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PDF LTC1646 Data sheet ( Hoja de datos )
| Número de pieza | LTC1646 | |
| Descripción | CompactPCI Dual Hot Swap Controller | |
| Fabricantes | Linear | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC1646 (archivo pdf) en la parte inferior de esta página. Total 20 Páginas | ||
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FEATURES
■ Allows Safe Board Insertion and Removal from a
Live, CompactPCITM Bus
■ Controls 3.3V and/or 5V Supplies
■ Programmable Foldback Current Limit During
Power-Up
■ Dual Level Circuit Breakers Protect Supplies from
Overcurrent and Short-Circuit Faults
■ LOCAL_PCI_RST# Logic On-Chip
■ PRECHARGE Output Biases I/O Pins During Card
Insertion and Extraction
■ User Programmable Supply Voltage Power-Up Rate
■ 15V High Side Drive for External N-Channel
MOSFETS
■ PWRGD, RESETOUT and FAULT Outputs
U
APPLICATIO S
■ CompactPCI Bus Removable Boards
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
LTC1646
CompactPCI Dual
Hot Swap Controller
DESCRIPTIO
The LTC®1646 is a Hot SwapTM controller that allows a
board to be safely inserted and removed from a live
CompactPCI bus slot. Two external N-Channel transistors
control the 3.3V and 5V supplies. The supplies can be
ramped-up in current limit or a programmable rate. Elec-
tronic circuit breakers protect both supplies against
overcurrent fault conditions. The PWRGD output indicates
when all of the supply voltages are within tolerance. The
OFF/ON pin is used to cycle the board power or reset the
circuit breaker. The PRECHARGE output can be used to
bias the bus I/O pins during card insertion and extraction.
PCI_RST# is logically combined on-chip with HEALTHY#
in order to generate LOCAL_PCI_RST# which can be used
to reset the CPCI card logic if either of the supply voltages
is not within tolerance.
The LTC1646 is available in the 16-pin narrow SSOP
package.
TYPICAL APPLICATIO
5V
LONG 5V
3.3V
LONG 3.3V
COMPACT PCI
BACKPLANE
CONNECTOR
(MALE)
COMPACT PCI
CIRCUIT CARD
CONNECTOR
(FEMALE)
2.7Ω
1.8Ω
V(I/O)
BD_SEL#
HEALTHY#
PCI_RST#
1.2k
V(I/O)
3k
Z1 Z2
R1 Q2
0.005Ω, 1% IRF7413
R2
0.007Ω Q1
1% IRF7413
0.1µF
1k
3k
0.1µF
R3
10Ω
8 9 10 7 12
3VIN 3VSENSE GATE 3VOUT 5VIN
15 OFF/ON
11
5VSENSE
R4
10Ω
R5
1k, 5%
5
5VOUT
2
TIMER
10k
3 FAULT
4 PWRGD
16 RESETIN
GND
6
LTC1646
PRECHARGE
13
DRIVE
18Ω 14
3VOUT
1
RESETOUT
3k
1k
5V
5A
3.3V
7.6A
C1
0.01µF
0.1µF
GROUND
I/O PIN 1
DATA BUS
Z1, Z2: BZX84C6V2
18Ω 4.7nF
12Ω
PRECHARGE OUT MMBT2222A
10k
1V ±10%
IOUT = ± 55mA
3VIN
10Ω DATA LINE EXAMPLE
DATA BUS
Figure 1
3VIN 5VIN
3.3V 5V
RESET#
I/O PCI
BRIDGE
(21154)
1646 F01
1646fa
1
1 page  
LTC1646
TYPICAL PERFOR A CE CHARACTERISTICS
Gate ISINK vs Temperature
10
FAULT = 0V
9
8
7
6
5
–50 –25
0
25 50
TEMPERATURE (°C)
75 100
1646 G13
Power Good Threshold Voltage vs
Temperature (5VOUT)
4.75
4.70
4.65
4.60
4.55
4.50
–50 –25 0
25 50
TEMPERATURE (°C)
75 100
1646 G16
3VSENSE Input Current vs
Temperature
70
69
68
67
66
65
64
63
62
61
60
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1646 G19
Gate Voltage vs Temperature
15.5
I = –1µA
15.0
5VIN = 5V
14.5
14.0
13.5
5VIN = 3.3V
13.0
12.5
