GS-C200 datasheet(25/31 Pages) STMICROELECTRONICS

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Let’s assume the following values are needed:

Irest = 0.25A

Iramp = 1.5A

Islew = 0.5A

The logic condition of the RAMP and MOV outputs

in the various states is:

During the ramping phase both pins 22 and

23 are high: Tr1 is ON and Tr2 is OFF.

During the slew phase pin 23 is low and pin

22 is high: Tr1 and Tr2 are OFF.

In stall condition Tr1 is OFF and Tr2 is ON.

The value of R1, R2, R3 is determined as follows

(for further details please see the GS-D200/200S

data sheet). The value of R3, that fixes the Islew =

= 0.5A (Tr1 and Tr2 OFF), is easily calculated by

referring to the GS-D data sheet:

Islew

− 0.933

⋅ Islew

= 937 Ω

The value of the R2 resistor, when paralleled to R3,

fixes the value of Irest = 0.25A (Tr1 OFF, Tr2 ON).

R2 //

Irest

− 0.933

⋅ I

rest

R2 // R3 = 326

Ω

R2 = 500

Ω

The value of R1, that depends on the value of R3

and the resistors contained in the GS-D200/200S

module, fixes Iramp = 1.5A (Tr1 ON, Tr2 OFF).

The values of the internal resistors are:

1.2k

Ω to ground and 10kΩ to VSS for the

GS-D200

750

Ω to ground and 10kΩ to VSS for the

GS-D200S

Assuming the GS-D200S is used, after some

straightforward calculations, it results:

R1 = 4245

Ω

of course all these values do not take into account the

transistors saturation losses and in some cases, when

a very precise current is needed, a trimming is required.

GALVANIC ISOLATION

The industrial environment, where normally a step-

per motor and its driving system operate, is very

noisy and for this reason it is often advisable to have

a galvanic isolation between the Host computer and

the motion system. Because the connection bet-

ween the Host and the GS-C module requires only

three wires (TxD, RxD and ground), the galvanic

isolation can be implemented as per fig. 12 that

uses only two optocouplers and two resistors, one

protection diode and a +12 or +15V source.

A +12 or +15V source is normally available on the

pin 6 and 8 of any RS232 connector. The source

impedance is quite high (in the range of 220 to

600

Ω) and for this reason the value of R2 must be

greater than 1000

Ω to avoid the source overload.

Figure 12. GS-C200 to Host galvanic isolation.

GS-C200 / GS-C200S

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