Chapter 5
Board power
The MIMXRT685-EVK re5 V input to power the on-board voltage low dropout linear regulators, of which there are 3.
Link2 Debug probe has a 2.5 V regulator (U14) which draws power from USB connector J5 (LINK USB) only. The debug probe
is unpowered if J5 is unconnected.
There are two other regulators, both providing the option of 3.3 V, one (U25) for Arduino Interface (
DCDC_3V3
), Accelerometer
sensor (
VDD_ACCEL
) and USART (
VDD_LDO_3V3
) the other for SD Card supply (U23); these regulators can be powered by any of
the following (+5V) sources:
• USB Debug Link connector (J5)
• USB Ex5V only connector (J6)
• USB High Speed connector (J7)
The +5 V sources above are connected via protection diodes to prevent reverse powering of any of them by another source. Note
that if J7 is configured as USB host port then that connector will not supply power to the board and another source must be
provided.
For further details on the power sequence needed by the RT600, please refer to Power Sequencing in the device data sheet.
5.1 Measuring MIMXRT685-EVK device supply current
Current supply to the RT685 Core can be measured via JP29 (
VDDCORE
). The voltage supplied can be measured on TP19 (
SW1_OUT
output voltage from PMIC).
GPIO current supplies can be measured via JP20 (
VDDIO_0
), JP23 (
VDDIO_1
) and JP27 (
VDDIO_2
).
Other headers to measure power are JP24 (
VDDA_BIAS
), JP25 (
VDDA_ADC1V8
), JP26 (
VDDA_AO
) and JP28 (
VDD1V8
).
For further details refer to boards schematics.
5.2 PMIC (PCA9420)
The MIMXRT685-EVK has a Power Management Integrated Circuit. Using the PMIC adds flexibility to configure the power supply
rails according to the needs of the application. PMIC has four output voltages,
SW1_OUT
,
SW2_OUT
,
LDO1_OUT
, and
LDO1_OUT
.
Table 3. PMIC Output voltages
PMIC output voltage
RT00 input voltage
Output voltage ranges
Default value
SW1_OUT
VDDCORE
0.5 - 1.5 V
1.0 V
SW2_OUT
VDDIO_0
VDD1V8
VDDA_ADC1V8
VDDIO_1
(JP12, 1-2)
1.5 - 2.1 V/2.7 - 3.3 V
1.8 V
LDO1_OUT
VDD_A0
1.7 - 1.9 V
1.8 V
LDO2_OUT
VDDIO_2
VDDIO_1
(JP12, 2-3)
1.5 - 2.1 V/2.7 - 3.3 V
3.3 V
PMIC is configured via I
2
C and external pins.
NXP Semiconductors
i.MX RT685 Evaluation Board, Rev. 0, March 20 2020
User's Guide
17 / 31