The Truth about Amps Rating in Motor Controller Chips and Systems

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.

View the Source

Author & Publication:

no author specified, Roboteq, Vendor website, Sep 09 2012

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