FEATURES
■
Allows Safe Board Insertion and Removal from a
Live PCI Slot
■
Works on either a Motherboard (LTC1643H) or
CompactPCITM Card (LTC1643L/LTC1643L-1)
■
Controls –12V, 3.3V, 5V, 12V Supplies
■
Programmable Foldback Current Limit with
Circuit Breaker
■
User-Programmable Supply Voltage Power-Up Rate
■
High Side Drive for External N-Channels
■
–12V and 12V On-Chip Switches
■
Fault and Power-Good Outputs
U
APPLICATIO S
■
PCI-Based Servers
■
CompactPCI Compliant Boards
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
CompactPCI is a trademark of PCI Industrial Computer Manufacturing Group.
LTC1643L/LTC1643L-1/LTC1643H
PCI-Bus Hot Swap
Controller
U
DESCRIPTIO
The LTC®1643 is a Hot SwapTM controller that allows a board
to be safely inserted and removed from a live PCI-Bus slot.
Two external N-channel transistors control the 3.3V and 5V
supplies while on-chip switches control the –12V and 12V
supplies. All supply voltages can be ramped up at a programmable rate. An electronic circuit breaker protects all four
supplies against overcurrent faults. The foldback current limit
feature limits current spikes and power dissipation when
shorts occur and allows boards with large capacitances to be
powered up without tripping the circuit breaker. The PWRGD
output indicates when all of the supply voltages are within
tolerance and the FAULT output indicates an overcurrent
condition. The ON(LTC1643H)/ON (LTC1643L/LTC1643L-1)
pin is used to cycle the board power or reset the circuit
breaker. The LTC1643L-1 has the ±12V power good comparators disabled.
The LTC1643 is available in a 16-pin narrow SSOP package.
TYPICAL APPLICATION
SYSTEM
POWER
SUPPLY
8
1
2
5
R3
PCI
POWER
SYSTEM
CONTROLLER
RESET
10k
10k
6
R4
7
U
0.005ΩQ2IRF7413
3V
IN
GND
12V
IN
V
EEIN
ON
FAULT
PWRGD
Hot Swappable PCI Supply
R2
R5
10Ω
109
11 3 13 12 14
3V
SENSE
GATE
3V
OUT
LTC1643H
5V
R1
0.007Ω
IN
5V
SENSE
Q1
IRF7413
R6
10Ω
5V
5A
3.3V
7.6A
R7
100Ω
C1
5V
OUT
12V
OUT
V
EEOUT
TIMER
0.047µF
16
15
4
C2
0.1µF
GND
12V
500mA
–12V
100mA
LOGIC
RESET
1643 TA01
1
LTC1643L/LTC1643L-1/LTC1643H
WW
W
ABSOLUTE MAXIMUM RATINGS
U
U
W
PACKAGE/ORDER INFORMATION
(Note 1)
Supply Voltages
12VIN................................................................ 13.2V
V
.............................................................. –13.2V
EEIN
Input Voltage (Pin 5) ................ –0.3V to (12VIN + 0.3V)
Output Voltages (Pins 6, 7) ...... –0.3V to (12VIN + 0.3V)
Analog Voltages
(Pins 3, 4, 9, 10 to 14) ........ –0.3V to (12VIN + 0.3V)
V
12V
............................................ –13.2V to + 0.3V
EEOUT
.............................................. –0.3V to 13.2V
OUT
Operating Temperature Range
Commercial .............................................0°C to 70°C
Industrial ........................................... –40°C to 85°C
12V
V
EEIN
3V
OUT
TIMER
ON/ON*
FAULT
PWRGD
GND
16-LEAD NARROW PLASTIC SSOP
* ON FOR LTC1643H, ON FOR LTC1643L
TOP VIEW
1
IN
2
3
4
5
6
7
8
GN PACKAGE
T
= 150°C, θJA = 135°C/ W
JMAX
ORDER PART
12V
16
OUT
15
V
EEOUT
14
5V
OUT
13
5V
IN
12
5V
SENSE
11
GATE
10
3V
SENSE
9
3V
IN
NUMBER
LTC1643HCGN
LTC1643LCGN
LTC1643L-1CGN
LTC1643HIGN
LTC1643LIGN
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Consult factory for Military grade parts.
