LTC4252A-1 [Linear]
Dual Supply Hot Swap Controller for Advanced Mezzanine Card; 双电源热插拔控制器，用于高级夹层卡
| 型号： | LTC4252A-1 |
| 厂家： | 
Linear |
| 描述： | Dual Supply Hot Swap Controller for Advanced Mezzanine Card |
| 文件： | 总24页 (文件大小：275K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4223-1/LTC4223-2
Dual Supply Hot Swap
Controller for Advanced
Mezzanine Card
FEATURES
DESCRIPTION
The LTC®4223 positive voltage Hot SwapTM controller
allows a board to be safely inserted and removed from
a live AMC or MicroTCA backplane. It controls the main
12V supply with an external N-channel MOSFET and the
3.3V auxiliary supply with an integrated switch. The 12V
output ramp rate is adjustable and includes inrush current
limiting. The 12V output is also protected against short
circuit faults with a fast acting current limit and a 5%
accurate timed circuit breaker. The 3.3V output includes
both soft start and overcurrent protection.
■
Allows Safe Insertion into Live AMC or MicroTCA
Backplane
■
Controls 12V Main and 3.3V Auxiliary Supplies
■
Limits Peak Fault Current in ≤1μs
Adjustable Current Limit with Circuit Breaker
Integrated 0.3Ω AUX Switch
High Side Current Sense
Gate Drive for External N-Channel MOSFET
Adjustable Response Time for Overcurrent Protection
Adjustable Supply Voltage Power-Up Rate
Thermal Shutdown Protection
LTC4223-1: Latch Off After Fault
LTC4223-2: Automatic Retry After Fault
16-Lead SSOP and 5mm × 4mm DFN Packages
■
■
■
■
■
■
■
The LTC4223 features a current monitor output for the
12V supply, and reports fault and power-good status for
both supplies. It also detects card presence and allows
independent control of the 12V and auxiliary 3.3V sup-
ply outputs. The LTC4223-1 features a latch-off circuit
breaker, while the LTC4223-2 provides automatic retry
after a fault.
■
■
■
APPLICATIONS
■
Advanced Mezzanine Card, MicroTCA Systems
■
Workstations and Server I/O
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
Telecom Networks
TYPICAL APPLICATION
Advanced Mezzanine Card Application
Normal Power-Up Waveform
6mΩ
Si7336ADP
12V
7.4A
EN
5V/DIV
12V
AUXOUT
5V/DIV
15nF
10Ω
47Ω
12V
12V
12V
12V
OUT
12V
OUT
5V/DIV
IN
SENSE
GATE
3.3V
150mA
3.3V
AUXIN
AUXOUT
AUXPGOOD
51Ω
330nF
5V/DIV
V
CC
12PGOOD
5V/DIV
LTC4223-1/LTC4223-2
AUXON
12ON
AUXPGOOD
12PGOOD
FAULT
20ms/DIV
422312 TA01b
IPMC
12IMON
ADC
EN
GND
TIMER
422312 TA01a
0.1μF
CARRIER MODULE
CONNECTOR CONNECTOR
422312f
1
LTC4223-1/LTC4223-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
12V
12V
................................................. –0.3V to 25V
GATE
OUT
Supply Voltages
- 12V
(Note 3) ................... –4.5V to 0.3V
GATE
12V ..................................................... –0.3V to 20V
IN
AUXOUT................................................. –0.3V to 10V
AUXIN.................................................... –0.3V to 10V
Operating Temperature Range
V ........................................................... –0.3V to 7V
CC
LTC4223-1C/ LTC4223-2C ....................... 0°C to 70°C
LTC4223-1I/ LTC4223-2I ..................... –40°C to 85°C
Storage Temperature Range
Input Voltages
12ON, AUXON, EN ................................... –0.3V to 7V
TIMER..........................................–0.3V to V + 0.3V
CC
GN Package ....................................... –65°C to 150°C
DHD Package..................................... –65°C to 125°C
Lead Temperature (Soldering, 10sec)
12V
............................................... –0.3V to 20V
SENSE
Output Voltages
FAULT, 12PGOOD, AUXPGOOD,
12IMON ................................................... –0.3V to 7V
GN Package ...................................................... 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
12V
SENSE
1
2
3
4
5
6
7
8
16 12V
15 12V
GATE
12V
SENSE
1
2
3
4
5
6
7
8
16 12V
15 12V
GATE
12V
IN
OUT
12V
IN
OUT
12IMON
12ON
14 12PGOOD
13 FAULT
12IMON
12ON
14 12PGOOD
13 FAULT
17
AUXIN
12 AUXOUT
11 AUXPGOOD
10 EN
AUXIN
12 AUXOUT
11 AUXPGOOD
10 EN
V
CC
V
CC
AUXON
GND
AUXON
GND
9
TIMER
9
TIMER
DHD PACKAGE
16-LEAD (5mm × 4mm) PLASTIC DFN
GN PACKAGE
16-LEAD PLASTIC SSOP
EXPOSED PAD (PIN 17) PCB GND CONNECTION OPTIONAL
MUST BE SOLDERED TO PCB TO OBTAIN
T
= 125°C, θ = 110°C/W
JA
JMAX
θ
= 43°C/W, OTHERWISE θ = 140°C/W, T
= 125°C
JA
JA
JMAX
ORDER INFORMATION
LEAD FREE FINISH
LTC4223CDHD-1#PBF
LTC4223CDHD-2#PBF
LTC4223IDHD-1#PBF
LTC4223IDHD-2#PBF
LTC4223CGN-1#PBF
LTC4223CGN-2#PBF
LTC4223IGN-1#PBF
LTC4223IGN-2#PBF
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
0°C to 70°C
LTC4223CDHD-1#TRPBF 42231
LTC4223CDHD-2#TRPBF 42232
16-Lead (5mm × 4mm) Plastic DFN
16-Lead (5mm × 4mm) Plastic DFN
16-Lead (5mm × 4mm) Plastic DFN
16-Lead (5mm × 4mm) Plastic DFN
16-Lead Plastic SSOP
0°C to 70°C
LTC4223IDHD-1#TRPBF
LTC4223IDHD-2#TRPBF
LTC4223CGN-1#TRPBF
LTC4223CGN-2#TRPBF
LTC4223IGN-1#TRPBF
LTC4223IGN-2#TRPBF
42231
42232
