Part Number: DRV2700
Good afternoon,
We've designed a board that uses the DRV2700 driver to drive a 1.5uF piezo actuator that positions a mirror. Its input is a 0-12V DC signal (mcoil-) that makes small (<1V) corrections up to 50k times per second. It is working quite nicely, though limited to 105V at the output in this configuration, but the output noise is canceled out in differential mode, so a big improvement over the flyback version.
However, we've had 3 of these drivers blow up. Suddenly the HV output drops low, as does the voltage present on the SW node. In circuit, I measure ~1.08k ohms between pins 8 (SW) and 11 (VBST). On a working driver, I measure ~800k ohms between these two nodes. One time the driver blew up when power was cycled, another time the driver blew up when the input signal (mcoil-) changed suddenly by a volt or two. After blowing up, the driver board draws excessive current (enough to burn up a zero ohm 0603 resistor in the 5V supply path).
With the bad parts removed from the board, I measure between pins 8 and 11. 50 ohms on one, 1.4k ohms on another. A working driver measures OPEN between these 2 nodes.
I see from the block diagram that there is a diode between pins 8 and 11, and sure enough, my DMM in diode mode measures .615V on a working part, and 0.558V on a bad part. One part (that measured 50 ohms) measures 0.056 across that diode, so nearly a short.
From the datasheet, I don't see ratings that I am exceeding. My schematic is attached below. Do you see any glaring problems with how this is configured? Or some known mode of operation that can lead to permanent damage to this part, and the apparent diode between SW and BST nodes in particular?
Thank you,
Andy
