IDX 7505 Manual (V1.17 / 2011-APR-11)
14
Copyright © 2011, TRINAMIC Motion Control GmbH & Co. KG
5.1
Practical maximum motor current ratings
The IDX 7505 uses eight high power 80V transistors with low internal on resistance of only 15mOhm
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 becomes a limiting point, 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 5.2.1: 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.
