CIII51010-3.0
Introduction
10. Hot Socketing and Power-On Reset in
Cyclone III Devices
Cyclone®III family devices (Cyclone III and Cyclone III LS devices) offer hot
socketing, which is also known as hot plug-in or hot swap, and power sequencing
support without the use of any external devices. You can insert or remove Cyclone III
family devices or a board in a system during system operation without causing
undesirable effects to the running system bus or the board that is inserted into the
system.
The hot socketing feature removes some of the difficulties that you encounter when
you use Cyclone III family devices on a PCB that contains a mixture of 3.0, 2.5, 1.8, 1.5
and 1.2 V devices. With the hot socketing feature of Cyclone III family devices, you no
longer need to ensure a proper power up sequence for each device on the board.
Cyclone III family devices hot socketing feature provides:
■ Board or device insertion and removal without external components or board
manipulation
■ Support for any power-up sequence
■ Non-intrusive I/O buffers to system buses during hot insertion
This chapter also discusses the power-on reset (POR) circuitry in Cyclone III family
devices. The POR circuitry keeps the devices in the reset state until the power supplies
are in operating range.
Hot-Socketing Specifications
Cyclone III family devices are hot-socketing compliant without the need for any
external components or special design requirements. Hot socketing support in
Cyclone III family devices have the following advantages:
■ You can drive the device before power up without damaging the device.
■ I/O pins remain tristated during power up. The device does not drive out before
or during power up, therefore not affecting other buses in operation.
Devices Driven Before Power-Up
You can drive signals into I/O pins, dedicated input pins, and dedicated clock pins of
Cyclone III family devices before or during power up or power down without
damaging the device. Cyclone III family devices support any power up or
power down sequence (V
CCIO
, V
) to simplify system level design.
CCINT
© June 2009 Altera Corporation Cyclone III Device Handbook, Volume 1
10–2 Chapter 10: Hot Socketing and Power-On Reset in Cyclone III Devices
Hot-Socketing Specifications
I/O Pins Remain Tristated During Power-Up
The output buffers of Cyclone III family devices are turned off during system
power up or power down. Cyclone III family devices do not drive out until the device
is configured and working in recommended operating conditions. The I/O pins are
tristated until the device enters user mode with a weak pull-up resistor (R) to V
You can power up or power down the V
The V
CCIO
, V
CCA
, and V
must have monotonic rise to their steady state levels. The
CCINT
CCIO
CCA
, and V
pins in any sequence.
CCINT
, V
maximum power ramp rate for fast POR time is 3 ms, and 50 ms for standard POR
time, respectively. The minimum power ramp rate is 50 µs. V
must be powered up during device operation. All V
pins must be powered to 2.5 V
CCA
for all I/O banks
CCIO
(even when PLLs are not used), and must be powered up and powered down at the
same time. V
must always be connected to V
CCD_PLL
through a decoupling
CCINT
capacitor and ferrite bead. During hot socketing, the I/O pin capacitance is less than
15 pF and the clock pin capacitance is less than 20 pF.
Cyclone III family devices meet the following hot socketing specification:
CCIO
.
■ The hot-socketing DC specification is | I
■ The hot-socketing AC specification is | I
| < 300 uA
IOPIN
| < 8 mA for the ramp rate of 10 ns or
IOPIN
more
For ramp rates faster than 10 ns on I/O pins, |I
| is obtained with the equation
IOPIN
I = C dv/dt, in which C is the I/O pin capacitance and dv/dt is the slew rate. The
hot-socketing specification takes into account the pin capacitance but not board trace
and external loading capacitance. You must consider additional or separate
capacitance for trace, connector, and loading. I
on the device. The DC specification applies when all V
is the current for any user I/O pins
IOPIN
supplied to the device is
CC
stable in the powered-up or powered-down conditions.
A possible concern for semiconductor devices in general regarding hot socketing is
the potential for latch up. Latch up can occur when electrical subsystems are
hot-socketed into an active system. During hot socketing, the signal pins may be
connected and driven by the active system before the power supply can provide
current to the V
and cause a low-impedance path from V
of the device and ground planes. This condition can lead to latch up
CC
to ground in the device. As a result, the
CC
device extends a large amount of current, thus possibly causing electrical damage.
The design of the I/O buffers and hot socketing circuitry ensures that Cyclone III
family devices are immune to latch up during hot socketing.
f For more information on the hot socketing specification, refer to the Cyclone III Device
Data Sheet and Cyclone III LS Device Data Sheet chapters in volume 2 of the Cyclone III
Device Handbook and the Hot-Socketing and Power-Sequencing Feature and Testing for
Altera Devices white paper.
Cyclone III Device Handbook, Volume 1 © June 2009 Altera Corporation
Chapter 10: Hot Socketing and Power-On Reset in Cyclone III Devices 10–3
Hot-Socketing Feature Implementation
Hot-Socketing Feature Implementation
Each I/O pin has the following circuitry shown in Figure 10–1. The hot socketing
circuit does not include CONF_DONE, nCEO, and nSTATUS pins to ensure that they are
able to operate during configuration. Thus, it is expected behavior for these pins to
drive out during power up and power down sequences.
