LINER LTC1643AL-1 Pci-bus hot swap controller Datasheet

LTC1643AL
LTC1643AL-1/LTC1643AH
PCI-Bus Hot Swap
Controller
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FEATURES
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DESCRIPTIO
Allows Safe Board Insertion and Removal from a
Live PCI Slot
Works on either a Motherboard (LTC1643AH) or
CompactPCITM Card (LTC1643AL/LTC1643AL-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-Channel MOSFETs
–12V and 12V On-Chip Switches
Fault and Power-Good Outputs
Available in a Narrow 16-Lead SSOP Package
The LTC®1643A 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(LTC1643AH)/ON (LTC1643AL/
LTC1643AL-1) pin is used to cycle the board power or reset
the circuit breaker. The LTC1643AL-1 has the ±12V power
good comparators disabled.
The LTC1643A is available in a 16-pin narrow SSOP package.
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APPLICATIO S
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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.
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TYPICAL APPLICATION
Hot Swappable PCI Supply
R1
0.007Ω
3.3V
7.6A
GND
SYSTEM
POWER
SUPPLY
R5
10Ω
9
3VIN
8
GND
1
12VIN
2
VEEIN
5
ON
RESET
5V
5A
R6
10Ω
Q2
IRF7413
R2
0.005Ω
PCI
POWER
SYSTEM
CONTROLLER
Q1
IRF7413
R3
10k
R4
10k
6
10
11
3VSENSE GATE
R7
100Ω
3
13
3VOUT 5VIN
12
5VSENSE
12VOUT
LTC1643AH
VEEOUT
FAULT
TIMER
7
PWRGD
C1
0.047µF
14
5VOUT
16
12V
500mA
15
–12V
100mA
4
C2
0.1µF
LOGIC
RESET
1643A TA01
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LTC1643AL
LTC1643AL-1/LTC1643AH
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
Supply Voltages
12VIN ................................................................ 13.2V
VEEIN .............................................................. –13.2V
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)
VEEOUT ............................................ –13.2V to + 0.3V
12VOUT .............................................. – 0.3V to 13.2V
Operating Temperature Range
LTC1643ALC/LTC1643AL-1C/
LTC1643AHC ........................................... 0°C to 70°C
LTC1643ALI/LTC1643AL-1I/
LTC1643AHI ...................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART NUMBER
TOP VIEW
12VIN 1
16 12VOUT
VEEIN 2
15 VEEOUT
3VOUT 3
14 5VOUT
TIMER 4
13 5VIN
ON/ON* 5
FAULT 6
PWRGD 7
GND 8
12 5VSENSE
11 GATE
10 3VSENSE
9
LTC1643AHCGN
LTC1643ALCGN
LTC1643AL-1CGN
LTC1643AHIGN
LTC1643ALIGN
LTC1643AL-1IGN
GN PART MARKING
3VIN
1643AH
1643AL
643AL1
643AHI
643ALI
43AL1I
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
*ON FOR LTC1643AH,
ON FOR LTC1643AL/LTC1643AL-1
TJMAX = 150°C, θJA = 135°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS The
● denotes specifications which apply over the full operating
temperature range, otherwise specifications are TA = 25°C. V12VIN = 12V, VEEIN = – 12V, V3VIN = 3.3V, V5VIN = 5V (Note 2)
