DC1054A/B - ANALOG DEVICES - Product.Network

LTC4242

1

DESCRIPTION

Demonstration Circuit 1054A

showcases the LTC4242 Dual Slot Hot

Swap Controller for PCI Express.

DC1054A features two PCI-X slots

into which DC1054B may be inserted.

Two DC1054B daughter cards are

included with each DC1054A.

LEDs indicate the presence of input

and output voltages, as well as

faults and "power good" conditions.

The daughter cards are loaded with

the maximum capacitance on each

supply.

Design files for this circuit board

are available. Call the LTC fac-

tory.

LTC is a trademark of Linear Technology Corporation

L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and

PolyPhase are registered trademarks of Linear Technology Cor-

poration. Adaptive Power, C-Load, DirectSense, Easy Drive,

FilterCAD, Hot Swap, LinearView, µModule, Micropower

SwitcherCAD, Multimode Dimming, No Latency , No Latency

Delta-Sigma, No R

SENSE

, Operational Filter, PanelProtect, Power-

Path, PowerSOT, SmartStart, SoftSpan, Stage Shedding,

SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of

Linear Technology Corporation. Other product names may be

trademarks of the companies that manufacture the products.

PERFORMANCE SUMMARY

Specifications are at TA = 25°C

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

CC

Input Supply Range

2.7 3.3 6.0 V

+12VIN

Input Supply Range 10.1 12 14.4 V

+3.3VIN

Input Supply Range 3.0 3.3 6.0 V

3.3VAUX

INPUT

Input Supply Range 3.0 3.3 6.0 V

I

12VOUT

Load Current

5.5

A

I

3.3VOUT

Load Current

3

A

I

3.3VAUXOUT

Load Current 375 m

A

OPERATING PRINCIPLES

Board Layout

Supply inputs and logic control

inputs are located along the left

side of DC1054B. Along the right

side are the supply outputs and

fault and power good outputs.

LEDs are located adjacent to in-

puts and outputs of interest.

The Vcc pin bypass capacitor is

located on the bottom of the

board, directly under the LTC4242

where it can be of greatest effi-

cacy.

DEMO CIRCUIT

1054A/B

QUICK START GUIDE

LTC4242 Dual Port,

PCI Express Hot Swap Controller

LTC4242

2

Input Bypassing

In a practical application, the

input supplies are bypassed near

the supply switches (MOSFETs Q1-

Q4). For the purposes of DC1054A,

bypassing has been omitted except

for the Vcc bypass capacitor C1,

located directly under the

LTC4242. This simplification af-

fects the operation of the board

in two ways. First, inductive re-

action on the inputs arising from

bench test leads during overload

or short circuit tests can cause

potentially damaging high voltage

surges or transients to appear at

the input pins of the LTC4242.

Transient voltage suppressors (Z1,

Z2 and Z3) have been included near

the input turrets to protect

against these transients. Surges

may also arise as a result of poor

loop response in a bench supply.

Second, dips in the input voltage

arising from load steps and wiring

resistance and inductance may ac-

tivate undervoltage lockout and

temporarily shut down the LTC4242,

particularly if both slots are

fully loaded. Take care to ensure

that the proper supply voltage is

delivered to the board, particu-

larly at the +3.3VIN input.

Input Supplies

There are three supply inputs

along the left side of DC 1054A,

with adjacent LEDs to indicate

when power is applied. In the

lower left are turrets for the

main supply inputs, +12VIN and

+3.3VIN. In the upper left is a

turret for connecting the 3.3VAUX

input.

1A supplies are adequate to power

the board, but to deliver full

power to both ports the following

ratings are recommended:

3.3VAUX 1A

+3.3VIN 7A

+12VIN 12A

Vcc for the LTC4242 may be ob-

tained from either the 3.3VAUX

supply or from the +3.3VIN supply

by setting jumper JP9. A separate

power supply for 3.3VAUX is not

strictly necessary; 3.3VAUX and

+3.3VIN may be powered from the

same source as long as adequate

current is available to power the

combined load.

