PCB Design Recommendations for EMMC Module Circuits

EMMC Module Circuit Profile

EMMC (Embedded Multi Media Card) is a standard specification for embedded memory established by the MMC Association, mainly for products such as cell phones or tablet PCs. EMMC integrates a controller into the package to provide a standard interface and manage the flash memory. The schematic circuit 8-bit data signals are shown in Figure 8-38; the address and control signals in Figure 8-39; and the power signals in Figure 8-40. The RK3588 EMMC controller has the following features:

figure 8 40 some emmc power pins — Figure 8-40 Some EMMC power pins

Compatible with 5.1, 5.0, 4.51, 4.41 specifications;

Supports 1bit, 4bit and 8bit data bus widths;

Supports HS400 mode and is backward compatible with HS200, DDR50 and other modes;

Support for CMD queue;

EMMC Circuit Design Recommendations

The RK3588 eMMC interface is multiplexed with the FSPI Flash (one multiplexed port, FSPI_M0) interface. When designing the eMMC interface, please refer to the circuit diagram shown in Figure 8-41 for the eMMC signaling, including the power supply decoupling capacitors for each circuit. When using eMMC, the boot code is placed in the eMMC.

figure 8 41 recommended circuit connections for emmc — Figure 8-41 Recommended circuit connections for EMMC

EMMC Circuit PCB Layout Wiring Requirements

figure 8 42 clk circuit packing diagram — Figure 8-42 CLK circuit packing diagram

figure 8 43 placement of the filter capacitor — Figure 8-43 Placement of the filter capacitor

#1. The EMMC controller should be placed close to the pin when placing the pull-down resistor for the clock signal; the clock signal needs to be wrapped around the ground for processing, and the ground line is punched with a ground over-hole every 200 mils, as shown in Figure 8-42.

#2. EMMC data signals, clocks, and control signals need to be controlled with a 50-ohm impedance.

#3. The filter capacitors of the EMMC power supply pins are placed close to the corresponding pins, as far as possible to ensure that one pin is independent, as shown in Figure 8-43.

#4. Clock, data, and CMD signals need to be serpentine, with an error of less than 120 mils, and the total length of the alignment should not exceed 3500 mils.

#5. There are many empty pins in the EMMC chip package for the 0.5-pitch BGA package. The alignment can be used after not using the EMMC pin alignment way out of the line, reducing the requirements of the PCB board spacing.

#6. Two holes should be the maximum number of holes in the EMMC signal. The ground plane is recommended as the reference layer before and after replacing the EMMC signal. It is recommended that a ground return be added through a hole in the center of the pass-hole and pass-hole distance (the 30 mils). The ground reference plane should be connected to the ground return through a hole before and after signal layer changes.