LINER LTC1647-3 Dual hot swap controller Datasheet

LTC1647-1/LTC1647-2/LTC1647-3
Dual Hot Swap Controllers
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DESCRIPTIO
FEATURES
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The LTC®1647-1/LTC1647-2/LTC1647-3 are dual Hot
SwapTM controllers that permit a board to be safely inserted and removed from a live backplane.
Allows Safe Board Insertion and Removal from a
Live Backplane
Programmable Electronic Circuit Breaker
FAULT Output Indication
Programmable Supply Voltage Power-Up Rate
High Side Drive for External MOSFET Switches
Controls Supply Voltages from 2.7V to 16.5V
Undervoltage Lockout
Using external N-channel MOSFETs, the board supply
voltages can be ramped up at a programmable rate. A high
side switch driver controls the MOSFET gates for supply
voltages ranging from 2.7V to 16.5V. A programmable
electronic circuit breaker protects against overloads and
shorts. The ON pins are used to control board power or
clear a fault.
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APPLICATIO S
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The LTC1647-1 is a dual Hot Swap controller with a
common VCC pin, separate ON pins and is available in an
SO-8 package. The LTC1647-2 is similar to the LTC1647-1
but combines a fault status flag with automatic retry at the
ON pins and is also available in the SO-8 package. The
LTC1647-3 has individual VCC pins, ON pins and FAULT
status pins for each channel and is available in a 16-lead
narrow SSOP package.
Hot Board Insertion
Electronic Circuit Breaker
Portable Computer Device Bays
Hot Plug Disk Drive
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATIO
VID Controller for Two Device Bays
Q1
1/2 MMDF3N02HD
DEVICE #1
R3**
R2
10Ω
CONNECTOR #1
R1
0.1Ω
3.3V VID
SUPPLY
+
CLOAD*
R4**
1394 PHY
AND/OR
USB PORT
ON/OFF Sequence
VON
ON1
ON2
2
3
4
SENSE 1
VCC
ON1
GATE 1
7
CLOAD IS USER-SELECTED BASED
ON THE DEVICE REQUIREMENTS
** R3, R4, R7 AND R8 ARE OPTIONAL DISCHARGE
RESISTORS WHEN DEVICES ARE POWERED-OFF
Q1, Q2: ON SEMICONDUCTOR
*
LTC1647-1
ON2
GND
SENSE 2
C1
4.7nF
GATE 2
VGATE
5
R6
10Ω
C3
4.7nF
R5
0.1Ω
VOUT
5ms/DIV
DEVICE #2
Q2
1/2 MMDF3N02HD
R7**
CONNECTOR #2
1
6
2.5V/DIV
8
+
CLOAD*
R8**
1647-1/2/3 TA01a
1394 PHY
AND/OR
USB PORT
1647-1/2/3 TA01
1
LTC1647-1/LTC1647-2/LTC1647-3
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ABSOLUTE
AXI U RATI GS
(Note 1)
Supply Voltage (VCC) ............................................... 17V
Input Voltage (SENSE) ................. – 0.3V to (VCC + 0.3V)
Input Voltage (ON) .....................................– 0.3V to 17V
Output Voltage (FAULT) .............................– 0.3V to 17V
Output Voltage (GATE) ......... Internally Limited (Note 3)
Operating Temperature Range
Commercial ............................................. 0°C to 70°C
Industrial ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
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PACKAGE/ORDER I FOR ATIO
TOP VIEW
VCC 1
8
ON1 2
TOP VIEW
TOP VIEW
7
SENSE 1
SENSE 2
VCC 1
8
ON1/FAULT 1 2
7
SENSE 1
VCC1
1
16 VCC2
SENSE 2
ON1
2
15 SENSE 1
FAULT 1
3
14 SENSE 2
ON2 3
6
GATE 1
ON2/FAULT 2 3
6
GATE 1
GND 4
5
GATE 2
GND 4
5
GATE 2
S8 PACKAGE
8-LEAD PLASTIC SO
ON2
4
13 GATE 1
FAULT 2
5
12 GATE 2
NC
6
11 NC
NC
7
10 NC
GND
8
9
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 130°C/W
TJMAX = 150°C, θJA = 130°C/W
NC
GN PACKAGE
16-LEAD PLASTIC SSOP
TJMAX = 150°C, θJA = 130°C/W
ORDER PART NUMBER
ORDER PART NUMBER
ORDER PART NUMBER
LTC1647-1CS8
LTC1647-1IS8
LTC1647-2CS8
LTC1647-2IS8
LTC1647-3CGN
LTC1647-3IGN
S8 PART MARKING
S8 PART MARKING
GN PART MARKING
16471
16471I
16472
16472I
16473
16473I
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise noted. (Note 2)
SYMBOL PARAMETER
CONDITIONS
VCC
VCCX Supply Range
Operating Range
●
ICC
VCC Supply Current (Note 4)
ON1, ON2 = VCC1 = VCC2, ICC = ICC1 + ICC2
●
1.0
6
mA
ICCX
VCCX Supply Current (Note 5, LTC1647-3)
ONX = VCCX, ICCX Individually Measured,
VCC1 = 5V, VCC2 = 12V or VCC1 = 12V, VCC2 = 5V
●
0.5
5
mA
VLKO
VCCX Undervoltage Lockout
Coming Out of UVLO (Rising VCCX)
●
2.30
2.45
2.60
VLKH
VCCX Undervoltage Lockout Hysteresis
VCB
Circuit Breaker Trip Voltage
VCB = VCCX – VSENSEX
●
40
50
60
mV
ICP
GATE X Output Current
ONX High, FAULT X High, VGATE = GND (Sourcing)
ONX Low, FAULT X High, VGATE = VCC (Sinking)
ONX High, FAULT X Low, VGATE = 15V (Sinking)
●
6
10
50
50
14
µA
µA
mA
2
MIN
TYP
2.7
MAX
UNITS
16.5
V
210
V
mV
LTC1647-1/LTC1647-2/LTC1647-3
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise noted. (Note 2)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
∆VGATE
External MOSFET Gate Drive
(VGATE – VCC), VCC1 = VCC2 = 5V
(VGATE – VCC), VCC1 = VCC2 = 12V
VONHI
●
●
10
10
13
15
17
19
V
V
ONX Threshold High
●
1.20
1.29
1.38
V
VONLO
ONX Threshold Low
●
1.17
1.21
1.25
V
VONHYST
ONX Hysteresis
IIN
ONX Input Current
ON = GND or VCC
●
VOL
FAULT X Output Low Voltage
(LTC1647-2, LTC1647-3)
IO = 1mA, VCC = 5V
IO = 5mA, VCC = 5V
●
ILEAK
FAULT X Output Leakage Current
(LTC1647-3)
No Fault, FAULT X = VCC = 5V
tFAULT
Circuit Breaker Delay Time
VCCX – VSENSEX = 0 to 100mV
tRESET
Circuit Breaker Reset Time
ONX High to Low, to FAULT X High
tON
Turn-On Time
ONX Low to High, to GATE X On
2
µs
tOFF
Turn-Off Time
ONX High to Low, to GATE X Off
1
µs
70
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 3: An internal Zener on the GATE pins clamp the charge pump
voltage to a typical maximum operating voltage of 28V. External overdrive
of the GATE pin beyond the internal Zener voltage may damage the device.