SYMBOL
PARAMETER
CONDITIONS
IDD
V12VIN Supply Current
ON = GND, ON = 3V
●
VLKO
Undervoltage Lockout
12VIN
3VIN
5VIN
●
VFB = (V5VIN – V5VSENSE), V5VOUT = 0V
VFB = (V5VIN – V5VSENSE), V5VOUT > 4V
VFB = (V3VIN – V3VSENSE), V3VOUT = 0V
VFB = (V3VIN – V3VSENSE), V3VOUT > 2V
●
VFB
Foldback Current Limit Voltage
tCB
Circuit Breaker Trip Filter Time
ICP
GATE Pin Output Current
9.5
2.5
2.5
10.8
2.75
2.75
4
40
4
40
7.5
53
7.5
53
12
65
12
65
mA
V
V
V
mV
mV
mV
mV
µs
100
200
mV
●
225
225
600
750
mV
(VEEOUT – VEEIN), IVEEIN = 100mA
●
125
250
mV
12VIN = 12V, 12VOUT = 0V
12VIN = 12V, 12VOUT = 10V
VEEIN = –12V, VEEOUT = 0V (LTC1643AL/LTC1643AH Only)
VEEIN = –12V, VEEOUT = – 10V
●
50
525
50
225
250
850
160
450
600
1500
500
800
mA
mA
mA
mA
10.8
10.4
11.1
11.1
11.4
11.4
V
V
– 10.2
– 10.0
– 10.5
– 10.5
– 10.8
– 10.8
V
V
(V12VIN – V12VOUT),
I12VOUT = 500mA
Power-Good Threshold Voltage
●
7
2.25
2.25
UNITS
µA
µA
mA
Internal Switch Voltage Drop
Thermal Shutdown Temperature
●
8
– 100
VDROP
VTH
●
MAX
3.5
– 62
200
17.5
(V12VIN – VGATE)
TTS
●
Charge Pump On, VGATE = GND, FAULT = High
Charge Pump Off, VGATE = 5V, FAULT = High
Charge Pump Off, VGATE = 2V, FAULT = Low
External Gate Voltage
Current Foldback
●
TYP
14.6
∆VGATE
ICL
MIN
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
– 20
●
3
●
●
●
●
°C
150
V12VOUT
LTC1643AH/LTC1643AL Only
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
VEEOUT
LTC1643AH/LTC1643AL Only
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
●
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LTC1643AL
LTC1643AL-1/LTC1643AH
DC ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
V12VIN = 12V, VEEIN = – 12V, V3VIN = 3.3V, V5VIN = 5V (Note 2)
SYMBOL
PARAMETER
CONDITIONS
VTH
Power-Good Threshold Voltage
V3VOUT
V5VOUT
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
●
VIL
Input Low Voltage
ON/ON, FAULT
●
VIH
Input High Voltage
ON/ON, FAULT
●
VOL
Output Low Voltage
FAULT, PWRGD, I = 3mA
●
IIN
ON/ON Pin Input Current
ON/ON = GND
ON/ON= 12VIN
●
5VSENSE Input Current
MIN
TYP
MAX
UNITS
2.8
2.75
2.9
2.9
3.0
3.0
V
V
4.5
4.4
4.65
4.65
4.75
4.75
V
V
0.8
V
2
V
0.4
V
●
± 0.08
± 0.08
±10
±10
µA
µA
5VSENSE = 5V
●
50
100
µA
3VSENSE Input Current
3VSENSE = 3V
●
50
100
µA
5VIN Input Current
5VIN = 5V
●
460
700
µA
3VIN Input Current
3VIN = 3V
●
320
600
µA
5VOUT Input Current
5VOUT = 5V, ON = 3V, ON = GND
●
240
500
µA
3VOUT Input Current
3VOUT = 3.3V, ON = 3V, ON = GND
●
220
500
µA
RDIS
5VOUT Discharge Impedance
3VOUT Discharge Impedance
12VOUT Discharge Impedance
VEEOUT Discharge Impedance
ON = GND or ON = 3V
ON = GND or ON = 3V
ON = GND or ON = 3V
ON = GND or ON = 3V
ITIMER
TIMER Pin Current
Timer On, VTIMER = GND
Timer Off, VTIMER = 5V
●
– 15
– 22
45
– 27
µA
mA
VTIMER
TIMER Threshold Voltage
(V12VIN – VTIMER)
●
0.5
0.9
1.3
V
Ω
Ω
Ω
Ω
100
70
450
1600
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.