DC ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
V
= 12V, VEE = –12V, V
12VIN
= 3.3V, V
3VIN
= 5V. (Note 2)
5VIN
U
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
DD
V
LKO
V
FB
t
CB
I
CP
∆V
V
DROP
I
CL
T
TS
V
TH
GATE
V
Supply Current ON = 3V, ON = GND ● 3.5 8 mA
12VIN
Undervoltage Lockout 12V
3V
5V
IN
IN
IN
Foldback Current Limit Voltage VFB = (V
= (V
V
FB
V
= (V
FB
= (V
V
FB
5VIN
5VIN
3VIN
3VIN
– V
– V
– V
– V
5VSENSE
5VSENSE
3VSENSE
3VSENSE
), V
), V
), V
), V
= 0V ● 4 7.5 12 mV
5VOUT
> 4V ● 40 53 65 mV
5VOUT
= 0V ● 4 7.5 12 mV
3VOUT
> 2V ● 40 53 65 mV
3VOUT
● 7 9.5 10.8 V
● 2.25 2.5 2.75 V
● 2.25 2.5 2.75 V
Circuit Breaker Trip Filter Time 14.6 µs
GATE Pin Output Current Charge Pump On, V
Charge Pump Off, V
Charge Pump Off, V
External Gate Voltage (V
Internal Switch Voltage Drop (V
(V
12VIN
12VIN
EEOUT
– V
– V
– V
GATE
12VOUT
EEIN
Current Foldback 12VIN = 12V, 12V
, 12V
12V
V
EEIN
V
EEIN
IN
= –12V, V
, V
= 12V ● 525 850 1500 mA
OUT
= –12V ● 225 450 800 mA
EEOUT
= GND, FAULT = High ● – 20 – 50 –100 µA
GATE
= 5V, FAULT = High 200 µA
GATE
= 2V, FAULT = Low ● 3 1020 mA
GATE
) 100 200 mV
), I
), I
VEEIN
OUT
EEOUT
= 500mAC Grade ● 250 600 mV
12VOUT
I Grade
● 250 750 mV
= 100mA ● 120 250 mV
= 0V ● 50 250 500 mA
= 0V ● 100 160 215 mA
Thermal Shutdown Temperature 150 °C
Power-Good Threshold Voltage V
12VOUT
LTC1643H/LTC1643L Only I Grade
V
EEOUT
LTC1643H/LTC1643L Only I Grade
C Grade ● 10.8 11.1 11.4 V
● 10.4 11.1 11.4 V
C Grade ● – 10.2 –10.5 –10.8 V
● –10.0 –10.5 –10.8 V
2
LTC1643L/LTC1643L-1/LTC1643H
DC
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
V
= 12V, VEE = –12V, V
12VIN
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
TH
V
IL
V
IH
V
OL
I
IN
Power-Good Threshold Voltage V
Input Low Voltage ON/ON, FAULT ● 0.8 V
Input High Voltage ON/ON, FAULT ● 2V
Output Low Voltage FAULT, PWRGD, I = 3mA ● 0.4 V
ON/ON Pin Input Current ON/ON = GND ● ±0.08 ±10 µA
5V
Input Current 5V
SENSE
3V
Input Current 3V
SENSE
5VIN Input Current 5VIN = 5V ● 460 700 µA
3VIN Input Current 3VIN = 3V ● 320 600 µA
5V
Input Current 5V
OUT
3V
Input Current 3V
OUT
R
DIS
I
TIMER
V
TIMER
5V
Discharge Impedance ON = GND or ON = 3V 100 Ω
OUT
Discharge Impedance ON = GND or ON = 3V 70 Ω
3V
OUT
12V
Discharge Impedance ON = GND or ON = 3V 450 Ω
OUT
Discharge Impedance ON = GND or ON = 3V 1600 Ω
V
EEOUT
TIMER Pin Current Timer On, V
TIMER Threshold Voltage (V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
= 3.3V, V
3VIN
= 5V.(Note 2)
5VIN
3VOUT
V
5VOUT
ON/ON= 12V
Timer Off, V
12VIN
C Grade ● 2.8 2.9 3.0 V
I Grade
● 2.75 2.9 3.0 V
C Grade ● 4.5 4.65 4.75 V
I Grade
IN
= 5V ● 50 100 µA
SENSE
= 3V ● 50 100 µA
SENSE
= 5V, ON = 3V, ON = GND ● 240 500 µA
OUT
= 3.3V, ON = 3V, ON = GND ● 220 500 µA
OUT
= GND ● –15 –22 –27 µA
TIMER
= 5V 45 mA
TIMER
– V
) ● 0.5 0.9 1.3 V
TIMER
● 4.4 4.65 4.75 V
● ±0.08 ±10 µA
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.
UW
TYPICAL PERFORMANCE CHARACTERISTICS
3.3V and 5V Current
Foldback Profile
11
10
9
3V
OUT
8
7
6
5
4
OUTPUT CURRENT (A)
3
2
1
0
1
0
OUTPUT VOLTAGE (V)
5V
OUT
R
= 0.005Ω
SENSE
3
4
2
5
1643 G01
12V Current Foldback Profile –12V Current Foldback Profile
1.0
0.5
OUTPUT CURRENT (A)
0
2
0
6
4
OUTPUT VOLTAGE (V)
810
1643 G02
1.0
0.5
OUTPUT CURRENT (A)
12
0
–2
0
–6
–4
OUTPUT VOLTAGE (V)
–8 –10
–12
1643 G03
3
LTC1643L/LTC1643L-1/LTC1643H
TEMPERATURE (°C)
–50
GATE CURRENT (µA)
90
80
70
60
50
40
0
50
75
1643 G06
–25
25
100
125
UW
TYPICAL PERFORMANCE CHARACTERISTICS
Timer Current vs Temperature
23.5
23.0
22.5
22.0
21.5
21.0
TIMER CURRENT (µA)
20.5
20.0
19.5
–50
050
–25 25 75 125
TEMPERATURE (°C)
Power Good Threshold Voltage vs
Temperature (12V
11.08
11.06
11.04
11.02
11.00
POWER GOOD THRESHOLD VOLTAGE (V)
10.98
–50
0
–25
TEMPERATURE (°C)
)
OUT
50
25
Gate Current vs Temperature
Power Good Threshold Voltage vs
Temperature (3V
2.904