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1646 G14
Timer Threshold Voltage vs
Temperature
1.30
1.28
1.26
1.24
1.22
1.20
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1646 G17
Power Good Threshold Voltage vs
Temperature (3VOUT)
3.00
2.95
2.90
2.85
2.80
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1646 G15
5VSENSE Input Current vs
Temperature
70
69
68
67
66
65
64
63
62
61
60
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1646 G18
3VIN Input Current vs Temperature
480
475
470
465
460
455
450
445
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1646 G20
Timer Current vs Temperature
–4.00
–4.25
–4.50
–4.75
–5.00
–5.25
–5.50
–5.75
–6.00
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1646 G21
1646fa
5
5 Page 
APPLICATIO S I FOR ATIO
LTC1646
GATE
10V/DIV
5VOUT
3VOUT
5V/DIV
GATE
10V/DIV
5VOUT
3VOUT
5V/DIV
TIMER
5V/DIV
TIMER
5V/DIV
BD_SEL#
5V/DIV
HEALTHY#
5V/DIV
LCL_PCI_RST#
5V/DIV
PRECHARGE
5V/DIV
20ms/DIV
Figure 2. Normal Power-Up Sequence
1646 F02
BD_SEL#
5V/DIV
HEALTHY#
5V/DIV
LCL_PCI_RST#
5V/DIV
PRECHARGE
5V/DIV
10ms/DIV
Figure 3. Normal Power-Down Sequence
1646 F03
Power-Down Sequence
When BD_SEL# is pulled high, a power-down sequence
begins (Figure 3).
Internal switches are connected to each of the output
supply voltage pins to discharge the bypass capacitors to
ground. The TIMER pin (Pin 2) is immediately pulled low.
The GATE pin (Pin 10) is pulled down by a 200µA current
source to prevent the load currents on the 3.3V and 5V
supplies from going to zero instantaneously in order to
prevent glitching the power supply voltages. When either
of the output voltages dips below its threshold, HEALTHY#
pulls high and LOCAL_PCI_RST# will be asserted low.
Once the power-down sequence is complete, the CPCI
card may be removed from the slot. During extraction, the
precharge circuit will continue to bias the bus I/O pins at
1V until the 5V and 3.3V long connector pin connections
are separated.
Timer
During a power-up sequence, a 5µA current source is
connected to the TIMER pin and current limit faults are
ignored until the voltage exceeds 1.25V. This feature
allows the chip to power up CPCI boards with widely
varying capacitive loads on the supplies. The power-up
time for either of the two outputs is given by:
tON
(XVOUT
)
=
2
•
CLOAD(XVOUT) • XVOUT
ILIMIT(XVOUT) – ILOAD(XVOUT)
(2)
Where XVOUT = 5VOUT or 3VOUT. For example, for
CLOAD(5VOUT) = 2000µF, ILIMIT = 7A, and ILOAD = 5A, the
5VOUT turn-on time will be ~10ms. By substituting the
variables in Equation 2 with the appropriate values, the
turn-on time for the 3VOUT output can also be calculated.
The timer period should be set longer than the maximum
supply turn-on time but short enough to not exceed the
maximum safe operating area of the pass transistor during
a short-circuit. The timer period for the LTC1646 is given
by:
tTIMER
=
C TIMER •1.25V
5µA
(3)
As a design aid, the timer period as a function of the timing
capacitor using standard values from 0.01µF to 1µF is
shown in Table 2.
1646fa
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC1646.PDF ] | |
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