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TYPICAL PERFORMANCE CHARACTERISTICS
3.3V and 5V Current
Foldback Profile
12V Current Foldback Profile
– 12V Current Foldback Profile
11
1.0
3VOUT
8
7
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
9
5VOUT
6
5
4
3
1.0
OUTPUT CURRENT (A)
10
0.5
0.5
2
1
0
RSENSE = 0.005Ω
0
0
1
3
4
2
OUTPUT VOLTAGE (V)
5
1643A G01
0
2
6
8
4
OUTPUT VOLTAGE (V)
10
12
1643A G02
0
0
–2
–6
–8
–10
–4
OUTPUT VOLTAGE (V)
–12
1643A G03
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LTC1643AL
LTC1643AL-1/LTC1643AH
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TYPICAL PERFORMANCE CHARACTERISTICS
Timer Current vs Temperature
Gate ISINK vs Temperature
23.5
Gate Current vs Temperature
90
25.0
FAULT = LOW
22.5
80
22.0
21.5
21.0
GATE CURRENT (µA)
22.5
GATE ISINK (mA)
20.0
17.5
15.0
20.5
19.5
–50 –25
25
0
50
75
10.0
–50 –25
125
100
TEMPERATURE (°C)
50
25
75
0
TEMPERATURE (°C)
1643A G04
11.10
11.08
11.06
4.67
4.66
4.65
4.64
4.63
50
25
75
0
TEMPERATURE (°C)
1643A G07
INTERNAL SWITCH VOLTAGE DROP (mV)
325
–10.56
–10.54
–10.52
–10.50
–10.48
–10.46
–10.44
–10.42
–50 –25
0
25
50
75
100
100
125
2.903
2.902
2.901
2.900
2.899
2.898
2.897
2.896
–50 –25
0
25
50
75
125
1643A G09
TEMPERATURE (°C)
1643A G10
300
275
250
225
200
175
50
25
75
0
TEMPERATURE (°C)
VEE Internal Switch Voltage Drop
vs Temperature
180
I12VOUT = 500mA
150
–50 –25
125
100
TEMPERATURE (°C)
12V Internal Switch Voltage Drop
vs Temperature
–10.58
125
Power Good Threshold Voltage vs
Temperature (3VOUT)
1643A G08
Power Good Threshold Voltage
vs Temperature (VEEOUT)
100
2.904
4.62
–50 –25
125
100
50
0
75
25
TEMPERATURE (°C)
1643A G06
POWER GOOD THRESHOLD VOLTAGE (V)
POWER GOOD THRESHOLD VOLTAGE (V)
POWER GOOD THRESHOLD VOLTAGE (V)
40
–50 –25
125
4.68
11.12
POWER GOOD THRESHOLD VOLTAGE (V)
100
Power Good Threshold Voltage vs
Temperature (5VOUT)
11.14
50
0
75
25
TEMPERATURE (°C)
60
1643A G05
Power Good Threshold Voltage vs
Temperature (12VOUT)
11.04
–50 –25
70
50
12.5
20.0
INTERNAL SWITCH VOLTAGE DROP (mV)
TIMER CURRENT (µA)
23.0
100
125
LT1643A G11
IVEEIN = 100mA
160
140
120
100
80
60
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1643A G12
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LTC1643AL
LTC1643AL-1/LTC1643AH
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TYPICAL PERFORMANCE CHARACTERISTICS
Timer Threshold Voltage
vs Temperature
1.0
TIMER THRESHOLD VOLTAGE (V)
CIRCUIT BREAKER TRIP FILTER TIME (µs)
15.50
15.25
15.00
14.75
14.50
14.25
14.00
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
3.72
V12VIN – VTIMER
0.9
0.8
0.7
–50 –25
125
12VIN Supply Current
vs Temperature
12VIN SUPPLY CURRENT (mA)
Circuit Breaker Trip Filter Time
vs Temperature
50
25
75
0
TEMPERATURE (°C)
100
0.87
0.86
0.85
266
264
262
260
50
25
75
0
TEMPERATURE (°C)
100
267.5
265.0
260.0
–50 –25
125
UNDERVOLTAGE LOCKOUT (V)
FAULT
250
200
150
PWRGD
100
100
125
1643A G19
9.515
2.454
9.510
2.452
9.505
9.500
9.495
9.490
9.485
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
5VIN Undervoltage Lockout
vs Temperature
UNDERVOLTAGE LOCKOUT (V)
I = 3mA
300
50
25
75
0
TEMPERATURE (°C)
1643A G18
12VIN Undervoltage Lockout
vs Temperature
VOL vs Temperature
VOL (mV)
270.0
LT1643A G17
1643A G16
50
25
75
0
TEMPERATURE (°C)
272.5
262.5
256
–50 –25
125
125
275.0
258
100
100
3VIN Supply Current
vs Temperature
3VIN SUPPLY CURRENT (µA)
5VIN SUPPLY CURRENT (µA)
VEEIN SUPPLY CURRENT (mA)
0.88
50
0
75
25
TEMPERATURE (°C)
1643A G15
268
0.89
50
–50 –25
3.64
3.62
–50 –25
125
270
0.90
350
3.66
5VIN Supply Current
vs Temperature