42231
42232
4223I1
4223I2
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
16-Lead Plastic SSOP
0°C to 70°C
16-Lead Plastic SSOP
–40°C to 85°C
–40°C to 85°C
16-Lead Plastic SSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
422312f
2
LTC4223-1/LTC4223-2
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are TA = 25°C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specified. (Note 2)
SYMBOL
Supplies
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
●
●
●
V
Input Supply Range
V
2.7
2.7
10
6
6
14
V
V
V
DD
CC
AUXIN
12V
IN
●
●
●
I
Input Supply Current
V
0.8
0.4
0.6
2
1
1
mA
mA
mA
DD
CC
AUXIN
12V
IN
●
●
●
V
Input Supply Undervoltage Lockout
V
Rising
2.3
2.4
9.4
2.45
2.5
9.7
2.6
2.6
10
V
V
V
DD(UVLO)
CC
V
Rising
Rising
AUXIN
V
12VIN
●
●
●
ΔV
HYST)
Input Supply Undervoltage Lockout
Hysteresis
V
40
70
70
110
110
110
180
150
150
mV
mV
mV
DD(UVLO,
CC
AUXIN
12V
IN
Current Limit
ΔV
SENSE(CB)
Circuit Breaker Trip Sense Voltage,
12VIN
●
(V
– V
)
12VSENSE
47.5
50
52.5
mV
ΔV
Active Current Limit Sense Voltage,
(V – V
SENSE(ACL)
●
●
)
12VSENSE
54
60
66
mV
mA
12VIN
I
AUXOUT Active Current Limit
Integrated Switch
Switch Resistance
V
= 0V
165
240
330
AUX(ACL)
AUXOUT
●
●
Ω
R
I
= 150mA (Note 4)
0.3
0.5
DS(ON)
AUXOUT
(V – V
)/I
AUXIN
AUXOUT AUXOUT
Gate Drive
ΔV
GATE
External N-Channel Gate Drive
(V – V
(Note 3)
4.5
6.2
7.9
V
)
12VOUT
12VGATE
●
●
I
I
External N-Channel Gate Pull-Up Current
External N-Channel Gate Pull-Down Current
Gate Drive On, V
= 0V
12VGATE
–7
–10
1
–14
2
μA
GATE(UP)
GATE(DN)
Gate Drive Off
0.5
mA
V
= 17V, V
= 12V
= 12V
12VGATE
12VOUT
12VOUT
●
●
I
External N-Channel Gate Fast Pull-Down
Current
Fast Turn Off
= 17V, V
90
160
250
mA
GATE(FPD)
V
12VGATE
Current Sense
G
12IMON Pin Gain Ratio
(V
(V
– V
) = (75mV, 25mV)
30
33
36
V/V
12IMON
12VIN
12VSENSE
ΔV
/Δ(V
– V
)
12VSENSE
12IMON
12VIN
●
●
●
●
●
V
12IMON Pin Output Voltage
– V
) = 75mV, V = 2.7V
2.25
82.5
2.9
2.475
2.7
V
mV
V
12IMON
12VIN
12VSENSE
CC
ΔV
12IMON Pin Maximum Input Sense Voltage
12IMON Pin Clamp Voltage
SENSE(MAX)
V
(V
12VIN
(V
12VIN
(V
12VIN
– V
– V
– V
) = 150mV, V = 2.7V
3.2
165
0
3.5
215
130
12IMON(CLP)
12VSENSE
12VSENSE
12VSENSE
CC
R
12IMON Pin Output Resistance
) = 0V
) = 0V
115
kΩ
mV
12IMON
V
12IMON Pin Minimum Output Voltage
12IMON(MIN)
Comparator Inputs
●
●
V
V
V
Power Good Threshold Voltage
V
Falling
10
10.3
10.6
2.97
V
V
PG(TH)
12VOUT
V
Falling
2.8
2.885
AUXOUT
●
●
Power Good Hysteresis
V
20
5
60
16
110
30
mV
mV
PG(HYST)
TMR(TH)
12VOUT
V
AUXOUT
●
●
TIMER Pin Threshold Voltage
V
TIMER
V
TIMER
Rising
Falling
1.198
0.15
1.235
0.2
1.272
0.25
V
V
422312f
3
LTC4223-1/LTC4223-2
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are TA = 25°C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specified. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
●
●
●
I
I
TIMER Pull-Up Current
V
V
V
= 1V, Initial Timing Cycle
= 0V, In AUX Fault Mode
= 0V, In 12V Fault Mode
–7
–7
–10
–10
–13
–13
μA
μA
μA
TMR(UP)
TIMER
TIMER
TIMER
–140
–200
–260
●
●
TIMER Pull-Down Current
V
TIMER
V
TIMER
= 2V, No Faults
= 2V, In Reset Mode
1.3
2
2
8
2.6
16
μA
mA
TMR(DN)
Open Drain Outputs
●
●
●
V
Output Low Voltage (FAULT, 12PGOOD,
AUXPGOOD)
I
= 3mA
OL
0.15
0.4
V
V
OL
V
Output High Voltage (FAULT, 12PGOOD,
AUXPGOOD)
(Note 5)
V
– 1
OH
CC
I
PU
Output Pin Pull-Up Current (FAULT,
12PGOOD, AUXPGOOD)
V
= 1.5V
–6
–10
–14
μA
PU
Logic Inputs
●
●
●
V
Logic Input Threshold (12ON, AUXON, EN)
Input Leakage Current (12ON, AUXON)
EN Pin Pull-Up Resistance
0.8
60
2
1
V
μA
kΩ
IN(TH)
I
V
V
= V
CC
IN(LEAK)
IN
R
100
140
PU
Other Pin Functions
●
●
I
I
12V
12V
Pin Input Current
= 12V
12VSENSE
10
20
50
50
100
100
μA
μA
12VSENSE
12VOUT
SENSE
Pin Input Current
Gate Drive On, V
= 12V
12VOUT
OUT
R
OUT Pin Discharge Resistance
12V
Gate Drive Off
OUT(DIS)
●
●
V
= 6V
400
375
800
750
1600
1500
Ω
Ω
OUT
12VOUT
V
AUXOUT
= 2V
AUXVOUT
Propagation Delays
●
t
t
AUX Circuit Breaker Trip Delay
Sense Voltage, (12V – 12V
After Power Up
12
25
50
μs
CB
●
●
)
ΔV
ΔV
= 300mV, C
= 100mV, C
= 10nF
= 10nF
0.5
5
1
12
μs
μs
PHL(SENSE)
IN
SENSE
SENSE
SENSE
12VGATE
12VGATE
High to 12V
Low
GATE
●
●
●
●
●
●
●
●
●
●
t
t
t
t
t
AUXON High to AUXOUT High
12ON High to 12V High
15
30
20
80
12
12
20
20
20
2
30
60
40
150
18
18
40
40
40
6
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
PHH(AUXON)
PHH(12ON)
RST(ON)
GATE
Input Low (12ON, AUXON) to FAULT High
Low to FAULT High
V
RST(VCC)
CC
12V Low to 12V Low
GATE
6
6
PLL(UVLO)
IN
AUXIN Low to AUXPGOOD High
EN High to 12V Low
t
t
PHL(GATE)
GATE
12V
Low to 12PGOOD High
PLH(PG)
OUT
AUXOUT Low to AUXPGOOD High
t
Input Sense Voltage Step to 12IMON
Propagation Delay
ΔV
= 100mV
SENSE
P(12IMON)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 3: An internal clamp limits the 12V
pin to a minimum of 4.5V
GATE
above 12V . Driving this pin to voltages beyond the clamp may damage
OUT
the device.
