7 Detailed Description

7.1 Overview

ISOUSB111 is a galvanically-isolated USB2.0 compliant repeater supporting Low Speed (1.5 Mbps) and Full

Speed (12 Mbps) signaling rates. The device supports automatic speed and connection detection, reflection

of pull-ups/pull-downs, and link power management allowing drop-in USB hub, host, peripheral and cable

isolation. Most microcontrollers integrate the USB PHY, and so offer only D+ and D- bus lines as external

pins. ISOUSB111 can isolate these pins from the USB bus without needing any other intervention from the

microcontroller. The device also supports automatic role reversal - if after disconnect, if a new connect is

detected on the Upstream facing port, then the Upstream and Downstream port definitions are reversed.

operate completely off a 4.25 V to 5.5 V supply (USB VBUS power) or from local 3.3-V supply, if available, on

both side 1 and side 2. This flexibility in supply voltages allows optimization for thermal performance based on

power rails available in the system.

7.2 Functional Block Diagram

A simplified functional block diagram of ISOUSB111 is shown in Figure 7-1. The device comprises the following:

1. Transmit and receive circuits and pull-up and pull-down resistors according to the USB standard.

2. Digital logic to handle bi-directional communication, and various state-transitions.

4. Galvanic isolation.

UD+

FSM

PU/PD

LDO

SERXD-

SERXD+

LSFSRX

LSFSTX

FSM

PU/PD

LDO

SERXD-

SERXD+

LSFSRX

LSFSTX

FSM

UD-

V

BUS1

V

3P3V1

DD+

DD-

V

BUS2

V

3P3V2

Figure 7-1. ISOUSB111 Simplified Functional Block Diagram

7.3 Feature Description

7.3.1 Power Supply Options

3.3-V supply can be connected to both. This second option is suitable for the side facing the microcontroller,

where a 5-V supply may not be available.

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ISOUSB111

SLLSFC6A – NOVEMBER 2021 – REVISED APRIL 2022

Copyright © 2022 Texas Instruments Incorporated

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