The Truth about Amps Rating in Motor Controller Chips and Systems
by no author specified, Roboteq, Vendor website, Sep 09 2012
Focus:
Vendors of motor control ICs and motor control systems typically specify a current or amps
rating for their products. This rating is generally viewed as the most important parameter
in product selection. However, when vendors determine the amps ratings of their products,
they do so using widely varying test conditions. This practice is intended to make the
products look good, yet makes it difficult for customers to compare products from different
vendors. This article explains why customers should use the on-resistance of the output
stage and its power dissipation (instead of amps) as the main parameters for comparing
motor control ICs and systems. This article explains where and how to obtain the on-
resistance value and then how calculate the power dissipation of different motor control
products at a given current level. It also describes how to determine the maximum allowable
power dissipation for a product, taking into account factors such as ambient temperature
and heatsink thermal resistance. Then, based on maximum allowable power dissipation and
total in-resistance, a true amps rating can be calculated for a product. The article also
discusses the distinctions between motor amps and battery amps and gives some rules of
thumb for the level of heatsinking required at different power levels.
What you’ll learn:
- How to understand why on-resistance and power dissipation are better selection criteria than amps ratings when evaluating motor control ICs and systems
- How to determine the power dissipation of motor control ICs and systems at a given current rating
Notes:
No publication date specified. This white paper was entered in the How2Power Design Guide on
09-09-2012.
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