USB

The QS Computer-on-Modules, such as QSMP and QS8M, contain two separate USB 2.0 compliant interfaces. High-speed USB operates at 480 Mb/s observing some basic rules or guidelines will usually guarantee successful operation.

VBUS

The QS modules does not include a signal for supplying the 5 V VBUS power for USB. An external power management chip or discrete logic for enabling VBUS is required for the host operation. The power distribution circuit must have over-current detection capability to be compliant with the USB standard. There are no dedicated pins reserved for this in the QS standard. Use General Purpose Input/Output (GPIO) pads as OE (VBUS_EN) and OC (VBUS_OC) for the VBUS power distribution circuit. Some QS modules have pins with dedicated VBUS_EN (Output) and VBUS_OC (Input) alternate functions, e.g. QS8M pin 71 - USB1_OTG_PWR and pin 72 USB1_OTG_OC. Using these may interfere with the use other standard QS interfaces. A switch designed specifically for USB power, such as the Maxim MAX1931, or a general purpose power-distribution chip, such as Micrel’s MIC2026, can be used.

Note

The i.MX8M Nano processor has only one integrated port.

Pin

Signal

type

I/O

Requirements

43

USB_VBUS_A

5V

IN

Can be connected to VBUS directly

44

USB_DN_A

USB

I/O

Route USB differential signals with 90 Ω differential impedance

45

USB_DP_A

USB

I/O

46

USB_VBUS_B

5V

IN

Can be connected to VBUS directly

47

USB_DN_B

USB

I/O

Route USB differential signals with 90 Ω differential impedance

48

USB_DP_B

USB

I/O

Wiring example

USB2.0 Design Recommendations

Parameter

MIN

TYP

MAX

Operating Speed

240 MHz

Signal Trace Length

15 cm

Differential Pair Skew

5 ps

Differential Trace Impedance

81 Ω

90 Ω

99 Ω

USB3 Super Speed

The QSXP provides a complete USB3.0 interface. To implement a USB Type-C interface (UFP, DFP, or DRP), external hardware must be added to manage the two configuration channel IOs (CC1 and CC2) as well as monitor the plug orientation and switch the single USB3 SS interface.

Route all USB differential signals with 90 Ω differential impedance.

Pin

Signal

Requirements

25A

USB_TXN

26A

USB_TXP

50A

USB_RXN

51A

USB_RXP

USB3 Super Speed Design Recommendations

Parameter

MIN

TYP

MAX

Operating Speed

2.5 GHz

Signal Trace Length

10 cm

Differential Pair Skew

1 ps

RX/TX Skew

1.6 ns

Differential Trace Impedance

85 Ω

90 Ω

95 Ω

See also

Texas Instruments High-Speed Interface Layout Guidelines

QS Standard Contact Group Index

Pins

Function

Pins

Function

Pins

Function

Pins

Function

1-4

SPI

5-10

I2C

11-14

CAN

15-18

SAI

19-35

Ethernet

36-42

SD Interface

43-48

USB

49-52

Power Supply, Reset and Boot mode

53-76

18-bit RGB Display Interface

77-78

Backlight and Display Control

53-72

Camera

79-88

MIPI DSI Display

89-96

UART

97-100

SPI

1A,75A,76A,100A

PCIe

25A,26A,50A,51A

USB3 Super Speed