Data Sheet

PYNQ-Z1 Board Reference Manual

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Figure 7.1. microSD slot signals.

Both low speed and high speed cards are supported, the maximum clock frequency being 50 MHz. A Class 4 card

or better is recommended.

Refer to section 3.1 for information on how to boot from an SD card. For more information, consult the Zynq

Technical Reference manual.

8 USB Host

The PYNQ-Z1 implements one of the two available PS USB OTG interfaces on the Zynq device. A Microchip

USB3320 USB 2.0 Transceiver Chip with an 8-bit ULPI interface is used as the PHY. The PHY features a complete HS-

USB Physical Front-End supporting speeds of up to 480Mbs. The PHY is connected to MIO Bank 1/501, which is

powered at 1.8V. The usb0 peripheral is used on the PS, connected through MIO[28-39]. The USB OTG interface is

configured to act as an embedded host. USB OTG and USB device modes are not supported.

The PYNQ-Z1 is technically an “embedded host”, because it does not provide the required 150 µF of capacitance

on VBUS required to qualify as a general purpose host. It is possible to modify the PYNQ-Z1 so that it complies with

the general purpose USB host requirements by loading C41 with a 150 µF capacitor. Only those experienced at

soldering small components on PCBs should attempt this rework. Many USB peripheral devices will work just fine

without loading C41. Whether the PYNQ-Z1 is configured as an embedded host or a general purpose host, it can

provide 500 mA on the 5V VBUS line. Note that loading C41 may cause the PYNQ-Z1 to reset when booting

embedded Linux while powered from the USB port, regardless of if any USB device is connected to the host port.

This is caused by the in-rush current that C41 causes when the USB host controller is enabled and the VBUS power

switch (IC9) is turned on.

Note that if your design uses the USB Host port (embedded or general purpose), then the PYNQ-Z1 should be

powered via a battery or wall adapter capable of providing more power (such as the one included in the PYNQ-Z1

accessory kit).