±1
mV
±10
µA
0.4
V
V
±10
µA
0.8
±1
µs
0.3
50
●
UNITS
100
µs
The GATE capacitance must be < 0.15µF at maximum VCC. If a lower GATE
pin clamp voltage is desired, use an external Zener diode.
Note 4: The total supply current ICC is measured with VCC1 and VCC2
connected internally (LTC1647-1, LTC1647-2) or externally (LTC1647-3).
Note 5: The individual supply current ICCX is measured on the LTC1647-3.
The lower of the two supplies, VCC1 and VCC2, will have its channel’s
current. The higher supply will carry the additional supply current of the
charge pump and the bias generator beside its channel’s current.
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PI TABLES
LTC1647-3 Pinout
LTC1647-1 Pinout
PIN
DESCRIPTION
PIN
DESCRIPTION
PIN
DESCRIPTION
PIN
DESCRIPTION
1
VCC
5
GATE 2
1
VCC1
9
NC
2
ON1
6
GATE 1
2
ON1
10
NC
3
ON2
7
SENSE 2
3
FAULT 1
11
NC
4
GND
8
SENSE 1
4
ON2
12
GATE 2
5
FAULT 2
13
GATE 1
6
NC
14
SENSE 2
7
NC
15
SENSE 1
8
GND
16
VCC2
LTC1647-1 does not have the FAULT status feature.
LTC1647-2 Pinout
PIN
DESCRIPTION
PIN
DESCRIPTION
1
VCC
5
GATE 2
2
ON1 and FAULT 1
(Internally Tied Together)
6
GATE 1
7
SENSE 2
3
ON2 and FAULT 2
(Internally Tied Together)
8
SENSE 1
4
GND
The ONX/FAULT X must be connected to a driver via a resistor if the
autoretry feature is being used..
3
LTC1647-1/LTC1647-2/LTC1647-3
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TYPICAL PERFOR A CE CHARACTERISTICS
ICC vs VCC
ICC vs Temperature
6
5
6
TA = 25°C
ICC = ICC1 + ICC2
VCC = VCC1 = VCC2 = ON1 = ON2
5
TA = 25°C
ICC = ICC1 + ICC2
VCC = VCC1 = VCC2 = ON1 = ON2
5
4
4
3
VCC = 15V
ICC1 (mA)
4
ICC (mA)
ICC (mA)
ICC1 vs VCC2
VCC = 12V
3
2
2
1
1
VCC = 5V
0
2
4
6
8
10 12
VCC (V)
14
16
VCC = 3V
VCC1 = 15V
VCC1 = 12V
2
VCC1 = 3V
1
14
20
12
10
8
6
0
0
2
4
6
8
30
VCC = 5V
4
6
8
10 12 14 16 18 20
VCC (V)
20
VCC = 15V
VCC1 = 12V
18
16
VCC = 5V
VGATE (V)
12
VCC = 3V
6
(VGATE1 – VCC1) (V)
25
14
VCC = 12V
20
15
VCC = 3V
10
4
0
–75 –50 –25
2
(VGATE1 – VCC1) vs Temperature
35
VCC = 12V
VCC = 15V
0
1647-1/2/3 G06
VGATE vs Temperature
20
(VGATE – VCC) (V)
0
10 12 14 16 18 20
VCC (V)
TA = 25°C
VCC = VCC1 = VCC2
1647-1/2/3 G05
(VGATE – VCC) vs Temperature
14
12
VCC1 = 5V
0 25 50 75 100 125 150
TEMPERATURE (°C)
5
0
–75 –50 –25
VCC = VCC1 = VCC2
0 25 50 75 100 125 150
TEMPERATURE (°C)
1647-1/2/3 G08
VCC1 = 15V
10
8
6
VCC1 = 3V
4
VCC = VCC1 = VCC2
1647-1/2/3 G07
4
5
TA = 25°C
VCC = VCC1 = VCC2
2
8 10 12 14 16 18 20
VCC2 (V)
15
10
6
1647-1/2/3 G04
2
8 10 12 14 16 18 20
VCC2 (V)
25
4
VCC1 = 5V
8
6
30
VGATE (V)
(VGATE – VCC) (V)
ICC2 (mA)
3
10
4
VGATE vs VCC
16
18
2
18
4
4
0
1647-1/2/3 G03
20
TA = 25°C
16
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
(VGATE – VCC) vs VCC
5
2
VCC1 = 5V
1647-1/2/3 G02
ICC2 vs VCC2
0
VCC1 = 12V
2
1
1647-1/2/3 G01
0
VCC1 = 15V
VCC1 = 3V
0
–75 –50 –25
18
3
2
0
0
2
4
6
TA = 25°C
(LTC1647-3)
8 10 12 14 16 18 20
VCC2 (V)
1647-1/2/3 G09
LTC1647-1/LTC1647-2/LTC1647-3
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TYPICAL PERFOR A CE CHARACTERISTICS
GATE Output Source Current vs
VCC
VGATE1 vs VCC2
VGATE1 (V)
25
VCC1 = 5V
VCC1 = 12V
20
15
VCC1 = 3V
10
TA = 25°C
(LTC1647-3)
5
0
2
4
6
13
12
11
10
9
8
7
6
8 10 12 14 16 18 20
VCC2 (V)
TA = 25°C
VCC = VCC1 =VCC2
0
2
4
6
8
1647-1/2/3 G10
70
60
50
40
30
20
2
4
6
8
53
52
51
50
49
48
47
45
–75 –50 –25
10 12 14 16 18 20
VCC (V)
30
20
10
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1647-1/2/3 G16
50
45
40
35
0
2
4
6
8
10 12 14 16 18 20
VCC (V)
1647-1/2/3 G15
