Excessive current draw when using battery for internal RTC

We are measuring excessive current draw on the Colibri’s VSS RTC rail when using the Colibri’s Internal RTC option upon power removal. We are using a CR1216 coin cell battery.

When 3.3V is removed from the Colibri, we measure levels of ~70uA, and over the span of a couple minutes the steady state draw is about 50uA. This would make coin cell battery replacement a regular occurrence.

IC manufacturers that offer solutions for RTC applications, including the external option recommended for the Aster, document current draws that are lower by a couple orders of magnitude.

Is there is a register setting that will allow significant reductions in current draw, or is there something else we should consider? Thank you.

The 50 uA internal RTC power consumption is a typical value. Please check Table 8-3 Typical Power Consumption of Colibri iMX6 datasheet. It’s defined by iMX6DL SOC and can not be improved.

From the chapter 5.10.1 Real-Time Clock (RTC) recommendation of the datasheet:

"The RTC on the module is not designed for ultra-low power consumption (typical current
consumption can be found in section 8.2). Therefore, a standard lithium coin cell battery can be
drain faster than required for certain designs. If a rechargeable RTC battery is not a solution, it is
recommended to use an external ultra-low power RTC IC on the carrier board instead. In this case,
add the external RTC to the I2C1 interface of the module and source the VCC_BACKUP pin from
the 3.3V rail that sources also the main module rail. A suitable reference schematic can be found
in the schematic diagram of the Colibri evaluation board
. "