VEEIN Supply Current
vs Temperature
50
25
75
0
TEMPERATURE (°C)
3.68
1643A G14
1643A G13
0.84
–50 –25
3.70
100
125
1643A G20
2.450
2.448
2.446
2.444
2.442
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1643A G21
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LTC1643AL
LTC1643AL-1/LTC1643AH
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TYPICAL PERFORMANCE CHARACTERISTICS
3VIN Undervoltage Lockout
vs Temperature
70
2.452
2.450
2.448
2.446
2.444
2.442
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
70
60
5VOUT = 5V
50
40
30
20
5VOUT = 0V
10
0
–50 –25
125
FOLDBACK CURRENT LIMIT VOLTAGE (mV)
FOLDBACK CURRENT LIMIT VOLTAGE (mV)
2.454
UNDERVOLTAGE LOCKOUT (V)
3VIN Foldback Current Limit
Voltage vs Temperature
5VIN Foldback Current Limit
Voltage vs Temperature
50
25
75
0
TEMPERATURE (°C)
100
VEE Current Foldback
vs Temperature
1200
500
1000
300
VEEOUT = 0V
100
75
100
3VOUT = 0V
10
50
25
75
0
TEMPERATURE (°C)
100
VOL vs ISINK (25°C)
700
FAULT
600
800
600
500
400
300
400
12VOUT = 0V
0
–50
125
800
PWRGD
200
200
50
25
0
TEMPERATURE (°C)
20
1643A G24
VOL (mV)
CURRENT FOLDBACK (mA)
CURRENT FOLDBACK (mA)
400
–25
30
0
–50 –25
125
12VOUT = 12V
0
–50
40
12V Current Foldback
vs Temperature
600
200
50
1643A G23
1643A G21
VEEOUT = –12V
3VOUT = 3.3V
60
100
0
–25
50
25
0
TEMPERATURE (°C)
1643A G25
75
100
1643A G26
0
2
4
6
ISINK (mA)
8
10
1643A G27
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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 12VOUT with a foldback current limit. An undervoltage lockout circuit prevents the switches from turning
on while the 12VIN pin voltage is less than 9.5V typically.
VEEIN (Pin 2): – 12V Supply Input. A 1.2Ω switch is
connected between VEEIN and VEEOUT with a foldback
current limit.
3VOUT (Pin 3): Analog Input. Used to monitor the 3.3V
output supply voltage. The PWRGD signal cannot go high
until the 3VOUT pin exceeds 2.9V typically.
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 22µA 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 LTC1643AL/LTC1643AL-1
have an active low enable, ON, and the LTC1643AH has an
active high enable, ON. When the ON pin is pulled high or
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LTC1643AL
LTC1643AL-1/LTC1643AH
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PIN FUNCTIONS
the ON pin pulled low, the GATE pin is pulled high by a
62µA 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.
3VSENSE (Pin 10): The 3.3V Current Limit Set Pin. With a
sense resistor placed in the supply path between 3VIN and
3VSENSE, the GATE pin voltage will be adjusted to maintain
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 3VOUT pin
approaches GND. To disable the current limit, 3VSENSE
and 3VIN can be shorted together.
GATE (Pin 11): High Side Gate Drive for the External
N-Channel Pass Transistors. 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 62µA
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 3VOUT or 5VOUT suppy
lines. During power-down, the slope of the falling voltage
is set by the 200µA current source connected to GND and
the external GATE capacitor.
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.
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.
PWRGD (Pin 7): Open-Drain Digital Power-Good Output.
PWRGD remains low while V12VOUT ≥ 11.4V, V3VOUT ≥ 3V,
V5VOUT ≥ 4.75V and VEEOUT ≤ – 10.8V. The LTC1643AL-1
has the power good comparators connected to the 12VOUT
and VEEOUT pins disabled, with only the 3VOUT and 5VOUT
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.
