LINER LTC1644IGN Compactpci bus hot swap controller Datasheet

LTC1644
CompactPCI Bus
Hot Swap Controller
DESCRIPTIO
U
FEATURES
■
■
■
■
■
■
■
Allows Safe Board Insertion and Removal from a
Live, CompactPCITM Bus
Controls –12V, 3.3V, 5V and 12V Supplies
Adjustable Foldback Current Limit with Circuit
Breaker
Dual-Level Circuit Breakers Protect 5V and 3.3V
Supplies from Overcurrent and Short-Circuit Faults
LOCAL_PCI_RST# Logic On-Chip
PRECHARGE Output Biases I/O Pins During Card
Insertion and Extraction
Adjustable Supply Voltage Power-Up Rate
The LTC®1644 is a Hot SwapTM controller that allows a board
to be safely inserted and removed from a CompactPCI bus
slot. External N-channel transistors control the 3.3V/5V
supplies, while on-chip switches control the
–12V and 12V supplies. The 3.3V and 5V supplies can be
ramped up at a programmable rate. Electronic circuit breakers protect all four supplies against overcurrent faults. The
PWRGD output indicates when all of the supply voltages are
within tolerance. The OFF/ON pin is used to cycle the board
power or reset the circuit breaker. The PRECHARGE output
can be used to bias the bus I/O pins during card insertion
and extraction. PCI_RST# is combined on-chip with
HEALTHY# in order to generate LOCAL_PCI_RST#.
Hot Board Insertion into CompactPCI Bus
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
CompactPCI is a trademark of the PCI Industrial Computer Manufacturers Group.
U
APPLICATIO S
■
U
TYPICAL APPLICATIO
C9
0.1µF
PER 10
POWER
PINS
C8
0.1µF
PER 10
POWER
PINS
PCB EDGE
BACKPLANE
CONNECTOR
5V
R2
0.007Ω
5VIN*
R22 2.74Ω
LONG 5V
3.3V
R1
0.005Ω
3VIN*
R21 1.74Ω
LONG 3.3V
C6
0.01µF
Z3
17
Z1
18
15
3VOUT
13
5VIN
2
–12V
5VIN
R20 1.2k
BD_SEL#
R19
1k
EARLY V(I/O)
5
6
R17
2k
R18
2k
HEALTHY#
7
9
PCI_RST#
R16
1Ω
3
5VOUT
VEEOUT
Z1, Z2: SMAJ12CA
Z3, Z4: 1PMT5.0AT3
12VOUT
12V AT 500mA
20
19
CLOAD(VEEOUT)
TIMER
FAULT
C2
0.1µF
R6
2k
PWRGD
RESETOUT
RESETIN
PRECHARGE
11
C3 4.7nF
R11
51k
10
3VOUT
DRIVE
12
R10
18Ω 5%
VEEOUT
–12V AT 100mA
4
R12
51k
R8 1k
R9
24Ω
1V
±10%
Q3
MMBT2222A
3VIN
R7
12Ω
RESET#
I/O #1
• • •
I/O DATA LINE 128
+
C1
0.047µF
LTC1644
20-PIN SSOP
OFF/ON
R13 10Ω
• • •
• • •
I/O PIN 128
14
5VSENSE
VEEIN
GROUND
I/O DATA LINE 1
3VOUT
3.3V AT 8A
12VIN
8
C5
0.01µF
+
CLOAD(12VOUT)
GND
I/O PIN 1
R5
1k
12VOUT
1
C4
0.01µF
R4
10Ω
Z2
12V
R15
1Ω
16
3VSENSE GATE
5VOUT
5V AT 5.7A
CLOAD(3VOUT)
R3
10Ω
3VIN
+
CLOAD(5VOUT)
Q1
IRF7413
Z4
C7
0.01µF
Q2
IRF7413
+
BACKPLANE
CONNECTOR
R14 10Ω
*5VIN AND 3VIN MAY BE USED AS SOURCES OF EARLY POWER
I/O #128
PCI
BRIDGE
CHIP
1644 F01
Figure 1
1644f
1
LTC1644
U
W W
W
ABSOLUTE
AXI U RATI GS
U
W
U
PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltages
12VIN ................................................................ 13.2V
VEEIN .................................................................. –14V
Input Voltages (Pins 5, 9) .......................– 0.3V to 13.5V
Output Voltages (Pins 6, 7, 10) ..............– 0.3V to 13.5V
Analog Voltages and Currents
Pins 3, 11 to 14, 16 to 18 ...................– 0.3V to 13.5V
Pins 4, 15 ............................. – 0.3V to (12VIN + 0.3V)
VEEOUT ...................................................– 14V to 0.3V
12VOUT ...............................................– 0.3V to 13.2V
Operating Temperature Range
LTC1644C ............................................... 0°C to 70°C
LTC1644I ............................................ – 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
20 12VOUT
VEEIN
2
19 VEEOUT
5VOUT
3
18 3VOUT
TIMER
4
17 3VIN
OFF/ON
5
16 3VSENSE
FAULT
6
15 GATE
PWRGD
7
14 5VSENSE
GND
8
13 5VIN
RESETIN
9
12 PRECHARGE
RESETOUT 10
LTC1644CGN
LTC1644IGN
11 DRIVE
GN PACKAGE
20-LEAD PLASTIC SSOP
TJMAX = 140°C, θJA = 135°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
V12VIN = 12V, VEEIN = –12V, V3VIN = 3.3V, V5VIN = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
IDD
V12VIN Supply Current
OFF/ON = 0V
●
MIN
TYP
MAX
3
8
VLKO
Undervoltage Lockout
12VIN, Ramping Down
3VIN, 5VIN, Ramping Down
●
●
VFB
Foldback Current Limit Voltage
VFB = (V5VIN – V5VSENSE), V5VOUT = 0V, TIMER = 0V
VFB = (V5VIN – V5VSENSE), V5VOUT = 3V, TIMER = 0V
VFB = (V3VIN – V3VSENSE), V3VOUT = 0V, TIMER = 0V
VFB = (V3VIN – V3VSENSE), V3VOUT = 2V, TIMER = 0V
VCB
Circuit Breaker Trip Voltage
tOC
6.00
2.25
8.30
2.48
10.80
2.75
●
●
●
●
8
40
8
40
12
51
12
51
15
70
15
70
mV
mV
mV
mV
VCB = (V5VIN – V5VSENSE), TIMER = FLOAT
VCB = (V3VIN – V3VSENSE), TIMER = FLOAT
●
●
40
40
55
55
70
70
mV
mV
Overcurrent Fault Response Time
(V5VIN – V5VSENSE) = 100mV, TIMER = FLOAT
(V3VIN – V3VSENSE) = 100mV, TIMER = FLOAT
●
●
30
30
45
45
60
60
µs
µs
tSC
Short-Circuit Response Time
(V5VIN – V5VSENSE) = 200mV, TIMER = FLOAT
(V3VIN – V3VSENSE) = 200mV, TIMER = FLOAT
●
●
0.1
0.1
1.0
1.0
µs
µs
ICP
GATE Pin Output Current
OFF/ON = 0V, VGATE = 0V, TIMER = 0V
VGATE = 5V, OFF/ON = 4V
OFF/ON = 0V, VGATE = 2V, TIMER = FLOAT, FAULT = 0V
●
– 65
225
10
–100
300
20
µA
µA
mA
●
– 20
100
3
UNITS
mA
V
V
∆VGATE
External Gate Voltage
∆VGATE = (V12VIN – VGATE), IGATE = –1µA
●
50
200
mV
VDROP
Internal Switch Voltage Drop
VDROP = (V12VIN – V12VOUT), I = 500mA
VDROP = (VEEOUT – VEEIN), IEE = 100mA
●
●
200
110
600
250
mV
mV
ICL
Current Foldback
12VIN = 12V, 12VOUT = 0V, TIMER = 0V
12VIN = 12V, 12VOUT = 10V, TIMER = 0V
VEEIN = –12V, VEEOUT = 0V, TIMER = 0V
VEEIN = –12V, VEEOUT = –10V, TIMER = 0V
●
●
●
●
–360
– 840
100
320
– 600
– 1500
300
650
mA
mA
mA
mA
TTS
Thermal Shutdown Temperature
– 50
– 525
20
200
130
°C
1644f
2
LTC1644
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
V12VIN = 12V, VEEIN = –12V, V3VIN = 3.3V, V5VIN = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VTH
Power Good Threshold Voltage
12VOUT
VEEOUT
3VOUT
5VOUT
●
●
●
●
10.8
– 10.4
2.8
4.50
11.1
– 10.5
2.9
4.62
11.4
– 11.1
3.0
4.75
V
V
V
V
V3VONLY
3V Only Window Voltage
V3VONLY = V5VIN – V3VIN, V5VOUT = V3VOUT = 3V
●
50
107
200
mV
VNOVEEIN
No VEEIN Threshold Voltage
VEEIN
●
–4
– 4.6
– 6.3
V
VIL
Input Low Voltage
OFF/ON, RESETIN, FAULT
●
0.8
V
VIH
Input High Voltage
OFF/ON, RESETIN, FAULT
●
IIN
OFF/ON, RESETIN Input Current
OFF/ON, RESETIN = 0V
OFF/ON, RESETIN = 12VIN
●
●
±0.08
±0.08
±10
±10
µA
µA
RESETOUT, FAULT Output Current
RESETOUT, FAULT = 5V, OFF/ON = 0V, RESETIN = 3.3V
●
±0.08
±10
µA
PWRGD Output Current
PWRGD = 5V, OFF/ON = 4V
●
±0.08
±10
µA
5VSENSE Input Current
5VSENSE = 5V, 5VOUT = 0V
●
55
100
µA
3VSENSE Input Current
3VSENSE = 3.3V, 3VOUT = 0V
●
55
100
µA
5VIN Input Current
5VIN = 5V, TIMER = 0V
●
1
1.5
mA
3VIN Input Current
3VIN = 3.3V, TIMER = FLOAT
3VIN = 3.3V, TIMER = 0V
●
●
490
380
625
550
µA
µA
5VOUT Input Current
5VOUT = 5V, OFF/ON = 0V, TIMER = 0V
●
102
400
µA
2
3VOUT Input Current
3VOUT = 3.3V, OFF/ON = 0V, TIMER = 0V
●
ITIMER
TIMER Pin Current
OFF/ON = 0V, VTIMER = 0V
VTIMER = 5V, OFF/ON = 4V
●
●
–15
30
VTIMER
TIMER Threshold Voltages
(V12VIN – VTIMER), FAULT = 0V
●
0.5
RDIS
5VOUT Discharge Impedance
3VOUT Discharge Impedance
12VOUT Discharge Impedance
VEEOUT Discharge Impedance
OFF/ON = 4V
OFF/ON = 4V
OFF/ON = 4V
OFF/ON = 4V
●
●
●
●
VOL
Output Low Voltage
PWRGD, RESETOUT, FAULT, I = 3mA
●
VPXG
PRECHARGE Reference Voltage
V5VIN = 5V
V5VIN = V3VIN = 3.3V
●
●
0.95
0.95
V
161
500
µA
– 21
45
–27
70
µA
mA
1
1.3
V
45
60
430
625
100
100
1000
1000
Ω
Ω
Ω
Ω
0.4
V
1.05
1.05
V
V
1.00
1.00
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.
