ISOUSB211DPR datasheet(21/44 Pages) TI

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power and serve a similar purpose as external 1.8-V LDOs, that is, reduce power dissipation inside ISOUSB211

and allow higher ambient temperature operation.

Refer to the Thermal Considerations section for further details on how to optimize ISOUSB211 internal power

dissipation according to the maximum ambient temperature required in the system, and for recommendations on

external resistors, LDOs and buck converters.

8.3.2 Power Up

Until all power supplies on both sides of ISOUSB211 are above their respective UVLO thresholds, the device

ignores any activity on the bus lines on both upstream and downstream side. Once the power supplies are

above their UVLO thresholds, the device is ready to respond to activity on the bus lines. When the power

supplies on side 1 are up, this is indicated on side 2 by V1OK = High. Similarly, V2OK = High indicates that Side

2 is fully powered up.

8.3.3 Symmetric Operation, Dual-Role Port and Role-Reversal

ISOUSB211 supports symmetric operation. Normally, UD+ and UD- are upstream facing ports and connect to a

host or hub. DD+ and DD- are downstream facing ports and connect to a peripheral. However, it is also possible

to connect UD+ and UD- to a peripheral and DD+ and DD- to a host or hub. Whichever side sees a connect

first (D+ or D- pulled up to 3.3 V) becomes the downstream facing side. This feature enables implementation of

dual-role port (for eg. Type-C dual-role port) and role-reversal (for eg. OTG Host Negotiation Protocol - HNP).

Refer to How to Implement an Isolated USB 2.0 High-Speed, Type-C® DRP application note for details. In the

rest of this document, DD+/DD- are treated as downstream facing ports, and UD+/UD- as upstream facing ports,

but the various operations and features described are equally applicable if this assignment is swapped.

8.3.4 Connect and Speed Detection

When there is no peripheral device connected to the downstream side of ISOUSB211, internal 15 kΩ pull-down

resistors on DD+ and DD- pins pull the bus lines to zero, creating an SE0 state. When either the DD+ or DD-

lines is pulled up higher than the VIH threshold, for a time period higher than TFILTCONN, the ISOUSB211 device

treats this as a connect. The ISOUSB211 device configures internal pull-up on the upstream side to match the

pull-up detected on the downstream side. After connect is detected, the ISOUSB211 device waits for a reset to

be asserted by the host/hub on the upstream side. Depending on whether DD+ or DD- is pulled up at the start

of reset, the speed of the ISOUSB211 repeater is set. Once set, the speed of the repeater can only be changed

after a power down or disconnect event.

A high-speed (HS) capable device is attached to the ISOUSB211 device would proceed to perform high-speed

handshake using chirp signaling as specified in the USB2.0 standard. This would be followed by chirp signals

from the host. The ISOUSB211 device reflects these chirp signals across the barrier, including HS idle (SE0)

states from downstream to upstream and vice versa. Upon successful completing of the HS handshake

ISOUSB211 speed is set to High speed. Once set to high-speed, the speed of the repeater can only be changed

after power down, HS disconnect event, or if the peripheral or host/hub do not perform HS handshake after a

reset.

8.3.5 Disconnect Detection

When in Full-speed (FS) and Low-speed (LS) modes, disconnection of a peripheral is indicated when the

host/hub is not driving any signal on the upstream side, and when the downstream bus is in the SE0 state ( Both

DD+ and DD- are below the VILthreshold) for a time period higher than TDDIS. Upon disconnect detection in FS

and LS modes, the ISOUSB211 device removes the pull-up resistor from the upstream side, thus allowing the

upstream UD+ and UD- lines to discharge to zero. The ISOUSB211 then waits for the next connect event to

occur.

When in High Speed (HS) mode, if the ISOUSB211 detects a continuous period of no transitions lasting

THSDIS, the devices samples the DD+ and DD- lines using the HS Disconnect detector. If the input differential

voltage crosses VHSDSC during THSDIS, the repeater removes the HS termination from both the downstream and

upstream terminals and transitions to a disconnect state. The ISOUSB211 then waits for the next connect event

to occur.

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ISOUSB211

SLLSFC5B – NOVEMBER 2021 – REVISED SEPTEMBER 2022

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