5VSENSE (Pin 12): 5V Current Limit Set Pin. With a sense
resistor placed in the supply path between 5VIN and
5VSENSE, the GATE pin voltage will be adjusted to maintain
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 5VOUT pin
approaches GND. To disable the current limit, 5VSENSE
and 5VIN can be shorted together.
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.
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 5VIN
pin is less than 2.5V typically.
5VOUT (Pin 14): Analog Input. Used to monitor the 5V
output supply voltage. The PWRGD signal cannot go high
until the 5VOUT pin exceeds 4.65V typically.
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LTC1643AL
LTC1643AL-1/LTC1643AH
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PIN FUNCTIONS
VEEOUT (Pin 15): –12V Supply Output. A 1.2Ω switch is
connected between VEEIN and VEEOUT. VEEOUT must
exceed –10.8V before the PWRGD signal can go high on
the LTC1643AH and LTC1643AL.
12VOUT (Pin 16): 12V Supply Output. A 0.5Ω switch is
connected between 12VIN and 12VOUT. 12VOUT must
exceed 11.4V before the PWRGD signal can go high on the
LTC1643AH and LTC1643AL.
W
BLOCK DIAGRAM
5VIN 5VSENSE
3VSENSE 3VIN
GATE
11
12
10
12VIN
–
+
5VOUT
3VOUT 5VOUT
9
3
14
–
+
3VOUT
62µA
+
+
–
Q8
–
Q5
2.5V
UVL
200µA
Q7
2.5V
UVL
CP3
ON/ON 5
+
13
–
Q3
CP4
LOGIC
PWRGD 7
REF
+
FAULT 6
–
Q4
12VIN
9.5V
UVL
Q1
REF
REF
Q9
Q2
22µA
+ CP5
+ CP7
Q6
–
Q10
–
REF
1643A BD
12VIN
12VOUT
LTC1643AH/LTC1643AL
ONLY
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16
4
2
15
TIMER
VEEIN
VEEOUT
LTC1643AH/LTC1643AL 8 GND
ONLY
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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 LTC1643A is designed to turn a board’s supply
voltages on and off in a controlled manner, allowing the
board to be 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 LTC1643AH is designed for motherboard applications, while the LTC1643AL/LTC1643AL-1 are designed
for CompactPCI applications where the chip resides on
the plug-in board.
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LTC1643AL
LTC1643AL-1/LTC1643AH
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APPLICATIONS INFORMATION
LTC1643A FEATURE SUMMARY
1. Allows safe board insertion and removal from either a
motherboard (LTC1643AH) or CompactPCI board
(LTC1643AL/LTC1643AL-1).
Some ±12V supplies in CompactPCI applications are not
well regulated and can violate the tolerance specification.
For these applications, the LTC1643AL-1 should be used
because the PWRGD signal does not depend on ±12V
outputs.
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.
Power-Up Sequence
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.
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.
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 LTC1643AL-1 which
only monitors 3VOUT and 5VOUT.
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
CAPACITIVE
LOAD
5V
5V ±5%
< 3000µF
3.3V
3.3V ±0.3V
< 3000µF
12V
12V ±5%
< 500µF
– 12V
–12V ±10%
< 120µF
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).
When the ON pin (Pin 5) is pulled high, the pass transistors
are allowed to turn on and a 22µA 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 = 62µA/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 (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.