2.903
2.902
2.901
2.900
2.899
2.898
2.897
POWER GOOD THRESHOLD VOLTAGE (V)
2.896
–50
050
–25 25 75 125
TEMPERATURE (°C)
OUT
)
100
1643 G09
100
1643 G04
25.0
22.5
20.0
(mA)
17.5
SINK
GATE I
15.0
12.5
10.0
Gate I
–50
vs Temperature
SINK
–25 0
TEMPERATURE (°C)
FAULT = LOW
50 100 125
25 75
1643 G05
Power Good Threshold Voltage vs
Temperature (5V
4.64
4.63
4.62
4.61
4.60
4.59
POWER GOOD THRESHOLD VOLTAGE (V)
100
125
1643 G07
75
4.58
–50
–25 0
TEMPERATURE (°C)
)
OUT
50 100 125
25 75
1643 G08
Power Good Threshold Voltage
vs Temperature (V
–10.50
–10.48
–10.46
–10.44
–10.42
–10.40
–10.38
–10.36
POWER GOOD THRESHOLD VOLTAGE (V)
–10.34
4
–50
050
–25 25 75 125
TEMPERATURE (°C)
EEOUT
)
100
1643 G10
12V Internal Switch Voltage Drop
vs Temperature
325
I
= 500mA
12VOUT
300
275
250
225
200
175
INTERNAL SWITCH VOLTAGE DROP (mV)
150
–50 25 75
–25 0
50 100 125
TEMPERATURE (°C)
LT1643 G11
VEE Internal Switch Voltage Drop
vs Temperature
180
I
= 100mA
VEEIN
160
140
120
100
80
INTERNAL SWITCH VOLTAGE DROP (mV)
60
–50
–25 0
TEMPERATURE (°C)
50 100 125
25 75
1643 G12
LTC1643L/LTC1643L-1/LTC1643H
UW
TYPICAL PERFORMANCE CHARACTERISTICS
Circuit Breaker Trip Filter Time
vs Temperature
15.50
15.25
15.00
14.75
14.50
14.25
CIRCUIT BREAKER TRIP FILTER TIME (µs)
14.00
–50
–25 0
V
Supply Current
EEIN
TEMPERATURE (°C)
50 100 125
25 75
vs Temperature
0.90
0.89
0.88
0.87
0.86
SUPPLY CURRENT (mA)
EEIN
V
0.85
1643 G13
Timer Threshold Voltage
vs Temperature
1.0
0.9
0.8
TIMER THRESHOLD VOLTAGE (V)
V
– V
12VIN
TIMER
0.7
–50
–25 0
25 75
TEMPERATURE (°C)
5VIN Supply Current
vs Temperature
270
268
266
264
262
SUPPLY CURRENT (µA)
260
IN
5V
258
50 100 125
1643 G14
12VIN Supply Current
vs Temperature
3.72
3.70
3.68
3.66
SUPPLY CURRENT (mA)
IN
3.64
12V
3.62
–50
–25
0
TEMPERATURE (°C)
3VIN Supply Current
vs Temperature
275.0
272.5
270.0
267.5
265.0
SUPPLY CURRENT (µA)
IN
3V
262.5
50
25
75
100
125
1643 G15
0.84
–50
–25 0
VOL vs Temperature
350
I = 3mA
300
250
(mV)
200
OL
V
150
100
50
–50
–25 0
50 100 125
25 75
TEMPERATURE (°C)
FAULT
PWRGD
50 100 125
25 75
TEMPERATURE (°C)
1643 G16
1643 G19
256
–50 25 75
–25 0
TEMPERATURE (°C)
12VIN Undervoltage Lockout
vs Temperature
9.515
9.510
9.505
9.500
9.495
UNDERVOLTAGE LOCKOUT (V)
9.490
9.485
–50
–25 0
25 75
TEMPERATURE (°C)
50 100 125
LT1643 G17
50 100 125
1643 G20
260.0
–50
–25 0
25 75
TEMPERATURE (°C)
5VIN Undervoltage Lockout
vs Temperature
2.454
2.452
2.450
2.448
2.446
UNDERVOLTAGE LOCKOUT (V)
2.444
2.442
–50
–25 0
25 75
TEMPERATURE (°C)
50 100 125
1643 G18
50 100 125
1643 G21
5
LTC1643L/LTC1643L-1/LTC1643H
TEMPERATURE (°C)
70
60
50
40
30
20
10
0
LT1643 G24
FOLDBACK CURRENT LIMIT VOLTAGE (mV)
–50 25 75
–25 0
50 100 125
3V
OUT
= 3.3V
3V
OUT
= 0V
UW
TYPICAL PERFORMANCE CHARACTERISTICS
3VIN Undervoltage Lockout
vs Temperature
2.454
2.452
2.450
2.448
2.446
UNDERVOLTAGE LOCKOUT (V)
2.444
2.442
–50
–25 0
25 75
TEMPERATURE (°C)
VEE Current Foldback
vs Temperature
600
500
400
300
200
CURRENT FOLDBACK (mA)
100
0
–50
–25 0
V
TEMPERATURE (°C)
50 100 125
= –12V
EEOUT
V
= 0V
EEOUT
50 100
25 75
1643 G21
1643 G25
5VIN Foldback Current Limit
Voltage vs Temperature
70
60
50
40
30
20
10
FOLDBACK CURRENT LIMIT VOLTAGE (mV)
0
–50 25 75
–25 0
5V
= 5V
OUT
5V
= 0V
OUT
50 100 125
TEMPERATURE (°C)
12V Current Foldback
vs Temperature
1200
12V
= 12V
1000
800
600
400
CURRENT FOLDBACK (mA)
200
0
–50
OUT
12V
OUT
–25 0
TEMPERATURE (°C)
= 0V
25 75
50 100
LT1643 G23
1643 G26
3VIN Foldback Current Limit
Voltage vs Temperature
800
700
600
500
(mV)
400
OL
V
300
200
100
VOL vs I
0
0
(25°C)
SINK
PWRGD
24 8
I
(mA)
SINK
6
FAULT
10
1643 G27
PIN FUNCTIONS
12VIN (Pin 1): 12V Supply Input. It powers all the chip’s
internal circuitry. A 0.5Ω switch is connected between
12VIN and 12V
undervoltage lockout circuit prevents the switches from
turning on while the 12VIN pin voltage is less than 9.5V
typically.