1644f
3
LTC1644
U W
TYPICAL PERFOR A CE CHARACTERISTICS
3.3V and 5V Current Foldback
Profile
1.0
10
0.9
– 12V Output Current
0.40
TA = 25°C
12VIN = 12V
6
5
4
3
OUTPUT CURRENT (A)
7
0.7
0.6
0.5
0.4
0.3
0.2
2
TA = 25°C
RSENSE = 0.005Ω
1
0.25
0.20
0.15
0.10
0
1
2
3
4
OUTPUT VOLTAGE (V)
5
0
0
2
4
6
8
OUTPUT VOLTAGE (V)
10
1644 G01
12
0
3.2
2.8
–50
–25
50
25
0
TEMPERATURE (°C)
75
RAMPING
UP
8.45
8.40
8.35
RAMPING
DOWN
8.30
8.25
8.20
–50
100
–25
25
50
0
TEMPERATURE (°C)
75
RAMPING
UP
3VIN UVLO THRESHOLD VOLTAGE (V)
2.55
2.54
2.53
2.52
2.51
2.50
2.49
RAMPING
DOWN
2.48
2.47
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G07
60
RAMPING
UP
2.53
2.52
2.51
2.50
RAMPING
DOWN
2.49
2.48
2.47
2.46
–50
100
–25
0
50
25
TEMPERATURE (°C)
75
100
1644 G06
5V Foldback Current Limit Voltage
vs Temperature
3V Foldback Current Limit Voltage
vs Temperature
TIMER = 0V
3V FOLDBACK CURRENT LIMIT VOLTAGE (mV)
5V FOLDBACK CURRENT LIMIT VOLTAGE (mV)
2.56
2.54
1644 G05
1644 G04
3VIN UVLO Threshold Voltage
vs Temperature
–12
2.55
5VIN UVLO THRESHOLD VOLTAGE (V)
12VIN UNDERVOLTAGE LOCKOUT (V)
2.9
–10
5VIN UVLO Threshold Voltage
vs Temperature
8.50
3.0
–4
–6
–8
OUTPUT VOLTAGE (V)
1644 G03
12VIN Undervoltage Lockout
vs Temperature
3.1
–2
1644 G02
12VIN Supply Current
vs Temperature
12VIN SUPPLLY CURRENT (mA)
0.30
0.05
0.1
0
0
TA = 25°C
VEEIN = –12V
0.35
0.8
5VOUT
3VOUT
8
OUTPUT CURRENT (A)
9
OUTPUT CURRENT (A)
12V Output Current
11
5VOUT = 3V
50
40
30
20
5VOUT = 0V
10
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G08
60
TIMER = 0V
3VOUT = 2V
50
40
30
20
3VOUT = 0V
10
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G09
1644f
4
LTC1644
U W
TYPICAL PERFOR A CE CHARACTERISTICS
5V/3.3V Circuit Breaker Overcurrent
Fault Response Time
vs Temperature
56.0
55.8
55.6
55.4
55.2
55.0
–25
50
25
0
TEMPERATURE (°C)
0.125
48.0
TIMER PIN FLOATING
54.8
–50
75
47.5
47.0
46.5
46.0
45.5
45.0
44.5
–50
100
–25
50
25
0
TEMPERATURE (°C)
75
1644 G10
0.105
0.100
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G12
GATE Pin Current vs Temperature
(VGATE = 0V, OFF/ON = 0V)
–40
VGATE = 5V
OFF/ON = 4V
–45
VGATE = 5V
OFF/ON = 4V
10
8
6
4
–50
GATE PIN CURRENT (A)
GATE PIN CURRENT (µA)
GATE PIN CURRENT (mA)
300
200
150
100
–55
–60
–65
–70
–75
50
2
–80
0
–50
–25
0
50
25
TEMPERATURE (°C)
75
0
–50
100
–25
50
25
0
TEMPERATURE (°C)
75
1644 G13
11.95
11.94
11.93
11.92
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
1644 G16
0
25
50
TEMPERATURE (°C)
0.35
0.18
I = 500mA
100
75
VEE Internal Switch Voltage Drop
vs Temperature
VEE INTERNAL SWITCH VOLTAGE DROP (V)
11.96
–25
1644 G15
12V Internal Switch Voltage Drop
vs Temperature
VCC INTERNAL SWITCH VOLTAGE DROP (V)
IGATE = –1µA
–85
–50
100
1644 G14
GATE Pin Voltage vs Temperature
GATE PIN VOLTAGE (V)
0.110
250
12
11.97
0.115
GATE Pin Current vs Temperature
(VGATE = 5V, OFF/ON = 4V)
VGATE = 2V
FAULT = 0V
14
100
0.120
1644 G11
GATE Pin Current vs Temperature
(VGATE = 2V, FAULT = 0V)
16
5V/3.3V Circuit Breaker ShortCircuit Response Time
vs Temperature
5V/3.3V CIRCUIT BREAKER SHORT-CIRCUIT
RESPONSE TIME (µs)
56.2
5V/3.3V CIRCUIT BREAKER OVERCURRENT
FAULT RESPONSE TIME (µs)
5V/3.3V CIRCUIT BREAKER TRIP VOLTAGE (mV)
5V/3.3V Circuit Breaker Trip
Voltage vs Temperature
IEE = 100mA
0.16
0.30
0.14
0.25
0.12
0.20
0.10
0.08
0.15
0.06
0.10
0.04
0.05
0
–50
0.02
–25
50
25
0
TEMPERATURE (°C)
75
100
1644 G17
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G18
1644f
5
LTC1644
U W
TYPICAL PERFOR A CE CHARACTERISTICS
12V Foldback Current Limit
vs Temperature
0.45
0.90
12VOUT = 10V
11.11
12VOUT PWRGD THRESHOLD VOLTAGE (V)
1.00
0.40
VEE FOLDBACK CURRENT LIMIT (A)
12V FOLDBACK CURRENT LIMIT (A)
12VOUT PWRGD Threshold
Voltage vs Temperature
VEE Foldback Current Limit
vs Temperature
0.80
VEEOUT = –10V
0.35
0.70
0.30
0.60
0.25
0.50
12VOUT = 0V
0.40
0.20
0.15
0.30
VEEOUT = 0V
0.10
0.20
0.05
0.10
0
–50
–25
0
25
50
TEMPERATURE (°C)
0
–50
100
75
–25
0
25
50
TEMPERATURE (°C)
VEEOUT PWRGD Threshold Voltage
vs Temperature
4.622
–10.48
–10.49
–10.50
–10.51
–10.52
–10.53
0
50
25
TEMPERATURE (°C)
75
11.07
11.06
11.05
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
4.620
1644 G21
3VOUT PWRGD Threshold Voltage
vs Temperature
2.903
4.618
2.901
4.616
2.899
4.614
2.897
4.612
4.610
–50
100
–25
0
25
50
TEMPERATURE (°C)
75
100
2.895
–50
60
0.13
–4.30
50
5VSENSE INPUT CURRENT (µA)
VEEIN THRESHOLD VOLTAGE (V)
–4.20
–4.40
–4.50
3VIN – 5VIN
–4.60
0.09
–4.70
0.08
75
0.07
–4.80
0.06
–50
–4.90
–50
100
5VSENSE Input Current vs
Temperature
0.14
0.10
0
25
50
TEMPERATURE (°C)
1644 G24
No VEEIN Threshold Voltage vs
Temperature
5VIN – 3VIN
–25
1644 G23
3V Only Window Voltage
vs Temperature
0.11
100
2.905
1644 G22
0.12
80
3VOUT PWRGD THRESHOLD VOLTAGE (V)
5VOUT PWRGD THRESHOLD VOLTAGE (V)
VEEOUT PWRGD THRESHOLD VOLTAGE (V)
–10.47
–25
11.08
5VOUT PWRGD Threshold Voltage
vs Temperature
–10.46
3V ONLY WINDOW VOLTAGE (V)
100
11.09
1644 G20
1644 G19
–10.54
–50
75
11.10
5VOUT = 0V
40
30
20
10
5VOUT = 3V
–25
0
50
25
TEMPERATURE (°C)
75
100
1644 G25
–25
50
25
0
TEMPERATURE (°C)
75
100
1644 G26
0
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
1644 G27
1644f
6
LTC1644
U W
TYPICAL PERFOR A CE CHARACTERISTICS
3VSENSE Input Current
vs Temperature
5VIN Input Current vs Temperature
1.04
40
30
20
10
–25
1.02
1.01
1.00
0.99
0.98
50
25
0
TEMPERATURE (°C)
0.96
–50
100
75
–25
50
25
0
TEMPERATURE (°C)
75
1644 G28
102
101
25
50
0
TEMPERATURE (°C)
75
164
21.6
163
21.4
162
161
160
159
–25
25
50
0
TEMPERATURE (°C)
75
10
–25
0
25
50
TEMPERATURE (°C)
75
21.0
20.8
100
1644 G34
–25
25
50
0
TEMPERATURE (°C)
75
5VOUT Discharge Resistance
vs Temperature
70
1.10
1.05
1.00
0.95
0.90
0.85
0.80
–50
100
1644 G33