Circuit Breaker Trip Voltage vs
Temperature
60
TA = 25°C
58
CIRCUIT BREAKER TRIP VOLTAGE (mV)
CIRCUIT BREAKER TRIP VOLTAGE (mV)
GATE FAST PULL-DOWN CURRENT (mA)
40
TA = 25°C
30
60
50
0 25 50 75 100 125 150
TEMPERATURE (°C)
55
Circuit Breaker Trip Voltage vs
VCC
80
60
7
1647-1/2/3 G14
GATE Fast Pull-Down Current vs
Temperature
70
8
GATE Fast Pull-Down Current vs
VCC
0 25 50 75 100 125 150
TEMPERATURE (°C)
1647-1/2/3 G13
VCC = VCC1 = VCC2 = 5V
9
60
VCC = 5V
54
46
10
0
10
1647-1/2/3 G12
GATE FAST PULL-DOWN CURRENT (mA)
GATE OUTPUT SINK CURRENT (µA)
GATE OUTPUT SINK CURRENT (µA)
80
11
6
–75 –50 –25
10 12 14 16 18 20
VCC (V)
55
TA = 25°C
12
GATE Output Sink Current vs
Temperature
100
90
VCC = VCC1 = VCC2 = 5V
13
1647-1/2/3 G11
GATE Output Sink Current vs VCC
0
GATE OUTPUT SOURCE CURRENT (µA)
30
0
14
14
VCC1 = 15V
GATE OUTPUT SOURCE CURRENT (µA)
35
GATE Output Source Current vs
Temperature
56
54
52
50
48
46
44
42
40
0
2
4
6
8
10 12 14 16 18 20
VCC (V)
1647-1/2/3 G17
58
56
54
VCC = 15V
VCC = 12V
VCC = 5V
VCC = 3V
52
50
48
46
44
42
40
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1647-1/2/3 G18
5
LTC1647-1/LTC1647-2/LTC1647-3
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TYPICAL PERFOR A CE CHARACTERISTICS
2.6
1.35
1.35
2.5
RISING EDGE
2.4
2.3
FALLING EDGE
2.2
1.30
HIGH
1.25
LOW
1.20
1.15
0 25 50 75 100 125 150
TEMPERATURE (°C)
VCC = 5V
0
2
4
6
8
FAULT VOL vs VCC
0.8
0.6
VCC = 5V
TA = 25°C
0.8
1.2
1.0
IOL = 5mA
0.8
0.6
0.4
0.6
0.4
0.4
IOL = 1mA
0.2
0
2
4
6
8
0.2
IOL = 1mA
0.2
0
–75 –50 –25
10 12 14 16 18 20
VCC (V)
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
1647-1/2/3 G22
VCC = 12V
0.2
VCC = 15V
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1647-1/2/3 G25
6
8
10 12 14 16 18 20
VCC (V)
60
TA = 25°C
CIRCUIT BREAKER RESET TIME (µs)
0.4
VCC = 5V
4
Circuit Breaker Reset Time vs
Temperature
70
CIRCUIT BREAKER RESET TIME (µs)
1.0
VCC = 3V
2
1647-1/2/3 G24
Circuit Breaker Reset Time vs VCC
0.8
0
1647-1/2/3 G23
TFAULT vs Temperature
6
TFAULT vs VCC
TFAULT (µs)
1.4
FAULT VOL (V)
FAULT VOL (V)
1.6
1.4
IOL = 5mA
0 25 50 75 100 125 150
TEMPERATURE (°C)
1.0
1.8
1.6
0.6
LOW
1.20
FAULT VOL vs Temperature
TA = 25°C
1.0
1.25
1647-1/2/3 G21
2.0
1.2
HIGH
1647-1/2/3 G20
2.0
1.8
1.30
1.15
–75 –50 –25
10 12 14 16 18 20
VCC (V)
1647-1/2/3 G19
0
ON THRESHOLD VOLTAGE (V)
TA = 25°C
2.1
–75 –50 –25
TFAULT (µs)
ON Threshold Voltage vs
Temperature
ON Threshold Voltage vs VCC
ON THRESHOLD VOLTAGE (V)
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
Undervoltage Lockout Threshold
vs Temperature
60
50
40
30
0
2
4
6
8
10 12 14 16 18 20
VCC (V)
1647-1/2/3 G26
58
56
VCC = 3V
54
52
50
48
VCC = 5V
VCC = 12V
46
VCC = 15V
44
42
40
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1647-1/2/3 G27
LTC1647-1/LTC1647-2/LTC1647-3
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PI FU CTIO S
VCC1 (LTC1647-3): Channel 1 Positive Supply Input. The
supply range for normal operation is 2.7V to 16.5V. The
supply current, ICC1, is typically 1mA. Channel 1’s undervoltage lockout (UVLO) circuit disables GATE 1 until the
supply voltage at VCC1 is greater than VLKO (typically
2.47V). GATE 1 is held at ground potential until UVLO
deactivates. If ON1 is high and VCC1 is above the UVLO
threshold voltage, GATE 1 is pulled high by a 10µA current
source. If VCC1 falls below (VLKO – VLKH), GATE 1 is pulled
immediately to ground. The internal reference and the
common charge pump are powered from the higher of the
two VCC inputs, VCC1 or VCC2.
