參數(shù)資料
型號(hào): LTC4222IUH#PBF
廠商: LINEAR TECHNOLOGY CORP
元件分類: 電源管理
英文描述: 2-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC32
封裝: 5 X 5 MM, LEAD FREE, PLASTIC, MO-220WHHD-X, QFN-32
文件頁數(shù): 9/32頁
文件大?。?/td> 280K
代理商: LTC4222IUH#PBF
LTC4222
17
4222fa
APPLICATIONS INFORMATION
Setting the CONFIG pin high allows the two channels to
start up and turn off independently. When both ON signals
are brought high sequentially, the channel turned on rst
immediately begins to start up and the second channel
has a 200ns window to assert it’s ON signal in order to
start up in the same timer period. If the second ON signal
is asserted after the 200ns window but before the end of
the rst channel’s start-up time, the second channel start-
up is delayed. The second channel will then start 100ms
after the rst channel’s start-up timer has expired and the
TIMER pin, if used, reaches its 200mV low threshold.
When an external TIMER capacitor is used, the TIMER
capacitor voltage ramps up with a 100μA current. Once the
TIMER pin reaches its 1.235V threshold the TIMER begins
to discharge. While the TIMER capacitor is discharging, the
ON signal for the second channel should not be asserted
for 2ms/μF of TIMER capacitance. This allows the TIMER
capacitor to return to its low state and ensures that the next
channel to start receives a full timer cycle. This wait time
is unnecessary when using the internal 100ms timer.
Board Present Change of State
The EN pins may be used to detect the presence of one or
two downstream cards. Whenever an EN pin toggles, FAULT
bit 4 is set to indicate a change of state. When the EN pin
goes high, indicating board removal, the corresponding
GATE turns off immediately (with a 1mA current to ground)
and the board present STATUS bit 4, is cleared. If the EN
pin is pulled low, indicating a board insertion, all fault bits
for that channel except FAULT bit 4 are cleared and enable
STATUS bit 4, is set. If the EN pin remains low for 100ms
the state of the ON pin is captured in ‘FET On’ CONTROL
bit 3. This turns the switch on if the ON pin is tied high.
There is an internal 10μA pull-up current source on the
EN pin. If the CONFIG pin is tied low, both EN pins must
be low for 100ms for the two channels to be enabled and
if either EN pin goes high both channels will turn off.
If a channel shuts down due to a fault, it may be desirable
to restart that channel simply by removing and reinserting
the related load card. In cases where the LTC4222 and the
switch reside on a backplane or midplane and the load
resides on a plug-in card, the EN pin detects when the
plug-in card is removed. Figure 4 shows an example where
the EN pin is used to detect insertion. Once the plug-in card
is reinserted the fault register is cleared except for FAULT
bit 4. After 100ms the state of the ON pin is latched into
bit 3 of the CONTROL register. At this point the channel
starts up again.
If a connection sense on the plug-in card is driving an EN
pin, insertion or removal of the card may cause the pin
voltage to bounce. This results in clearing the fault register
when the card is removed. The pin may be debounced
using a lter capacitor, CEN, on the EN pin as shown in
Figure 4. The lter time is given by:
tFILTER = CEN 123 (ms/μF)
Figure 4. Plug-In Card Insertion/Removal
+
1.235V
GND
MOTHERBOARD
CONNECTOR
PLUG-IN
CARD
SOURCE
OUT
LTC4222
10μA
EN
CEN
LOAD
4222 F04
FET Short Fault
A FET short fault is reported if the data converter measures
a current sense voltage greater than or equal to 2mV while
the corresponding GATE is turned off. This condition sets
FET short bit, Fault bit 5.
Power-Bad Fault
A power-bad fault is reported if a FB pin voltage drops
below its 1.235V threshold for more than 2μs when the
corresponding GATE is above the 4.3V gate to source
threshold. This pulls the GPIO pin low immediately in the
default power good conguration, and sets power-bad
present bit, STATUS bit 3, and power-bad bit, FAULT bit 3.
A circuit prevents power-bad faults if the GATE-to-SOURCE
voltage is low, eliminating false power-bad faults during
power-up or power-down. If the FB pin voltage subsequently
rises back above the threshold, a power good congured
GPIO pin returns to a high impedance state and STATUS
bit 3 is reset.
相關(guān)PDF資料
PDF描述
LTC4227CGN-2#TRPBF POWER SUPPLY MANAGEMENT CKT, PDSO16
LTC4227IGN-1#PBF POWER SUPPLY MANAGEMENT CKT, PDSO16
LTC4227CUFD-1#TRPBF POWER SUPPLY MANAGEMENT CKT, PQCC20
LTC4227CUFD-2#TRPBF POWER SUPPLY MANAGEMENT CKT, PQCC20
LTC4227IGN-1#TRPBF POWER SUPPLY MANAGEMENT CKT, PDSO16
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