Figure 10–1 shows the hot socketing circuit block diagram for Cyclone III family
devices.
Figure 10–1. Hot Socketing Circuit Block Diagram for Cyclone III Family Devices
Power On
Reset
V
CCIO
Monitor
Weak
Pull-Up
Resistor
PAD
R
Tolerance
Input Buffer
to Logic Array
Voltage
Control
Output Enable
Hot Socket
Output
Pre-Driver
The POR circuit monitors the voltage level of power supplies and keeps the I/O pins
tristated until the device is in user mode. The weak pull-up resistor (R) in Cyclone III
family devices I/O element (IOE) keeps the I/O pins from floating. The 3.0-V
tolerance control circuit permits the I/O pins to be driven by 3.0 V before V
and V
supplies are powered up, and it prevents the I/O pins from driving out
CCA
when the device is not in user mode.
1 Altera
®
uses GND as reference for hot-socketing operation and I/O buffer designs. To
ensure proper operation, Altera recommends connecting the GND between boards
before connecting the power supplies. This prevents the GND on your board from
being pulled up inadvertently by a path to power through other components on your
board. A pulled up GND can otherwise cause an out-of-specification I/O voltage or
current condition with the Altera device.
CCIO
, VCC,
© June 2009 Altera Corporation Cyclone III Device Handbook, Volume 1
10–4 Chapter 10: Hot Socketing and Power-On Reset in Cyclone III Devices
POR Circuitry
POR Circuitry
Cyclone III family devices contain POR circuitry to keep the device in a reset state
until the power supply voltage levels have stabilized during power up. During POR,
all user I/O pins are tristated until the V
In addition, the POR circuitry also ensures the V
that contains configuration pins reach an acceptable level before configuration is
triggered.
reaches the recommended operating levels.
CC
level of I/O banks 1, 6, 7, and 8
CCIO
The POR circuit of the Cyclone III device monitors the V
CCINT
, V
CCIO
, and V
CCA
pins
during power-on. The enhanced POR circuit of the Cyclone III LS device includes
monitoring V
to ensure that V
CCBAT
is always at the minimum requirement voltage
CCBAT
level.
1 The V
for Cyclone III LS devices only, and Cyclone III devices do not have V
power supply is the new design security feature power supply introduced
CCBAT
power
CCBAT
supply.
After Cyclone III family devices enter user mode, the POR circuit continues to
monitor the V
detected. If the V
mode, the POR circuit resets the device. If the V
CCINT
and V
CCINT
pins so that a brown-out condition during user mode is
CCA
and V
voltage sag below the POR trip point during user
CCA
voltage sags during user mode,
CCIO
the POR circuit does not reset the device.
In some applications, it is necessary for a device to wake up very quickly to begin
operation. Cyclone III family devices offer the Fast-On feature to support fast
wake-up time applications. For Cyclone III family devices, the MSEL[3..0] pin
settings determine the POR time (t
) of the device. Fast POR ranges from 3 ms to
POR
9 ms while standard POR ranges from 50 ms to 200 ms.
f For more information on the MSEL[3..0] pin settings, refer to the Configuration,
Design Security, and Remote System Upgrades in Cyclone III Devices chapter in volume 1
of the Cyclone III Device Handbook.
f For more information on the V
pin connection, refer to the Cyclone III Device
CCBAT
Family Pin Connection Guidelines.
Cyclone III Device Handbook, Volume 1 © June 2009 Altera Corporation
Chapter 10: Hot Socketing and Power-On Reset in Cyclone III Devices 10–5
Chapter Revision History
Chapter Revision History
Tab le 1 0– 1 shows the revision history for this chapter.
Table 10–1. Chapter Revision History
Date and
Document
Version Changes Made Summary of Changes
June 2009
v3.0
October 2008
v1.2
July 2007
v1.1
March 2007
v1.0
■ Updated chapter part number
■ Updated “I/O Pins Remain Tristated During
■ Updated to include Cyclone III LS information
Power-Up” on page 10–2
■ Updated “Hot-Socketing Feature
Implementation” on page 10–3
■ Updated “POR Circuitry” on page 10–4
■ Updated chapter to new template
■ Added handnote to the “Cyclone III
—
Hot-Socketing Specifications” section
■ Updated “I/O Pins Remain Tri-stated During
Power-Up” section
■ Updated Figure 10–3
■ Added chapter TOC and “Referenced
Added information that the power supply voltages
must rise monotonically to their steady state levels
Documents” section
Initial release. —
© June 2009 Altera Corporation Cyclone III Device Handbook, Volume 1
10–6 Chapter 10: Hot Socketing and Power-On Reset in Cyclone III Devices
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.
Chapter Revision History
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