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LTC1643AL
LTC1643AL-1/LTC1643AH
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APPLICATIONS INFORMATION
R1
Q1
1 0.007Ω 2 IRF7413
3
R2
1 0.005Ω 2
3
R6
10Ω
Q2
IRF7413
3.3V
7.6A
4
GND
SYSTEM
POWER
SUPPLY
R5
10Ω
9
3VIN
GND
1
12VIN
2
VEEIN
5
ON
8
PCI
POWER
SYSTEM
CONTROLLER
5V
5A
4
R3
10k
R4
10k
6
10
11
3VSENSE GATE
R7
100Ω
3
13
3VOUT 5VIN
12
5VSENSE
5VOUT
12VOUT
LTC1643AH
VEEOUT
FAULT
TIMER
7
C1
0.047µF
14
PWRGD
RESET
16
12V
500mA
15
–12V
100mA
4
C2
0.1µF
LOGIC
RESET
1643A F01
Figure 1. Typical PCI Application
ON
10V/DIV
ON
10V/DIV
TIMER
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
GATE
10V/DIV
12VOUT
5V/DIV
5VOUT
5V/DIV
3VOUT
5V/DIV
12VOUT
5V/DIV
5VOUT
5V/DIV
3VOUT
5V/DIV
VEEOUT
5V/DIV
VEEOUT
5V/DIV
FAULT
10V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
PWRGD
10V/DIV
10ms/DIV
Figure 2. Normal Power-Up Sequence
1643A F02
10ms/DIV
1643A F03
Figure 3. Normal Power-Down Sequence
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LTC1643AL
LTC1643AL-1/LTC1643AH
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APPLICATIONS INFORMATION
Timer
During a power-up sequence, a 22µA 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 12VIN
(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:
t ON ≅ 2
CSUPPLY • VSUPPLY
ILIMIT − ILOAD
For CSUPPLY = 2000µF, VSUPPLY = 5V, ILIMIT = 7A, ILOAD
= 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 =
CTIMER • 11.1V
22µA
For CTIMER = 0.1µF, the timer period will be ~ 50ms. The
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.
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 14.6µs,
all of the supplies will be latched off. The 14.6µs delay
prevents quick current spikes—for example, from a fan
turning on—from causing false trips of the circuit breaker.
The chip will stay in the latched-off state until ON pin
(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 5VSENSE
(Pin 12) and between 3VIN (Pin 9) and 3VSENSE (Pin 10).
The current limit will be set by:
ILIMIT = 53mV/RSENSE
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. R4 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.
CompactPCI Application
The LTC1643AL 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 LTC1643AL 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
1643afa
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LTC1643AL
LTC1643AL-1/LTC1643AH
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APPLICATIONS INFORMATION
ON
10V/DIV
ON
10V/DIV
TIMER
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
GATE
10V/DIV
12VOUT
5V/DIV
12VOUT
5V/DIV
5VOUT
5V/DIV
3VOUT
5V/DIV
3VOUT
5V/DIV
5VOUT
5V/DIV
VEEOUT
5V/DIV
VEEOUT
5V/DIV
FAULT
10V/DIV
FAULT
10V/DIV
PWRGD
10V/DIV
PWRGD
10V/DIV
20ms/DIV
20ms/DIV
1643A F04
Figure 4. Power-Up into a Short on 3.3V Output
Figure 5. Short Circuit on 5V Followed by Circuit Breaker Reset
R1
1 0.007Ω 2
5V
3.3V
3
R2
1 0.005Ω 2
3
R4
20Ω
Q2
IRF7413
9
3VIN
R3
20Ω
10
Q1
IRF7413
5V
5A
4
R6
10Ω
3.3V
7.6A
C3
1µF
4
C2
1µF
1643A F05
R5
10Ω
11
3VSENSE GATE
R7
100Ω
3
13
3VOUT 5VIN
12
5VSENSE
14
C1
0.047µF
5VOUT
LTC1643AL
1643A F06
Figure 6. Delay in the Current Limit Loop
1643afa
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LTC1643AL
LTC1643AL-1/LTC1643AH
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APPLICATIONS INFORMATION
R2
Q1
0.007Ω
1%
1
2 IRF7413
MED 5V
R1
0.005Ω
1 1% 2
MED 3.3V
3
R11
10Ω†
5%
C6
0.1µF
9
R8
1.2k
5%
3VIN
1
CompactPCI CONNECTOR
HEALTHY#
2
R9 2k 5% 5
V(I/O)
R13
2k
5%
3.3V
7.6A
4
R4
10Ω
5%
R5
100Ω
5%
V(I/O)
D3*
12V
R12 3Ω 5%
BD_SEL#
Q2
IRF7413
5V
5A
4
R3
10Ω
5%
12V
–12V
3
10
11
3VSENSE GATE
3
13
3VOUT 5VIN
12
5VSENSE
5VOUT
12VIN
12VOUT
VEEIN
VEEOUT
ON
LTC1643AL
6
16
15
12V
500mA
–12V
100mA
FAULT
R10 2k 5%
7
C5
0.1µF
PWRGD
LONG
3.3V
PRECHARGE OUT
D1
1V ±20%
IOUT = ±40mA 1N4148
V(I/O)
D2*
12V
C1
0.047µF
14
GND
TIMER
8
4
C3
0.01µF
R11
24Ω
5%
C2
0.1µF
LONG GND
LT1117
R6
130Ω
1%
R7
56.2Ω
1%
IN
OUT
ADJ
C4
1µF
V(I/O)
LOCAL_PCI_RESET#
PCI_RST#
DATA LINE EXAMPLE
I/O
R14
10Ω, 5%
R13
10k
5%
I/O
LONG LONG
3.3V
5V
3.3V
5V
RESET#
PCI
BRIDGE
(21154)
DATA BUS
1643A F07
* BZX84C15 (SOT-23)
† VALUE MAY VARY FOR BACKPLANES WITHOUT BYPASS CAPACITANCE
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.
