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LTC1644IGN#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24
LTC1644
19
1644f
APPLICATIO S I FOR ATIO
WUU
U
Figure 12. No 5V Supply Application Circuit
C1
0.047µF
GND
3V
IN
3V
IN
R21 1.74Ω
3V
SENSE
17
3V
OUT
18
5V
IN
LTC1644*
13
C6
0.01µF
5V
OUT
3
5V
SENSE
14 16
GATE
15
8
R3
10Ω
3V
OUT
1644 F12
R5
1k
R1
0.005Ω
Q1
IRF7413
Z3: 1PMT5.0AT3
*ADDITIONAL PINS OMITTED FOR CLARITY
PCB EDGE
BACKPLANE
CONNECTOR
BACKPLANE
CONNECTOR
3.3V
LONG 3.3V
GROUND
Z3
C8 0.1µF
PER 10
POWER PINS
C1
0.047µF
C4
0.01µF
GND
12V
IN
V
EEIN
OFF/ON
FAULT
PWRGD
RESETIN
3V
IN
3V
IN
*
R22 2.74Ω
5V
IN
*
3V
SENSE
17
3V
OUT
18
5V
IN
LTC1644
13
PRECHARGE DRIVE
5V
OUT
3
5V
SENSE
1416
GATE
15
1
2
5
6
7
9
12V
OUT
V
EEOUT
TIMER
RESETOUT
20
19
4
EARLY V(I/O)
R18
2k
R19
1k
R20 1.2k
R3
10Ω
5V
IN
R21 1.74Ω
R4
10Ω
R17
2k
5V
OUT
3V
OUT
12V
OUT
V
EEOUT
NC
R5
1k
R1
0.005Ω
Q1
IRF7413
Q2
IRF7413
R2
0.007Ω
C2
0.1µF
R15
1Ω
12 11
10
Z1
Z1: SMAJ12CA Z3, Z4: 1PMT5.0AT3
*5V
IN
AND 3V
IN
MAY BE USED AS SOURCES OF EARLY POWER
I/O DATA LINE 1
I/O DATA LINE 128
I/O #1
1644 F11
Q3
MMBT2222A
8
R11
51k
R10
18Ω 5%
3V
IN
3V
OUT
R13
10Ω
I/O #128
R14
10Ω
R12
51k
1V
±10%
R6
2k
R8 1k
R7
12Ω
C3 4.7nF
R9
24Ω
RESET#
PCI
BRIDGE
(21154)
PCB EDGE
BACKPLANE
CONNECTOR
C8 0.1µF
PER 10
POWER
PINS
Z3
C7
0.01µF
C6
0.01µF
BACKPLANE
CONNECTOR
5V
LONG 5V
3.3V
LONG 3.3V
12V
BD_SEL#
HEALTHY#
PCI_RST#
GROUND
I/O PIN 1
I/O PIN 128
• • •
I/O #1
I/O #128
• • •
• • •
C
LOAD(5VOUT)
C
LOAD(3VOUT)
C
LOAD(12VOUT)
Z4
C9 0.1µF
PER 10
POWER
PINS
+
+
+
Figure 11. No V
EE
(–12V) Supply Application Circuit
LTC1644
20
1644f
C1
0.047µF
GND
5V
IN
5V
IN
D1
5V
SENSE
13
5V
OUT
3
3V
IN
LTC1644*
17
3V
OUT
18
3V
SENSE
16 14
GATE
15
8
R4
10Ω
5V
OUT
1644 F13
R5
1k
R2
0.007Ω
Q2
IRF7413
D2
NCZ4
D1, D2: BAV99
Z4: 1PMT5.0AT3
*ADDITIONAL PINS OMITTED FOR CLARITY
PCB EDGE
BACKPLANE
CONNECTOR
BACKPLANE
CONNECTOR
5V
LONG 5V
GROUND
R22 2.74Ω
C6
0.01µF
C9 0.1µF
PER 10
POWER PINS
Figure 13. No 3.3V Supply Application Circuit
APPLICATIO S I FOR ATIO
WUU
U
Figure 14. BD_SEL# Pushbutton Toggle Switch
GND
LTC1644*
8
1.2k
PUSHBUTTON
SWITICH
100Ω
5V
IN
1k
GROUND
OFF/ON
5
BD_SEL#
1644 F14
*ADDITIONAL PINS OMITTED FOR CLARITY
PCB EDGE
BACKPLANE
CONNECTOR
BACKPLANE
CONNECTOR
restricts the choice of power MOSFETs to those devices
with very low R
DS(ON)
. Table 9 lists some power MOSFETs
that can be used with the LTC1644.
Power MOSFETs are classified into two categories: stan-
dard MOSFETs (R
DS(ON)
specified at V
GS
= 10V) and logic-
level MOSFETs (R
DS(ON)
specified at V
GS
= 5V). Since
external pass transistors are required for the 3.3V and 5V
supply rails, logic-level power MOSFETs should be used
with the LTC1644.