V
connected between V
current limit.
3V
output supply voltage. The PWRGD signal cannot go high
until the 3V
6
(Pin 2): –12V Supply Input. A 1.2Ω switch is
EEIN
(Pin 3): Analog Input. Used to monitor the 3.3V
OUT
OUT
pin exceeds 2.9V typically.
OUT
UUU
with a foldback current limit. An
EEIN
and V
with a fold-back
EEOUT
TIMER (Pin 4): Analog Current Fault Inhibit Timing Input.
Connect a capacitor from TIMER to GND. With the chip
turned off (ON = GND or ON = High) or the internal circuit
breaker tripped (FAULT = GND), the TIMER pin is internally
held at GND. When the chip is turned on, a 20µA pull-up
current source is connected to TIMER. Current limit faults
will be ignored until the voltage at the TIMER pin rises to
within 0.9V of 12VIN.
ON/ON (Pin 5): Digital Input.The LTC1643L/LTC1643L-1
have an active low enable, ON, and the LTC1643H has an
active high enable, ON. When the ON pin is pulled high or
UUU
PIN FUNCTIONS
LTC1643L/LTC1643L-1/LTC1643H
the ON pin pulled low, the GATE pin is pulled high by a
50µA current source and the internal 12V and –12V
switches are turned on. When the ON pin is pulled low or
the ON pin pulled high, the GATE pin will be pulled to
ground by a 200µA current source and the 12V and –12V
switches turned off.
The ON/ON pin is also used to reset the electronic circuit
breaker. If the ON/ON pin is cycled following the trip of the
circuit breaker, the circuit breaker is reset and a normal
power-up sequence will occur.
FAULT (Pin 6): Open-Drain Digital I/O. FAULT is pulled low
when a current limit fault is detected. Current limit faults
are ignored while the voltage at the TIMER pin is less than
12VIN – 0.9V. Once the TIMER cycle is complete, FAULT
will pull low typically 14.6µs after any of the supplies go
into current limit. At the same time the GATE and TIMER
pins are pulled to GND and the 12V and –12V switches are
turned off. The chip will remain latched in the off state until
the ON/ON pin is toggled or the power is cycled.
Forcing the FAULT pin low with an external pull-down will
immediately turn off the internal switches and force the
GATE and TIMER pins to GND independent of the state of
the ON/ON pin. However, the chip is not latched into the off
state, so when the FAULT pin is released, the state of the
chip will be determined by the ON pin.
PWRGD (Pin 7): Open-Drain Digital Power-Good Output.
PWRGD remains low while V
V
≥ 4.75V and V
5VOUT
EEOUT
has the power good comparators connected to the 12V
and V
pins disabled, with only the 3V
EEOUT
12VOUT
≥ 11.4V, V
3VOUT
≥ 3V,
≤ –10.8V. The LTC1643L-1
OUT
and 5V
OUT
OUT
outputs being monitored to generate PWRGD. When one
of the supplies falls below its power-good threshold
voltage, PWRGD will go high after a 15µs deglitching time.
The switches will
not
be turned off when PWRGD goes
high.
GND (Pin 8): Chip Ground.
3VIN (Pin 9): 3.3V Supply Sense Input. An undervoltage
lockout circuit prevents the switches from turning on
when the voltage at the 3VIN pin is less than 2.5V typically.
If no 3.3V input supply is available, tie 3VIN to the 5VIN pin.
3V
(Pin 10): The 3.3V Current Limit Set Pin. With a
SENSE
sense resistor placed in the supply path between 3VIN and
3V
, the GATE pin voltage will be adjusted to maintain
SENSE
a constant voltage across the sense resistor and a constant current through the switch. A foldback feature makes
the current limit decrease as the voltage at the 3V
approaches GND. To disable the current limit, 3V
OUT
SENSE
pin
and 3VIN can be shorted together.
GATE (Pin 11): High Side Gate Drive for the External
N-Channels. Requires an external series RC network for
the current limit loop compensation and setting the minimum ramp-up rate. During power-up, the slope of the
voltage rise at the GATE is set by the 50µA current source
connected to 12VIN and the external capacitor connected
to GND or by the 3.3V or 5V current limit and the bulk
capacitance on the 3V
OUT
or 5V
suppy lines. During
OUT
power-down, the slope of the falling voltage is set by the
200µA current source connected to GND and the external
GATE capacitor.
The voltage at the GATE pin will be modulated to maintain
a constant current when either the 3V or 5V supplies go
into current limit. When a current limit fault occurs after
the inhibit period set by the TIMER pin capacitance, the
undervoltage lockout circuit on 3.3V, 5V or 12V trips or
the FAULT pin is pulled low, the GATE pin is immediately
pulled to GND.
