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Application Brief

Application Brief

Protect your Designs with Low-Emissions USB 2.0
Compliant 480 Mbps Isolators

Anant Kamath
Mohana Krishna Bhat
Manasa GadiyarIntroduction
The use of the Universal Serial Bus (USB) has grown in industrial applications: for software uploads andconfiguration, diagnostics, maintenance, and connecting peripheral modules such as Wi-Fi routers, display
screens, and human-machine interface (HMI) modules.
Since USB was primarily defined as a consumer electronics interface it is not inherently capable of handlinglarge noise disturbances, ground bounce and ground potential differences that are common in industrialapplications. In some applications, such as Uninterrupted Power Supply (UPS), controllers with the USB
interface are on the high-voltage or ‘hot’ side, needing protective isolation to the USB connector. Systemdesigners also worry that any faults or ESD events on the exposed USB connector could interfere with thefunctionality of the industrial equipment. Due to these reasons, galvanically isolating the USB interface has
become necessary in a broad spectrum of applications including factory automation, motor drives, medicalequipment, power delivery, e-meters and data concentrators, in-flight entertainment and gaming consoles.
In this application brief, we discuss new isolated USB solutions from Texas Instruments, and their benefits overexisting solutions.
VBUS (5.0 V)
Ferrite
Bead

11 µF

3.3 V

20.1 µF

3VBUS
100 nF

1.8 V 2 µF 0.1 µF 10 nF

DD+8Upstream
PortConnector

910ISOGround

2 µF 0.1 µF 10 nF 1112
3.3 V

VBUS2 28

V3P3V1V3P3V2GND1GND2 2627

1314

3.3 VLV (local supply)
0.1 µF

1 µF
VCC

ISOUSB211
V1P8V2 25245VCC1VCC2236V2OK
V1OK47GND

VBUS1V1P8V1

10 nF 0.1 µF 2 µF

3.3 VLV

DD- 22

UDUD+DD+EQ10EQ20EQ11EQ21 19

V1P8V1V1P8V2

GND1GND2CDPENZ1CDPENZ2NC

NCDM

2120

Peripheral
MCU

DP
3.3 VLV
DGND

180V
10 nF 0.1 µF 2 µF

DigitalGround

1716

3.3 VLV

15

Galvanic
Isolation Barrier

Figure 1. Isolating an Existing USB 2.0 HS Port with Minimum Components using ISOUSB211

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1Application Brief

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New Solutions for Isolated USB
Texas Instruments’ ISOUSB211 and ISOUSB111 devices are isolated USB repeaters that are compliant to USB
2.0 standard. Both devices offer basic and reinforced versions, with isolation rating up-to 5.7 kVRMS, surge test
voltage up to 12.8 kV, and working voltage up to 1.5 kVRMS.
Figure 1 shows how an existing MCU high-speed USB 2.0 port can be easily isolated with ISOUSB211.
ISOUSB211 supports High Speed (HS, 480 Mbps) operation in addition to Full Speed (FS, 12 Mbps) and Low
Speed (LS, 1.5 Mbps) modes and has the following benefits vs. existing solutions:
1. ISOUSB211 is the first USB 2.0 compliant isolated repeater to support 480 Mbps data-rate, comparedto 12 Mbps of older solutions. Higher data rate enables quick transfer of large firmware and diagnostic
files, low-latency communication, real-time applications like video displays and data-logging, and backplane
communication.
2. Automatic Upstream-Downstream role detection and role reversal, allowing applications like OTG and TypeC dual-role port and allowing the same part number to be used for host, peripheral, hub or cable isolation.
3. 50% smaller footprint than equivalent competing solution.
4. Easy to use solution that meets High Speed Signal Quality without needing external crystal oscillator or clock
input. The incremental jitter is added by ISOUSB211 is low enough to meet USB eye-diagram specification
without re-timing. Figure 2 shows the high-speed eye-diagram obtained by connecting ISOUSB211EVM inseries with a USB 2.0 compliant golden host (PC).
5. Built-in, adjustable equalization and pre-emphasis that can compensate for insertion losses and ISI causedby board traces and internal cabling, providing flexibility for system design.
6. Charging Downstream Port (CDP) signaling according to Battery Charger 1.2 (BC 1.2) standard for hoststhat look to advertise >1.5 A power delivery on the VBUS connector.
7. Indication of Upstream VBUS state on the downstream side, enabling indication of host attach in peripheral
mode.

Figure 2. ISOUSB211 Eye-Diagram When used with USB 2.0 Golden Host PC

2Protect your Designs with Low-Emissions USB 2.0 Compliant 480 Mbps
Isolators
Copyright © 2021 Texas Instruments Incorporated

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Application Brief

ISOUSB111 supports LS and FS modes for applications that do not need high bandwidth, with the following
advantages over the current solutions:
1. More than 20 dB lower emissions that ease compliance to CISPR32 Class B standard.
2. 16-SSOP package option (DWX) that is 40% smaller in size than the smallest existing solution in the market,
in addition to a 16-SOIC option (DW) pin compatible with competition.
3. Indication of Upstream VBUS state on the downstream side, enabling indication of host attach in peripheral
mode (available in DWX option) .
Figure 3 shows how an existing MCU full-speed/low-speed USB 2.0 port can be easily isolated with ISOUSB111.
11 µF

FerriteBead

20.1 µF

VBUS1

VBUS2

GND1GND2153
V3P3V1

VBUS
100 nF

V3P3V2NC 135 NC

PIN

D+

3.3V (local supply)
1 µF

VCC
144 NC

D-120.1 µF

Peripheral
MCU

ISOUSB111
6GND7Upstream
PortConnector

168ISOGroundUD-DD-UD+
GND1DD+
GND2

GalvanicIsolation Barrier

1110DMDP

DGND

90VDigitalGroundFigure 3. Isolating an Existing USB 2.0 FS/LS Port with Minimum Components using ISOUSB111CISPR32 Class B Emissions
EMC performance is a key care in industrial applications. Figure 4 shows the comparison of ISOUSB111
emissions performance with an equivalent competition device. The test setup was communication between a PC
and a USB drive through ISOUSB111 and a 1 meter cable. ISOUSB111 has more than 20 dB lower emissions
than competition and easily meets the CISPR32 Class B limit, while the competing device shows emissions
higher than the limit.

Figure 4. ISOUSB111 CISPR32 Class B Emissions Compared to Competition

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Application Brief

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Figure 5 shows ISOUSB211 emissions performance. The test setup was communication between a PC and a
USB drive through ISOUSB211 and a 1 meter cable. ISOUSB211meets the CISPR32 Class B limit with margin.
The noise peaking around 80 MHz is coming from isolated power converter included on the ISOUSB211EVM
and not from ISOUSB211.

Figure 5. ISOUSB211 CISPR32 Class B Emissions
Comparing ISOUSB211 and ISOUSB111 with Competing Solutions
Figure 6 shows a summary of the ISOUSB211 and ISOUSB111 comparisons with competition that werediscussed in the preceding sections.

Figure 6. ISOUSB211 and ISOUSB111 vs. Competition

4

Protect your Designs with Low-Emissions USB 2.0 Compliant 480 Mbps
Isolators
Copyright © 2021 Texas Instruments Incorporated

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