LTC1643AL-1
The LTC1643AL-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 12VOUT and VEEOUT pins are disabled.
The VEEIN pin can be connected to GND and the part will
still operate normally if a – 12VOUT 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 LTC1643AL-1
application circuit.
1643afa
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LTC1643AL
LTC1643AL-1/LTC1643AH
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APPLICATIONS INFORMATION
Increasing 12V and – 12V Current Capability
for PCI Applications
be reached when the internal current reaches 1A and the
external current is 2A or 3A load current.
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, N-channel transistor Q6 is used to
provide the extra load current. When the LTC1643AH 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 LTC1643AH turns off, the VEEOUT pin is
pulled up to ground, diode D1 is reversed biased, and
transistor Q5 turns off, which allows resistor R10 to turn
off Q6.
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.
The internal –12V switch provides the current limit for the
supply, but because the high RDS(ON) of the internal switch
(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.
Because Q4 is in parallel with the internal 12V switch, the
load current will be shared in proportion to their respective
RDS(ON) values. For example, if the RDS(ON) of the external
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
Q4
Si9400
Q3
TP0610T
10Ω
C3
0.1µF
R8
100k
1
R2
Q2
1 0.005Ω 2 IRF7413
SYSTEM
POWER
SUPPLY
3
Q1
IRF7413
2
R1
0.007Ω
3
12V
1.5A
5V
5A
4
4
3.3V
7.6A
R6
10Ω
GND
R5
10Ω
1
8
2
5
PCI
POWER
SYSTEM
CONTROLLER
R3
10k
R4
10k
6
7
9
12VIN 3VIN
10
11
R7
100Ω
3
3VSENSE GATE 3VOUT
13
5VIN
12
C1
0.047µF
16
5VSENSE 12VOUT
GND
Q5
TP0610T
VEEIN
ON
LTC1643AH
FAULT
VEEOUT
15
R9
200Ω
TIMER
4
C2
0.1µF
PWRGD
NOTE: INTENDED FOR PCI APPLICATIONS ONLY
D1
1N4148
R10
200Ω
Q6
Si9410DY
–12V
1.5A
1643A F08
Figure 8. Increasing 12V and – 12V Current Capability for PCI Applications
1643afa
14
LTC1643AL
LTC1643AL-1/LTC1643AH
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PACKAGE DESCRIPTION
GN Package
16-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641)
.189 – .196*
(4.801 – 4.978)
.045 ±.005
.009
(0.229)
REF
16 15 14 13 12 11 10 9
.254 MIN
.150 – .165
.229 – .244
(5.817 – 6.198)
.0165 ± .0015
.150 – .157**
(3.810 – 3.988)
.0250 TYP
RECOMMENDED SOLDER PAD LAYOUT
1
.015 ± .004
× 45°
(0.38 ± 0.10)
.007 – .0098
(0.178 – 0.249)
2 3
4
5 6
.053 – .068
(1.351 – 1.727)
8
7
.004 – .0098
(0.102 – 0.249)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
.0250
(0.635)
BSC
.008 – .012
(0.203 – 0.305)
NOTE:
1. CONTROLLING DIMENSION: INCHES
INCHES
2. DIMENSIONS ARE IN
(MILLIMETERS)
3. DRAWING NOT TO SCALE
*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) 0502