Note 4: For the DFN package, the AUX switch on resistance, R
limit
DS(ON)
Note 2: All currents into device pins are positive; all currents out of
the device pins are negative. All voltages are referenced to GND unless
otherwise specified.
is guaranteed by correlation to wafer test measurements.
Note 5: The output pins FAULT, 12PGOOD and AUXPGOOD have an internal
pull-up to V of 10μA. However, an external pull-up resistor may be used
CC
when faster rise time is required or for V voltages greater than V
.
CC
OH
422312f
4
LTC4223-1/LTC4223-2
TYPICAL PERFORMANCE CHARACTERISTICS Specifications are TA = 25°C, VCC = 3.3V, VAUXIN
=
3.3V, V12VIN =12V, unless otherwise specified.
12IMON Gain Ratio vs
Temperature
ICC vs VCC
Supply Current vs Temperature
1.0
0.8
0.6
0.4
1.6
1.2
0.8
0.4
35
34
33
32
V
CC
12V
IN
AUXIN
0.2
0
0
31
–50
0
25
50
75
100
–25
2.5 3.0
3.5 4.0 4.5 5.0 5.5 6.0
(V)
–50
–25
0
25
50
70
100
TEMPERATURE (°C)
V
TEMPERATURE (°C)
CC
422312 G02
422312 G01
422312 G03
12IMON Output Voltage vs Sense
Voltage
12VOUT Power-Good Threshold vs
Temperature
AUXOUT Power-Good Threshold
vs Temperature
10.4
10.3
10.2
10.1
2.92
2.90
2.88
2.86
4
3
2
1
RISING
RISING
FALLING
FALLING
10.0
2.84
0
–50
–25
0
25
50
75
100
–50
–25
0
25
50
75
100
0
20
40
60
80 100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
SENSE VOLTAGE (mV)
422312 G05
422312 G06
422312 G04
Circuit Breaker Trip Voltage vs
Temperature
Active Current Limit Sense
Voltage vs Temperature
AUX Active Current Limit vs
Temperature
250
240
230
220
52
51
50
49
62
61
60
59
210
200
48
58
–50
–25
0
25
50
75
100
–50
–25
0
25
50
75
100
–50
0
25
50
75
100
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
422312 G07
422312 G08
422312 G09
422312f
5
LTC4223-1/LTC4223-2
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are TA = 25°C, VCC = 3.3V, VAUXIN
=
3.3V, V12VIN =12V, unless otherwise specified.
AUX Switch On Resistance vs
Temperature
Gate Drive vs Temperature
Gate Drive vs IGATE
7
0.5
0.4
0.3
0.2
6.3
6.2
6.1
6.0
6
5
4
3
2
1
0
0.1
5.9
–8
–12
0
–2
–4
–6
(μA)
–10
–50
–25
0
25
50
75
100
100
100
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
I
GATE
422312 G12
422312 G10
422312 G11
Gate Pull-Up Current vs
Temperature
AUX Circuit Breaker Trip Delay vs
Temperature
Active Current Limit Delay vs
Sense Voltage
100
10
1
30
25
20
15
–11.0
–10.5
–10.0
–9.5
0.1
–9.0
0.01
–50
–25
0
25
50
75
–50
0
25
50
75
100
–25
50
100
150
200
250
300
TEMPERATURE (°C)
TEMPERATURE (°C)
SENSE VOLTAGE (mV)
422312 G15
422312 G13
422312 G14
Gate Fast Pull-Down Current vs
Temperature
Output Discharge Resistance vs
Temperature
Logic Input Threshold vs VCC
1200
1000
800
250
200
150
100
3.0
2.5
2.0
1.5
HIGH
LOW
12V
OUT
AUXOUT
600
1.0
0.5
0
400
200
50
–50
–25
0
25
50
75
–50
0
25
50
75
100
–25
4.5
(V)
5.5
6.0
2.5 3.0
3.5 4.0
5.0
TEMPERATURE (°C)
TEMPERATURE (°C)
V
CC
422312 G16
422312 G17
422312 G18
422312f
6
LTC4223-1/LTC4223-2
PIN FUNCTIONS
12V
(Pin 1): 12V Current Sense Input. Connect this
AUXPGOOD (Pin 11): Auxiliary Supply Power Status
Output. Open drain output that is normally pulled high
by an internal 10μA current source or an external pull-up
SENSE
pintotheoutputofthecurrentsenseresistor.Theelectronic
circuitbreakertripsifthevoltageacrossthesenseresistor
exceeds 50mV for more than a fault filter delay.
resistor to V . It pulls low when the AUXOUT pin voltage
CC
exceeds the power-good threshold of 2.901V.
12V (Pin 2): 12V Supply Input. Undervoltage lockout
IN
disables the 12V supply until the input at 12V exceeds
AUXOUT (Pin 12): Auxiliary Supply Output. This pin is
the output from the internal switch connected between
AUXINandAUXOUTpins. ItsignalsAUXPGOODlowwhen
it exceeds 2.901V. A 750Ω active pull-down discharges
AUXOUT to ground when the internal switch is turned
off.
IN
9.7V.
12IMON (Pin 3): 12V Current Sense Monitoring Output.
This pin monitors the sense voltage between 12V and
IN
12V
. The gain ratio between this pin’s voltage and
SENSE
the sense voltage is 33.
FAULT (Pin 13): Auxiliary and 12V Supply Fault Status
Output.Opendrainoutputthatisnormallypulledhighbyan
internal10μAcurrentsourceoranexternalpull-upresistor
12ON (Pin 4): 12V Supply On Control Digital Input. A ris-
ing edge turns on the external N-channel MOSFET if EN
is pulled low and a falling edge turns it off. A high-to-low
transition on this pin will clear the 12V supply faults.
to V . It pulls low when the circuit breaker is tripped due
CC
to an overcurrent fault on auxiliary or 12V supply.
AUXIN (Pin 5): Auxiliary Supply Input. An internal 0.3Ω
switch is connected between AUXIN and AUXOUT pins.
Undervoltage lockout holds the switch off until the input
at AUXIN exceeds 2.5V.
12PGOOD (Pin 14): 12V Supply Power Status Output.
Open drain output that is normally pulled high by an in-
ternal 10μA current source or an external pull-up resistor
to V . It pulls low when the 12V
pin voltage exceeds
CC
OUT
V
(Pin 6): Bias Supply Input. This pin provides power
the power-good threshold of 10.36V.
CC
to the device’s internal circuitry and operates from 2.7V to
12V (Pin 15): 12V Gate Drive Return and Power-Good
OUT
6V. Undervoltage lockout circuit disables the device until
the input at V exceeds 2.45V. Bypass with 330nF.
Input. Connect this pin to the source of the external N-
channel MOSFET for gate drive return. This pin signals
12PGOOD low when it exceeds 10.36V. When the external
CC
AUXON (Pin 7): Auxiliary Supply On Control Digital Input.