5V
(Pin 12): 5V Current Limit Set Pin. With a sense
SENSE
resistor placed in the supply path between 5VIN and
5V
, the GATE pin voltage will be adjusted to maintain
SENSE
a constant voltage across the sense resistor and a constant current through the switch. A foldback feature makes
the current limit decrease as the voltage at the 5V
approaches GND. To disable the current limit, 5V
OUT
SENSE
pin
and 5VIN can be shorted together.
5VIN (Pin 13): Analog Input. Used to monitor the 5V input
supply voltage. An undervoltage lockout circuit prevents
the switches from turning on when the voltage at the 5V
IN
pin is less than 2.5V typically.
5V
(Pin 14): Analog Input. Used to monitor the 5V
OUT
output supply voltage. The PWRGD signal cannot go high
until the 5V
pin exceeds 4.65V typically.
OUT
7
LTC1643L/LTC1643L-1/LTC1643H
UUU
PIN FUNCTIONS
V
connected between V
(Pin 15): –12V Supply Output. A 1.2Ω switch is
EEOUT
EEIN
and V
EEOUT
. V
EEOUT
must
exceed –10.8V before the PWRGD signal can go high on
the LTC1643H and LTC1643L.
W
BLOCK DIAGRAM
ON/ON
FAULT
PWRGD
5V
IN5VSENSE
13
12 11 10 9 3 14
–
5V
+
2.5V
UVL
5
6
Q3
7
Q4
OUT
+
–
GATE
12V
Q5
LOGIC
12V
connected between 12VIN and 12V
(Pin 16): 12V Supply Output. A 0.5Ω switch is
OUT
. 12V
OUT
OUT
must
exceed 11.4V before the PWRGD signal can go high on the
LTC1643H and LTC1643L.
3V
IN
50µA
200µA
3V
SENSE
IN
3V
OUT
–
+
+
–
2.5V
UVL
C
C
3V
5V
OUT
OUT
Q8
P3
+
–
REF
P4
+
–
Q7
12V
9.5V
UVL
Q1
1 16 4 2 15 8
12V
12V
IN
U
Q9
REF
LTC1643H/LTC1643L
OUT
WUU
+
–
ONLY
C
P7
IN
20µA
Q6
TIMER
APPLICATIONS INFORMATION
Hot Circuit Insertion
When a circuit board is inserted into a live PCI slot, the
supply bypass capacitors on the board can draw huge
transient currents from the PCI power bus as they charge
up. The transient currents can cause permanent damage
to the connector pins and cause glitches on the power bus,
causing other boards in the system to reset.
The LTC1643 is designed to turn a board’s supply voltages
on and off in a controlled manner, allowing the board to be
REF
Q2
C
P5
+
Q10
V
V
EEIN
EEOUT
–
LTC1643H/LTC1643L
ONLY
REF
1643 BD
GND
safely inserted or removed from a live PCI slot without
glitching the system power supplies. The chip also protects the PCI supplies from shorts and monitors the
supply voltages.
The LTC1643H is designed for motherboard applications, while the LTC1643L/LTC1643L-1 are designed for
CompactPCI applications where the chip resides on the
plug-in board.
8
LTC1643L/LTC1643L-1/LTC1643H
U
WUU
APPLICATIONS INFORMATION
LTC1643 FEATURE SUMMARY
1. Allows safe board insertion and removal from either a
motherboard (LTC1643H) or CompactPCI board
(LTC1643L/LTC1643L-1).
2. Controls all four PCI supplies: –12V, 12V, 3.3V and 5V.
3. Programmable foldback current limit: a programmable
analog current limit with a value that depends on the
output voltage. If the output is shorted to ground, the
current limit drops to keep power dissipation and
supply glitches to a minimum.
4. Programmable circuit breaker: if a supply remains in
current limit too long, the circuit breaker will trip, the
supplies will be turned off and the FAULT pin pulled low.
5. Current limit power-up: the supplies are allowed to
power up in current limit. Allows the chip to power up
boards with widely varying capacitive loads without
tripping the circuit breaker. The maximum allowable
power-up time is programmable using the TIMER pin.
6. –12V and 12V power switches on chip.
7. Power good output: monitors the voltage status of the
four supply voltages, except the LTC1643L-1 which
only monitors 3V
8. Space saving 16-pin SSOP package.
PCI Power Requirements
PCI systems usually require four power rails: 5V, 3.3V,
12V and –12V. Systems implementing the 3.3V signaling
environment are usually required to provide all four rails in
every system. Systems implementing the 5V signaling
environment may either ship the 3.3V supply with the
system or provide a means to add it afterward. The
tolerance of the supplies as measured at the components
on the plug-in card is summarized in Table 1.
Table 1. PCI Power Supply Requirements
SUPPLY TOLERANCE LOAD
5V 5V ±5% <3000µF
3.3V 3.3V ±0.3V < 3000µF
12V 12V ±5% <500µF
–12V –12V ±10% <120µF
OUT
and 5V
CAPACITIVE
OUT
.
Some ±12V supplies in CompactPCI applications are not
well regulated and can violate the tolerance specification.
For these applications, the LTC1643L-1 should be used
because the PWRGD signal does not depend on ±12V
outputs.
Power-Up Sequence
The power supplies are controlled by placing external
N-channel pass transistors in the 3.3V and 5V power
paths, and internal pass transistors for the 12V and –12V
power paths (Figure 1).