5VOUT DISCHARGE RESISTANCE (Ω)
20
VTIMER = 0V
ON = 0V
20.4
–50
100
1.15
TIMER THRESHOLD VOLTAGE (V)
TIMER PIN CURRENT (mA)
30
100
21.2
TIMER Threshold Voltage
vs Temperature
40
75
1644 G32
TIMER Pin Current
vs Temperature (OFF/ON = 4V)
50
0
25
50
TEMPERATURE (°C)
20.6
157
–50
100
VTIMER = 5V
OFF/ON = 4V
–25
TIMER Pin Current
vs Temperature (ON = 0V)
1644 G31
0
–50
350
1644 G30
158
60
TIMER = 0V
300
–50
100
TIMER PIN CURRENT (µA)
3VOUT INPUT CURRENT (µA)
5VOUT INPUT CURRENT (µA)
103
70
400
3VOUT Input Current
vs Temperature
104
–25
450
1644 G29
5VOUT Input Current
vs Temperature
100
–50
TIMER PIN FLOATING
500
0.97
3VOUT = 2V
0
–50
TIMER = 0V
3VIN INPUT CURRENT (µA)
50
3VIN Input Current vs Temperature
550
1.03
3VOUT = 0V
5VIN INPUT CURRENT (mA)
3VSENSE INPUT CURRENT (µA)
60
–25
50
25
0
TEMPERATURE (°C)
75
100
1644 G35
60
50
40
30
20
10
0
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
1644 G36
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3VOUT Discharge Resistance
vs Temperature
12VOUT Discharge Resistance
vs Temperature
70
60
50
40
30
20
10
–25
0
25
50
TEMPERATURE (°C)
75
VEEOUT DISCHARGE RESISTANCE (Ω)
8O
0
–50
900
700
12VOUT DISCHARGE RESISTANCE (Ω)
3VOUT DISCHARGE RESISTANCE (Ω)
90
VEEOUT Discharge Resistance
vs Temperature
600
500
400
300
200
100
0
–50
100
–25
50
25
0
TEMPERATURE (°C)
75
1.005
PRECHARGE REFERENCE VOLTAGE (V)
I = 3mA
0.25
FAULT
0.20
VOL (V)
600
500
400
300
200
100
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G39
Precharge Reference Voltage
vs Temperature
VOL vs Temperature
V5VIN = 5V
1.004
RESETOUT
0.15
PWRGD
1.003
0.10
0.05
0
–50
700
1644 G38
1644 G37
0.30
100
80O
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G40
1.002
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1644 G41
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12VIN (Pin 1): 12V Supply Input. 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
8.3V. 12VIN also provides power to the LTC1644’s internal
circuitry.
VEEIN (Pin 2): –12V Supply Input. A 1Ω switch is connected between VEEIN and VEEOUT with a foldback current
limit. If no VEE supply input is available, tie the VEEIN pin to
the GND pin in order to disable the VEEOUT power good
function.
5VOUT (Pin 3): 5V Output Sense. The PWRGD pin will not
pull low until the 5VOUT pin voltage exceeds 4.62V. If no 5V
input supply is available, tie the 5VOUT pin to the 3VOUT pin
in order to disable the 5VOUT power good function.
TIMER (Pin 4): Current Fault Inhibit Timing Input. Connect
a capacitor from TIMER to GND. With the chip turned off
(OFF/ON = HIGH), the TIMER pin is internally held at GND.
When the chip is turned on, a 21µA pull-up current source
is connected to TIMER. Current limit faults will be ignored
until the voltage at the TIMER pin rises to within 1V of
12VIN.
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OFF/ON (Pin 5): Digital Input. Connect the CPCI BD_SEL#
signal to the OFF/ON pin. When the OFF/ON pin is pulled
low, the GATE pin is pulled high by a 65µA current source
and the internal 12V and –12V switches are turned on.
When the OFF/ON pin is pulled high, the GATE pin will be
pulled to ground by a 225µA current source and the 12V
and –12V switches turn off.
5VIN (Pin 13): 5V Supply Sense Input. An undervoltage
lockout circuit prevents the switches from turning on
when the voltage at the 5VIN pin is less than 2.48V. If no
5V input supply is available, tie the 5VIN to the 3VIN pin.
The OFF/ON pin is also used to reset the electronic circuit
breaker. If the OFF/ON pin is cycled high and low following
the trip of the circuit breaker, the circuit breaker is reset
and a normal power-up sequence will occur.
5VSENSE (Pin 14): 5V Current Limit Sense. With a sense
resistor placed in the supply path between 5VIN and
5VSENSE, the GATE pin voltage will be adjusted to maintain
a constant 51mV across the sense resistor and a constant
current through the switch while the TIMER pin is low. A
foldback feature reduces the current limit as the voltage at
the 5VOUT pin approaches GND.
FAULT (Pin 6): Open-Drain Digital I/O. FAULT is pulled low
when a current limit fault is detected. Current limit faults
are ignored until the voltage at the TIMER pin is within 1V
of 12VIN. Once the TIMER cycle is complete, FAULT will
pull low and the chip latches off in the event of an
overcurrent fault. The chip will remain latched in the off
state until the OFF/ON pin is cycled high then low.
When the TIMER pin is high, the circuit breaker function is
enabled. If the voltage across the sense resistor exceeds
55mV but is less than 150mV, the circuit breaker is tripped
after a 45µs time delay. In the event the sense resistor
voltage exceeds 150mV, the circuit breaker trips immediately and the chip latches off. To disable the current limit,
5VSENSE and 5VIN can be shorted together.
Forcing the FAULT pin low with an external pull-down will
cause the chip to be latched into the off state after a 45µs
deglitching time.
GATE (Pin 15): High Side Gate Drive for the External 3.3V
and 5V N-Channels pass transistors. Requires an external
series RC network to compensate the current limit loop
and set the minimum ramp-up rate. During power up, the
slope of the voltage rise at the GATE is set by the 65µA
current source connected to 12VIN and the external capacitor connected to GND (C1, see Figure 1) or by the 3.3V
or 5V current limit and the bulk capacitance on the 3VOUT
or 5VOUT supply lines (CLOAD(5VOUT) or CLOAD(3VOUT), see
Figure␣ 1). During power down, the slew rate of the GATE
voltage is set by the 225µA current source connected to
GND and the external GATE capacitor (C1, see Figure 1).
