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Chapter 4 Handshaking between
SMARC T335x Module and Carrier
SMARC module has specific handshaking rules to the carrier by SMARC
hardware specification. To design the carrier board, users need to follow these
rules or it might not boot up. Some pull-up and pull-down also need to be cared
to make all functions work.
4.1 SMARC T335x Module Power
4.1.1. Input Voltage / Main Power Rail
The allowable Module DC input voltage range for T335x is from 3.35V to
5.25V. This voltage is brought in on the VDD_IN pins and returned through
the numerous GND pins on the connector. The SMARC specification defines
the input voltage range should extend down to 3.0V. The SMARC T335X
lower limit is determined by a non-volatile register setting in the TI PMIC
used and is set 3.35V by default. A single 5V DC input is recommended.
Ten pins are allocated to VDD_IN. The connector pin current rating is 0.5A
per pin. This works out to 5A total for the 10 pins. At the lowest allowed
Module input voltage, this would allow up to 16.75W of electrical power to be
brought in (with no de-rating on the connector current capability). With a
40% connector current de-rating, up to 10W may be brought in at 3.35V.
T335x typically consumes 1.5W and is pretty safe in using the connector.
4.1.2. No Separate Standby Voltage
There is no separate voltage rail for standby power, other than the very low
current RTC voltage rail. SMARC T335x operating and standby power
comes from the single set of VDD_IN pins. This suits battery power sources
well, and is also easy to use with non-battery sources.
SMARC T335x Computer on Module User's Manual v.1.2
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