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參數資料
| 型號： | LTC4242CUHF#TRPBF |
| 廠商： | Linear Technology |
| 文件頁數： | 17/24頁 |
| 文件大?。?/td> | 350K |
| 描述： | IC CNTRLR HOT SWAP 38-QFN |
| 標準包裝： | 2,500 |
| 類型： | 熱交換控制器 |
| 應用： | 通用型，PCI Express? |
| 內部開關： | 無 |
| 電源電壓： | 2.7 V ~ 6 V |
| 工作溫度： | 0°C ~ 70°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 38-WFQFN 裸露焊盤 |
| 供應商設備封裝： | 38-QFN（5x7） |
| 包裝： | 帶卷 (TR) |
LTC4242
17
4242f
V
CC
Power Supply
The LTC4242 derives its power from V
CC
. A bypass capacitor
of 1礔 should be connected between this pin and ground.
If V
CC
is derived from the input supplies of 3V
IN
or AUXIN,
a lowpass lter shown in Figure 11 should be used.
This RC network allows the LTC4242 to ride through a
3V
IN
/AUXIN short-circuit transient without collapsing
below the V
CC
UVLO threshold. AUXIN or 3V
IN
may have
narrow but high glitches due to parasitic inductance. Since
the absolute maximum rating for V
CC
is 7V compared to
10V for AUXIN and 3V
IN
, the R
S
and C1 values should be
chosen to damp the peak voltage seen by V
CC
below 7V.
Figure 11. RC Network for V
CC
Filtering
APPLICATIO S I FOR ATIO
U
U
U
3V
SENSE
3V
OUT
EN
BD_PRST
3.3V
R
AUTO
200k
C
AUTO
0.1礔
3V
IN
3V
GATE
Q2
Si7336ADP
R2
13m&
GND
LTC4242*
FAULT
*ADDITIONAL DETAILS OMITTED FOR CLARITY
ON
LOAD
4242 F09
1.235V
ON/FAULT
3V
IN
3V
GATE
3V
IN
3V
SENSE
0.6V
V
OL
V
TH
V
CB
t
CB
t
OFF
4242 F10
Figure 9. Auto-Retry Application
Figure 10. Auto-Retry Timing
GATE Pin Voltage
The minimum gate drive voltage is 4.5V, therefore, logic
level N-channel MOSFETs should be used for the external
switches to maintain adequate gate enhancement. The
GATE pins are clamped at a typical value of 5.5V above
the respective OUT pins.
Compensating the Active Current Loop
The active current limit circuit is compensated using the
resistor R
G
and the slew rate control capacitor C
G
. The value
of C
G
is selected based on the inrush current allowed. The
R
G
value should be experimentally determined. A suggested
value range for R
G
is between 10?and 100?
C1
1
F
4242 F11
R
S
33
AUXIN
OR
3V
IN
V
CC
Force ON Operation
When the FON pin is pulled high and EN is low, the
LTC4242 operates in the diagnostic mode. All the input
supplies power switches are forced to turn on, regardless
of undervoltage conditions on the input supplies, status of
the ON pins and the fault latch. The contents in the fault
latch would be preserved during this time and no change
of state would occur after the part is con gured to operate
in the diagnostic mode. If the output current exceeds the
ECB threshold, FAULT/AUXFAULT is pulled low immedi-
ately, but does not latch. The undervoltage lockout on V
CC
turns off all the switches, regardless of the status of FON.
During thermal shutdown, the internal switch is shut off to
prevent overheating, even if FON is high. The main power
switches remain on as FON is high. Care must be taken to
ensure the outputs are not short circuited since there is
no current limit mechanism in diagnostic mode.
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