User notes

SPMD250STP

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9.5

Module protections

The SPMD250STP outputs are protected against short circuits to Gnd, Vs and to another

output. When the current exceeds the maximum value, the output is automatically disabled.

The module protection is of the latching type, i.e. when an overload condition is detected the

unit outputs are disabled. To restart the operations it is necessary to disable the unit

(pin 11 = Low) or to switch off the supply voltage for at least 100 ms.

9.6

Motor connection

The motor is normally quite far from the module and long cables are needed for connection.

The use of a twisted pair cable with appropriate cross section for each motor phase is

recommended to minimize DC losses and RFI problems.

9.7

Unused inputs

All the SPMD250STP logic inputs have an internal pull-up, and they are high when

unconnected.

9.8

Phase current programming

The output current is factory set to a standard 2 A value.

The phase current value can be changed by connecting an appropriate resistor between pin

9 and ground or Vss (see Figure 14). In the first case the phase current will decrease, in the

latter it will increase.

The maximum phase current must be limited to 2.5 A, to avoid permanent damage to the

module.

SPMD250STP phase current programming:

Equation 1

Equation 2

I2A

>

Ri

10

0.33 I

⋅

–

0.473 I

1

–

⋅

------------------------------

k

Ω

=

=

Ri

50k

Ω

≥

I2A

<

Rd

I

3.03

1.43

–

I

⋅

-----------------------------------

k

Ω

=

=