Datasheet

TUSB2036

SLLS372F –MARCH 2000–REVISED SEPTEMBER 2013

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DESCRIPTION

The TUSB2036 hub is a 3.3-V CMOS device that provides up to three downstream ports in compliance with the

USB 2.0 specification. Because this device is implemented with a digital state machine instead of a

microcontroller, no firmware programming is required. Fully-compliant USB transceivers are integrated into the

ASIC for all upstream and downstream ports. The downstream ports support both full-speed and low-speed

devices by automatically setting the slew rate according to the speed of the device attached to the ports. The

configuration of the BUSPWR terminal selects either the bus-powered or the self-powered mode. The

introduction of the DP0 pullup resistor disable terminal, DP0PUR, makes it much easier to implement an on-

board bus/self-power dynamic-switching circuitry. With the new function terminal, the end-equipment vendor can

reduce the total board cost while adding additional product value.

The EXTMEM (terminal 26) enables or disables the optional EEPROM interface. When EXTMEM is high, the

vendor and product IDs (VID and PID) use defaults, such that the message displayed during enumeration is

General Purpose USB Hub. For this configuration, terminal 6 functions as the GANGED input terminal and the

EECLK (terminal 5) is unused. If custom VID and PID descriptors are desired, the EXTMEM must be tied low

(EXTMEM = 0) and a SGS Thompson M93C46 EEPROM, or equivalent, stores the programmable VID, PID, and

GANGED values. For this configuration, terminals 5 and 6 function as the EEPROM interface signals with

terminal 5 as EECLK and terminal 6 as EEDATA, respectively.

The TUSB2036 supports both bus-powered and self-powered modes. External power-management devices,

such as the TPS2044, are required to control the 5-V power source switching (on/off) to the downstream ports

and to detect an overcurrent condition from the downstream ports individually or ganged. Outputs from external

power devices provide overcurrent inputs to the TUSB2036 OVRCUR terminals in case of an overcurrent

condition, the corresponding PWRON terminals are disabled by the TUSB2036. In the ganged mode, all PWRON

signals transition simultaneously, and any OVRCUR input can be used. In the nonganged mode, the PWROR

outputs and OVRCUR inputs operate on a per-port basis.

The TUSB2036 provides the flexibility of using either a 6-MHz or a 48-MHz clock. The logic level of the MODE

terminal controls the selection of the clock source. When MODE is low, the output of the internal APLL circuitry is

selected to drive the internal core of the chip. When MODE is high, the XTAL1 input is selected as the input

clock source and the APLL circuitry is powered down and bypassed. The internal oscillator cell is also powered

down while MODE is high. For 6-MHz operation, TUSB2036 requires a 6-MHz clock signal on XTAL1 terminal

(with XTAL2 for a crystal) from which its internal APLL circuitry generates a 48-MHz internal clock to sample the

data from the upstream port. For 48-MHz operation, the clock cannot be generated with a crystal, using the

XTAL2 output, since the internal oscillator cell only supports the fundamental frequency. If low-power suspend

and resume are desired, a passive crystal or resonator must be used, although the hub supports the flexibility of

using any device that generates a 6-MHz clock. Because most oscillators cannot be stopped while power is on,

their use prohibits low-power suspend, which depends on disabling the clock. When the oscillator is used, by

connecting its output to the XTAL1 terminal and leaving the XTAL2 terminal open, its TTL output level can not

exceed 3.6 V. If a 6-MHz oscillator is used, it must be stopped at logic low whenever SUSPND is high. For

crystal or resonator implementations, the XTAL1 terminal is the input and the XTAL2 terminal is used as the

feedback path. A sample crystal tuning circuit is shown in Figure 7.

The hub silicon can accurately reflect the system port configuration by the NP3 and NPINT1-0 terminals. When

NP3 is low, the hub is configured as a 3-port hub; when it is high, the hub is configured as a 2-port hub. The

NPINT1-0 terminals tell the hub silicon how many ports have permanently attached devices, according to

Table 1.

Product Folder Links: TUSB2036