DS90UB954-Q1: LOCK and PASS current capability

Hi David,

The current the DS90UB954 drives from the LOCK and PASS pins depends on the I/O voltage. Since the LOCK/PASS can be considered as GPIO’s, they are themselves driven by LVCMOS which can either be 1.8V or 3.3V.

For 1.8V, the output short circuit current would be 25 mA. For 3.3V, the output short circuit current would be 40mA. Since the LOCK and PASS drive the LED directly, you wouldn’t need a MOSFET.

For further reference, check pages 12 and 13 of the datasheet for current information: http://www.ti.com/lit/ds/symlink/ds90ub954-q1.pdf

Check page 31 of the user’s guide for a schematic of the LOCK/PASS LED configuration: http://www.ti.com/lit/ug/snlu223/snlu223.pdf

Best regards,

Liban H.