AN 496: Using the Internal Oscillator Intel® FPGA IP

ID 683653
Date 4/01/2024

Internal Oscillators

Most designs require a clock for normal operation. You can use the Internal Oscillator Intel® FPGA IP for clock source in user design or debug purposes. With an internal oscillator, the supported Intel® devices do not require external clocking circuitry. For example, you can use the internal oscillator to meet the clocking requirement of an LCD controller, system management bus (SMBus) controller, or any other interfacing protocol, or to implement a pulse width modulator. This helps minimize component count and board space, and reduces the total cost of the system.

You can instantiate the internal oscillator without instantiating the user flash memory (UFM) by using the supported Intel® devices' oscillator IP core in the Quartus® Prime software for MAX® II and MAX® V devices. For MAX® 10 devices, the oscillators are separate from the UFM.

The oscillator’s output frequency, osc, is one-fourth of the undivided frequency of the internal oscillator.

Table 1.  Frequency Range for Supported Intel® Devices
Device Output Clock from Internal Oscillator 1 (MHz)
MAX® II 3.3 – 5.5
MAX® V 3.9 – 5.3
MAX® 10 55 – 116 2, 35 – 77 3
Cyclone® III 4 80 (max)
Cyclone® IV 80 (max)
Cyclone® V 100 (max)
Cyclone® 10 GX 100 (max)
Cyclone® 10 LP 80 (max)
Arria® II GX 100 (max)
Arria® V 100 (max)
Arria® 10 100 (max)
Stratix® V 100 (max)
Stratix® 10 170 – 230
Agilex™ 5 160 – 230
Agilex™ 7 160 – 230
Figure 1. Internal Oscillator as Part of the UFM for MAX® II and MAX® V Devices

The internal oscillator is part of the Program Erase Control block, which controls the programming and erasing of the UFM. The data register holds the data to be sent or retrieved from the UFM. The address register holds the address from which data is retrieved or the address to which the data is written.

The internal oscillator for the UFM block is enabled when the ERASE, PROGRAM, and READ operation is executed.

Table 2.  Pin Description for the Internal Oscillator Intel® FPGA IP
Signal Description
oscena Use to enable the internal oscillator. Input high to enable the oscillator.
osc/clkout 5 Output of the internal oscillator.
1 The output port for Internal Oscillator Intel® FPGA IP is osc in MAX® II and MAX® V devices, and clkout in all other supported devices.
2 For 10M02, 10M04, 10M08, 10M16, and 10M25.
3 For 10M40 and 10M50.
4 Supported in the Quartus® Prime software version 13.1 and earlier.
5 Not applicable to Stratix® 10 devices.