Controlling the LTC4242

There are several ways to control

the LTC4242. Each port is fully

independent and identical to the

other, so this discussion will de-

scribe the operation of port 1.

Note that external logic signals

are applied via the turrets adja-

cent to each jumper.

Port 1 is activated by pulling low

the enable pin, EN1#. Jumper JP7

provides 4 options for controlling

EN#. It can be forced HIGH or LOW,

connected to an external logic

signal (EXT), or operated by the

short pins on the daughter card

using the J1(A1) jumper position.

For normal operation, JP7 should

LTC4242

3

be in the J1(A1) position to allow

the short, A1 finger of the daugh-

ter card to initiate port activa-

tion.

Fingers B17 and A1 are connected

together on the daughter card.

When the daughter card is inserted

into the edge connector, B17 is

grounded by DC 1054A. In turn A1

and EN1# are grounded, turning on

the card.

EN1# is a "global" port enable,

but two other pins also exercise

control over the individual supply

outputs. The main 12V and 3.3V

outputs are gated by the ON1 pin.

Using jumper JP2, ON1 may be con-

nected HIGH, LOW, or connected to

an external logic signal. The aux-

iliary 3.3V output has its own

control line, AUXON1, which is

connected HIGH, LOW or an external

logic signal using JP3. In order

for ON1 and AUXON1 to have any ef-

fect, EN1# must be low.

One last pin can exert control

over the outputs. The Force ON

pin, FON1 overrides all other

logic commands. FON1 is set by JP1

to HIGH, LOW, or EXT. Care must be

exercised in using FON1. If EN1#

is low, FON1 overrides both the

various enable inputs and short

circuit current limiting. If one

of the main outputs is shorted the

MOSFET and current sense resistor

may be destroyed. If EN1# is high,

FON1 forces all outputs on and

current limiting is present, but

the circuit breaker function is

disabled. Again, a short circuit

will lead to the eventual destruc-

tion of the external MOSFET. Treat

FON1 as a "battle override"

switch, or use it for debugging

purposes where a daughter card is

consuming more current than speci-

fied, but does not have a hard

short across its supply. See the

LTC4242 data sheet for further in-

formation on the FON1 pin.

Activating a Port

To consolidate the foregoing dis-

cussion into a simple procedure

for activating port 1, set ON1 and

AUXON1 high using JP2 and JP3; set

FON1 low using JP1, and set EN1#

(JP7) to the J1(A1) position to

monitor for card insertion. The

port will turn on automatically

when the card is inserted into

edge connector J1.

Outputs, Power Good, and Faults

The supply outputs are brought out

to turrets on the daughter cards

(DC 1054B), with LEDs to show when

the outputs are powered.

Along the right side of DC 1054A

are not only the supply outputs,

but also the power good and fault

outputs. Every power and signal

line has a turret for external

connections and an LED to indicate

the operating condition. Outputs

and power good signals have green

LEDs, while faults are shown with

red LEDs. Under normal conditions

5 green LEDs will light up per

port (3 outputs and 2 power good

signals) when the port is enabled.

LTC4242

4

QUICK START PROCEDURE

Check that the jumpers are in the

following default positions:

FON: LOW

ON: HIGH

AUXON: HIGH

EN#: J1(A1) and J2(A1)

Connect a 12V and 3.3V supply to

+12VIN and +3.3VIN. 3.3VAUX INPUT

may be powered from the same sup-

ply as +3.3VIN, or from a separate

3.3V supply. Turn the supplies on-

-there is no requirement for any

particular sequence. To verify

that all 3 supplies are present,

check to see that the LEDs (D1,

D2, D3) are lit.

Next, insert one of the DC 1054B

daughter cards into edge connector

J1 or J2. The port will turn on

automatically when the card is in-

serted, and turn off when with-

drawn

.

Figure 1. Proper Measurement Equipment Setup

LTC4242

5

LTC4242

6