Datasheet

TMC2209 DATASHEET (Rev. 1.03 / 2019-JUN-26) 66

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Once a short condition is safely detected, the corresponding driver bridge (A or B) becomes switched

off, and the s2ga or s2gb flag, respectively s2vsa or s2vsb becomes set. In order to restart the motor,

disable and re-enable the driver. Note, that short protection cannot protect the system and the power

stages for all possible short events, as a short event is rather undefined and a complex network of

external components may be involved. Therefore, short circuits should basically be avoided.

15.3 Open Load Diagnostics

Interrupted cables are a common cause for systems failing, e.g. when connectors are not firmly

plugged. The TMC2209 detects open load conditions by checking, if it can reach the desired motor coil

current. This way, also undervoltage conditions, high motor velocity settings or short and

overtemperature conditions may cause triggering of the open load flag, and inform the user, that

motor torque may suffer. In motor stand still, open load cannot always be measured, as the coils

might eventually have zero current.

Open load detection is provided for system debugging.

In order to safely detect an interrupted coil connection, read out the open load flags at low or

nominal motor velocity operation, only. If possible, use SpreadCycle for testing, as it provides the

most accurate test. However, the ola and olb flags have just informative character and do not cause

any action of the driver.

15.4 Diagnostic Output

The diagnostic output DIAG and the index output INDEX provide important status information. An

active DIAG output shows that the driver cannot work normally, or that a motor stall is detected,

when StallGuard is enabled. The INDEX output signals the microstep counter zero position, to allow

referencing (homing) a drive to a certain current pattern. The function set of the INDEX output can be

modified by UART. Figure 15.1 shows the available signals and control bits.

INDEX

DIAG

Power-on reset

Toggle upon each step

Charge pump undervoltage (uv_cp)

Short circuit (s2vs, s2g) over temperature (ot)

drv_err

Power stage disable (e.g. pin ENN)

Index pulse

GCONF.index_otpw

GCONF.index_step

MUX

Overtemperature prewarning (otpw)

Overtemperature (ot)

StallDetection

(gated by TPWMTHRS<=TSTEP<=VCOOLTHRS)

Figure 15.1 DIAG and INDEX outputs

UART