Microchip USB3333 Bedienungsanleitung


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 2013 - 2015 Microchip Technology Inc. DS00001863B-page 1
INTRODUCTION
The purpose of this application note is to provide a list of items that need to be considered when designing systems that
incorporate the following categories of Microchip USB products:
• USB 2.0 Hubs
• USB 3.1 Gen 1 Hubs
• Flash Media Controllers
• Flash Media Controller Hub Combo
• USB Transceivers
The target audience of this document is system engineers and layout professionals who are familiar with industry stan-
dard practices. This application note must be used in conjunction with the device data sheet, reference design, and other
relevant application notes.
Overview
This document includes the following chapters:
•Schematic Guidelines
•Layout Guidelines
Each chapter begins with a sub-section on the general design considerations for all products. Subsequent sub-sections
detail design considerations for specific product categories and their applications. The order of these lists are arbitrary.
References
• Application Notes:
- AN 18.16, PCB Design Guidelines for USB223x/i & USB225x/i Controllers
- AN 26.2, Implementation Guidelines for Microchip’s USB 2.0 and USB 3.1 Gen 1 Hub Devices
- AN 18.15, PCB Design Guidelines for QFN and DQFN Packages
- AN 19.17, ULPI Design Guide
- WP 2.10, PCB Design for WLCSP BGA Packages
• The data sheet for the respective product(s)
• Applicable USB specifications and ECNs available at usb.org
AN 26.21
USB Device Design Checklist
Author: Rejo Titus
Microchip Technology Inc.
AN 26.21
DS00001863B-page 2  2013 - 2015 Microchip Technology Inc.
1.0 SCHEMATIC GUIDELINES
1.1 General Considerations
â–¡ A. Confirm the pin-out functions of the schematic symbol of the USB product matches what is provided in
the product data sheet.
â–¡ B. For designs with exposed USB connectors, connect the USB cable shield to digital ground with an RC
network. Refer to the Microchip AN 26.2 application note for additional details.
â–¡ C. Ensure that the power rails, such as VDD12 or VDD33, are not noisy and are stable and accurate across
all power consumption ranges. Refer to the Microchip AN 26.2 application note and the product data sheets
for additional details.
â–¡ D. RESETn should be asserted buy a supervisory circuit when either VDD12 or VDD33 are below their
thresholds or asserted under manual or host control. Refer to the Microchip AN 26.2 application note for addi-
tional details.
â–¡ E. To use in-system OTP programming through SMBus, SM_DAT should be pulled up with an external
resistor and SM_CLK should be pulled down with an external resistor. The programmer pulls SM_CLK up
with a resistor when connected to the PCB. Refer to the Microchip AN 26.2 application note for additional
details.
â–¡ F. Make sure that the crystal and load capacitors are chosen correctly for proper operation. Refer to the
product data sheet for additional details.
â–¡ G. If the Microchip product has internal regulators, place regulator capacitors on the regulator pins as
described in the product data sheet.
â–¡ H. Internal regulators of the Microchip product must have the proper input voltage. No external voltage
should be applied to the output of these internal regulators. Refer to the product data sheet for additional
details.
â–¡ I. Place a 2.2uF capacitor on upstream Vbus to comply with the USB-IF decoupling capacitance require-
ments with margin for capacitor tolerances. Refer to the USB 2.0 Specification for additional details.
â–¡ J. VBUS_DET should be connected to the upstream VBUS through a resistor divider for stand-alone appli-
cations. Embedded applications should actively control this pin with a 3.3V signal. Refer to the Microchip AN
26.2 application note for additional details.
â–¡ K. The Rbias resistor must be the correct value and have, at worst, a 1% tolerance. Refer to the product
data sheet for additional information.
â–¡ L. Pins that are identified as no connect should not be connected to any net. Refer to the product data sheet
for additional information.
â–¡ M. Ensure that the product is configured correctly by either puling the relevant strap pins up/down appropri-
ately, or via SMBus/I2C. Refer to the product data sheet for additional information.
FIGURE 1-1: SHIELD TO DIGITAL GROUND CONNECTION
 2013 - 2015 Microchip Technology Inc. DS00001863B-page 3
AN 26.21
â–¡ N. Ensure that any SPI or EEPROM devices are compatible with the Microchip product. Refer to the product
data sheet for additional information.
1.1.1 USB2.0 SIGNALS
â–¡ A. Do not use common mode chokes unless needed. Chokes must have a DIFFERENTIAL IMPEDANCE of
90 ohms. Refer to the Microchip AN 26.2 application note for additional details.
1.1.2 USB 3.1 GEN 1 SIGNALS
â–¡ A. Do not use common mode chokes unless needed. Chokes must have a DIFFERENTIAL IMPEDANCE of
90 ohms. Refer to the Microchip AN 26.2 application note for additional details.
â–¡ B. Do not place ESD protection ICs on SuperSpeed Tx and Rx differential pairs unless proven necessary.
Refer to the Microchip AN 26.2 application note for additional details.
1.2 USB Hubs
â–¡ A. The PRT_PWR/PRT_CTL pins should be connected to the USB Power switch IC with an open drain
overcurrent signal when using individual port power for exposed downstream ports.
â–¡ B. For downstream embedded devices, the appropriate PRT_PWR or PRT_CTL pin should be connected to
the input of the downstream device that controls its enumeration.
â–¡ C. Place a 150uF capacitor on Vbus pin on any exposed downstream ports to comply with the USB-IF
requirements with margin for capacitor tolerances. Refer to USB 2.0 Specification.
1.3 Flash Media Signals
â–¡ A. Place a capacitor on CRD_PWR pins with the appropriate value to meet the system requirements.
□ B. Ensure that the flash media card connector’s card detect and write protect switch logic are compatible
with the respective inputs to the controller. Refer to the product data sheet for additional information.
□ C. If the flash media card connector’s card detect or write protect switches are connected to the shield,
make sure that the shield is connected to ground appropriately.


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Modell: USB3333

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