Resistors R1 and R2 provide current fault detection and
R7 and C1 provide current control loop compensation.
Resistors R5 and R6 prevent high frequency oscillations
in Q1 and Q2.
When the ON pin (Pin 5) is pulled high, the pass transistors
are allowed to turn on and a 20µA current source is
connected to the TIMER pin (Pin 4) (Figure 2).
The current in each pass transistor increases until it
reaches the current limit for each supply. Each supply is
then allowed to power up at the rate dv/dt = 50µA/C1 or as
determined by the current limit and the load capacitance
whichever is slower. Current limit faults are ignored while
the TIMER pin (Pin 4) voltage is ramping up and is less
than 0.9V below 12VIN (Pin 1). Once all four supply
voltages are within tolerance, the PWRGD pin (Pin 7) will
pull low.
Power-Down Sequence
When the ON (Pin 5) is pulled low, a power-down
sequence begins (Figure 3).
Internal switches are connected to each of the output
supply voltage pins to discharge the bypass capacitors to
ground. The TIMER pin (Pin 4) is immediately pulled low.
The GATE pin (Pin 11) is pulled down by a 200µA current
source to prevent the load currents on the 3.3V and 5V
supplies from going to zero instantaneously and glitching
the power supply voltages. When any of the output
voltages dip below its threshold, the PWRGD pin (Pin 7)
pulls high.
9
LTC1643L/LTC1643L-1/LTC1643H
U
WUU
APPLICATIONS INFORMATION
R2
0.005ΩQ2IRF7413
SYSTEM
POWER
SUPPLY
109
3V
3V
IN
SENSE
IN
Figure 1. Typical Application
PCI
POWER
SYSTEM
CONTROLLER
RESET
10k
10k
8
GND
1
12V
2
V
EEIN
5
ON
R3
6
FAULT
R4
7
PWRGD
R1
0.007Ω
R5
10Ω
11 3 13 12 14
3V
GATE
OUT
LTC1643H
5V
IN
5V
SENSE
Q1
IRF7413
R6
10Ω
5V
5A
3.3V
7.6A
R7
100Ω
C1
5V
OUT
12V
OUT
V
EEOUT
TIMER
0.047µF
16
15
4
C2
0.1µF
GND
12V
500mA
–12V
100mA
LOGIC
RESET
1643 F01
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
12V
OUT
5V/DIV
5V
OUT
5V/DIV
3V
OUT
5V/DIV
V
EEOUT
5V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
ON
ON
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
12V
OUT
5V/DIV
5V
OUT
5V/DIV
3V
OUT
5V/DIV
V
EEOUT
5V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
10
10ms/DIV
Figure 2. Normal Power-Up Sequence
1643 F02
10ms/DIV
Figure 3. Normal Power-Down Sequence
1643 F03
LTC1643L/LTC1643L-1/LTC1643H
U
WUU
APPLICATIONS INFORMATION
Timer
During a power-up sequence, a 20µA current source is
connected to the TIMER pin (Pin 4) and current limit faults
are ignored until the voltage ramps to within 0.9V of 12V
(Pin 1). This feature allows the chip to power up a PCI slot
that can accept boards with widely varying capacitive
loads on the supplies. The power-up time will be:
CV
t
ON
For C
SUPPLY
= 5A, the turn-on time will be ~10ms. The timer period
should be set longer than the maximum supply turn-on
time but short enough to not exceed the maximum safe
operating area of the pass transistor during a short circuit.
The timer period will be:
t
TIMER
For C
TIMER
TIMER pin (Pin 4) is immediately pulled low when ON
(Pin 5) goes low.
Thermal Shutdown
The internal switches for the 12V and –12V supplies are
protected by an internal current limit and thermal shutdown circuit. When the temperature of chip reaches
150°C, all switches will be latched off and the FAULT pin
(Pin 6) will be pulled low.
Short-Circuit Protection
During a normal power-up sequence, if the TIMER (Pin 4)
is done ramping and a supply is still in current limit, all of
the pass transistors will be immediately turned off and the
FAULT pin (Pin 6) will be pulled low as shown in Figure 4.
SUPPLY SUPPLY
≅−2
= 2000µF, V
C
=
= 0.1µF, the timer period will be ~50ms. The
•
II
LIMIT LOAD
SUPPLY
1
V
•.11
TIMER
A
22µ
= 5V, I
LIMIT
= 7A, I
IN
LOAD
turning on —from causing false trips of the circuit breaker.
The chip will stay in the latched-off state until ON (Pin 5)
is cycled low then high, or the 12VIN pin (Pin 1) power
supply is cycled.
To prevent excessive power dissipation in the pass transistors and to prevent voltage spikes on the supplies
during short-circuit conditions, the current limit on each
supply is designed to be a function of the output voltage.
As the output voltage drops, the current limit decreases.
Unlike a traditional circuit breaker function where huge
currents can flow before the breaker trips, the current
foldback feature assures that the supply current will be
kept at a safe level and prevent voltage glitches when
powering up into a short.
The current limit for the 5V and 3.3V supplies is set by
placing a sense resistor between 5VIN (Pin 13) and 5V
(Pin 12) and between 3VIN (Pin 9) and 3V
The current limit will be set by:
I
= 53mV/R
LIMIT
For a 0.005Ω resistor, the current limit will be set at 10.6A
and fold back to 1.5A when the output is shorted. For a
0.007Ω resistor, the current limit will be set at 7.6A and
fold back to 1.1A when the output is shorted.