PWRGD (Pin 7): Open-Drain Digital Power Good Output.
Connect the CPCI HEALTHY# signal to the PWRGD pin.
PWRGD remains low while V12VOUT ≥ 11.1V, V3VOUT ≥
2.9V, V5VOUT ≥ 4.62V and VEEOUT ≤ –10.5V. When any of
the supplies falls below its power good threshold voltage,
PWRGD will go high after a 10µs deglitching time.
GND (Pin 8): Chip Ground.
RESETIN (Pin 9): Digital Input. Connect the CPCI PCI_RST#
signal to the RESETIN pin. Pulling RESETIN low will cause
RESETOUT to pull low.
RESETOUT (Pin 10): Open-Drain Digital Output. Connect
the CPCI LOCAL_PCI_RST# signal to the RESETOUT pin.
RESETOUT is the logical combination of RESETIN and
PWRGD.
DRIVE (Pin 11): Precharge Base Drive Output. Provides
base drive for an external NPN emitter-follower which in
turn biases the PRECHARGE node.
PRECHARGE (Pin 12): Precharge Monitor Input. An onchip error amplifier servos the DRIVE pin voltage to keep
the precharge node at 1V.
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 while the TIMER pin is low. In the event
of a fault or an undervoltage condition, the GATE pin is
immediately pulled to GND.
3VSENSE (Pin 16): 3.3V Current Limit Set. With a sense
resistor placed in the supply path between 3VIN and
3VSENSE, the GATE pin voltage will be adjusted to maintain
a constant 51mV across the sense resistor and a constant
current through the switch while the TIMER pin is low. A
foldback feature reduces the current limit as the voltage at
the 3VOUT pin approaches GND.
1644f
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When the TIMER pin is high, the circuit breaker function is
enabled. If the voltage across the sense resistor exceeds
55mV but is less than 150mV, the circuit breaker is tripped
after a 45µs time delay. In the event the sense resistor
voltage exceeds 150mV, the circuit breaker trips immediately and the chip latches off. To disable the current limit,
3VSENSE and 3VIN can be shorted together.
3VOUT (Pin 18): Analog Input used to monitor the 3.3V
output supply voltage. The PWRGD pin cannot pull low
until the 3VOUT pin voltage exceeds 2.9V. If no 3.3V input
supply is available, tie the 3VOUT pin to the 5VOUT pin.
VEEOUT (Pin 19): –12V Supply Output. A 1Ω switch is
connected between VEEIN and VEEOUT. VEEOUT must exceed –10.5V before the PWRGD pin pulls low unless the
VEE PWRGD function is disabled by grounding the VEEIN
pin.
3VIN (Pin 17): 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 2.48V. If no
3.3V input supply is available, connect two series diodes
between 5VIN and 3VIN (tie anode of first diode to 5VIN and
cathode of second diode to 3VIN, see Figure 11).
12VOUT (Pin 20): 12V Supply Output. A 0.5Ω switch is
connected between 12VIN and 12VOUT. 12VOUT must
exceed 11.1V before the PWRGD pin can pull low.
W
BLOCK DIAGRA
5VIN
5VSENSE
13
14
+–
TIMER
3VSENSE
GATE
15
5VOUT
12VIN
+
+–
Q1
3
TIMER
–+
–
225µA
+
+
CP1
+–
18
A2
–
55mV
3VOUT 5VOUT
3VIN
17
–+
+
65µA
A1
51mV, TIMER LO
150mV, TIMER HI
16
3VOUT
CP2
–
Q2
51mV, TIMER LO
150mV, TIMER HI
55mV
–+
–
Q3
2.5V
UVL
2.5V
UVL
CP3
+
OFF/ON 5
–
FAULT 6
REF
Q11
CP4
+
LOGIC
PWRGD 7
–
Q10
10 RESETOUT
REF
Q4
RESETIN 9
8.3V
UVL
Q6
Q9
REF
12VIN
–
Q8
Q12
21µA
+
CP7
+
Q7
CP5
1V
A3
+
12 PRECHARGE
Q5
–
–
REF
1
20
4
2
19
12VIN
12VOUT
TIMER
VEEIN
VEEOUT
8
GND
11
1644 BD
DRIVE
NOTE: V12VIN – VTIMER < 1V = TIMER HI, V12VIN – VTIMER > 1V = TIMER LOW
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TI I G DIAGRA S
tSC Short-Circuit Fault Detect
tOC Overcurrent Fault Detect
5V OR 3.3V
V5VSENSE OR
V3VSENSE
100mV
FALL TIME ≤ 1µs
5VIN = 5V, 3VIN = 3.3V
5V OR 3.3V
V5VSENSE OR
V3VSENSE
200mV
tOC
FALL TIME ≤ 10ns
5VIN = 5V, 3VIN = 3.3V
tSC
FAULT
FAULT
1644 TD01
1644 TD02
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APPLICATIO S I FOR ATIO
Hot Circuit Insertion
When a circuit board is inserted into a live CompactPCI
(CPCI) slot, the supply bypass capacitors on the board can
draw huge supply transient currents from the CPCI power
bus as they charge up. The transient currents can cause
glitches on the power bus, causing other boards in the
system to reset.
The LTC1644 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 CPCI slot without
glitching the system power supplies. The chip also protects
the supplies from shorts, precharges the bus I/O pins during
insertion and extraction and monitors the supply voltages.
The LTC1644 is specifically designed for CPCI applications where the chip resides on the plug-in board.
LTC1644 Feature Summary
• Allows safe board insertion and removal from a CPCI
backplane.
• Controls all four CPCI supplies: –12V, 12V, 3.3V and 5V.
• Adjustable foldback current limit: an adjustable 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.
• 12V and –12V circuit breakers: if either supply remains
in current limit too long, the circuit breaker will trip, the
supplies are turned off and the FAULT pin is pulled low.
• Dual-level, adjustable 5V and 3.3V circuit breakers: if
either supply exceeds current limit for too long, the
circuit breaker will trip, the supplies will be turned off
and the FAULT pin will be asserted. In the event that
either supply exceeds 3 times the nominal current level,
all supplies will be turned off and the FAULT pin will be
asserted immediately.
• Current limit during power up: the supplies are allowed
to power up in current limit. This allows the chip to
power up boards with widely varying capacitive loads
without tripping the circuit breaker. The maximum
allowable power-up time is adjustable using the TIMER
pin.
• 12V and –12V power switches on chip.
• PWRGD output: monitors the voltage status of the four
supply voltages.
• PCI_RST# combined on-chip with HEALTHY# to create
LOCAL_PCI_RST# output. If HEALTHY# deasserts,
LOCAL_PCI_RST# is asserted independent of
PCI_RST#.
• Precharge output: on-chip reference and amplifier provide 1V for biasing bus I/O connector pins during CPCI
card insertion and extraction.
• Space saving 20-pin SSOP package.
CPCI Power Requirements
CPCI systems usually require four power rails: 5V, 3.3V,
12V and –12V. The tolerance of the supplies as measured
at the components on the plug-in card is summarized in
Table 1.
Table 1. Compact PCI Power Specifications
SUPPLY
TOLERANCE
MAX RIPPLE (P-P)
5V
+5%/–3%
50mV
3.3V
+5%/–3%
50mV
12V
±5%
240mV
–12V
±5%
240mV
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Power-Up Sequence
The LTC1644 is specifically designed for live insertion and
removal of CPCI boards. The typical application is shown
in Figure 1. The 3.3V, 5V, 12V and –12V inputs to the
LTC1644 come from the medium length power pins. The
long 5V and 3.3V connector pins are connected through
decoupling resistors to the medium length 5V and 3.3V
connector pins on the CPCI plug-in card and provide early
power for the LTC1644’s precharge circuit, pull-up resistors and the PCI bridge chip. The BD_SEL# signal is
connected to the OFF/ON pin while the PWRGD pin is
connected to the HEALTHY# signal. The HEALTHY# signal
is combined with the PCI_RST# signal on-chip to generate
the LOCAL_PCI_RST# signal which is available at the
RESETOUT pin.
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
R5 and C1 provide current control loop compensation.
Resistors R3 and R4 prevent high frequency oscillations
in Q1 and Q2. Shunt RC snubbers R15-C4 and R16-C5 and
zener diodes Z1 and Z2 prevent the 12VIN and VEEIN pins,
respectively, from ringing beyond the absolute maximum
rated supply voltages during hot insertion.