A rising edge turns on the internal switch if EN is pulled
low and a falling edge turns it off. A high-to-low transi-
tion on both this pin and 12ON pin will clear the auxiliary
supply faults.
MOSFET is turned off, 12V
is discharged to ground
OUT
through a 800Ω active pull-down.
12V (Pin 16): Gate Drive for 12V Supply External N-
GATE
ChannelMOSFET.Aninternal10μAcurrentsourcecharges
GND (Pin 8): Device Ground.
the gate of the external N-channel MOSFET. An internal
clamp limits the gate voltage to 6.2V above 12V . A
OUT
TIMER (Pin 9): Timer Capacitor Terminal. Connect a
capacitor between this pin and ground to set a 741ms/μF
duration for initial timing cycle, 123ms/μF for AUX current
limitduringpower-upand6ms/μFdurationfor12Vcurrent
limit before the external MOSFET is turned off.
resistor and capacitor network from this pin to ground
sets the turn-on rate and compensates the active current
limit.Duringturn-off,a1mApull-downcurrentdischarges
12V
to ground. During short circuit or undervoltage
GATE
lockout,a160mApull-downcurrentbetween12V
and
GATE
EN (Pin 10): Enable Input Intended for Card Presence
Detect. Ground this pin to enable the external N-channel
MOSFET and internal switch to turn on. If this pin is pulled
high, the switches are not allowed to turn on. An internal
100k resistor pulls up this pin. A high-to-low transition
will clear faults.
12V
is activated.
OUT
Exposed Pad (Pin 17, DHD Package): Exposed pad may
be left open or connected to device ground.
422312f
7
LTC4223-1/LTC4223-2
FUNCTIONAL DIAGRAM
R
IN
5k
A1
+
–
12IMON
R
OUT
165k
10μA
CHARGE
PUMP
12V
GATE
60mV
6.2V
12V
IN
ACL
+
–
+
–
12V
OUT
GATE
DRIVER
12V
SENSE
1mA
50mV
ECB
+
+
–
–
+
–
12V PWRGD
10.3V
PG2
V
CC
12V SUPPLY
CONTROL
10μA
12ON
12V FET ON
12PGOOD
V
CC
R2
EN
CARD PRESENCE
V
CC
UVLO3
10μA
+
–
12V
IN
9.7V
FAULT
V
UVLO2
UVLO1
CP2
CC
+
–
12V FAULT
AUX FAULT
SYSTEM
CONTROL
2.45V
V
V
CC
CC
+
–
AUXIN
2.5V
200μA
10μA
+
–
0.2V
TIMER
CP1
+
–
V
CC
1.235V
2μA
10μA
AUXPGOOD
AUXON
AUX FET ON
AUX SUPPLY
CONTROL
GND
+
–
AUX PWRGD
THERMAL
SHUTDOWN
2.885V
PG1
CHARGE
PUMP
10μA
AUXIN
AUXOUT
RSNS
MFET
422312 FD
422312f
8
LTC4223-1/LTC4223-2
OPERATION
The LTC4223 is designed to control the power on an Ad-
vanced Mezzanine Card (AMC) or MicroTCA backplane,
allowing boards to be safely inserted and removed. It
controlsthe12Vmainand3.3Vauxiliarypowerthroughan
externalN-channelMOSFETandintegratedpasstransistor.
Thesetwosuppliescanbeturnedonandoffindependently
by their respective ON control pins.
value, an internal analog current limit (ACL) amplifier
servos the gate to force 60mV across the external sense
resistor connected between 12VIN and 12V
pins.
SENSE
During this period, TIMER pin capacitor is charged by a
200μA pull-up. If the load is fully charged and no longer in
current limit before the TIMER reaches 1.235V, 12PGOOD
pulls low. Otherwise 12V shuts off and FAULT pulls low
when TIMER reaches 1.235V.
If either AUXON or 12ON is pulled high, an initial tim-
ing cycle set by the TIMER capacitor value is initiated
once all these conditions are met: input supplies out of
undervoltage lockout; TIMER < 0.2V and EN low. At the
end of the initial timing cycle, if the AUXON pin is high, the
internal pass transistor turns on. It enters into an active
current limit loop if the inrush current charging the load
capacitor exceeds 240mA. When the load is in current
limit, a 10μA pull-up charges the TIMER pin capacitor. If
the load capacitor is fully charged and the switch is no
longer in current limit before the TIMER reaches 1.235V,
AUXPGOOD pulls low indicating that power is good.
Otherwise the internal switch turns off and FAULT pulls
low when TIMER reaches 1.235V.
If an overcurrent fault occurs on the auxiliary supply after
power-up, thecurrentislimitedto240mAandaftera25μs
delay, the circuit breaker trips and FAULT pulls low. Ther-
mal shutdown protects the internal pass transistor from
overheating by shutting it off at 150°C. If an overcurrent
fault occurs on the 12V supply, the current is limited to
60mV/R
. After a timing cycle delay set by 200μA
SENSE
charging the TIMER capacitor, the circuit breaker trips
and FAULT pulls low. An overcurrent fault on the auxiliary
supply shuts off 12V; a fault on the 12V supply does not
affect the auxiliary supply.
The LTC4223 provides high side current sensing informa-
tion for the 12V supply at the 12IMON pin. The 12IMON
output voltage is 33 times the sense voltage, allowing it
to be used with an external ADC.
If 12ON pin is high at the end of the initial timing cycle,
an internal charge pump charges the gate of the external
MOSFET with 10μA pull-up. Connecting an external gate
capacitor limits the inrush current charging the load ca-
pacitor. If the inrush current exceeds its limited current
In the off condition, 12V
and AUXOUT are discharged
OUT
to ground by internal N-channel pull downs.
422312f
9
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
CARRIER AMC MODULE AMC
CONNECTOR CONNECTOR
R
Q1
S
6mΩ
Si7336ADP
PWR
12V
12V
7.4A
C
G
BULK SUPPLY
BYPASS CAPACITOR
R3
10Ω
R
G
15nF
47Ω
2
1
16
12V
12V
12V
SENSE GATE
IN
5
6
15
12
3.3V
AUXIN
12V
OUT
MP
R2
3.3V
150mA
AUXOUT
51Ω
BULK SUPPLY
V
CC
BYPASS CAPACITOR
C2
330nF
MP ENABLE
7
4
AUXON
12ON
PWR ENABLE
3.3V 3.3V 3.3V
LTC4223-1
R6* R5* R4*
10k 10k 10k
MP GOOD
PWR GOOD
FAULT
11
14
13
AUXPGOOD
12PGOOD
FAULT
3.3V
INTELLIGENT
PLATFORM
MANAGEMENT
CONTROLLER
1μF
5
8
10
PS1
PS0
3
V
V
2
3
7
6
1
3
EN
REF
CC
12IMON
CLK
D
+IN
LTC1197L
OUT
CS
–IN
GND
TIMER
9
3.3V
2.2k
GND
4
422312 F01
8
C
T
0.1μF
3.3V
10k
PRESENCE
ENABLE
RESET
*OPTIONAL
Figure 1. Advanced Mezzanine Card/MicroTCA Application
The typical LTC4223 application is in a Carrier board
for Advanced Mezzanine Cards (AMC), delivering 3.3V
auxiliary and 12V power to the AMC module. A control-
ler on the Carrier board sequences the turn-on of power
supplies and manages the fault and power-good reports
from the LTC4223.