The current limit for the internal 12V switch is set at
850mA folding back to 250mA and the –12V switch at
450mA folding back to 160mA.
In systems where it is possible to exceed the current limit
for a short amount of time, it might be necessary to
prevent the analog current loop from responding quickly
so the output voltage does not droop. This can be accomplished by adding an RC filter across the sense resistor as
shown in Figure 6. R1 should be 20Ω or less to prevent
offset errors. A 0.1µF capacitor gives a delay of about
1.5µs and a 1µF capacitor gives a delay of about 15µs.
SENSE
SENSE
SENSE
(Pin 10).
If a short circuit occurs after the supplies are powered up,
the shorted supply’s current will drop immediately to the
limit value (Figure 5).
If the supply remains in current limit for more than 15µs,
all of the supplies will be latched off. The 15µs delay
prevents quick current spikes—for example, from a fan
CompactPCI Application
The LTC1643L is designed for hot swapping CompactPCI
boards. The typical application is shown in Figure 7. The
3.3V, 5V, 12V and –12V inputs to the LTC1643L come
from the medium length power pins. The long 3.3V, 5V and
V(I/O) pins power up the pull-up resistors, bus precharge
11
LTC1643L/LTC1643L-1/LTC1643H
U
WUU
APPLICATIONS INFORMATION
ON
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
12V
OUT
5V/DIV
5V
OUT
5V/DIV
3V
OUT
5V/DIV
V
EEOUT
5V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
ON
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
12V
OUT
5V/DIV
3V
OUT
5V/DIV
5V
OUT
5V/DIV
V
EEOUT
5V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
20ms/DIV
Figure 4. Power-Up into a Short on 3.3V Output
5V
R2
3.3V
0.005ΩQ2IRF7413
C2
R3
1µF
20Ω
3VIN3V
SENSE
R5
10Ω
11 3
GATE
Figure 6. Delay in the Current Limit Loop
1643 F05
3V
OUT
LTC1643L
5V
0.007Ω
1µF
13
IN
20ms/DIV
1643 F04
Figure 5. Short Circuit on 5V
R1
C3
5V
R4
20Ω
12 14109
SENSE
Q1
IRF7413
R6
10Ω
5V
5V
5A
3.3V
7.6A
R7
100Ω
C1
0.047µF
OUT
1643 F06
12
LTC1643L/LTC1643L-1/LTC1643H
U
WUU
APPLICATIONS INFORMATION
MED 5V
MED 3.3V
12V
–12V
BD_SEL#
HEALTHY#
LONG GND
PCI_RST#
CompactPCI CONNECTOR
I/O
D2*
12V
C6
0.1µF
*1SMA12CAT3
R8
1.2k
5%
C7
0.1µF
V(I/O)
V(I/O)
R10
2k
5%
R9
2k
5%
V(I/O)
1
2
5
6
7
R1
0.005Ω
1%
3V
IN
12V
IN
V
EEIN
ON
FAULT
PWRGD
DATA LINE EXAMPLE
3V
SENSE
DATA BUS
109
R2
0.007Ω
1%
Q2
IRF7413
R3
10Ω
5%
11 3 13 12 14
5V
5V
IN
LOCAL_PCI_RESET#
10Ω, 5%
SENSE
GND
GATE
8
3V
OUT
LTC1643L
IRF7413
TIMER
R14
Q1
4
R4
10Ω
5%
C2
0.1µF
5V
5A
3.3V
7.6A
R5
100Ω
5%
C1
5V
OUT
12V
OUT
V
EEOUT
0.047µF
16
12V
500mA
15
–12V
100mA
PRECHARGE OUT
1V ±20%
I
= ±40mA
OUT
C3
0.01µF
R13
LONG
10k
5%
I/O
RESET#
3.3V
3.3V
D1
1N4148
R11
24Ω
5%
LONG
PCI
BRIDGE
(21154)
LONG
3.3V
LT1117
IN
1643 F07
OUT
C4
1µF
ADJ
R6
130Ω
1%
R7
56.2Ω
1%
5V
5V
Figure 7. Typical CompactPCI Application
circuit, PCI bridge chip and the LOCAL_PCI_RESET# logic
circuitry. The BD_SEL# signal is connected to the ON pin
while the PWRGD pin is connected to the HEALTHY#
signal. The HEATHLY# signal is combined with the
PCI_RESET# signal to generate the LOCAL_PCI_RESET#
signal. Capacitors C6 and C7 provide chip bypassing on
the 12V and –12V inputs. Diode D2 protects the part from
voltage surges below –13.2V on the –12V supply.
The 1V precharge voltage for the data bus lines is generated by an LT1117 low dropout regulator. The output of the
LT1117 is set to 1.8V, then the voltage is dropped by a
1N4148 diode to generate 1V. The precharge circuit is
capable of sourcing and sinking 40mA.
LTC1643L-1
The LTC1643L-1 is designed for CompactPCI designs
where the ±12V supplies are not being used on the board
or the supplies are not well regulated. The power good
comparators on the 12V
The V
pin can be connected to GND and the part will
EEIN
still operate normally if a –12V
OUT
and V
OUT
pins are disabled.
EEOUT
output is not needed.
However, 12V is still required at the 12VIN pin for the part
to function. Refer to Figure 10 for a typical LTC1643L-1
application circuit.