When the CPCI card is inserted, the long 5V and 3.3V
connector pins and GND pins make contact first. The
LTC1644’s precharge circuit biases the bus I/O pins to 1V
during this stage of the insertion (Figure 2). The 12V, –12V
and 5V and 3.3V medium length pins make contact during
the next stage of insertion. At this point the LTC1644
powers on but slot power is disabled as long as the OFF/ON
pin is pulled high by the 1.2k pull-up resistor to 5VIN.
During the final stage of board insertion, the BD_SEL#
short connector pin makes contact and the OFF/ON pin can
be pulled low. This enables the pass transistors to turn on
and a 21µA current source is connected to TIMER (Pin␣ 4).
The current in each pass transistor increases until it
reaches the current limit for each supply. The 5V and 3.3V
supplies are then allowed to power up based on one of the
following rates:
Power-up rate:
(1)
I
I
dV 65µA
=
, or = LIMIT (5 V) , or = LIMIT (3 V)
dt
C1
C LOAD(5 VOUT )
C LOAD(3 VOUT )
whichever is slower.
Current limit faults are ignored while the TIMER pin
voltage is ramping up and is less than 1V below 12VIN (Pin
1). Once all four supply voltages are within tolerance,
HEALTHY# (Pin 7) will pull low and LOCAL_PCI_RST# is
free to follow PCI_RST#.
Power-Down Sequence
When the BD_SEL# is pulled high, 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 is immediately pulled low. The
GATE pin (Pin 15) is pulled down by a 225µA 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 dips below its threshold, the HEALTHY# signal pulls
high and LOCAL_PCI_RST# will be asserted low.
Once the power-down sequence is complete, the CPCI
card may be removed from the slot. During extraction, the
precharge circuit will continue to bias the bus I/O pins at
1V until the 5V and 3.3V long connector pin connections
are broken.
1644f
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APPLICATIO S I FOR ATIO
TIMER
10V/DIV
TIMER
10V/DIV
GATE
5V/DIV
GATE
5V/DIV
12VOUT
10V/DIV
12VOUT
10V/DIV
5VOUT
10V/DIV
3VOUT
10V/DIV
5VOUT
10V/DIV
3VOUT
10V/DIV
VEEOUT
10V/DIV
VEEOUT
10V/DIV
BD_SEL#
5V/DIV
BD_SEL#
5V/DIV
LOCAL_PCI_RST#
5V/DIV
LOCAL_PCI_RST#
5V/DIV
HEALTHY#
5V/DIV
HEALTHY#
5V/DIV
PRECHARGE
5V/DIV
PRECHARGE
5V/DIV
10ms/DIV
1644 F02
1644 F03
Figure 3. Normal Power-Down Sequence
Figure 2. Normal Power-Up Sequence
TIMER
During a power-up sequence, a 21µA current source is
connected to the TIMER pin (Pin 4) and current limit faults
are ignored until the voltage ramps to within 1V of 12VIN
(Pin 1). This feature allows the chip to power up CPCI
boards with widely varying capacitive loads on the supplies. The power-up time for any one of the four outputs is
given by Equation 2:
 C LOAD(XVOUT) • XVOUT 
tON ( XVOUT ) = 2 • 

 ILIMIT (XVOUT) − ILOAD(XVOUT) 
10ms/DIV
(2)
where XVOUT = 5VOUT, 3VOUT, 12VOUT or VEEOUT (–12V).
For example, for CLOAD(5VOUT) = 2000µF, ILIMIT(5VOUT) =
7A and ILOAD(5VOUT) = 5A, the 5VOUT turn-on time will be
~10ms. By substituting the variables in Equation 2 with the
appropriate values, the turn-on time for the other three
outputs can be calculated.
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 for the LTC1644 is given
by:
tTIMER =
C TIMER • 11V
21µA
(3)
As a design aid, the timer period as a function of the timing
capacitor using standard values from 0.01µF to 1µF is
shown in Table 2.
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Table 2. tTIMER vs CTIMER
CTIMER
tTIMER
CTIMER
tTIMER
0.01µF
5.24ms
0.22µF
115ms
0.022µF
11.5ms
0.33µF
173ms
0.033µF
17.3ms
0.47µF
246ms
0.047µF
24.6ms
0.68µF
356ms
0.068µF
35.6ms
0.82µF
430ms
0.082µF
43.0ms
1µF
524ms
0.1µF
52.4ms
The TIMER pin is immediately pulled low when the BD_SEL#
signal goes high.
Thermal Shutdown
The internal switches for the 12V and –12V supplies are
protected by an internal current limit and a thermal shutdown circuit. When the temperature of the chip reaches
130°C, all switches will be latched off and the FAULT pin
(Pin␣ 6) will be pulled low.
After power-up, the 5V and 3.3V supplies are protected
from overcurrent and short-circuit conditions by duallevel circuit breakers. In the event that either supply
current exceeds the nominal limit but is less than 3 times
the current limit, an internal timer is started. If the supply
is still overcurrent after 45µs, the circuit breaker trips and
all the supplies are turned off (Figure 5). If a short-circuit
occurs and the supply current exceeds 3 times the set
limit, the circuit breakers trip without any delay and the
chip latches off (Figure 6). The chip will stay in the latched
off state until OFF/ON (Pin 5) is cycled high then low or the
12VIN (Pin 1) power supply is cycled off then on.
The current limit and the foldback current level for the 5V
and 3.3V outputs are both a function of the external sense
resistor (R1 for 3VOUT and R2 for 5VOUT, see Figure 1). As
shown in Figure 1, a sense resistor is connected between
5VIN (Pin 13) and 5VSENSE (Pin 12) for the 5V supply. For
the 3V supply, a sense resistor is connected between 3VIN
(Pin 9) and 3VSENSE (Pin 10). The current limit and the
foldback current level are given by Equations 4 and 5:
Short-Circuit Protection
During a normal power-up sequence, if the TIMER (Pin 4)
is done ramping and any supply is still in current limit, all
of the pass transistors will be immediately turned off and
FAULT (Pin 6) will be pulled low as shown in Figure 4.
In order 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 large
currents can flow before the breaker trips, the current
foldback feature assures that the supply current will be
kept at a safe level. In addition, current foldback prevents
voltage glitches when powering up into a short.
If either the 12V or –12V supply exceeds current limit after
power up, the shorted supply’s current will drop immediately to its ILIMIT value. If that supply remains in current
limit for more that 45µs, all of the supplies will be latched
off. The 45µs delay prevents quick current spikes—for
example, from a fan turning on—from causing false trips
of the circuit breaker.
ILIMIT (XVOUT) =
51mV
(4)
RSENSE(XVOUT)
IFOLDBACK(XVOUT) =
12mV
(5)
RSENSE(XVOUT)
where XVOUT = 5VOUT or 3VOUT.
As a design aid, the current limit and foldback level for
commonly used values for RSENSE is shown in Table 3.
Table 3. ILIMIT(XVOUT) and IFOLDBACK(XVOUT) vs RSENSE
RSENSE (Ω)
ILIMIT(XVOUT)
IFOLDBACK(XVOUT)
0.005
10.2A
2.4A
0.006
8.5A
2.0A
0.007
7.3A
1.7A
0.008
6.4A
1.5A
0.009
5.7A
1.3A
0.01
5.1A
1.2A
where XVOUT = 3VOUT or 5VOUT.
The current limit for the internal 12V switch is set at
840mA folding back to 360mA and the –12V switch at
320mA folding back to 100mA.
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APPLICATIO S I FOR ATIO
TIMER
10V/DIV
GATE
5V/DIV
12VOUT
10V/DIV
5VOUT
5V/DIV
3VOUT
5V/DIV
VEEOUT
10V/DIV
LOCAL_PCI_RST#
5V/DIV
BD_SEL#
5V/DIV
FAULT
5V/DIV
HEALTHY#
5V/DIV
PRECHARGE
5V/DIV
20ms/DIV
1644 F04
Figure 4. Power-Up into a Short on 3.3V Output
TIMER
10V/DIV
TIMER
10V/DIV
GATE
10V/DIV
GATE
10V/DIV
5VIN – 5VSENSE
100mV/DIV
50mV
150mV
5VIN – 5VSENSE
100mV/DIV
FAULT
5V/DIV
FAULT
5V/DIV
20µs/DIV
Figure 5. Overcurrent Fault on 5V
1644 F05
10µs/DIV
1644 F06
Figure 6. Short-Circuit Fault on 5V
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APPLICATIO S I FOR ATIO
Calculating RSENSE
An equivalent circuit for one of the LTC1644’s circuit
breakers useful in calculating the value of the sense
resistor is shown in Figure 7. To determine the most
appropriate value for the sense resistor first requires the
maximum current required by the load under worst-case
conditions.
