PIMXRT406LCAF4A datasheet(12/71 Pages) NXP

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i.MX RT1015 Crossover Processors Data Sheet for Consumer Products, Rev. 2, 03/2021

NXP Semiconductors

Modules list

3.1

Special signal considerations

Table 3 lists special signal considerations for the i.MX RT1015 processors. The signal names are listed in

alphabetical order.

The package contact assignments can be found in Section 6, Package information and contact

assignments. Signal descriptions are provided in the i.MX RT1015 Reference Manual (IMXRT1015RM).

Table 3. Special signal considerations

Signal name

Remarks

DCDC_PSWITCH

PAD is in DCDC_IN domain and connected the ground to bypass DCDC.

To enable DCDC function, assert to DCDC_IN with at least 1ms delay for DCDC_IN rising edge.

RTC_XTALI/RTC_XTALO If the user wishes to configure RTC_XTALI and RTC_XTALO as an RTC oscillator, a 32.768 kHz

crystal, (

100 k ESR, 10 pF load) should be connected between RTC_XTALI and RTC_XTALO.

Keep in mind the capacitors implemented on either side of the crystal are about twice the crystal

load capacitor. To hit the exact oscillation frequency, the board capacitors need to be reduced to

account for board and chip parasitics. The integrated oscillation amplifier is self biasing, but

relatively weak. Care must be taken to limit parasitic leakage from RTC_XTALI and RTC_XTALO

to either power or ground (>100 M

). This will debias the amplifier and cause a reduction of

startup margin. Typically RTC_XTALI and RTC_XTALO should bias to approximately 0.5 V.

If it is desired to feed an external low frequency clock into RTC_XTALI the RTC_XTALO pin must

remain unconnected or driven with a complimentary signal. The logic level of this forcing clock

should not exceed VDD_SNVS_CAP level and the frequency should be <100 kHz under typical

conditions.

In case when high accuracy real time clock are not required system may use internal low

frequency ring oscillator. It is recommended to connect RTC_XTALI to GND and keep

RTC_XTALO unconnected.

XTALI/XTALO

A 24.0 MHz crystal should be connected between XTALI and XTALO. External load capacitance

value depends on the typical load capacitance of crystal used and PCB design.

The crystal must be rated for a maximum drive level of 250

W. An ESR (equivalent series

resistance) of typical 80

 is recommended. NXP SDK software requires 24 MHz on

XTALI/XTALO.

The crystal can be eliminated if an external 24 MHz oscillator is available in the system. In this

case, XTALO must be directly driven by the external oscillator and XTALI mounted with 18 pF

capacitor. The logic level of this forcing clock cannot exceed NVCC_PLL level.

If this clock is used as a reference for USB, then there are strict frequency tolerance and jitter

requirements. See OSC24M chapter and relevant interface specifications chapters for details.

GPANAIO

This signal is reserved for NXP manufacturing use only. This output must remain unconnected.

JTAG_nnnn

The JTAG interface is summarized in Table 4. Use of external resistors is unnecessary. However,

if external resistors are used, the user must ensure that the on-chip pull-up/down configuration is

followed. For example, do not use an external pull down on an input that has on-chip pull-up.

JTAG_TDO is configured with a keeper circuit such that the non-connected condition is eliminated

if an external pull resistor is not present. An external pull resistor on JTAG_TDO is detrimental and

should be avoided.

JTAG_MOD is referenced as SJC_MOD in the i.MX RT1015 reference manual. Both names refer

to the same signal. JTAG_MOD must be externally connected to GND for normal operation.

Termination to GND through an external pull-down resistor (such as 1 k

) is allowed. JTAG_MOD

set to hi configures the JTAG interface to mode compliant with IEEE1149.1 standard. JTAG_MOD

set to low configures the JTAG interface for common SW debug adding all the system TAPs to the

chain.

These signals are No Connect (NC) and should be disconnected by the user.

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