Increasing 12V and –12V Current Capability
The internal switches in the LTC1643 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.
13
LTC1643L/LTC1643L-1/LTC1643H
U
WUU
APPLICATIONS INFORMATION
For the 12V supply, P-channel transistor Q4 is placed in
parallel with the internal switch. When the LTC1643H 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 LTC1643H 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
be reached when the internal current reaches 1A and the
external current is 2A or 3A load current.
values. For example, if the R
DS(ON)
of the external
DS(ON)
For the –12V supply, N-channel transistor Q6 is used to
provide the extra load current. When the LTC1643H is
turned on, the internal VEE switch is turned on and the
–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 LTC1643H turns off, the V
EEOUT
pin is
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
of the internal switch
DS(ON)
(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.
Q4
Si9400
Q3
TP0610T
12V
1.5A
SYSTEM
POWER
SUPPLY
PCI
POWER
SYSTEM
CONTROLLER
10k
10k
5V
12
SENSE
C3
0.1µF
12V
V
EEOUT
TIMER
16
OUT
Q1
IRF7413
15
4
R6
10Ω
C2
0.1µF
R7
100Ω
Q5
TP0610T
R9
200Ω
R10
200Ω
Si9410DY
D1
1N4148
Q6
5V
5A
3.3V
7.6A
GND
C1
0.047µF
–12V
1.5A
1643 F08
R8
100k
R1
R2
0.005ΩQ2IRF7413
R5
10Ω
1
3V
3V
12V
IN
IN
8
GND
2
V
EEIN
5
ON
R3
6
FAULT
R4
7
PWRGD
109
SENSE
GATE
11 3 13
3V
OUT
LTC1643H
0.007Ω
5V
IN
Figure 8. Increasing 12V and –12V Current Capability
14
PACKAGE DESCRIPTION
LTC1643L/LTC1643L-1/LTC1643H
U
Dimensions in inched (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)
16
15
14
12 11 10
13
0.009
(0.229)
9
REF
0.007 – 0.0098
(0.178 – 0.249)
0.016 – 0.050
(0.406 – 1.270)
* 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
U
TYPICAL APPLICATIONS
SYSTEM
POWER
SUPPLY
8
GND
1
12V
2
V
5
ON
PCI
POWER
SYSTEM
CONTROLLER
10k
10k
R3
6
FAULT
R4
7
PWRGD
EEIN
IN
0.015
0° – 8° TYP
3V
IN
± 0.004
(0.38 ± 0.10)
0.007Ω
5V
IN
× 45°
R1
109
3V
SENSE5VSENSE
LTC1643H
0.229 – 0.244
(5.817 – 6.198)
0.053 – 0.068
(1.351 – 1.727)
0.008 – 0.012
(0.203 – 0.305)
Q1
IRF7413
R6
10Ω
1113 12 143
GATE
0.150 – 0.157**
(3.810 – 3.988)
5
OUT
12V
V
EEOUT
TIMER
3
R7
100Ω
OUT
4
678
0.004 – 0.0098
(0.102 – 0.249)
0.0250
(0.635)
BSC
GN16 (SSOP) 1098
5V
5A
GND
C1
0.047µF
16
15
4
C2
0.1µF
12V
500mA
–12V
100mA
1643 G09
12
5V
3V
OUT
Figure 9. System Without 3.3V Supply
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.
15
LTC1643L/LTC1643L-1/LTC1643H
U
TYPICAL APPLICATIONS
MED 5V
MED 3.3V
12V
BD_SEL#
HEALTHY#
LONG GND
1.2k
CompactPCI CONNECTOR
C7
0.1µF
R8
5%
V(I/O)
V(I/O)
R10
2k
5%
R9
2k
5%
V(I/O)
1
2
5
6
7
3V
12V
IN
V
EEIN
ON
FAULT
PWRGD
0.005Ω
1%
IN
R1
3V
Q2
IRF7413
R3
10Ω
5%
11 3 13 12 14
109
3V
GATE
SENSE
LTC1643L-1
GND
8
OUT
5V
R2
0.007Ω
1%
IN
5V
IRF7413
SENSE
TIMER
Q1
5V
5A
3.3V
R4
10Ω
100Ω
5%
5%
5V
OUT
12V
OUT
V
EEOUT
4
C2
0.1µF
R5
16
15
PRECHARGE OUT
1V ±20%
= ±40mA
I
OUT
7.6A
C1
0.047µF
C3
0.01µF
D1
1N4148
R11
24Ω
5%
R6
130Ω
1%
R7
56.2Ω
1%
LT1117
OUT
C4
1µF
ADJ
LONG
3.3V
IN
R13
LONG
3.3V
3.3V
RESET#
BRIDGE
(21154)
PCI
LONG
5V
5V
1643 F10
PCI_RST#
LOCAL_PCI_RESET#
R14
I/O
*1SMA12CAT3
DATA LINE EXAMPLE
DATA BUS
10Ω, 5%
10k
5%
I/O
Figure 10. CompactPCI Application Without ±12V Outputs
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LTC1421 Hot Swap Controller Multiple Supply
LTC1422 Hot Swap Controller Single Supply, SO-8 Package
LT1640 –48V Hot Swap Controller Negative High Voltage Supplies, SO-8 Package
LTC1642 Fault Protected Hot Swap Controller Operation up to 15V, Handles Surges to 33V
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear-tech.com
1643fs, sn1643 LT/TP 0899 4K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1998
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