Turn-On Sequence
The power supplies delivered to an AMC module are
controlled by the external N-channel pass transistor, Q1 in
the 12V power path and an internal pass transistor in the
3.3V auxiliary power path. Sense resistor R monitors the
S
12V load current for fault detection and current sensing
The LTC4223 detects board presence during insertion and
extraction, allowing power to be delivered in a controlled
manner without damaging the connector. The typical
LTC4223 application circuit is shown in Figure 1. External
component selection is discussed in detail in the Design
Example section.
information. GATE capacitor C provides gate slew rate
G
control to limit the inrush current. Resistor R with C
G
G
compensates the current control loop while R3 prevents
parasitic oscillations in Q1.
422312f
10
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
Several conditions must be met before the external and
Once AUXOUT signals power is good and the TIMER pin
returns to <0.2V, the external MOSFET is then allowed to
turnonbycharginguptheGATEwitha10μAcurrentsource
(Figure 2). The voltage at the GATE pin rises with a slope
internal switches are allowed to turn on. First V and
CC
the input supplies (12V , AUXIN) must exceed their
IN
undervoltage lockout thresholds. Next TIMER must be
<0.2V and EN must be pulled low.
equal to 10μA/C and the supply inrush current flowing
G
into the load capacitor C (see Figure 14) is limited to:
L1
Once these conditions are met, a debounce timing cycle is
initiated when AUXON or 12ON pin is toggled from low to
high. These two control pins turn on/off the 3.3V auxiliary
and 12V supplies. At the end of the debounce cycle, the
ON pins and fault status are checked. If both ON pins are
high and fault is cleared, the 3.3V auxiliary supply starts
up first followed by the 12V supply. Note that the turn-on
delay for the AUXON and 12ON pins is 15μs and 30μs.
Figure 2 shows the two supplies turning on in sequence
after EN goes low.
C
CG
I
=
L1 •10µA
INRUSH
The12VoutputfollowstheGATEvoltagewhentheMOSFET
turns on. If the voltage across the current sense resistor
R becomes too high, the inrush current is limited by the
S
internal current limit circuitry. Once the output, 12V
OUT
exceeds its power-good threshold, 12PGOOD also pulls
low.
By default, the internal pass transistor turns on first if
both ON pins are high and start-up conditions met. The
output is current limited at 240mA by its internal ACL
amplifier as the load current charging the output capaci-
tor increases. This causes the TIMER to ramp up with a
10μA pull-up. Normally the AUXOUT voltage exceeds its
power-good threshold before TIMER time-out and then
AUXPGOOD pulls low.
If only the 12ON pin is high at the end of debounce cycle,
the external MOSFET turns on first. After that, if AUXON
pulls high, the internal switch turns on only after the 12V
output signals power is good and TIMER <0.2V.
Table 1. 12V and Auxiliary Supply Turn-Off Conditions
CONDITION
RESULT
CLEARED BY
AUX
12V
AUXON Goes
Low
Turns Off
No Effect AUXON High
EN
5V/DIV
TIMER
2V/DIV
AUXOUT
5V/DIV
12ON Goes Low
EN Goes High
No Effect
Turns Off
Turns Off
Turns Off
No Effect
Turns Off
Turns Off 12ON High
Turns Off EN Low
UVLO on V
Turns Off
V
> UVLO
CC
CC
12V
OUT
5V/DIV
UVLO on AUXIN
UVLO on 12V
No Effect AUXIN > UVLO
Turns Off 12V > UVLO
IN
IN
AUXPGOOD
5V/DIV
12PGOOD
5V/DIV
AUX Overcurrent
Fault
Turns Off AUXON and 12ON Low,
EN High-to-Low, UVLO
on V
CC
12V Overcurrent
Fault
No Effect
Turns Off
Turns Off 12ON Low, EN High-to-
Low, UVLO on V
20ms/DIV
CC
422312 F02
Thermal
Shutdown
Turns Off AUXON and 12ON Low,
EN High-to-Low, UVLO
Figure 2. Normal Power-Up Sequence
on V , Temperature <
CC
120°C
422312f
11
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
Turn-Off Sequence
the bounces internally with a TIMER ramp up period given
by C • 123[ms/μF] as shown in Figure 4.
T
The switches can be turned off by various conditions and
this is summarized in Table 1.
Timer Functions
When the 12ON pin goes low, the external switch is turned
off with the GATE pin pulled to ground by 1mA current
sink. The 12PGOOD pin pulls high indicating that power is
nolongergood, whileaninternalN-channeltransistordis-
charges the output to ground. Similarly, when the AUXON
pin goes low, the internal switch is turned off, AUXPGOOD
pullshighwhileitsoutputisdischargedtogroundthrough
an internal N-channel transistor. Figure 3 shows the two
supplies being turned off by EN going high.
An external capacitor C connected from the TIMER pin
T
to ground is used to perform several functions.
1. Ignore contact debouncing during card insertion when
the device is enabled. The debounce cycle is given
by ramping up C with 10μA current to TIMER high
T
threshold (1.235V) and then ramping down with 2μA
currenttobelowTIMERlowthreshold(0.2V).Thisgives
an average debounce cycle time of C • 741[ms/μF].
T
After that, if any ON pin is pulled high and EN pin is
Card Presence Detect
low, the switches can be turned on.
2. Blanking contact bounce on the EN pin that might
trigger unwanted fault clearing during card removal.
In an AMC system, PS1 and PS0 signals are used to
detect the presence of a card upon insertion or removal.
Normally PS1 is connected to the EN pin with a pull-up
resistor. If AUXON or 12ON is high when the EN pin goes
low, indicatingaboardinsertion, atimingcycleforcontact
debouncingisinitiated.Uponinsertion,anybouncesonthe
EN pin will re-start the timing cycle. When TIMER finally
reaches its threshold during ramp up, the fault latches
will be cleared. If the EN pin remains low at the end of the
timing cycle, the switches are allowed to turn on.
The blanking time is given by C • 123[ms/μF].
T
3. Faultfilteringduringauxiliarysupplypower-upinanalog
current limit. TIMER pulls up with 10μA and pulls down
with 2μA. The filter time is given by C • 123[ms/μF].
T
4. 12V supply fault filtering during and after power-up
in analog current limit. TIMER pulls up with 200μA
and pulls down with 2μA. The filter time is given by
C • 6[ms/μF].
T
5. For cooling off during an auto-retry cycle after
If the EN pin is toggled from low to high, indicating board
removal,alltheswitcheswillbeturnedoffaftera20μsdelay.
