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LTC1643L Datasheet, PDF (6/16 Pages) Linear Technology – PCI-Bus Hot Swap Controller
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LTC1643L/LTC1643L-1/LTC1643H
TYPICAL PERFORMANCE CHARACTERISTICS
3VIN Undervoltage Lockout
vs Temperature
2.454
2.452
2.450
2.448
2.446
2.444
2.442
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1643 G21
VEE Current Foldback
vs Temperature
600
500
VEEOUT = –12V
400
300
200
VEEOUT = 0V
100
0
–50 –25
0 25 50
TEMPERATURE (°C)
75 100
1643 G25
5VIN Foldback Current Limit
Voltage vs Temperature
70
60
5VOUT = 5V
50
40
30
20
10
5VOUT = 0V
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
LT1643 G23
12V Current Foldback
vs Temperature
1200
1000
12VOUT = 12V
800
600
400
12VOUT = 0V
200
0
–50 –25
0 25 50
TEMPERATURE (°C)
75 100
1643 G26
3VIN Foldback Current Limit
Voltage vs Temperature
70
60
3VOUT = 3.3V
50
40
30
20
10
3VOUT = 0V
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
LT1643 G24
VOL vs ISINK (25°C)
800
700
FAULT
600
500
400
300
PWRGD
200
100
0
0
2
4
6
8
10
ISINK (mA)
1643 G27
PIN FUNCTIONS
12VIN (Pin 1): 12V Supply Input. It powers all the chip’s
internal circuitry. A 0.5Ω switch is connected between
12VIN and 12VOUT with a foldback current limit. An
undervoltage lockout circuit prevents the switches from
turning on while the 12VIN pin voltage is less than 9.5V
typically.
VEEIN (Pin 2): – 12V Supply Input. A 1.2Ω switch is
connected between VEEIN and VEEOUT with a fold-back
current limit.
3VOUT (Pin 3): Analog Input. Used to monitor the 3.3V
output supply voltage. The PWRGD signal cannot go high
until the 3VOUT pin exceeds 2.9V typically.
6
TIMER (Pin 4): Analog Current Fault Inhibit Timing Input.
Connect a capacitor from TIMER to GND. With the chip
turned off (ON = GND or ON = High) or the internal circuit
breaker tripped (FAULT = GND), the TIMER pin is internally
held at GND. When the chip is turned on, a 20µA pull-up
current source is connected to TIMER. Current limit faults
will be ignored until the voltage at the TIMER pin rises to
within 0.9V of 12VIN.
ON/ON (Pin 5): Digital Input.The LTC1643L/LTC1643L-1
have an active low enable, ON, and the LTC1643H has an
active high enable, ON. When the ON pin is pulled high or
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