GENERAL DESCRIPTION

The ADuM31601 is a USB port isolator based on Analog Devices, Inc., iCouple technology. Combining high speed CMOS and monolithic air core transformer technology, this isolation component provides outstanding performance characteristics and is easily integrated with low and full speed USB-compatible peripheral devices. Many microcontrollers implement USB so that it presents only the D+ and D− lines to external pins. This is desirable in many cases because it minimizes external components and simplifies the design; however, this presents particular challenges when isolation is required. Because the USB lines must switch between actively driving D+/D− and allowing external resistors to set the state of the bus, the ADuM3160 provides mechanisms for detecting the direction of data flow and control over the state of the output buffers. Data direction is determined on a packet-by-packet basis. The ADuM3160 uses the edge detection based iCoupler technology in conjunction with internal logic to implement  a transparent, easily configured, upstream-facing port isolator. Isolating the upstream port provides several advantages in simplicity, power management, and robust operation. The isolator has a propagation delay comparable to that of a standard hub and cable. It operates with the bus voltage on either side ranging from 4.5 V to 5.5 V, allowing connection directly to VBUSx by internally regulating the voltage to the signaling level. The ADuM3160 provides isolated control of the pull-up resistor to allow the peripheral to control connection timing. The device draws low enough idle current that a suspend state is not required. A 5 kV, reinforced insulation version, the ADuM4160, is available.

 

FEATURES

USB 2.0 compatible

Low and full speed data rate: 1.5 Mbps and 12 Mbps

Bidirectional communication

4.5 V to 5.5 V VBUS operation

7 mA maximum upstream supply current at 1.5 Mbps

8 mA maximum upstream supply current at 12 Mbps

2.3 mA maximum upstream idle current

Upstream short-circuit protection

Class 3A contact ESD performance per ANSI/ESD STM5.1-2007

High temperature operation: 105°C

High common-mode transient immunity: >25 kV/μs

16-lead SOIC wide body package

RoHS compliant

Qualified for automotive applications

Safety and regulatory approvals

UL recognition: 2500 V rms for 1 minute per UL 1577

CSA Component Acceptance Notice #5A IEC 60950-1: 600 V rms (basic)

VDE certificate of conformity

DIN V VDE V 0884-10 (VDE V 0884-10):2006-12 VIORM = 560 V peak

 

APPLICATIONS

USB peripheral isolation

Isolated USB hub

 

APPLICATIONS INFORMATION

FUNCTIONAL DESCRIPTION

USB isolation in the D+/D− lines is challenging for several reasons. First, access to the output enable signals is normally required to control the transceiver. Some level of intelligence must be built into the isolator to interpret the data stream and determine when to enable and disable its upstream and downstream output buffers. Second, the signal must be faithfully reconstructed on the output side of the coupler while retaining precise timing and not passing transient states such as invalid SE0 and SE1 states. In addition, the part must meet the low power requirements of the suspend mode. The iCoupler technology is based on edge detection and, therefore, lends itself well to the USB application. The flow of data through the device is accomplished by monitoring the inputs for activity and setting the direction for data transfer based on a transition from the idle state. After data directionality is established, data is transferred until either an end of packet (EOP) or a sufficiently long idle state is encountered. At this point, the coupler disables its output buffers and monitors its inputs for the next activity. During the data transfers, the input side of the coupler holds its output buffers disabled. The output side enables its output buffers and disables edge detection from the input buffers. This allows the data to flow in one direction without wrapping back through the coupler, causing the iCoupler to latch. Timing is based on the differential input signal transition. Logic is included to eliminate any artifacts due to different input thresholds of the differential and single-ended buffers. The input state is transferred across the isolation barrier as one of three valid states, J, K, or SE0. The signal is reconstructed at the output side with a fixed time delay from the input side differential input. The iCoupler does not have a special suspend mode, nor does it need one because its power supply current is below the suspend current limit of 2.5 mA when the USB bus is idle. The ADuM3160 is designed to interface with an upstream-facing low/full speed USB port by isolating the D+/D− lines. An upstreamfacing port supports only one speed of operation; therefore, the speed-related parameters, J/K logiclevels, and D+/D− slew rate are set to match the speed of the upstream-facing peripheral port A control line on the downstream side of the ADuM3160 activates the idle state pull-up resistor. This allows the downstream port to control when the upstream port attaches to the USB bus. The PIN input can be tied to a 3.3 V control logic signal or to the VDD2 rail depending on whether enumeration must be controlled or will occur when power is first applied.