Overvoltage Transient Protection
Good engineering practice calls for bypassing the supply
rail of any analog circuit. Bypass capacitors are often
placed at the supply connection of every active device, in
addition to one or more large-value bulk bypass capacitors
per supply rail. If power is connected abruptly, the large
bypass capacitors slow the rate of rise of the supply
voltage and heavily damp any parasitic resonance of lead
or PC track inductance working against the supply bypass
capacitors.
The opposite is true for LTC1644 Hot Swap circuits
mounted on plug-in cards. In most cases, there is no
supply bypass capacitor present on the powered 12V
(12V
IN
), –12V (V
EEIN
) of the PCB edge connector or on the
3.3V (3V
IN
) or the 5V (5V
IN
) side of the MOSFET switch. An
abrupt connection, produced by inserting the board into a
backplane connector, results in a fast rising edge applied
on these input supply lines of the LTC1644.
Since there is no bulk capacitance to damp the parasitic
track inductance, supply voltage transients excite para-
sitic resonant circuits formed by the power MOSFET
capacitance and the combined parasitic inductance from
the wiring harness, the backplane and the circuit board
traces. These ringing transients appear as a fast edge on
the input supply lines, exhibiting a peak overshoot up to
2.5 times the steady-state value followed by a damped
LTC1644
21
1644f
APPLICATIO S I FOR ATIO
WUU
U
that in all LTC1644 circuit schematics, zener diodes and
snubber networks have been added to the 12V
IN
and V
EEIN
(–12V) supply rail and should be used always. Since the
absolute maximum supply voltage of the LTC1644 is
13.2V, snubber networks are not necessary on the 3V
IN
or
the 5V
IN
supply lines. Zener diodes, however, are recom-
mended as these devices provide large-scale transient
protection for the LTC1644 against PCI backplane fault
occurrences. All protection networks should be mounted
very close to the LTC1644’s supply voltage using short
lead lengths to minimize lead inductance. This is shown
schematically in Figures 15 and 16 and a recommended
layout of the transient protection devices around the
LTC1644 is shown in Figure 17.
sinusoidal response whose duration and period is depen-
dent on the resonant circuit parameters. Since the abso-
lute maximum supply voltage of the LTC1644 is 13.2V,
transient protection against 12V
IN
and V
EEIN
supply volt-
age spikes and ringing is highly recommended.
In these applications, there are two methods for eliminat-
ing these supply voltage transients: using Zener diodes to
clip the transient to a safe level and snubber networks.
Snubber networks are series RC networks whose time
constants are experimentally determined based on the
board’s parasitic resonant circuits. As a starting point, the
capacitors in these networks are chosen to be 10× to 100×
the power MOSFET’s C
OSS
under bias. The series resistor
is a value determined experimentally and ranges from 1Ω
to 50Ω, depending on the parasitic resonant circuit. Note
Figure 15. Place Transient Protection Devices Close to LTC1644’s 5V
IN
and 3V
IN
Pins
C1
0.047µF
3V
IN
3V
IN
3.3V
5V
IN
5V
3V
SENSE
17
3V
OUT
18
5V
IN
13
5V
OUT
3
5V
SENSE
1416
GATE
15
R3
10Ω
R4
10Ω
5V
OUT
5V
3V
OUT
3.3V
R5
1k
R1
0.005Ω
Q1
IRF7413
Q2
IRF7413
R2
0.007Ω
Z3 Z4
LTC1644*
1644 F15
GND
8
Z3, Z4: 1PMT5.0AT3
*ADDITIONAL DETAILS OMITTED FOR CLARITY
Figure 16. Place Transient Protection Devices
Close to LTC1644’s 12V
IN
and V
EEIN
Pins
Figure 17. Recommended Layout for Transient Protection Components
12V
IN
1
V
EEIN
12V
IN
–12V
IN
2
Z1 Z2
R16
1Ω
C5
0.01µF
LTC1644*
1644 F16
GND
8
Z1, Z2: SMAJ12CA
*ADDITIONAL DETAILS OMITTED FOR CLARITY
R15
1Ω
C4
0.01µF
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
VIAS TO
GND PLANE
C4
R13
GND
5V
IN
LTC1644*
*ADDITIONAL DETAILS OMITTED FOR CLARITY
DRAWING IS NOT TO SCALE!
1644 F17
3V
IN
V
EEIN
12V
IN
Z1
Z2
Z3 Z4
C5
R14
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24

LTC1644IGN#TRPBF

Mfr. #:
Buy LTC1644IGN#TRPBF
Manufacturer:
Analog Devices Inc.
Description:
Hot Swap Voltage Controllers CompactPCI Bus Hot Swap Cntr
Lifecycle:
New from this manufacturer.
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