ILOAD(MAX)
The second step is to determine the nominal value of
the sense resistor which is dependent on its tolerance
(RTOL␣ = ±1%, ±2%, or ±5%) and standard sense resistor
values. Equation 7 can be used to calculate the nominal
value from the maximum value found by Equation 6:
RSENSE(N0M) =
RSENSE
5VIN
13
14
VCB
+
–
LTC1644*
+
–
*ADDITIONAL DETAILS OMITTED FOR CLARITY
VCB(MAX) = 70mV
VCB(NOM) = 55mV
VCB(MIN) = 40mV
1644 F07
Figure 7. Circuit Breaker Equivalent
Circuit for Calculating RSENSE
Two other parameters affect the value of the sense resistor. First is the tolerance of the LTC1644’s circuit breaker
threshold. The LTC1644’s nominal circuit breaker threshold is VCB(NOM) = 55mV; however, it exhibits ±15mV
tolerance over process and temperature. Second is the
tolerance (RTOL) in the sense resistor. Sense resistors are
available in RTOLs of ±1%, ±2% and ±5% and exhibit
temperature coefficients of resistance (TCRs) between
±75ppm/°C and ±100ppm/°C. How the sense resistor
changes as a function of temperature depends on the I2R
power being dissipated by it. The power rating of the sense
resistor should accommodate steady-state fault current
levels so that the component is not damaged before the
circuit breaker trips.
The first step in calculating the value of RSENSE is based on
ILOAD(MAX) and the lower limit for the circuit breaker
threshold, VCB(MIN). The maximum value for RSENSE in this
case is expressed by Equation 6:
RSENSE =
VCB(MIN)
ILOAD(MAX)
(7)
Often, the result of Equation 7 may not yield a standard
sense resistor value. In this case, two sense resistors with
the same RTOL can be connected in parallel to yield
RSENSE(NOM).
5VSENSE
5VIN
RSENSE(MAX)
 RTOL
1+ 

 100 
The last step requires calculating a new value for ITRIP(MAX)
(ITRIP(MAX,NEW)) based on a minimum value for RSENSE
(RSENSE(MIN)) and the upper limit for the circuit breaker
threshold, VCB(MAX). The new value for ITRIP(MAX,NEW) is
given by Equation 8:
ITRIP(MAX,NEW) =
VCB(MAX)
RSENSE(MIN)
(8)
  RTOL 
where RSENSE(MIN) = RSENSE(NOM) • 1 − 

  100  
Table 4 lists ITRIP(MIN) and ITRIP(MAX) versus some suggested values of RSENSE. Table 8 lists manufacturers and
part numbers for these resistor values.
Table 4. ITRIP vs RSENSE Table
RSENSE (1% RTOL)
ITRIP(MIN)
ITRIP(MAX)
0.005Ω
7.92A
14.14A
0.007Ω
5.66A
10.10A
0.011Ω
3.60A
6.43A
0.028Ω
1.41A
2.53A
0.055Ω
0.72A
1.29A
(6)
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Output Voltage Monitor
The status of all four output voltages is monitored by the
power good function. In addition, the PCI_RST# signal is
logically combined on-chip with the HEALTHY# signal to
create LOCAL_PCI_RST# (see Table 5). As a result,
LOCAL_PCI_RST# will be pulled low whenever HEALTHY#
is pulled high independent of the state of the PCI_RST#
signal.
Table 5. LOCAL_PCI_RST# Truth Table
PCI_RST#
HEALTHY#
LOCAL_PCI_RST#
LO
LO
LO
LO
HI
LO
HI
LO
HI
HI
HI
LO
If any of the output voltages drop below the power good
threshold for more than 10µs, the PWRGD pin will be
pulled high and the LOCAL_PCI_RST# signal will be
asserted low.
Precharge
The PRECHARGE input and DRIVE output pins are intended for use in generating the 1V precharge voltage that
is used to bias the bus I/O connector pins during board
insertion. The LTC1644 is also capable of generating
precharge voltages other than 1V. Figure 8 shows a circuit
that can be used in applications requiring a precharge
voltage less than 1V. The circuit in Figure 9 can be used for
applications that need precharge voltages greater than 1V.
Table 6 lists suggested resistor values for R10A and R10B
vs precharge voltage for the application circuits shown in
Figures 8 and 9.
Table 6. R10A and R10B Resistor Values vs Precharge Voltage
VPRECHARGE
R10A
R10B
VPRECHARGE
R10A
R10B
1.5V
18Ω
9.09Ω
0.9V
16.2Ω
1.78Ω
1.4V
18Ω
7.15Ω
0.8V
14.7Ω
3.65Ω
1.3V
18Ω
5.36Ω
0.7V
12.1Ω
5.11Ω
1.2V
18Ω
3.65Ω
0.6V
11Ω
7.15Ω
1.1V
18Ω
1.78Ω
0.5V
9.09Ω
9.09Ω
1V
18Ω
0Ω
Due to leakage current constraints, precharge resistor
values of less than 50k are often required. In these
precharge applications, it may also be necessary to disconnect the individual resistors from the LTC1644’s
PRECHARGE pin when the plug-in board is completely
seated in the board slot. The circuit in Figure 10 uses a bus
switch to connect the individual precharge resistors to the
LTC1644’s PRECHARGE pin while the BD_SEL# pin voltage is pulled up to 5VIN, i.e., when the BD_SEL# short
connector pin is still unconnected. After the plug-in board
is completely seated, the BD_SEL# pin voltage will drop to
approximately 3.8V (assuming BD_SEL# isn’t asserted
low), and the bus switch OE pin is pulled high by Q2. When
the plug-in card is removed from the connector, the
BD_SEL# connection is broken first and the BD_SEL# pin
voltage pulls up to 5V. This causes Q2 to turn off, which reenables the bus switch and the precharge resistors are
reconnected to the LTC1644’s PRECHARGE pin for the
remainder of the board extraction process.
Other CompactPCI Applications
The LTC1644 can be easily configured for applications
where no VEE supply is present by simply connecting the
VEEIN pin to GND and floating the VEEOUT pin (Figure␣ 11).
For CPCI applications where no 5V supply input is required, short both the 5VIN and 5VSENSE pins to the 3VIN
pin and short the 5VOUT pin to the 3VOUT pin (Figure␣ 12).
If no 3.3V supply input is required, Figure 13 illustrates
how the LTC1644 should be configured. First, 3VSENSE
(Pin 16) is connected to 3VIN (Pin 17), 3VOUT (Pin 18) is
connected to 5VOUT (Pin 3) and the LTC1644’s 3VIN pin is
connected through a pair of signal diodes (BAV99) to 5VIN.
For applications where the BD_SEL# connector pin is
typically grounded on the backplane, the circuit in
Figure␣ 14 allows the LTC1644 to be reset simply by
pressing a pushbutton switch on the CPCI plugin board.
This arrangement eliminates the requirement to extract
and reinsert the CPCI board in order to reset the LTC1644’s
circuit breakers.
Power MOSFET Selection Criteria
Three device parameters are key in selecting the optimal
power MOSFET for Hot Swap applications. The three
parameters are: (1) device power dissipation (PD); (2)
device drain-source channel ON resistance, RDS(ON); and
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LTC1644*
GND
8
LTC1644*
PRECHARGE DRIVE
12
11
C3 4.7nF
R9
18Ω
R10A
R10B
GND
8
R8
1k
R7
12Ω
3VIN
R22 2.74Ω
LONG 5V
R7
12Ω
MMBT2222A
3VIN
*ADDITIONAL DETAILS OMITTED FOR CLARITY
1644 F08
13
R20
1.2k
5%
BD_SEL#
1644 F09
Figure 9. Precharge Voltage >1V Application Circuit
C9 0.1µF
PER 10
POWER PINS
5VIN
5V
R9
18Ω
R8
1k
PRECHARGE OUT
R10A + R10B
VPRECHARGE =
• 1V
R10A
Figure 8. Precharge Voltage <1V Application Circuit
PCB EDGE
BACKPLANE
CONNECTOR
R10B
R10A
*ADDITIONAL DETAILS OMITTED FOR CLARITY
DRIVE
11
C3 4.7nF
MMBT2222A
PRECHARGE OUT
R10A
VPRECHARGE =
• 1V
R10A + R10B
BACKPLANE
CONNECTOR
PRECHARGE
12
R19
1k 5% 5
5VIN
LTC1644*
OFF/ON
GND
C7
0.01µF
PRECHARGE
8
DRIVE
12
11
R8
1k 5%
Z4
R10
18Ω 5%
C3 4.7nF
GROUND
R23
51k 5%
Q1
R7
MMBT2222A 12Ω 5%
PRECHARGE OUT
1V ±10%
IOUT = ±55mA
Q2
MMBT3906
R24
75k
5%
OE
BUS SWITCH
R11
10k
5%
R13
10Ω 5%
R9
24Ω
R12
10k
5%
I/O
I/O PIN 1
UP TO 128 I/O LINES
I/O PIN 128
Z4: 1PMT5.0AT3
*ADDITIONAL PINS OMITTED FOR CLARITY
• • •
• • •
• • •
R14
10Ω 5%
DATA BUS
3VIN
I/O
PCI
BRIDGE
CHIP
1644 F10
Figure 10. Precharge Circuit with Bus Switch
(3) the gate-source (VGS) voltage drive for the specified
RDS(ON). Power MOSFET power dissipation is dependent
on four parameters: current delivered to the load, ILOAD;
device RDS(ON); device thermal resistance, junction-toambient, θJA; and the maximum ambient temperature to
which the circuit will be exposed, TA(MAX). All four of these
parameters determine the junction temperature of the
MOSFET. For reliable circuit operation, the maximum
junction temperature (TJ(MAX)) for a power MOSFET should
not exceed the manufacturer’s recommended value. For a
given set of conditions, the junction temperature of a
power MOSFET is given by Equation 9:
MOSFET Junction Temperature,
TJ(MAX) ≤ TA(MAX) + θJA • PD
(9)
where PD = ILOAD • RDS(ON)
PCB layout techniques for optimal thermal management
of power MOSFET power dissipation help to keep device
θJA as low as possible. See PCB Layout Considerations
section for more information.