Any latched faults will not be cleared. However, removing
thecardcouldcausetheENpinvoltagetobounce,clearing
thefaultlatchesundesirably. Thisispreventedbyblanking
an overcurrent fault on auxiliary or 12V supply
(LTC4223-2). The cool-off time is given by C • 1482
T
[ms/μF]afteranauxiliarysupplyfaultandC •1358[ms/
T
μF] after a 12V supply fault.
EN
5V/DIV
AUXOUT
5V/DIV
EN
2V/DIV
12V
OUT
5V/DIV
TIMER
1V/DIV
AUXPGOOD
5V/DIV
12PGOOD
5V/DIV
FAULT
2V/DIV
100ms/DIV
5ms/DIV
422312 F03
422312 F04
Figure 3. Normal Power-Down Sequence
Figure 4. Debouncing by TIMER during Card Removal
422312f
12
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
As the TIMER capacitor is used for fault filtering during
power-up for both the auxiliary and 12V supplies, only
one supply can be started up at any one time. The other
supply waits until the power-good signal is generated by
the powering-up supply and the TIMER pin voltage falls
below 0.2V. By default, the 3.3V auxiliary supply starts up
first if both AUXON and 12ON are high at the end of the
debounce cycle.
shortcircuitsorexcessiveloadcurrenton12Vsupply. The
voltage across the external sense resistor is monitored by
the analog current limit (ACL) amplifier and the electronic
circuit breaker (ECB) comparator. If an overcurrent fault
occurs that causes the sense voltage to reach the ACL
threshold(60mV),theACLamplifierregulatestheMOSFET
topreventanyfurtherincreaseincurrent.Thisovercurrent
condition results in a sense voltage that exceeds the ECB
threshold. As a result, the TIMER capacitor is charged
by a 200μA current. If the condition persists, the TIMER
pin voltage will reach its threshold (1.235V). When this
occurs, the FAULT pin pulls low and a 1mA current pulls
the GATE pin to ground causing the MOSFET to turn off.
The circuit breaker time delay, the time required for the
TIMER pin capacitor to charge from ground to the TIMER
Whenever both AUXON and 12ON are pulled low, the de-
vice is in reset mode and TIMER capacitor is discharged
to ground by an 8mA current sink.
Thermal Shutdown
The internal 3.3V auxiliary supply switch is protected by
thermal shutdown. If the switch’s temperature reaches
150°C, theauxswitchwillshutoffimmediatelyandFAULT
will pull low. The external 12V supply switch also turns
off. The switches are allowed to turn on again by cycling
both the AUXON and 12ON pins low then high after the
internal switch’s temperature falls below 120°C.
pin threshold, is given by C • 6[ms/μF].
T
After the MOSFET turns off, the TIMER pin capacitor dis-
charges with a 2μA pull-down current. For the auto-retry
version (LTC4223-2), if the TIMER discharges to below
0.2V, a new start-up cycle will begin. The TIMER starts
ramping up and clears faults when it exceeds 1.235V;
thereafter it ramps down (see the section on Auto-Retry
for details). Figure 5 shows an overcurrent fault on the
12V output.
Overcurrent Fault
TheLTC4223featuresanadjustablecurrentlimitwithcircuit
breakerfunctionthatprotectstheexternalMOSFETagainst
In the event of a severe short-circuit fault on 12V output
as shown in Figure 6, the output current can surge to
tens of amperes. The LTC4223 responds within a very
short time to bring the current under control by pulling
the MOSFET’s GATE-to-SOURCE pin voltage down to zero
volts.Thereafter,theGATEoftheMOSFETrecoversrapidly
FAULT
5V/DIV
I
LOAD
5A/DIV
12V
OUT
5V/DIV
due to the R /C compensation network and enters into
G
G
active current limiting until the TIMER times out. Due to
parasitic supply lead inductance, an input supply without
any bypass capacitor will collapse during the high cur-
rent surge and then spike upwards when the current is
interrupted. An input supply transient protection network
comprising of Z1, R1 and C1 shown in Figure 13 is recom-
mended if there is no input capacitance.
12V
GATE
5V/DIV
0.1ms/DIV
422312 F05
Figure 5. Overcurrent Fault on 12V Output
422312f
13
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
Therearetwodifferentmodesoffaulttime-outforthe3.3V
auxiliarysupply:adjustabledelaythroughTIMERcapacitor
during power-up when AUXPGOOD not asserted; fixed
25μs delay after power-up when AUXPGOOD asserted
low. Under the situation whereby AUXON toggles low then
high for short duration after power-up while AUXPGOOD
still pulling low due to output load capacitor, 25μs fault
time-out applies.
Whenever the 3.3V auxiliary supply trips off due to an
overcurrent fault, the 12V supply also shuts off. The
auxiliary supply is, however, unaffected by faults on the
12V supply. In either case FAULT latches low when the
affected channels turn off, and FAULT is cleared by tog-
gling the ON pins. Faults are cleared automatically in the
LTC4223-2 auto-retry version.
If there is significant supply lead inductance, a severe
output short may collapse the input to ground before the
LTC4223 can bring the current under control. In this case
the undervoltage lockout will activate after a 12μs filter
delay, and pull the gate down. Then the ACL amplifier will
take control and regulate the output in active current limit.
Under this situation, the fault time-out is set by TIMER
delay instead of 25μs filter delay.
When the auxiliary supply is powered up into an output
short, the ACL amplifier will regulate the gate of the
internal pass transistor to produce 240mA output cur-
rent. At this time a 10μA pull-up current starts charging
up the TIMER pin capacitor until it exceeds its threshold
(1.235V). The internal pass transistor then turns off and
FAULT pulls low. Thereafter, the TIMER is discharged by
a 2μA pull-down current. The fault filter delay is given by
Undervoltage Fault
C • 123[ms/μF].
T
An undervoltage fault occurs if either AUXIN or 12V falls
After a successful power-up cycle, the ACL amplifier pro-
tectstheauxiliarysupplyfromovercurrentbypullingdown
the gate of the internal pass transistor rapidly as shown
in Figure 7. Thereafter, the gate recovers and servos the
output current to about 240mA for 25μs before pulling
down to ground gently, turning the transistor off. At this
time, FAULT pulls low and the 12V external MOSFET is
also turned off by the 1mA GATE pull-down current.
IN
belowitsundervoltagethresholdforlongerthan12μs.This
turns off the affected supply’s switch instantly, but does
not clear the fault latches. Further, an undervoltage fault
on one supply does not affect the operation of the other
supply. If the bias supply input, V falls below its UVLO
CC
thresholdformorethan80μs,allsupplyswitchesareturned
off and the fault latches are cleared. Operation resumes
from a fresh start-up cycle when V is restored.
CC
FAULT
5V/DIV
ΔV
SENSE
200mV/DIV
12V
OUT
I
LOAD
5V/DIV
1A/DIV
12V
GATE
5V/DIV
AUXOUT
5V/DIV
5μs/DIV
5μs/DIV
422312 F06
422312 F07
Figure 6. Short-Circuit Fault on 12V Output
Figure 7. Short-Circuit Fault on 3.3VAUX Output
422312f
14
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
Power-Good Monitor
Auto-Retry after a Fault (LTC4223-2)
Internal circuitry monitors the output voltages, AUXOUT
At time point 1 in Figure 8, if a fault latched-off the 3.3V
auxiliary supply after power-up, a cool-off cycle begins.
