DC1054A/B - Demo Manual

DEMO CIRCUIT 1054A/B
QUICK STARTLTC4242
GUIDE
LTC4242 Dual Port,
PCI Express Hot Swap Controller
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.
L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and
PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy Drive,
FilterCAD,
Hot
Swap,
LinearView,
µModule,
Micropower
SwitcherCAD, Multimode Dimming, No Latency
, No Latency
Delta-Sigma, No RSENSE, Operational Filter, PanelProtect, PowerPath, 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.
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 factory.
LTC is a trademark of Linear Technology Corporation
PERFORMANCE SUMMARY
SYMBOL
VCC
+12VIN
+3.3VIN
3.3VAUX
INPUT
I12VOUT
I3.3VOUT
I3.3VAUXOUT
PARAMETER
Input Supply
Input Supply
Input Supply
Input Supply
Specifications are at TA = 25°C
CONDITIONS
Range
Range
Range
Range
Load Current
Load Current
Load Current
MIN
2.7
10.1
3.0
3.0
TYP
3.3
12
3.3
3.3
MAX
6.0
14.4
6.0
6.0
UNITS
V
V
V
V
5.5
3
375
A
A
mA
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 inputs 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 efficacy.
1
LTC4242
Input Bypassing
In a practical application, the
input supplies are bypassed near
the supply switches (MOSFETs Q1Q4). For the purposes of DC1054A,
bypassing has been omitted except
for the Vcc bypass capacitor C1,
located
directly
under
the
LTC4242. This simplification affects the operation of the board
in two ways. First, inductive reaction 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,
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:
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 describe the operation of port 1.
Note that external logic signals
are applied via the turrets adjacent to each jumper.
2
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 activate 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, particularly at the +3.3VIN input.
3.3VAUX
+3.3VIN
+12VIN
1A
7A
12A
Vcc for the LTC4242 may be obtained 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.
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
be in the J1(A1) position to allow
the short, A1 finger of the daughter card to initiate port activation.
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 connected HIGH, LOW, or connected to
an external logic signal. The auxiliary 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 effect, EN1# must be low.
Activating a Port
To consolidate the foregoing discussion 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#
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
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 destruction 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 specified, but does not have a hard
short across its supply. See the
LTC4242 data sheet for further information on the FON1 pin.
(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.
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.
3
LTC4242
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 supply 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 inserted, and turn off when withdrawn.
Figure 1. Proper Measurement Equipment Setup
4
LTC4242
5
LTC4242
6
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