Microchip USB3327 Bedienungsanleitung


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2008-2019 Microchip Technology Inc. DS00002959A-page 1
INTRODUCTION
For customers who want to integrate the USB3320 and are looking to the USB3340/USB83340 for future products, this
document describes the hardware and software considerations required to accomplish that migration with the least
impact to customer design resources. By following the design guidelines outlined in this document, a designer can use
a common PCB and software platform that can be used for both the USB3320 and USB3340/USB83340 with nothing
more than a change to the Bill of Materials (BOM) being required.
REFERENCES
Microchip USB Transceiver Data Sheets:
• USB3320
• USB334x
• USB83340
DESIGNING A COMMON PCB FOR THE USB3320 AND USB3340/USB83340
A common PCB design can be engineered to support both the USB3320 and USB3340/USB83340 transceivers.
Observing a few simple design considerations will provide a seamless transition from USB3320 to USB3340/
USB83340. Unless otherwise specified within this document, all PCB layout design guidelines that apply to the
USB3320 shall apply to the USB3340/USB83340.
To design a common hardware platform for both USB transceivers, there are three design changes that must be made:
Depopulate or disable the 1.8V regulator input.
Change the capacitor on the VDD18 pin from a 0.1
F to a 1.0
F low-ESR capacitor.
VBAT min voltage raised from 3.1V to 4.0V for the USB83340 only. (USB3340 VBAT min voltage lowered to 3.0V).
Other optional changes that can be made:
Change the capacitor on the VDD33 pin from a 2.2
F low-ESR to a 1.0
F low-ESR Capacitor.
Change the resister on the RVBUS pin from a 10k to 20k resistor.
Integrating the 1.8V Regulator
The USB3340/USB83340 integrates the 1.8V regulator that was external to the USB3320. The VDD18 pin of the
USB3320 is an input and requires an external voltage source to be applied to the pin. Conversely, the VDD18 pin of the
USB3340/USB83340 is an output that must never be presented with an externally sourced voltage.
AN 19.0
Migrating USB Designs from the USB3320 to the
USB3340/USB83340
AN 19.0
DS00002959A-page 2 2008-2019 Microchip Technology Inc.
If the 1.8V regulator in the USB3320 application is dedicated to the USB3320, as shown in Figure 1, then it can simply
be removed from the design by removing all of its associated components. An alternative to this is using hardware or
software to merely disable the external regulator, but this approach is discouraged because this external regulator will
likely carry some additional capacitance as well as a possible current path for the internal 1.8V regulator output of the
USB3340/USB83340.
If the 1.8V regulator in the USB3320 application is shared between the USB3320 and other system elements, installing
a zero ohm precision resistor between the 1.8V source and the USB3320 will allow for this external source to be dis-
connected from the USB3340/USB83340 by removing it from the BOM at the time that the USB3340/USB83340 is
installed. Figure 3 shows the two application circuits with arrows highlighting the removal of the zero ohm resistor when
migrating the application to the USB3340/USB83340.
FIGURE 1: USB3320 APPLICATION
FIGURE 2: USB3340/USB83340 APPLICATION
USB3320
VDD33
VDD18
2.2uF
0.1uF
1.8V
Source
USB83340
VDD33
VDD18
1.0uF
1.0uF
2008-2019 Microchip Technology Inc. DS00002959A-page 3
AN 19.0
VDD18 Capacitor
It is recommended in applications using the USB3320 that a 0.1 F decoupling capacitor be placed near the VDD18 pin
of the USB3320, as shown in Figure 1. However, for the USB3340/USB83340, this capacitor is required for regulator
stability and must be 1.0 F (<1 ESR), as shown in Figure 2.
VDD33 Capacitor
It is required in applications using the USB3320 that a 2.2 F (<1ESR) capacitor be placed near the VDD33 pin of the
USB3320 for regulator stability, as shown in Figure 1. For USB3340/USB83340 applications, the value of this capacitor
may be reduced to be 1.0 F (<1ESR), as shown in Figure 2.
RVBUS Resistor
It is required in applications using the USB3320 that a 10 kexternal resistor be placed in series with the RVBUS pin.
For the USB3340/USB83340 it is recommended to change that resistor to a 20 kexternal resistor. Please refer to
Microchip’s white paper titled “Optimal VBUS detection in USB Devices” for more extensive details on this topic.
VBAT Voltage
For the USB83340, it is required to change the minimum operating VBAT voltage to 4.0V. The USB3340 will operate
with a VBAT voltage down to 3.0V.
SOFTWARE
Migrating applications from the USB3320 to the USB3340/USB83340 does not require any software change.
All features supported on the USB3320 will function on the USB3340/USB83340 without any modification required to
the software. However, there are three features which are available to USB3340/USB83340 applications if the software
is written to take advantage of them.
Link Power Management
High Speed Receiver Compensation
Charging Host Detection
FIGURE 3: REMOVING ZERO OHM RESISTOR TO DISCONNECT 1.8V SOURCE
Note: Refer to Module 2 of the USB3340 Errata as there is a difference in the chips that can affect the LINK.
USB3320
VDD33
VDD18
2.2uF
0.1uF
1.8V
Source
USB83340
VDD33
VDD18
1.0uF
1.0uF
1.8V
Source
0 Ohm


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Marke: Microchip
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Modell: USB3327

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