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PDF LTC4241 Data sheet ( Hoja de datos )
| Número de pieza | LTC4241 | |
| Descripción | PCI-Bus | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Allows Safe Board Insertion and Removal from a
Live PCI Slot
s Controls 3.3V, 5V, –12V, 12V and 3.3V Auxiliary
Supplies
s Independent 3.3V Auxiliary Supply Hot SwapTM
Controller
s Adjustable Foldback Current Limit with Circuit
Breaker
s Adjustable Supply Voltage Power-Up Rate
s High Side Drive for External N-Channel FETs
s –12V and 12V On-Chip Switches
s Fault and Power Good Outputs
U
APPLICATIO S
s PCI-Based Servers
s Computer Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
LTC4241
PCI-Bus with 3.3V Auxiliary
Hot Swap Controller
DESCRIPTIO
The LTC®4241 is a Hot Swap controller that allows a board
to be safely inserted and removed from a live PCI-bus slot.
It has a primary controller that controls the four PCI
supplies and an independent auxiliary controller to control
the 3.3V auxiliary supply. External N-channel transistors
are used to control the 3.3V, 5V and 3.3V auxiliary supplies
while on-chip switches control the –12V and 12V supplies.
The 3.3V, 5V and 3.3V auxiliary supplies can be ramped up
at an adjustable rate. Electronic circuit breakers protect all
five supplies against overcurrent faults. The foldback
current limit feature reduces current spikes and power
dissipation when shorts occur. The PWRGD output of the
primary controller indicates when all four PCI supplies are
within tolerance. The FAULT output indicates an overcurrent
condition for any of the five supplies.
The LTC4241 is available in the 20-pin narrow SSOP
package.
TYPICAL APPLICATIO
R1 Q1
0.007Ω IRF7413
GND
5V
5A
R2
0.005Ω
Q2
IRF7413
R4 3.3V
10Ω 7.6A
SYSTEM
POWER
SUPPLY
PCI
POWER
SYSTEM
CONTROLLER
RESET
R3
0.07Ω
Q3
Si2306DS
R5
10Ω
3.3VAUX
500mA
C3
10nF
R6
10Ω
11 10
9 13
14 15 3
8 AUXIN AUXSENSE AUXGATE 3VIN 3VSENSE GATE 3VOUT
GND
1
2 12VIN
12 VEEIN
AUXON
5
ON
LTC4241
R8 10k
17 16 18
5VIN 5VSENSE 5VOUT
20
12VOUT
19
VEEOUT
6
R9 10k
FAULT
4
TIMER
7
PWRGD
R7
100Ω
C1
0.047µF
12V
500mA
–12V
100mA
BACKPLANE
C2 CONNECTOR
0.1µF
LOGIC
RESET
4241 F01
Figure 1. Hot Swappable PCI and 3.3V Auxiliary Supplies
sn4241 4241f
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TYPICAL PERFOR A CE CHARACTERISTICS
LTC4241
GATE, AUXGATE Output Sink
Current vs Temperature
350
300
GATE
250
200 AUXGATE
150
100
50
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G10
AUXGATE Voltage vs Temperature
11.75
11.60
11.45
11.30
11.15
11.00
10.85
10.70
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G13
Power Good Threshold Voltage
vs Temperature (12VOUT)
11.20
11.15
11.10
11.05
11.00
10.95
10.90
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G16
GATE, AUXGATE Fast Pull-Down
Current vs Temperature
80
70
60
50 AUXGATE
40
GATE
30
20
10
0
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G11
12V Internal Switch Voltage Drop
vs Temperature
325
I12VOUT = 500mA
300
275
250
225
200
175
150
125
100
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G14
Power Good Threshold Voltage
vs Temperature (5VOUT)
4.68
4.67
4.66
4.65
4.64
4.63
4.62
4.61
4.60
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G17
(VAUXGATE – VAUXIN)
vs Temperature
8.20
AUXIN = 3.3V
8.15
8.10
8.05
8.00
7.95
7.90
7.85
7.80
7.75
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G12
VEE Internal Switch Voltage Drop
vs Temperature
200
IVEEIN = 100mA
180
160
140
120
100
80
60
40
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G15
Power Good Threshold Voltage
vs Temperature (3VOUT)
2.915
2.910
2.905
2.900
2.895
2.890
2.885
2.880
2.875
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G18
sn4241 4241f
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APPLICATIO S I FOR ATIO
LTC4241
ON
10V/DIV
ON
10V/DIV
TIMER
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
12VOUT
5V/DIV
5VOUT 5V/DIV
3VOUT 5V/DIV
VEEOUT
5V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
10ms/DIV
4241 F02
Figure 2. Normal Power-Up Sequence
The current in each pass transistor increases until it
reaches the current limit for each supply. Each supply is
allowed to power up at the rate dV/dt = 60µA/C1 or as
determined by the current limit and the load capacitance
on the supply line, whichever is slower. Current limit faults
are ignored while the TIMER pin voltage is ramping up and
is less than 0.9V below 12VIN. Once all four PCI supply
voltages are within tolerance, the PWRGD pin will pull low.
Power-Down Sequence for PCI Power Supplies
When the ON pin is pulled low, a power-down sequence
begins for all the PCI power supplies (Figure 3).
Internal switches are connected to each of the output
supply voltage pins to discharge the load capacitors to
ground. The TIMER pin is immediately pulled low and the
internal 12V and –12V switches are turned off. The GATE
pin is pulled to ground by an internal 200µA current
source. This turns off the external pass transistors in a
controlled manner and prevents the load current on the
3.3V and 5V supplies from going to zero instantaneously
and glitching the power supply voltages. When any of the
output voltages dips below its threshold, the PWRGD pin
pulls high.
GATE
10V/DIV
12VOUT
5V/DIV
5VOUT 5V/DIV
3VOUT 5V/DIV
VEEOUT
5V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
10ms/DIV
4241 F03
Figure 3. Normal Power-Down Sequence
Timer
During a power-up sequence for the PCI power supplies,
a 22µA current source is connected to the TIMER pin and
current limit faults are ignored until the voltage ramps to
within 0.9V of 12VIN. This feature allows the chip to power
up a PCI slot that can accommodate boards with a wide
range of capacitive loads on the supplies. The power-up
time for any one of the four outputs will be:
tON
≅
2
•
CLOAD • VOUT
ILIMIT – ILOAD
For example, for CLOAD = 2000µF, VOUT = 5V, ILIMIT = 7A,
ILOAD = 5A, the 5VOUT turn-on time will be ~10ms. By
substituting the variables in the above equation with the
appropriate values, the turn-on time for the other three
outputs can 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
is given by:
tTIMER
=
C TIMER •11.1V
22µA
sn4241 4241f
11
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4241.PDF ] | |
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