ep2c35 Altera Corporation, ep2c35 Datasheet - Page 86

• Manufacturer Part Number: ep2c35
• Description: Cyclone Ii Device Family Data Sheet
• Manufacturer: Altera Corporation

Hot-Socketing Feature Implementation in Cyclone II Devices
Figure 4–1. Hot-Socketing Circuit Block Diagram for Cyclone II Devices
4–4
Cyclone II Device Handbook, Volume 1
Resistor
f
Pull-Up
Weak
PAD
The POR circuit monitors V
tri-stated until the device is in user mode. The weak pull-up resistor (R)
from the I/O pin to V
tolerance control circuit permits the I/O pins to be driven by 3.3 V before
V
driving out when the device is not in user mode.
For more information, see the DC Characteristics & Timing Specifications
chapter in Volume 1 of the Cyclone II Device Handbook for the value of the
internal weak pull-up resistors.
Figure 4–2
I/O buffers. This design ensures that the output buffers do not drive
when V
than V
socketing. The V
circuit capacitance.
R
CCIO
Output
and/or V
CCIO
CCIO
. This also applies for sudden voltage spikes during hot
shows a transistor level cross section of the Cyclone II device
is powered before V
CCINT
PAD
leakage current charges the voltage tolerance control
are powered, and it prevents the I/O pins from
CCIO
Input Buffer
to Logic Array
Tolerance
Voltage
Control
keeps the I/O pins from floating. The voltage
CCINT
CCINT
Output Enable
voltage level and keeps I/O pins
or if the I/O pad voltage is higher
Hot Socket
Pre-Driver
Output
Power-On
Monitor
Reset
Altera Corporation
February 2007