VCC2 (LTC1647-3): Channel 2 Positive Supply Input. See
VCC1 for functional description.
VCC: The Common Positive Supply Input for the LTC1647-1
and the LTC1647-2. VCC1 and VCC2 are internally connected together.
GND: Chip Ground.
ON1: Channel 1 ON Input. The threshold at the ON1 pin is
set at 1.28V with 70mV hysteresis. If UVLO and the circuit
breaker of channel 1 are inactive, a logic high at ON1
enables the 10µA charge pump current source, pulling the
GATE 1 pin above VCC1. If the ON1 pin is pulled low, the
GATE 1 pin is pulled to ground by a 50µA current sink.
ON1 resets channel 1’s electronic circuit breaker by pulling ON1 low for greater than one tRESET period (50µs). A
low-to-high transition at ON1 restarts a normal GATE 1
pull-up sequence.
ON2: Channel 2 ON Input. See ON1 for functional description.
FAULT 1: Channel 1 Open-Drain Fault Status Output.
FAULT 1 pin pulls low after 0.3µs (tFAULT) if the circuit
breaker measures greater than 50mV across the sense
resistor connected between VCC1 and SENSE 1. If FAULT 1
pulls low, GATE 1 also pulls low. FAULT 1 remains low until
ON1 is pulled low for at least one tRESET period.
FAULT 2: Channel 2 Open-Drain Fault Status Output. See
FAULT 1 for functional description.
SENSE 1: Channel 1 Circuit Breaker Current Sense Input.
Load current is monitored by a sense resistor connected
between VCC1 and SENSE 1. The circuit breaker trips if the
voltage across the sense resistor exceeds 50mV (VCB). To
disable the circuit breaker, connect SENSE 1 to VCC1. In
order to obtain optimum performance, use Kelvin-sense
connections between the VCC and SENSE pins to the
current sense resistor.
SENSE 2: Channel 2 Circuit Breaker Current Sense Input.
See SENSE 1 for functional description.
GATE 1: Channel 1 N-Channel MOSFET Gate Drive Output.
An internal charge pump guarantees at least 10V of gate
drive from a 5V supply. Two Zener clamps are incorporated at the GATE 1 pin; one Zener clamps GATE 1
approximately 15V above VCC and the second Zener
clamps GATE 1 appoximately 28V above GND. The rise
time at GATE 1 is set by an external capacitor connected
between GATE 1 and GND and an internal 10µA current
source provided by the charge pump. The fall time at GATE
1 is set by the 50µA current sink if ON1 is pulled low. If the
circuit breaker is tripped or the supply voltage hits the
UVLO threshold, a 50mA current sink rapidly pulls GATE 1
low.
GATE 2: Channel 2 N-Channel MOSFET Gate Drive Output.
See GATE 1 for functional description.
NC: No Connection.
7
LTC1647-1/LTC1647-2/LTC1647-3
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BLOCK DIAGRA S
LTC1647-1
+
–
50mV
CHANNEL ONE
+
CP
–
SENSE 1 8
10µA
+
1.21V
50µs
FILTER
6 GATE 1
–
ON1 2
50µA
2.45V
UVL
VCC 1
GND 4
REFERENCE
1.21V
CHARGE
PUMP
CP
CHANNEL TWO
(DUPLICATE OF CHANNEL ONE)
SENSE 2 7
5 GATE 2
ON2 3
1647-1/2/3 BD1
LTC1647-2
+
–
50mV
CHANNEL ONE
+
CP
–
SENSE 1 8
1.21V
10µA
+
50µs
FILTER
ON1/FAULT 1 2
6 GATE 1
–
50µA
2.45V
UVL
FAULT
VCC 1
GND 4
SENSE 2 7
REFERENCE
1.21V
CHARGE
PUMP
CP
CHANNEL TWO
(DUPLICATE OF CHANNEL ONE)
5 GATE 2
ON2/FAULT 2 3
1647-1/2/3 BD2
8
LTC1647-1/LTC1647-2/LTC1647-3
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BLOCK DIAGRA S
LTC1647-3
VCC1 1
+
–
50mV
CHANNEL ONE
+
CP
–
SENSE 1 15
1.21V
10µA
+
50µs
FILTER
13 GATE 1
–
ON1 2
50µA
2.45V
UVL
FAULT 1 3
FAULT
GND 8
REFERENCE
1.21V
CHARGE
PUMP
CP
VCC
SELECTION
VCC2 16
12 GATE 2
CHANNEL TWO
(DUPLICATE OF CHANNEL ONE)
SENSE 2 14
ON2 4
FAULT 2 5
1647-1/2/3 BD3
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VCC Selection Circuit
The LTC1647-3 features separate supply inputs (VCC1 and
VCC2) for each channel. The reference and charge pump
circuit draw supply current from the higher of the two
supplies. An internal VCC selection circuit detects and
makes the power connection automatically. This allows a
3V channel to have standard MOSFET gate overdrive when
the other channel is 5V. An internal Zener clamps GATE
about 15V above VCC.
