I have an application where I want many small signal relays driven by an I/O expander chip. In this case, I have selected the Microchip MCP23017 (Datasheet) as an I2C to GPIO expander. I have also selected low-current reed relays with the intent that I drive the relays directly from the I/O pin. (5mA coil current, 24mA I/O current). Normally, with a relay, I would expect to use a clamping diode across the coil to protect the output device - this is standard practice. However, I noticed this bit in the datasheet of the expander, where the absolute maximum clamp current is specified:
With my coil current of 5mA, I'm not close to the maximum rating, which to me, suggests that I'm OK with omitting the normal external clamp diode. However, nowhere else in the datasheet is the clamping current mentioned, which (again, to me) suggests that the internal diodes should not be used during normal operation.
Do I play it safe and put in the external clamping diode, or do I assume that if it's less than the Absolute Maximum Ratings, it's safe?