The RDS(ON) of the external pass transistor should be low
to make its drain-source voltage (VDS) a small percentage
of 3VIN or 5VIN. For example, at 3VIN = 3.3V, VDS + VCB =
0.1V yields a 3% error at maximum load current. This
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BACKPLANE
CONNECTOR
C8 0.1µF
PER 10
POWER
PINS
PCB EDGE
BACKPLANE
CONNECTOR
C9 0.1µF
PER 10
POWER
PINS
R2
0.007Ω
5VIN*
5V
Q2
IRF7413
R22 2.74Ω
LONG 5V
3.3V
R1
0.005Ω
3VIN*
R21 1.74Ω
Z3
LONG 3.3V
C6
0.01µF
Q1
IRF7413
Z4
R3
10Ω
17
16
R4
10Ω
18
15
3VSENSE GATE
3VIN
12V
2
5VIN
R20 1.2k
BD_SEL#
R19
1k 5
EARLY V(I/O)
6
R17
2k
R18
2k 7
HEALTHY#
9
PCI_RST#
3VOUT
13
5VIN
14
3
5VSENSE
5VOUT
20
VEEIN
LTC1644
VEEOUT
NC
4
TIMER
C2
0.1µF
FAULT
R6
2k
PWRGD
10
RESETOUT
RESETIN
PRECHARGE
8
11
R10
18Ω 5%
C3 4.7nF
R11
51k
R13
10Ω
3VOUT
DRIVE
12
R12
51k
R8 1k
R9
24Ω
GROUND
1V
±10%
3VIN
Q3
MMBT2222A
R7
12Ω
RESET#
I/O #1
• • •
• • •
• • •
I/O PIN 128
19
VEEOUT
OFF/ON
C4
0.01µF
I/O DATA LINE 128
12VOUT
+
12VIN
GND
I/O PIN 1
3VOUT
CLOAD(12VOUT)
R15
1Ω
I/O DATA LINE 1
+
C1
0.047µF
R5
1k
12VOUT
1
5VOUT
CLOAD(3VOUT)
C7
0.01µF
Z1
+
CLOAD(5VOUT)
R14
10Ω
I/O #128
Z1: SMAJ12CA Z3, Z4: 1PMT5.0AT3
*5VIN AND 3VIN MAY BE USED AS SOURCES OF EARLY POWER
PCI
BRIDGE
(21154)
1644 F11
Figure 11. No VEE (–12V) Supply Application Circuit
BACKPLANE
CONNECTOR
3.3V
PCB EDGE
BACKPLANE
CONNECTOR
C8 0.1µF
PER 10
POWER PINS
3VIN
R1
0.005Ω
Q1
IRF7413
3VOUT
R21 1.74Ω
LONG 3.3V
R3
10Ω
C6
Z3
0.01µF
13
5VIN
8
GROUND
GND
14
5VSENSE
17
3VIN
16
3VSENSE
15
GATE
R5
1k
18
3
3VOUT
5VOUT
C1
0.047µF
LTC1644*
1644 F12
Z3: 1PMT5.0AT3
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 12. No 5V Supply Application Circuit
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BACKPLANE
CONNECTOR
C9 0.1µF
PER 10
POWER PINS
5VIN
PCB EDGE
BACKPLANE
CONNECTOR
5V
R2
0.007Ω
5VOUT
R22 2.74Ω
D1
LONG 5V
C6
Z4
0.01µF
R4
10Ω
NC
D2
17
3VIN
8
GROUND
Q2
IRF7413
16
3VSENSE
13
5VIN
GND
14
R5
1k
3
18
5VOUT
3VOUT
15
GATE
5VSENSE
C1
0.047µF
LTC1644*
1644 F13
D1, D2: BAV99
Z4: 1PMT5.0AT3
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 13. No 3.3V Supply Application Circuit
5VIN
BACKPLANE
CONNECTOR
PCB EDGE
BACKPLANE
CONNECTOR
PUSHBUTTON
SWITICH
100Ω
BD_SEL#
1.2k
1k
5
OFF/ON
LTC1644*
GROUND
8
*ADDITIONAL PINS OMITTED FOR CLARITY
GND
1644 F14
Figure 14. BD_SEL# Pushbutton Toggle Switch
restricts the choice of power MOSFETs to those devices
with very low RDS(ON). Table 9 lists some power MOSFETs
that can be used with the LTC1644.
Power MOSFETs are classified into two categories: standard MOSFETs (RDS(ON) specified at VGS = 10V) and logiclevel MOSFETs (RDS(ON) specified at VGS = 5V). Since
external pass transistors are required for the 3.3V and 5V
supply rails, logic-level power MOSFETs should be used
with the LTC1644.
Overvoltage Transient Protection
Good engineering practice calls for bypassing the supply
rail of any analog 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 large
bypass capacitors slow the rate of rise of the supply
voltage and heavily damp any parasitic resonance of lead
or PC track inductance working against the supply bypass
capacitors.
The opposite is true for LTC1644 Hot Swap circuits
mounted on plug-in cards. In most cases, there is no
supply bypass capacitor present on the powered 12V
(12VIN), –12V (VEEIN) of the PCB edge connector or on the
3.3V (3VIN) or the 5V (5VIN) side of the MOSFET switch. An
abrupt connection, produced by inserting the board into a
backplane connector, results in a fast rising edge applied
on these input supply lines of the LTC1644.
Since there is no bulk capacitance to damp the parasitic
track inductance, supply voltage transients excite parasitic resonant circuits formed by the power MOSFET
capacitance and the combined parasitic inductance from
the wiring harness, the backplane and the circuit board
traces. These ringing transients appear as a fast edge on
the input supply lines, exhibiting a peak overshoot up to
2.5 times the steady-state value followed by a damped
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sinusoidal response whose duration and period is dependent on the resonant circuit parameters. Since the absolute maximum supply voltage of the LTC1644 is 13.2V,
transient protection against 12VIN and VEEIN supply voltage spikes and ringing is highly recommended.
that in all LTC1644 circuit schematics, zener diodes and
snubber networks have been added to the 12VIN and VEEIN
(–12V) supply rail and should be used always. Since the
absolute maximum supply voltage of the LTC1644 is
13.2V, snubber networks are not necessary on the 3VIN or
the 5VIN supply lines. Zener diodes, however, are recommended as these devices provide large-scale transient
protection for the LTC1644 against PCI backplane fault
occurrences. All protection networks should be mounted
very close to the LTC1644’s supply voltage using short
lead lengths to minimize lead inductance. This is shown
schematically in Figures 15 and 16 and a recommended
layout of the transient protection devices around the
LTC1644 is shown in Figure 17.
In these applications, there are two methods for eliminating these supply voltage transients: using Zener diodes to
clip the transient to a safe level and snubber networks.
Snubber networks are series RC networks whose time
constants are experimentally determined based on the
board’s parasitic resonant circuits. As a starting point, the
capacitors in these networks are chosen to be 10× to 100×
the power MOSFET’s COSS under bias. The series resistor
is a value determined experimentally and ranges from 1Ω
to 50Ω, depending on the parasitic resonant circuit. Note
R2
0.007Ω
5VIN
5V
R1
0.005Ω
3VIN
3.3V
Q2
IRF7413
Q1
IRF7413
3VOUT
3.3V
R3
10Ω
17
16
3VIN
5VOUT
5V
15
3VSENSE GATE
R4
10Ω
18
13
3VOUT
Z3
5VIN
14
R5
1k
C1
0.047µF
3
5VOUT
5VSENSE
Z4
LTC1644*
GND
Z3, Z4: 1PMT5.0AT3
*ADDITIONAL DETAILS OMITTED FOR CLARITY
8
1644 F15
Figure 15. Place Transient Protection Devices Close to LTC1644’s 5VIN and 3VIN Pins
11
12
14
15
16
17
18
–12VIN
19
20
12VIN
13
5VIN
3VIN
Z3
LTC1644*
C4
8
1644 F16
Z1, Z2: SMAJ12CA
*ADDITIONAL DETAILS OMITTED FOR CLARITY
Figure 16. Place Transient Protection Devices
Close to LTC1644’s 12VIN and VEEIN Pins
R13
Z2
Z1
12VIN
10
C5
0.01µF
9
C5
R14
8
VIAS TO
GND PLANE
7
GND
Z2
6
LTC1644*
R16
1Ω
5
VEEIN
4
C4
0.01µF
12VIN
3
R15
1Ω
2
Z1
Z4
2
1
1
1644 F17
VEEIN
GND
*ADDITIONAL DETAILS OMITTED FOR CLARITY
DRAWING IS NOT TO SCALE!
