tus, they can be expanded to 64-byte maximum packet sizes, which will improve USB throughput. For isochronous designs, endpoints will need to be converted from end- point 1 to endpoints 8 through 15.
| Cypress | Intel |
Feature | EZ-USB Family | 8x930Ax |
| | |
Endpoint Pairs | 16 | 4/6 |
| | |
Max. Packet Size | | |
| | |
Isochronous (bytes) | 1024 | 512/256 |
| | |
Bulk (bytes) | 64 | 16/32 |
| | |
5.Lower power/Easier power management
The Intel 8x930Ax has a 150-mA maximum current spec- ification under normal operation. The USB specification requires a device to consume no more than 100 mA during the initial plug-in. This is because bus-powered hubs can only supply a maximum of 100 mA per port during bus enumeration. Following the chip reset, the 8x930Ax oper- ates in low-clock mode, wherein the CPU and on-chip pe- ripherals are clocked at a reduced rate until bus enumera-
tion is complete. This reduces the ICC to meet the USB 100-mA requirement. Thus the Intel 8x930Ax requires the USB microcontroller to be in idle mode operation during initial power-on.
Remote wake-up on the 8x930Ax is performed using a register bit (RWU). Firmware must be used to drive re- sume signaling on the USB lines. The USB microcontroller must be awake in order for firmware to be accessed and generate the remote wake-up operation. However, this makes it difficult for remote activity peripherals such as modems and telephones, which are usually in a suspend- ed state when not in use to save power. An external stim- ulus, such as a phone call, requires careful timing by the peripheral designer as it must pull the USB microcontroller out of suspend operation and write to firmware before ini- tiating the next series of events. Normally, an external stim- ulus should trigger a series of events, including the resume signalling in the host PC right away.
In addition, there is a restriction on the Intel 8x930Ax. If the 8x930Ax is put into power-down mode prior to receiving a USB Suspend signal from the host, a USB Resume will not properly wake up the 8x930Ax from the power-down mode.
EZ-USB uses ¼ of the power of the Intel 8x930Ax, making it ideal for power-sensitive or portable peripherals. As a result, there is no idle operation mode, since EZ-USB only has a 50-mA (25-mA typical) maximum current specifica- tion under the normal operating conditions. If a peripheral requires between 500 and 600 mA, then the reduction of 100 mA by switching to EZ-USB will allow the peripheral manufacturer to eliminate the power supply and become a bus-powered peripheral, thereby saving significant costs.
In addition, EZ-USB resume operation can be performed with the toggle of an external pin (WAKEUP#), thus mak- ing it easy for hardware to implement the wake-up opera- tion. No timing considerations due to waking the USB mi- crocontroller are necessary.
Converting to EZ-USB requires a 3.3V regulator, as EZ-USB is powered under 3.3V as opposed to the Intel 8x930Ax which can run off Vbus.
| Cypress | Intel |
Feature | EZ-USB Family | 8x930Ax |
| | |
Voltage (volts) | 3.0–3.6 | 4.0–5.25 |
| | |
Max. Power (Active) | 180 mW | 788 mW |
| | |
Max. Current (Active) | 50 mA | 150 mA |
| | |
6.Smaller board density
The Intel 8x930Ax is housed in a 68 PLCC, which has an approximate body size of 24 x 24. The EZ-USB family is packaged in both the 44 PQFP (10 x 10 mm) and 80 PQFP (14 x 10 mm). The 44 PQFP is useful for applications not needing the address bus. As a result, a 44 PQFP can use ¼ the board space of the Intel solution.
| Cypress | Intel |
Feature | EZ-USB Family | 8x930Ax |
| | |
Package | 44 PQFP | 68 PLCC |
| 80 PQFP | |
| | |
Package Board | 170 sq. mm | 625 sq. mm |
Density | 432 sq. mm | |
| | |
7.More product options
While the Intel 8x930Ax offers only one product option which supports both isochronous and bulk, the EZ-USB family has 10 product options. All the options differ in inter- nal RAM size, I/O performance, and the support of bulk only versus isochronous support (see Table 2).
Additional Hardware Issues To Consider When Converting
8.VID/PID/DID Implementation
With the Intel 8x930Ax, VID/PID/DID information was em- bodied into the internal ROM or external ROM/EPROM.
If the peripheral designer is implementing the firmware download feature of EZ-USB, then the VID/PID/DID infor-
mation is housed in a tiny 16-byte (or larger) EEPROM which is connected through the EZ-USB I2C port. Should
the peripheral designer use an 8K EEPROM to load the entire firmware through the I2C port, then the VID/PID/DID information is contained in the 8K EEPROM. Of course, if the peripheral designer requires more than 8K of firmware and uses external memory for firmware, the VID/PID/DID information is embodied in external memory as with the 8x930Ax.
9.1.5-kΩ Pull-up Resistor
The 8x930Ax uses a standard implementation for USB, attaching a 1.5-kΩ resistor from D+ to Vbus. However, EZ-USB performs special tricks with the USB signal lines
in performing the ReNumeration operation. As a result, the 1.5-kΩ resistor is connected directly to our DISCON# pin.
Even if ReNumeration operation is not required, the de- signer should still connect the 1.5-kΩ resistor to the DISCON# pin.
