We are using the LMR16010 in a circuit that provides closed-loop current control for a 0.5H, 60-ohm solenoid coil.
In this application, the LMR16010 GND pin is connected to -15V and its VIN is connected to +15V. Signal THP is connected to the GND pin. Signal RT_SYNC is connected to the GND pin through 133 Kohms. The BOOT pin is connected to the SW pin through a 0.15 uF capacitor. The SW pin is connected to (1) an LC filter and (2) a 100V zener diode clamp to the GND pin.
The FB pin is driven by an instrumentation amplifier that can drive between GND (-15V) and the positive supply (+15V). The instrumentation amplifier is connected to the LMR16010 FB pin through a 10.5 Kohm resistor. We have noted that this design configuration can violate the absolute maximum rating of the feedback pin because the LMR16010PDDA is rated for a difference of -0.3V to 7V above the GND pin. In our application, since GND = -15V and FB can swing to 0V, we could potentially exceed the absolute maximum by 8V under certain start-up conditions. As indicated above, we do limit the current into the FB pin through a 10.5 Kohms resistor that would ensure current into FB pin does not exceed 1 mA.
Is the FB pin sensitive to voltage (i.e. must never exceed the 7V) or can the limit be exceeded provided the current is limited? We experienced the failure of about 3 LMR16010 devices out of an initial batch of 10 boards (3 LMR16010 per board) and are reviewing the design to identify root cause.