If both supplies are connected together (internally for
LTC1647-1 and LTC1647-2 or externally for LTC1647-3),
the reference and charge pump circuit draw equal current
from both pins.
Electronic Circuit Breaker
Each channel of the LTC1647 features an electronic circuit
breaker to protect against excessive load current and
short-circuits. Load current is monitored by sense resistor R1 as shown in Figure 1. The circuit breaker threshold,
VCB, is 50mV and it exhibits a response time, tFAULT, of
approximately 300ns. If the voltage between VCC and
SENSE exceeds VCB for more than tFAULT, the circuit
breaker trips and immediately pulls GATE low with a 50mA
current sink. The MOSFET turns off and FAULT pulls low.
The circuit breaker is cleared by pulling the ON pin low for
a period of at least tRESET (50µs). A timing diagram of these
events is shown in Figure 2.
The value of the sense resistor R1 is given by
R1 = VCB/ITRIP(Ω)
where VCB is the circuit breaker trip voltage (50mV) and
ITRIP is the value of the load current at which the circuit
breaker trips. Kelvin-sense layout techniques between the
sense resistor and the VCC and SENSE pins are highly
recommended for proper operation.
9
LTC1647-1/LTC1647-2/LTC1647-3
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The circuit breaker trip voltage has a tolerance of 20%;
combined with a 5% sense resistor, the total tolerance is
25%. Therefore, calculate R1 based on a trip current ITRIP
of no less than 125% of the maximum operating current.
Do not neglect the effect of ripple current, which adds to
the maximum DC component of the load current. Ripple
current may arise from any of several sources, but the
worst offenders are switching supplies.
Q1
IRF7413
R1
0.01Ω
VCC
+
R3
1.5k
C3
10nF
VOUT
CLOAD
R2
10Ω
IPK = 7.5A
IAV = 2.5A
ITRIP = VCB/R1 = 5A
tDELAY = 10µs
C1
10nF
VCC
SENSE
GATE
LTC1647
1647-1/2/3 F03
A switching regulator on the load side will attempt to draw
some ripple current from the backplane and this current
passes through the sense resistor. Similarly, output ripple
from a switching regulator supplying the backplane will
flow through the sense resistor and into the load capacitor.
Minimize the effects of ripple current by either filtering the
VOUT line or adding an RC filter to the SENSE pin. A series
inductance of 1µH to 10µH inserted between Q1 and CLOAD
is adequate ripple current suppression in most cases.
Alternatively, a filter, consisting of R3 and C3(Figure 3),
simply filters the ripple component from the SENSE pin at
the expense of response time. The added delay is given by
tDELAY = – R3•C3•ln[1 – (VCB/R1 – IAV)/(IPK – IAV)]
R1
0.01Ω
Q1
IRF7413
VCC
VOUT
+
R3
10k
ON
FAULT
CLOAD
R2
10Ω
2
3
8
1
15
13
VCC
SENSE
GATE
ON1
C1
10nF
LTC1647-3
FAULT
GND
1647-1/2/3 F01
Figure 1. Supply Control Circuitry
Figure 3. Filtering Current Ripple/Glitches
Power MOSFET Selection
Power MOSFETs are classified into two catagories: standard MOSFETs (RDS(ON) specified at VGS = 10V) and logiclevel MOSFETs (RDS(ON) specified at VGS = 5V). The
absolute maximum rating for VGS is typically 20V for
standard MOSFETs. The maximum rating for logic-level
MOSFETs is lower and ranges from 8V to 16V depending
on the manufacturer and specific part number. Some
logic-level MOSFETs have a 20V maximum VGS rating. The
LTC1647 is primarily targeted for standard MOSFETs; low
supply voltage applications should use logic-level
MOSFETs. GATE overdrive as a function of VCC is illustrated in the Typical Performance Curves. If lower GATE
overdrive is desired, connect a diode in series with a Zener
between GATE and VCC or between GATE and VOUT as
shown in Figure 4.
The RDS(ON) of the external pass transistor must be low to
make VDS a small percentage of VCC. At VCC = 3.3V, VDS +
VCB = 0.1V yields 3% error at maximum load current. This
restricts the choice of MOSFETs to very low RDS(ON). At
higher VCC voltages, the RDS(ON) requirement can be
relaxed. MOSFET package dissipation (PD and TJ) may
restrict the value of RDS(ON).
R1
Q1
VCC
VOUT
VON
VCC – VSENSE
VGATE
D1*
D2
1N4148
D4*
t FAULT
t RESET
VFAULT
Figure 2. Current Fault Timing
10
D2
1N4148
1647-1/2/3 F02
*USER SELECTED VOLTAGE CLAMP
1N4688 (5V)
1N4692 (7V): LOGIC-LEVEL MOSFET
1N4695 (9V)
1N4702 (15V): STANDARD-LEVEL MOSFET
Figure 4. Optional Gate Clamp
1647-1/2/3 F04
LTC1647-1/LTC1647-2/LTC1647-3
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Power Supply Ramping
VOUT is controlled by placing MOSFET Q1 in the power
path (Figure 1). R1 provides load current fault detection
and R2 prevents MOSFET high frequency oscillation. By
ramping the gate of the pass transistor at a controlled rate
(dV/dt = 10µA/C1), the transient surge current
(I = CLOAD•dV/dt = 10µA•CLOAD/C1) drawn from the main
backplane is limited to a safe value when the board is
inserted into the connector.
When power is first applied to VCC, the GATE pin pulls low.
A low-to-high transition at the ON pin initiates GATE rampup. The rising dV/dt of GATE is set by 10µA/C1 (Figure 5),
where C1 is the total external capacitance between GATE
and GND. The ramp-up time for VOUT is equal to
t = (VCC•C1)/10µA.
