consumption! In typical applications a 50% current

reduction during stand still is reasonable.