Figure 17. Recommended Layout for Transient Protection Components
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PCB Layout Considerations
For proper operation of the LTC1644’s circuit breaker
operation, 4-wire Kelvin-sense connections between the
sense resistor and the LTC1644’s 5VIN and 5VSENSE pins
and 3VIN and 3VSENSE pins are strongly recommended.
The PCB layout should be balanced and symmetrical to
minimize wiring errors. In addition, the PCB layout for the
sense resistors and the power MOSFETs should include
good thermal management techniques for optimal device
power dissipation.
A recommended PCB layout for the sense resistor, the
power MOSFET and the GATE drive components around
the LTC1644 is illustrated in Figure 18. In Hot Swap
applications where load currents can be 10A, narrow PCB
tracks exhibit more resistance than wider tracks and
operate at more elevated temperatures. Since the sheet
resistance of 1 ounce copper foil is approximately
0.45mΩ/■
■ , track resistances add up quickly in high
current applications. Thus, to keep PCB track resistance
and temperature rise to a minimum, the suggested trace
width in these applications for 1 ounce copper foil is 0.03"
for each ampere of DC current.
In the majority of applications, it will be necessary to use
plated-through vias to make circuit connections from
component layers to power and ground layers internal to
the PC board. For 1 ounce copper foil plating, a general rule
is 1 ampere of DC current per via, making sure the via is
properly dimensioned so that solder completely fills any
void. For other plating thicknesses, check with your PCB
fabrication facility.
Table 7. Manufacturers’ Web Site
MANUFACTURER
International Rectifier
ON Semiconductor
IRC-TT
WEB SITE
www.irf.com
www.onsemi.com
www.irctt.com
Vishay-Dale
www.vishay.com
Vishay-Siliconix
www.vishay.com
Diodes, Inc.
www.diodes.com
Obtaining Information on Specific Parts
For more information regarding or to request a copy of the
CompactPCI specification, contact the PCI Industrial Computer Manufacturers Group at:
PCI Industrial Computer Manufacturers Group
Wakefield, MA 01880 USA
Phone: 01 (617) 224-1100
Web Site: http://www.picmg.com
TransZorb SMAJ12CA and diodes BAV99 are supplied by:
Diodes, Incorporated
Westlake Village, CA 91362 USA
Phone: 01 (805) 446-4800
Web Site: http://www.vishay-liteon.com or
http://www.diodes.com
Transistors MMBT2222A and TVS 1PMT5.0AT3 are
supplied by:
Semiconductor Components Industries, LLC
Phoenix, AZ 85008 USA
Phone: 01 (602) 244-6600
Web Site: http://www.onsemi.com
Power MOSFET and Sense Resistor Selection
Table 8 lists some current sense resistors that can be used
the LTC1644’s circuit breakers and Table 9 list some
power MOSFET transistors that are available. Table 7 lists
supplier web site addresses for discrete component mentioned throughout the LTC1644 data sheet.
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Table 8. Sense Resistor Selection Guide
CURRENT LIMIT VALUE
PART NUMBER
DESCRIPTION
MANUFACTURER
1A
LR120601R055F
WSL1206R055
0.055Ω, 0.5W, 1% Resistor
IRC-TT
Vishay-Dale
2A
LR120601R028F
WSL1206R028
0.028Ω, 0.5W, 1% Resistor
IRC-TT
Vishay-Dale
5A
LR120601R011F
WSL2010R011
0.011Ω, 0.5W, 1% Resistor
IRC-TT
Vishay-Dale
7.6A
WSL2512R007
0.007Ω, 1W, 1% Resistor
Vishay-Dale
10A
WSL2512R005
0.005Ω, 1W, 1% Resistor
Vishay-Dale
Table 9. N-Channel Power MOSFET Selection Guide
CURRENT LEVEL (A)
PART NUMBER
DESCRIPTION
MANUFACTURER
0 to 2
MMDF3N02HD
RDS(ON) = 0.1Ω
Dual N-Channel SO-8
ON Semiconductor
2 to 5
MMSF5N02HD
RDS(ON) = 0.025Ω
Single N-Channel SO-8
ON Semiconductor
5 to 10
MTB50N06V
RDS(ON) = 0.028Ω
Single N-Channel DD Pak
ON Semiconductor
5 to 10
IRF7413
RDS(ON) = 0.01Ω
Single N-Channel SO-8
International Rectifier
5 to 10
Si4410DY
RDS(ON) = 0.01Ω
Single N-Channel SO-8
Vishay-Siliconix
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PACKAGE DESCRIPTIO
GN Package
20-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641)
.337 – .344*
(8.560 – 8.737)
.045 ±.005
20 19 18 17 16 15 14 13 12
.254 MIN
.150 – .165
.0165 ± .0015
11
.229 – .244
(5.817 – 6.198)
.058
(1.473)
REF
.150 – .157**
(3.810 – 3.988)
.0250 TYP
1
RECOMMENDED SOLDER PAD LAYOUT
.015 ± .004
× 45°
(0.38 ± 0.10)
.007 – .0098
(0.178 – 0.249)
2 3
4
5 6
7
8
.053 – .068
(1.351 – 1.727)
9 10
.004 – .0098
(0.102 – 0.249)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
.008 – .012
(0.203 – 0.305)
NOTE:
1. CONTROLLING DIMENSION: INCHES
INCHES
2. DIMENSIONS ARE IN
(MILLIMETERS)
.0250
(0.635)
BSC
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
GN20 (SSOP) 0502
1644f
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.
23
LTC1644
U
U
W
U
APPLICATIO S I FOR ATIO
CURRENT FLOW
TO LOAD
3VIN
3.3V
CURRENT FLOW
TO LOAD
SENSE
RESISTOR
SO-8
W
D
G
D
S
D
S
D
S
VIA/PATH
TO GND
R3
TRACK WIDTH W:
0.03" PER AMPERE
ON 1OZ Cu FOIL
3VOUT
3.3V
W
GATE
R5
12
11
10
13
9
14
8
15
7
16
17
18
19
20
C1
6
5
4
3
2
1
LTC1644*
CTIMER
CURRENT FLOW
TO SOURCE
VIA TO
GND PLANE
W
GND
*ADDITIONAL DETAILS OMITTED FOR CLARITY
DRAWING IS NOT TO SCALE!
GND
1644 F18
Figure 18. Recommended Layout for Power MOSFET, Sense Resistor and GATE Components for the 3.3V Rail
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1421
Hot Swap Controller
Dual Supplies from 3V to 12V, Additionally –12V
LTC1422
Hot Swap Controller in SO-8
Single Supply from 3V to 12V, RESET Output
LT1640AL/LT1640AH
Negative Voltage Hot Swap Controllers in SO-8
Negative High Voltage Supplies from –10V to – 80V
LT1641-1/LT1641-2
Positive Voltage Hot Swap Controller in SO-8
Supplies from 9V to 80V, Latch Off/Autoretry
LTC1642
Fault Protected Hot Swap Controller
3V to 15V, Overvoltage Protection Up to 33V
LTC1643AL/LTC1643AL-1/LTC1643AH
PCI Bus Hot Swap Controllers
3.3V, 5V, 12V, –12V Supplies for PCI Bus
LTC1645
2-Channel Hot Swap Controller
Operates from 1.2V to 12V, Power Sequencing
LTC1646
Dual CompactPCI Hot Swap Controller
3.3V, 5V Supplies Only, 1V Precharge, PCI Reset Logic
LTC1647
Dual Hot Swap Controller
Dual ON Pins for Supplies from 3V to 15V
LTC4211
Hot Swap Controller with Multifunction Current Control
Single Supply, 2.5V to 16.5V, 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, Active Current Limiting
LTC4251
– 48V Hot Swap Controller in SOT-23
Floating Supply, Active Current Limiting and
Fast Circuit Breaker
1644f
24
Linear Technology Corporation
LT/TP 0203 2K • PRINTED IN USA
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●
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 LINEAR TECHNOLOGY CORPORATION 2001