VGATE
VCC + ∆VGATE
RAMP-UP
SLOPE = 10µA/C1
RAMP-DOWN
SLOPE = –50µA/C1
VOUT
VCC
CLOAD DISCHARGES
0V
A high-to-low transition at the ON pin initiates a GATE
ramp-down at a slope of – 50µA/C1. This rate is usually
adequate as the supply bypass capacitors take time to
discharge through the load.
If the ON pin is connected to VCC, or is pulled high before
VCC is first applied, GATE is held low until VCC rises above
the undervoltage lockout threshold, VLKO (Figure 6). Once
the threshold is exceeded, GATE ramps at a controlled rate
of 10µA/C1. When the power supply is disconnected, the
body diode of Q1 holds VCC about 700mV below VOUT. The
GATE voltage droops at a rate determined by VCC. If VCC
drops below VLKO – VLKH, the LTC1647 enters UVLO and
GATE pulls down to GND.
Autoretry
The LTC1647-2 and LTC1647-3 are designed to allow an
automatic reset of the electronic circuit breaker after a
fault condition occurs. This is accomplished by pulling the
ON/FAULT (LTC1647-2) pin or the ON and FAULT pins tied
together (LTC1647-3) high through a resistor, R3, as
shown in Figure 7. An autoretry sequence begins if a fault
occurs. If the circuit breaker trips, FAULT pulls the ON pin
low. After a tRESET interval elapses, FAULT resets and R3
VON
VCC
0V
Q1
IRF7413
R1
0.01Ω
1647-1/2/3 F05
VCC
+
Figure 5. Supply Turn-On/Off with ON
VCC + ∆VGATE
RAMP-UP
SLOPE = 10µA/C1
VGATE DROOP
DUE TO VCC
FAST RAMP-DOWN
AT UNDERVOLTAGE
LOCKOUT
4
ON/FAULT
8
C1
10nF
6
SENSE
GATE
LTC1647-2
GND
VCC – VSENSE
t RESET
VGATE
OUT OF UVLO
VLKO
0V
VCC
2
FAULT
C3
0.1µF
CLOAD DISCHARGES
0V
1
R3
15k
VOUT
VCC
VCC
CLOAD
R2
10Ω
ON
(5V LOGIC)
VGATE
VOUT
VCC
VCC
UNPLUGGED
t DELAY
INTO UVLO
VLKO – VLKH
VFAULT
tRAMP
1647-1/2/3 F06
1647-1/2/3 F07
Figure 7. Autoretry Sequence
11
LTC1647-1/LTC1647-2/LTC1647-3
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pulls the ON pin up. C3 delays GATE turn-on until the
voltage at the ON pin exceeds VIH. The delay time is
tDELAY = –R3•C3•ln[1–(VIH – VOL)/(VON – VOL)]
GATE ramps up at 10µA/C1 until Q1 conducts. If VOUT is
still shorted to GND, the cycle repeats. The ramp interval
is about tRAMP = VTH•C1/10µA where VTH is the threshold
voltage of the external MOSFET.
Hot Circuit Insertion
When circuit boards are inserted into a live backplane or
a device bay, the supply bypass capacitors on the board
can draw huge transient currents from the backplane or
the device bay power bus as they charge up. The transient
currents can damage the connector pins and glitch the
system supply, causing other boards in the system to
reset or malfunction.
The LTC1647 is designed to turn two positive supplies on
and off in a controlled manner, allowing boards to be safely
inserted or removed from a live backplane or device bay.
The LTC1647 can be located before or after the connector
as shown in Figure 8. A staggered PCB connector can
sequence pin conections when plugging and unplugging
circuit boards. Alternatively, the control signal can be
generated by processor control.
Ringing
Good engineering practice calls for bypassing the supply
rail of any circuit. Bypass capacitors are often placed at the
supply connection of every active device, in addition to one
or more large value bulk bypass capacitors per supply rail.
If power is connected abruptly, the bypass capacitors slow
the rate of rise of voltage and heavily damp any parasitic
resonance of lead or trace inductance working against the
supply bypass capacitors.
The opposite is true for LTC1647 Hot Swap circuits on a
daughterboard. In most cases, on the powered side of the
MOSFET switch (VCC) there is no supply bypass capacitor
present. An abrupt connection, produced by plugging a
board into a backplane connector, results in a fast rising
edge applied to the VCC line of the LTC1647.
12
No bulk capacitance is present to slow the rate of rise and
heavily damp the parasitic resonance. Instead, the fast
edge shock excites a resonant circuit formed by a combination of wiring harness, backplane and circuit board
parasitic inductances and MOSFET capacitance. In theory,
the peak voltage should rise to 2X the input supply, but in
practice the peak can reach 2.5X, owing to the effects of
voltage dependent MOSFET capacitance.
The absolute maximum VCC potential for the LTC1647 is
17V; any circuit with an input of more than 6.8V should be
scrutinized for ringing. A well-bypassed backplane should
not escape suspicion: circuit board trace inductances of as
little as 10nH can produce sufficient ringing to overvoltage
VCC.
Check ringing with a fast storage oscilloscope (such as a
LECROY 9314AL DSO) by attaching coax or a probe to VCC
and GND, then repeatedly inserting the circuit board into
the backplane. Figures 9a and 9b show typical results in a
12V application with different VCC lead lengths. The peak
amplitude reaches 22V, breaking down the ESD protection
diode in the process.
There are two methods for eliminating ringing: clipping
and snubbing. A transient voltage suppressor is an effective means of limiting peak voltage to a safe level.
Figure 10 shows the effect of adding an ON Semiconductor, 1SMA12CAT3, on the waveform of Figure 9.
