Why does my motor driver become so hot when powered by the adapter?

[Amynio]

I have a TB6612FNG motor driver module( TB6612FNG,C,8,EL - Toshiba Semiconductor and Storage - PMIC - Motor Drivers, Controllers - Kynix Semiconductor ). I am trying to control one DC motor (toy DC motor) via Arduino. When I try to run this setup using a 9V battery the motor runs as expected (albeit really slow). But when I change the power supply to a 9V DC 1A AC-DC adapter the motor controller IC gets super hot. When I check the current from the adapter to the circuit, it shows 1.5A, and the voltage across the supply is 4.5 V. The motor runs for a second or two, then it stops. I guess it is because the supplied voltage dropped below the Arduinos operating voltage.So, my questions are:Why does the IC become hot when powered by the adapter? (I guess I burnt one chip already. Shouldn't there be a thermal shutdown?)Why does the voltage drop? I guess probably because the adapter is unregulated, but I am not sure. Do I need to get a different adapter? If yes, what should be the specs? (When I bought this adapter, I did not know about regulated vs. unregulated. The Arduino website suggested 9V 1A, so I got that.)How can I avoid overheating of the IC when running with an adapter?FYI: I am a hobbyist and a newbie in electronics. Please feel free to suggest alternatives and point out the mistakes. I need to control 4 DC motors.Thanks

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[CNCMAN172]

Mostly likely because you are providing voltage higher than the driver board was designed for and there is no thermal heat sink to dissipate the heat. Read the specs on the driver board, the motors can typically handle over voltage but the driver board needs to be at or below what it is rated at or it will get far too hot and burn out.

[Jim Dawson]

Given that it works fine on a 9V battery, could the polarity on the AC adapter be reversed? Also is the output of the AC adapter DC or AC? I have some that are 9V AC output, you might want to double check.