IDX Manual (V1.15 / September 26
th
, 2008)
9
Copyright © 2005-2008, TRINAMIC Motion Control GmbH & Co. KG
4.1
Practical maximum motor current ratings
The IDX 7505 (IDX) uses eight high power 80V (60V) transistors with low internal on resistance of
only 15mOhm (24mOhm) to drive the motor. Due to this, power loss is just a few watts at maximum
current. In order to avoid EMV problems and to keep electromagnetic emission low, the transistors
are switched smoothly on and off with 300ns transitions. On the other hand, this produces dynamic
losses and thus additional power dissipation. The resulting power dissipation has to be cooled away
by air convection and via the metal base plate, in order to keep transistor and board temperature well
below 125°C (Integrated thermal limit). This especially becomes a limiting point for the IDX7505,
because of its high voltage capability. The following table gives some examples for the current
capability in a typical mounting situation, where the module is mounted to a metal base plate (heat
sink with fins, overall dimensions 100*50*15mm³). In this situation the base plate was always kept at
maximum 60°C. However, the actual motor type and velocity setting also influences power dissipation
of the module.
Chopper
mode
Supply
voltage
Maximum
I
COIL
RMS
for continuous operation
Maximum duty
cycle for full
current
0, 1
75V
3.5A
50%
0, 1
70V
4A
60%
0, 1
60V
4.5A
80%
0, 1
≤50V
5A
100%
2
15V … 75V
4A *)
n/a
Table 4.2.1: Practical motor current limitations for IDX 7505
*) This limit is due to the higher current ripple in chopper mode 2, which allows a maximum of 75%
to 90% of the maximum current setting. It is not a thermal limit.