Figures 11a and 11b show the effects of snubbing with
different RC networks. The capacitor value is chosen as
10X to 100X the MOSFET COSS under bias and R is
selected for best damping—1Ω to 50Ω depending on the
value of parasitic inductance.
Supply Glitching
LTC1647 Hot Swap circuits on the backplane are generally
used to provide power-up/down sequence at insertion/
removal as well as overload/short-circuit protection. If a
short-circuit occurs at supply ramp-up, the circuit breaker
trips. The partially enhanced MOSFET, Q1, is easily disconnected without any supply glitch.
LTC1647-1/LTC1647-2/LTC1647-3
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If a dead short occurs after a supply connection is made
(Figure 12), the sense resistor R1 and the RDS(ON) of fully
enhanced Q1 provide a low impedance path for nearly
unlimited current flow. The LTC1647 discharges the GATE
pin in a few microseconds, but during this discharge time
current on the order of 150 amperes flows from the VCC
power supply. This current spike glitches the power supply, causing VCC to dip (Figure 12a and 12b).
On recovery from overload, some supplies may overshoot. Other devices attached to this supply may reset or
malfunction and the overshoot may also damage some
components. An inductor (1µH to 10µH) in series with
Q1’s source limits the short-circuit di/dt, thereby limiting
the peak current and the supply glitch (Figure 12c and
12d). Additional power supply bypass capacitance also
reduces the magnitude of the VCC glitch.
VID Power Controller
The two Hot Swap channels of the LTC1647 are ideally
suited for VID power control in portable computers.
Figure 13 shows an application using the LTC1647-2 on
the system side of the device bay interface (1394 PHY and/
or USB). The controller detects the presence of a peripheral in each device bay and controls the LTC1647-2. The
timing waveform illustrates the following sequence of
events: t1, rising out of undervoltage lockout with GATE 1
ramping up; t2, load current fault at R1; t3, circuit breaker
resets with R5/C3 delay; t4/t5, controller gates off/on
device supply with RC delay; t6, device enters undervoltage lockout.
If C6 is not connected in Figure 13, FAULT 2 and ON2 will
have similar waveforms. t7 initiates an ON sequence; t8, a
load fault is detected at R7 with FAULT 2 pulling low. If the
controller wants to stretch the interval between retries, it
can pull ON2 low at t9 ( t9 – t8 < 0.4•tRESET). At t10/t11, the
controller initiates a new power-up/down sequence.
13
LTC1647-1/LTC1647-2/LTC1647-3
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BACKPLANE
CONNECTOR
STAGGERED PCB
EDGE CONNECTOR
Q1
R1
VCC
VOUT
+
R4
CLOAD
R5
R2
ON
R3
Q2
2
3
FAULT
8
1
15
13
VCC
SENSE
GATE
C1
ON
FAULT
LTC1647-3
GND
(a) HOT SWAP CONTROLLER ON MOTHERBOARD
BACKPLANE
CONNECTOR
STAGGERED PCB
EDGE CONNECTOR
Q1
R1
VCC
+
R4
VOUT
CLOAD
R2
FAULT
R3
2
3
8
1
15
13
VCC
SENSE
GATE
ON
FAULT
LTC1647-3
GND
(b) HOT SWAP CONTROLLER ON DAUGHTERBOARD
Figure 8. Staggered Pins Connection
14
C1
1647-1/2/3 F08
LTC1647-1/LTC1647-2/LTC1647-3
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Q1
IRF7413
R1
0.01Ω
8'
+
12V
+
–
POWER
LEADS
VOUT
CLOAD
R2
10Ω
SCOPE
PROBE
C1
10nF
LTC1647
1647-1/2/3 F09
24V
4V/DIV
4V/DIV
24V
0V
0V
1µs/DIV
1647-1/2/3 F09a
(a) Undamped VCC
Waveform (48" Leads)
1µs/DIV
1647-1/2/3 F09b
(b) Undamped VCC
Waveform (8" Leads)
Figure 9. Ring Experiment
15
LTC1647-1/LTC1647-2/LTC1647-3
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Q1
IRF7413
R1
0.01Ω
VOUT
12V
CLOAD
R2
10Ω
D1*
2V/DIV
+
–
POWER
LEADS
PCB EDGE CONNECTOR
12V
BACKPLANE CONNECTOR
+
C1
10nF
LTC1647
0V
1647-1/2/3 F10
1µs/DIV
ON SEMICONDUCTOR
* 1SMA12CAT3
1647-1/2/3 F10a
VCC Waveform Clamped
by a Transient Suppressor
Figure 10. Transient Suppressor Clamp
Q1
IRF7413
R1
0.01Ω
+
–
PCB EDGE CONNECTOR
12V
POWER
LEADS
BACKPLANE CONNECTOR
+
R3
10Ω
VOUT
CLOAD
R2
10Ω
C1
0.1µF
C1
10nF
LTC1647
1647-1/2/3 F11
12V
2V/DIV
2V/DIV
12V
0V
0V
1µs/DIV
1647-1/2/3 F11a
(a) VCC Waveform Damped
by a Snubber (15Ω, 6.8nF)
1647-1/2/3 F11b
(b) VCC Waveform Damped
by a Snubber (10Ω, 0.1µF)
Figure 11. Snubber “Fixes”
16
1µs/DIV
LTC1647-1/LTC1647-2/LTC1647-3
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+
+
–
Q1
IRF7413
L1
2µH
R2
10Ω
C2
100µF
C1
10nF
