NXP Semiconductors

UM12262

FRDM-IMX91 Board User Manual

Figure 8. Boot configuration schematic

2.6 PDM interface

The pulse density modulated (PDM) microphone interface of the processor provides PDM/MQS support on the

FRDM-IMX91, and it connects to a 3.5 mm audio jack (P15).

Part identifier

Manufacturing part number Description

P15

PJ_3536X

3.5 mm audio jack for onboard MQS analog input / output

Table 13. Audio jack

2.7 LPDDR4 DRAM memory

The FRDM-IMX91 board features one 512 M × 16 (1 channel ×16 I/O × 1 rank) LPDDR4 SDRAM chip

(NT6AN512M16AV-J1) for a total of 1 GB of RAM memory. The LPDDR4 DRAM memory is connected to the

i.MX 91 DRAM controller.

The ZQ calibration resistors (R209 and R2941) used by the LPDDR4 chip are 240 Ω 1% to LPD4/x_VDDQ and

the ZQ calibration resistor DRAM_ZQ used at i.MX 91 SoC side is 120 Ω 1% to GND.

In the physical layout, the LPDDR4 chip is placed at the top side of the board. The data traces are not

necessarily connected to the LPDDR4 chips in sequential order. Instead, the data traces are connected as best

determined by the layout and other critical traces for the ease of routing.

UM12262

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User manual

Rev. 3.0 — 22 April 2025

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