?/DIV>
4225 offers ideal diode and Hot Swap" functions
for two power rails by controlling external series connected
N-channel MOSFETs. MOSFETs acting as ideal diodes
replace two high power Schottky diodes and the associ-
ated heat sinks, saving power and board area. Hot Swap
control MOSFETs allow boards to be safely inserted and
removed from a live backplane by limiting inrush current.
The supply output is also protected against short-circuit
faults with a fast acting current limit and internal timed
circuit breaker.
The LTC4225 regulates the forward voltage drop across
the back-to-back MOSFETs to ensure smooth current
transfer from one supply to the other without oscillation.
The ideal diodes turn on quickly to reduce the load voltage
droop during supply switch-over. If the input supply fails
or is shorted, a fast turn-off minimizes reverse-current
transients.
The LTC4225 allows independent on/off control, and reports
fault and power good status for the supply. The LTC4225-1
features a latch-off circuit breaker, while the LTC4225-2
provides automatic retry after a fault.
礣CA Application
applicaTions
n
Power Path and Inrush Current Control for
Redundant Supplies
n
Low Loss Replacement for Power Schottky Diodes
n
Allows Safe Hot Swapping from a Live Backplane
n
2.9V to 18V Operating Range
n
Controls N-Channel MOSFETs
n
Limits Peak Fault Current in d1祍
n
0.5祍 Turn-On and Reverse Turn-Off Time
n
Adjustable Current Limit with Circuit Breaker
n
Smooth Switchover without Oscillation
n
Adjustable Current Limit Fault Delay
n
Fault and Power Status Output
n
LTC4225-1: Latch Off After Fault
n
LTC4225-2: Automatic Retry After Fault
n
24-Lead 4mm ?5mm QFN and SSOP Packages
n
Redundant Power Supplies
n
Supply Holdup
n
MicroTCA Systems and Servers
n
Telecom Networks
n
Power Prioritizer
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
CPO1
ON1
137k
12V
12V
ON2
INTV
CC
GND
0.1礔
0.1礔
0.1礔
47nF
47nF
12V
7.6A
PLUG-IN
CARD 1
PLUG-IN
CARD 2
BACKPLANE
422512 TA01a
IN1
SENSE1  DGATE1
Si7336ADP
LTC4225
0.004
Si7336ADP
Si7336ADP
0.004
Si7336ADP
HGATE1  OUT1
CPO2
IN2
SENSE2  DGATE2
HGATE2  OUT2
FAULT1
PWRGD1
EN1
TMR1
TMR2
EN2
PWRGD2
FAULT2
20k
20k
137k
12V
7.6A
Power Dissipation vs Load Current
LOAD CURRENT (A)
0
0
0.5
1.0
1.5
2.0
2.5
3.0
2
4
6
8
422512 TA01
DIODE
(SBG1025L)
MOSFET
(Si7336ADP)
POWER SAVED