The TIMER capacitor charges up to 1.235V with a 10μA
current and then discharges with a 2μA current to 0.2V at
time point 3. This is followed by a debounce timing cycle
whereby the fault latch is cleared, and FAULT pulls high
when TIMER reaches its threshold at time point 4. At the
end of debounce cycle, the internal switch is allowed to
turn on. If the output short persists, the auxiliary supply
powers up into a short with active current limiting. At time
point 7, the fault filter delay begins with TIMER ramping
up with a 10μA current. If the TIMER times out at time
point 8, FAULT will be pulled low and a new cool-off cycle
begins with TIMER ramping down with a 2μA current.
The whole process repeats itself until the output-short
is removed.
and 12V . The power-good status is reported via their
OUT
respectiveopendrainoutputs,AUXPGOODand12PGOOD.
Several conditions must be met before the power-good
outputs assert low.
1. The monitored output should be above its power-
good threshold and hysteresis.
2. The input supply is above undervoltage lockout.
3. EN is low.
4. The associated ON pin is high.
5. Thermal shutdown is not activated.
If any of the supply outputs falls below its power-good
threshold for more than 20μs, the respective power-good
output will be pulled high by the external pull-up resistor
or internal 10μA pull-up.
In Figure 9, a fault latches off the 12V supply at time point
1; a cool-off cycle begins by discharging the TIMER ca-
pacitor with 2μA current from 1.235V to 0.2V threshold.
At time point 2 a new debounce timing cycle is initiated
wherethefaultlatchiscleared,andFAULTpullshighwhen
TIMER reaches its threshold at time point 3. At the end of
the debounce cycle, the 12V GATE is allowed to start up. If
the output short persists, the 12V supply powers up into a
short with active current limiting. At time point 6, the fault
filter delay begins with TIMER ramping up with a 200μA
current. The TIMER times out at time point 7, FAULT pulls
low and a new cool-off cycle begins with TIMER ramping
down with a 2μA current. The whole process repeats itself
until the output-short is removed.
Resetting Faults (LTC4223-1)
Any supply faults tripping the circuit breaker are latched
and FAULT asserts low. For the latched-off version
(LTC4223-1), to reset a fault latch due to overcurrent or
thermalshutdownonauxiliarysupply,pullbothAUXONand
12ON pins low together for at least 100μs, after which the
FAULTwillgohigh.TogglingboththeONpinshightogether
again initiates the debounce timing cycle, thereafter the
auxiliary supply starts up first followed by 12V supply. To
skip the debounce timing cycle, first pull only AUXON low
then high for at least 50μs before toggling 12ON low then
high. The fault latch clears on the falling edge of 12ON
and the auxiliary supply powers up. Thereafter, the 12V
supply powers up if 12ON pulls high.
The auto-retry duty cycle is given by:
To reset a fault on the 12V supply and re-start the output,
toggle only the 12ON pin low and then high again. Tog-
gling the EN pin high then low again or bringing the bias
tFILTER •100%
DutyCycle =
tCOOL + tDEBOUNCE + tFILTER
input, V below its UVLO threshold for more than 100μs
CC
For example, if TIMER capacitor, C = 0.1μF, the auto-retry
T
will initiate the debounce timing cycle and reset all fault
duty cycle for auxiliary and 12V supply is 6.5% and 0.5%
latchesbeforepower-up.BringingAUXINor12V belowits
IN
respectively.
undervoltage threshold will not reset the fault latches. For
the auto-retry version (LTC4223-2), the latched fault will
be cleared automatically after a cool-off timing cycle.
422312f
15
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
GATE Pin Voltage
then be fed into an LTC1197L ADC as shown in Figure 10
for data conversion. The current sense information can be
usedbythesystemcontrollertomanagethepowerbudget
allocated to the modules on the card. Full scale input to
the current sense amplifier is 82.5mV, corresponding to
an output of about 2.7V. If the input exceeds 100mV, the
output clamps at 3.2V.
The gate drive at 12V
is compatible with any logic
GATE
level MOSFET. The guaranteed range of gate drive is 4.5V
to 7.9V, with a typical of 6.2V.
Active Current Loop Compensation
The compensation network consisting of resistor R and
G
gate slew rate control capacitor C stabilizes the internal
V
CC
Supply Filtering
G
activecurrentlimitcircuit.ThevalueofC isselectedbased
G
The internal circuitry of the LTC4223 is powered from the
pin. Bypass V with at least 330nF to ground. If V
on the inrush current allowed. The suggested value for
V
CC
CC
CC
R is 47Ω. The value of C should be ≤330nF and R is
G
G
G
is derived from the same supply as is AUXIN, include a
decoupling resistor as shown in Figure 11. This RC net-
between 10Ω and 100Ω for optimum performance.
work allows the V pin to ride out supply glitches caused
CC
High Side Current Sense
by short circuits on the auxiliary output or on adjacent
The12Vloadcurrentismonitoredviathevoltageacrossan
external sense resistor. The LTC4223 features a high side
current sense amplifier that translates the sense voltage
from the positive rail to the negative rail using a resistor
ratio of 33 times. The output voltage at 12IMON pin can
boards, thus preventing an undervoltage lockout condi-
tion on V . Since the absolute maximum rating for V
CC
CC
is 7V as compared to 10V for AUXIN, select R2 and C2 to
keep the peak voltage seen by V below 7V during any
CC
voltage spikes.
END OF DEBOUNCE CYCLE
FAULT PULLS LOW DUE TO AUX
OVERCURRENT FAULT AFTER POWER UP
START OF COOL-OFF CYCLE
START AUX INTERNAL GATE RAMP WHEN STARTUP CONDITIONS ARE MET
AUX OUTPUT IN CURRENT LIMIT
START OF
FAULT PULLS LOW AND RESTART OF
COOL-OFF CYCLE DURING POWER UP
RESTART OF
DEBOUNCE CYCLE
RESET FAULT HIGH
4
DEBOUNCE CYCLE
1
2
3
5
6
7
8
9
10
FAULT
TIMER
V
V
V
V
TMR
TMR
TMR
TMR
10μA
2μA
10μA
2μA
10μA
2μA
10μA
2μA
10μA
FILTER DELAY
COOL-OFF CYCLE
DEBOUNCE CYCLE
COOL-OFF CYCLE
AUX INTERNAL GATE REGULATES
I
AUXOUT
12V
OUT
422312 F08
Figure 8. Auto-Retry after AUX Overcurrent Fault
422312f
16
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
END OF DEBOUNCE CYCLE
FAULT PULLS LOW DUE TO
12V OVERCURRENT FAULT
START OF COOL-OFF CYCLE
START 12V GATE RAMP WHEN STARTUP CONDITIONS ARE MET
12V OUTPUT IN CURRENT LIMIT
START OF
FAULT PULLS LOW AND
RESTART OF
DEBOUNCE CYCLE
RESET FAULT HIGH
3
RESTART OF COOL-OFF CYCLE DEBOUNCE CYCLE
1
2
4
5
6
7
8
FAULT
TIMER
V
V
V
TMR
TMR
TMR
200μA
2μA
10μA
2μA
200μA
2μA
10μA
FILTER DELAY
COOL-OFF CYCLE
COOL-OFF CYCLE
DEBOUNCE CYCLE
12V
REGULATES
GATE
12V
GATE
60mV
60mV
12V - 12V
IN
SENSE
12V
OUT
422312 F08
Figure 9. Auto-Retry after 12V Overcurrent Fault
V
SENSE
I
Supply Transient Protection
LOAD
Q1
–
+
12V
The supply inputs, AUXIN and 12V are fed directly from
IN
12V
12V
IN
SENSE
the regulated output of the backplane supply, where bulk
bypassing assures a spike-free operating environment.
