LTC1643AL-1CGN#TRPBF Linear Technology, LTC1643AL-1CGN#TRPBF Datasheet - Page 14

• Manufacturer Part Number: LTC1643AL-1CGN#TRPBF
• Description: IC CTRLR HOTSWAP PCI BUS 16SSOP
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC1643AL-1CGN#TRPBF

• Applications: CompactPCI™
• Internal Switch(s): No
• Voltage - Supply: 3.3V, 5V, ±12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS
LTC1643AL
LTC1643AL-1/LTC1643AH
Increasing 12V and – 12V Current Capability
for PCI Applications
The internal switches of the LTC1643A are designed for up
to 500mA loads on 12V and 200mA on –12V. If more
current is needed, then the circuits in Figure 8 can be used.
For the 12V supply, P-channel transistor Q4 is placed in
parallel with the internal switch. When the LTC1643AH is
turned off, the GATE pin is held low and transistor Q3 is
turned on which pulls the gate of Q4 high, turning it off.
When the LTC1643AH is turned on, the GATE pin goes
high, turning off Q3 and allowing R8 to pull the gate of Q4
low to turn it on.
Because Q4 is in parallel with the internal 12V switch, the
load current will be shared in proportion to their respective
R
switch is 0.2Ω and the internal switch is 0.4Ω, then, at
1.5A load current, the external switch will provide 1A and
the internal switch 500mA. The circuit breaker current will
14
DS(ON)
values. For example, if the R
CONTROLLER
SYSTEM
SYSTEM
SUPPLY
POWER
POWER
PCI
U
10k
10k
INFORMATION
R3
R4
U
Figure 8. Increasing 12V and – 12V Current Capability for PCI Applications
NOTE: INTENDED FOR PCI APPLICATIONS ONLY
8
2
5
6
7
ON
FAULT
PWRGD
12V
GND
V
EEIN
1
W
IN
DS(ON)
3
3V
1
IN
0.005Ω
9
R2
3V
of the external
SENSE
2
4
10
IRF7413
U
GATE
Q2
11
R5
10Ω
LTC1643AH
3V
OUT
3
3
5V
IN
13
Q3
TP0610T
R8
100k
1
0.007Ω
be reached when the internal current reaches 1A and the
external current is 2A or 3A load current.
For the –12V supply, N-channel transistor Q6 is used to
provide the extra load current. When the LTC1643AH is
turned on, the internal V
–12V output starts to pull down through D1 and turns on
Q5. When Q5 turns on, the gate of Q6 starts to rise, turning
it on. When the LTC1643AH turns off, the V
pulled up to ground, diode D1 is reversed biased, and
transistor Q5 turns off, which allows resistor R10 to turn
off Q6.
The internal –12V switch provides the current limit for the
supply, but because the high R
(1.2Ω) is in series with D1, very large currents can flow
through Q6 before the circuit breaker trips. However, if a
short to ground occurs on the –12V output, diode D1 will
prevent Q5 from turning on, which will prevent Q6 from
turning on.
R1
5V
2
Si9400
Q4
SENSE
4
12
10Ω
C3
0.1µF
12V
V
TIMER
EEOUT
OUT
16
IRF7413
15
4
Q1
R6
10Ω
C2
0.1µF
100Ω
R7
EE
Q5
TP0610T
R9
200Ω
R10
200Ω
switch is turned on and the
Si9410DY
DS(ON)
Q6
1N4148
D1
C1
0.047µF
of the internal switch
12V
1.5A
5V
5A
3.3V
7.6A
GND
–12V
1.5A
1643A F08
EEOUT
pin is
1643afb