ALTERA Cyclone III Devices User Guide

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