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TYPICAL APPLICATIONS
R1
Q1
IRF7413
1 0.007Ω 2
3
5V
5A
4
GND
R6
10Ω
R7
100Ω
SYSTEM
POWER
SUPPLY
C1
0.047µF
9
8
GND
1
12VIN
2
VEEIN
5
ON
PCI
POWER
SYSTEM
CONTROLLER
R3
10k
R4
10k
6
3VIN
13
5VIN
10
12
11
3VSENSE 5VSENSE GATE
3
14
3VOUT 5VOUT
12VOUT
LTC1643AH
VEEOUT
FAULT
TIMER
7
PWRGD
16
12V
500mA
15
–12V
100mA
4
C2
0.1µF
1643A G09
Figure 9. System Without 3.3V Supply
1643afa
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
LTC1643AL
LTC1643AL-1/LTC1643AH
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TYPICAL APPLICATIONS
R2
Q1
0.007Ω
1%
1
2 IRF7413
MED 5V
R1
0.005Ω
1%
1
2
MED 3.3V
3
R9
2k
5%
HEALTHY#
CompactPCI CONNECTOR
12V
BD_SEL#
R11
1Ω†
5%
3.3V
7.6A
R4
10Ω
5%
R3
10Ω
5%
R8
1.2k
5%
9
1
R12
2k
5%
2
V(I/O)
6
5
R10
2k
5%
10
3VIN
7
5V
5A
4
4
V(I/O)
D2*
12V
3
Q2
IRF7413
11
3
3VSENSE GATE
13
3VOUT 5VIN
12
R5
100Ω
5%
5VOUT
12VIN
12VOUT
VEEIN
VEEOUT
ON
LTC1643AL-1
GND
TIMER
8
4
C7
0.1µF
16
15
NC
LONG
3.3V
NC
PRECHARGE OUT
D1
1V ±20%
IOUT = ±40mA 1N4148
FAULT
PWRGD
C1
0.047µF
14
5VSENSE
C3
0.01µF
R15
24Ω
5%
C2
0.1µF
LONG GND
LT1117
R6
130Ω
1%
R7
56.2Ω
1%
OUT
IN
ADJ
C4
1µF
V(I/O)
LOCAL_PCI_RESET#
PCI_RST#
DATA LINE EXAMPLE
I/O
R14
10Ω, 5%
R13
10k
5%
I/O
LONG LONG
3.3V
5V
3.3V
5V
RESET#
PCI
BRIDGE
(21154)
DATA BUS
1643A F10
* BZX84C15 (SOT-23)
† VALUE MAY VARY FOR BACKPLANES WITHOUT BYPASS CAPACITANCE
Figure 10. CompactPCI Application without ±12V Outputs
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1421
Hot Swap Controller
Multiple Supplies from 3V to 12V and –12V
LTC1422
Hot Swap Controller in SO-8
Single Supply form 3V to 12V, RESET Output
LT 1640A
– 48V Hot Swap Controller in SO-8
–10V to – 80V Supplies
LT1641-1/LT1641-2
Positive High Voltage Hot Swap Controller in SO-8
Operates from 9V to 80V, Active Current Limiting
LTC1642
Fault Protected Hot Swap Controller
Operation Up to 15V, Handles Surges to 33V
LTC1644
CompactPCI Hot Swap Controller
3.3V, 5V, ±12V, Local Reset Logic, 1V Precharge
LTC1645
2-Channel Hot Swap Controller
Operates from 1.2V to 12V, Power Sequencing
LTC1646
Dual CompactPCI Hot Swap Controller
3.3V, 5V Supplies, 1V Precharge, Local Reset Logic
LTC1647
Dual Hot Swap Controller
Dual ON Pins for Supplies from 3V to 15V
LTC4211
Hot Swap Controller with Multifunction Current Control
2.5V to 16.5V Operation, MSOP
LTC4230
Triple Hot Swap Controller
1.7V to 16.5V Operation, Multifunction Current Control
LT4250
– 48V Hot Swap Controller in SO-8
– 20V to –80V Supplies, Active Current Limiting
LTC4251
– 48V Hot Swap Controller in SOT-23
–15V Minimum Floating Supply, Active Current Limiting
LTC4252
– 48V Hot Swap Controller in MSOP
Floating Supply, Power Good, Active Current Limiting
®
1643afa
16
Linear Technology Corporation
LT/TP 0104 1K REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2002