NXP Semiconductors
UM11192
User Manual for LPCXpresso54S018M Development Board
UM11192
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© NXP B.V. 2019. All rights reserved.
User manual
Rev. 1.0
— 13th February 2019
20 of 34
7.1.3 LPC54S018J4M VDD current measurement
The LPCXpresso54S018M board has an on-board current measurement circuit
consisting of a MAX9634T (U18) current monitor chip and a 12-bit ADC (ADC122S021,
U23) with a 12-bit sample at 50k to 200ksps. The on-board MAX9634T current monitor
measures the voltage across the LPC54S018J4M VDD Vsense resistors; either 2
Ω or 1
Ω if JP4 jumper 3-4 is installed. The MAX9634 multiplies the sense voltage by 25 to
provide a voltage range suitable for the ADC to measure. A 2-input analog mux selects
between the LPC54S018J4M current monitor and the output off a MAX9634T current
monitor chip on an expansion board (with compatible current measurement circuit on-
board). The current measurement circuit is controlled by the Link2 processor and is not
user programmable. Power measurement utilities to use this feature are available in the
MCUXpresso IDE.
Due to input offset voltage variations in the MAX9634, the current measurement circuit is
not recommended for measuring current below 150 uA. See
Fig 6
as a guideline for
measurement error versus measured current.
Fig 6.
Current measurement circuit error
% Error
LPC546xx current (µA)