LTC4210 LINER [Linear Technology], LTC4210 Datasheet - Page 9

• Manufacturer Part Number: LTC4210
• Description: Dual Supply Hot Swap Controller for Advanced Mezzanine Card
• Manufacturer: LINER [Linear Technology]

OPERATION
The LTC4223 is designed to control the power on an Ad-
vanced Mezzanine Card (AMC) or MicroTCA backplane,
allowing boards to be safely inserted and removed. It
controls the 12V main and 3.3V auxiliary power through an
external N-channel MOSFET and integrated pass transistor.
These two supplies can be turned on and off independently
by their respective ON control pins.
If either AUXON or 12ON is pulled high, an initial tim-
ing cycle set by the TIMER capacitor value is initiated
once all these conditions are met: input supplies out of
undervoltage lockout; TIMER < 0.2V and ⎯ E ⎯ N low. At the
end of the initial timing cycle, if the AUXON pin is high, the
internal pass transistor turns on. It enters into an active
current limit loop if the inrush current charging the load
capacitor exceeds 240mA. When the load is in current
limit, a 10μA pull-up charges the TIMER pin capacitor. If
the load capacitor is fully charged and the switch is no
longer in current limit before the TIMER reaches 1.235V,
⎯ A ⎯ U ⎯ X ⎯ P ⎯ G ⎯ O ⎯ O ⎯ D pulls low indicating that power is good.
Otherwise the internal switch turns off and ⎯ F ⎯ A ⎯ U ⎯ L ⎯ T pulls
low when TIMER reaches 1.235V.
If 12ON pin is high at the end of the initial timing cycle,
an internal charge pump charges the gate of the external
MOSFET with 10μA pull-up. Connecting an external gate
capacitor limits the inrush current charging the load ca-
pacitor. If the inrush current exceeds its limited current
value, an internal analog current limit (ACL) amplifi er
servos the gate to force 60mV across the external sense
resistor connected between 12VIN and 12V
During this period, TIMER pin capacitor is charged by a
200μA pull-up. If the load is fully charged and no longer in
current limit before the TIMER reaches 1.235V, ⎯ 1 ⎯ 2 ⎯ P ⎯ G ⎯ O ⎯ O ⎯ D
pulls low. Otherwise 12V shuts off and ⎯ F ⎯ A ⎯ U ⎯ L ⎯ T pulls low
when TIMER reaches 1.235V.
If an overcurrent fault occurs on the auxiliary supply after
power-up, the current is limited to 240mA and after a 25μs
delay, the circuit breaker trips and ⎯ F ⎯ A ⎯ U ⎯ L ⎯ T pulls low. Ther-
mal shutdown protects the internal pass transistor from
overheating by shutting it off at 150°C. If an overcurrent
fault occurs on the 12V supply, the current is limited to
60mV/R
charging the TIMER capacitor, the circuit breaker trips
and ⎯ F ⎯ A ⎯ U ⎯ L ⎯ T pulls low. An overcurrent fault on the auxiliary
supply shuts off 12V; a fault on the 12V supply does not
affect the auxiliary supply.
The LTC4223 provides high side current sensing informa-
tion for the 12V supply at the 12IMON pin. The 12IMON
output voltage is 33 times the sense voltage, allowing it
to be used with an external ADC.
In the off condition, 12V
to ground by internal N-channel pull downs.
SENSE
LTC4223-1/LTC4223-2
. After a timing cycle delay set by 200μA
OUT
and AUXOUT are discharged
SENSE
pins.
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