LTC1647
BOARD WITH POSSIBLE
SHORT-CIRCUIT FAULT
12V
R1
0.01Ω
BACKPLANE CONNECTOR
SUPPLY
GLITCH
1647-1/2/3 F12
4V/DIV
25A/DIV
GATE
VCC
1µs/DIV
1µs/DIV
1647-1/2/3 F12a
(a) VCC Short-Circuit
Supply Current Glitch
without Any Limiting
1647-1/2/3 F12b
(b) VCC Supply Glitch
without Any Limiting
4V/DIV
5A/DIV
GATE
1µs/DIV
VCC
1µs/DIV
1647-1/2/3 F12c
(c) VCC Short-Circuit
Supply Current Glitch with
2µH Series Inductor
1647-1/2/3 F12d
(d) VCC Supply Glitch
with 2µH Series Inductor
Figure 12. Supply Glitch
17
LTC1647-1/LTC1647-2/LTC1647-3
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Q1
1/2 MMDF3N02HD
DEVICE #1
R3**
R2
10Ω
ON1
CONNECTOR #1
R1
0.1Ω
3.3V VID
SUPPLY
+
CLOAD*
R4**
1394 PHY
AND/OR
USB PORT
R5
10Ω
8
C3
0.1µF
1
2
3
4
R6
10Ω
FAULT 2
C1
10nF
6
SENSE 1
GATE 1
VCC
ON1/FAULT 1
CLOAD IS USER-SELECTED BASED
ON THE DEVICE REQUIREMENTS
** R3, R4, R7 AND R8 ARE OPTIONAL DISCHARGE
RESISTORS WHEN DEVICES ARE POWERED-OFF
Q1, Q2: ON SEMICONDUCTOR
*
LTC1647-2
ON2/FAULT 2
GND
SENSE 2
GATE 2
7
C6
0.1µF
5
C4
10nF
R8
10Ω
R7
0.1Ω
DEVICE #2
Q2
1/2 MMDF3N02HD
VID
VLKO
R9**
CONNECTOR #2
FAULT 1
DEVICE BAY
CONTROLLER
WITH 1394 PHY
AND/OR USB
ON2
+
VLKO – VLKH
VON1
t4
t5
FAULT 1 WAVEFORM SHOWN WITH C3
VFAULT1
VIH
VIH
VIL
VR1
VGATE1
t2
t1
t3
t6
VON2
t9
t10
t11
FAULT 2 WAVEFORM SHOWN WITHOUT C6
VFAULT2
t7
VR7
t8
VGATE2
1647-1/2/3 F13
Figure 13. VID Power Controller with Fault Status and Retry Sequence
18
CLOAD*
R10**
1394 PHY
AND/OR
USB PORT
LTC1647-1/LTC1647-2/LTC1647-3
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PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
GN Package
16-Lead Plastic SSOP (Narrow 0.150)
(LTC DWG # 05-08-1641)
0.189 – 0.196*
(4.801 – 4.978)
0.009
(0.229)
REF
16 15 14 13 12 11 10 9
0.229 – 0.244
(5.817 – 6.198)
0.150 – 0.157**
(3.810 – 3.988)
1
0.015 ± 0.004
× 45°
(0.38 ± 0.10)
0.007 – 0.0098
(0.178 – 0.249)
2 3
5 6
4
7
0.053 – 0.068
(1.351 – 1.727)
8
0.004 – 0.0098
(0.102 – 0.249)
0° – 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.0250
(0.635)
BSC
0.008 – 0.012
(0.203 – 0.305)
* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
GN16 (SSOP) 1098
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SO8 1298
19
LTC1647-1/LTC1647-2/LTC1647-3
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TYPICAL APPLICATIO
Hot Swapping Two Supplies
Two separate supplies can be independently controlled by
using the LTC1647-3. In some applications, sequencing
between the two power supplies is a requirement. For
example, it may be necessary to ramp-up one supply first
before allowing the second supply to power-up, as well as
requiring that this same supply ramp-down last on powerdown. Figure 14’s circuit illustrates how to program the
delays between the two pass transistors using the ON1
Q1
IRF7413
R1
0.01Ω
5V SUPPLY
+
R3
100Ω
R4
4.7k
ON1
ON2
VCC1
2
CONNECTOR
FAULT
15
1
R5
10k
R6
10k
3
4
5
8
GND
R7
12k
SENSE 1
and ON2 pins (time events t1 to t4). t5 and t7 show both
channels being switched on simultaneously where sequencing is not crucial.
Some applications require that both channels be gated off
if a fault occurs in one channel. This is accomplished in
Figure 14 by using a crisscross FAULT-to-SENSE arrangement of R3/R4 and R7/R8. t6 and t9 illustrate the circuit’s
operation.
VOUT1
(5A)
CLOAD
R2
10Ω
VR1
C1
10nF
13
GATE 1
t6
VR10
t9
ON1
VON1
FAULT 1
t2
LTC1647-3
ON2
FAULT 2
t1
GND
VCC2
t3
VON2
SENSE 2
16
GATE 2
14
t4
t5
t7
t8
VOUT1
12
R8
100Ω
C3
10nF
R9
10Ω
R10
0.02Ω
12V SUPPLY
Q2
IRF7413
+
VOUT2
1647-1/2/3 F14
VOUT2
(2.5A)
CLOAD
Figure 14. Hot Swapping Two Supplies
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1421
2-Channel Hot Swap Controller
24-Pin, Operates from 3V to 12V and Supports –12V
LTC1422
Hot Swap Controller in SO-8
System Reset Output with Programmable Delay
LT1640L/LT1640H
Negative Voltage Hot Swap Controller in SO-8
Operates from –10V to –80V
LT1641
High Voltage Hot Swap Controller in SO-8
Operates from 9V to 80V
LT1642
Fault Protected Hot Swap Controller
Operates Up to 16.5V, Protected to 33V
LTC1643L/LTC1643H
PCI-Bus Hot Swap Controller
3.3V, 5V and ±12V in Narrow 16-Pin SSOP
LT1645
2-Channel Hot Swap Controller
Operates from 1.2V to 12V, Power Sequencing
20
Linear Technology Corporation
1647f LT/TP 0100 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1999