In other applications where the bulk bypassing is located
far from the LTC4223, spikes generated during output
short circuit events could exceed the absolute maximum
R
IN
5k
LOAD
12V
GATE
1μF
3.3V
ratings for AUXIN and 12V . To minimize such spikes,
12IMON
V
OUT
IN
V
V
CC
REF
LTC1197L
GND
+IN
–IN
CLK
use wider traces or heavier trace plating to reduce the
power trace inductance. Also, bypass locally with a 10μF
electrolytic and 100nF ceramic, or alternatively clamp
the input with a transient voltage suppressor (Z1, Z2) as
shown in Figure 13. A 10Ω, 100nF snubber damps the
response and eliminates ringing. A recommended layout
of the 12V transient protection devices Z1, R1 and C1
around the LTC4223 is shown in Figure 12.
TO SYSTEM
CONTROLLER
D
OUT
R
OUT
165k
CS
LTC4223
422312 F10
R
OUT
V
OUT
=
• V
= 33 • V
SENSE SENSE
R
IN
Figure 10. High Side Current Sense with LTC1197L ADC
422312f
17
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
CURRENT FLOW
TO LOAD
CURRENT FLOW
TO LOAD
R2
SENSE
RESISTOR
POWER PAK
SO-8
51Ω
AUXIN
V
CC
C2
330nF
12V
12V
OUT
IN
W
W
422312 F11
TRACK WIDTH W:
0.03" PER AMPERE
ON 1OZ Cu FOIL
R3
VIA TO
GND PLANE
12V
GATE
Figure 11. RC Network for VCC Filtering
R
G
•
C
G
PCB Layout Considerations
1
2
16
15
Z1
R1
C1
LTC4223CGN*
For proper operation of the LTC4223’s circuit breaker,
Kelvin-connection to the sense resistor is strongly rec-
ommended. The PCB layout should be balanced and
symmetrical to minimize wiring errors. In addition, the
PCB layout for the sense resistor and the power MOSFET
should include good thermal management techniques for
optimal device power dissipation. A recommended PCB
layout for the 12V sense resistor and the power MOSFET
is illustrated in Figure 12.
8
CURRENT FLOW
TO SOURCE
VIA TO
GND PLANE
•
W
GND
GND
422312 F12
*ADDITIONAL DETAILS OMITTED FOR CLARITY, DRAWING NOT TO SCALE!
Figure 12. Recommended Layout for Power MOSFET, Sense
Resistor and GATE Components on 12V Rail
In applications where load current exceeds 10A, wide
PCB traces are recommended to minimize resistance
and temperature rise. The suggested trace width for 1
oz copper foil is 0.03” for each ampere of DC current to
keep PCB trace resistance, voltage drop and temperature
rise to a minimum. Note that the sheet resistance of 1 oz
copper foil is approximately 0.5mΩ/square, and voltage
drops due to trace resistance add up quickly in high cur-
rent applications.
The first step is to select the appropriate value of R
SENSE
for the 12V supply. Calculating R
value is based on
SENSE
the maximum load current and the lower limit for the
circuit breaker threshold, ΔV
.
SENSE(CB)(MIN)
ΔVSENSE(CB)(MIN)
47.5mV
7.4A
RSENSE
=
=
= 6mΩ
ILOAD(MAX)
If a 1% tolerance is assumed for the 6mΩ sense resistor,
the minimum and maximum circuit breaker trip current is
calculated as follows:
In most applications, it will be necessary to use plated-
through via to make circuit connections from component
layers to power and ground layers internal to the PCB. For
1 oz copper foil plating, a general rule is 1A of DC current
per via. Consult your PCB fabrication facility for design
rules pertaining to other plating thicknesses.
Table 2. AMC Power Supply Requirements
SUPPLY VOLTAGE
MAXIMUM LOAD
CURRENT
MAXIMUM LOAD
CAPACITANCE
12V
7.4A
800μF
150μF
It is important to place the V bypass capacitor C2 as
CC
close as possible between V and GND. The transient
3.3V
150mA
AUX
CC
voltage suppressors Z1 and Z2 are also placed between
the supply inputs and ground using short wide traces.
Table 3. MicroTCA Power Supply Requirements
SUPPLY VOLTAGE
MAXIMUM LOAD
CURRENT
MAXIMUM LOAD
CAPACITANCE
Design Example
12V
7.6A
1600μF
150μF
As a design example, consider the AMC Hot Swap ap-
plication shown earlier in Figure 1 with the power supply
requirements given in Table 2.
3.3V
150mA
AUX
422312f
18
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
2
ΔVSENSE(CB)(MIN)
47.5mV
6.06mΩ
CL1•12VOUT
2• tCHARGE
ITRIP(MIN)
=
=
= 7.8A
PAVG
=
RSENSE(MAX)
ΔVSENSE(CB)(MAX)
52.5mV
5.94mΩ
The inrush current can be limited by using the GATE ca-
pacitance(C )sothatthepowerdissipatedintheMOSFET
ITRIP(MAX)
=
=
= 8.8A
RSENSE(MIN)
G
is well within its safe operating area (SOA). For I
=
GATE
Forproperoperation,I
mustexceedthemaximum
TRIP(MIN)
10μA and C = 800μF, we choose C = 15nF to set the
L1
G
load current with margin, so R
for the 12V supply.
= 6mΩ should suffice
SENSE
inrush current to 0.5A.
CL1•IGATE
I
=
= 0.5A
The second step is to determine the TIMER capacitance
based on the time required to charge up completely the
output load capacitor on auxiliary supply in active current
limit without exceeding the fault filter delay. The worst-
case start-up time is calculated using the minimum active
current limit value for the auxiliary supply.
INRUSH
CG
CL1•12VOUT
tCHARGE
=
=19ms
I
INRUSH
This results in P
= 3W and the MOSFET selected must
AVG
be able to tolerate 3W for 19ms. The increase in steady
state junction temperature due to power dissipated in
CL2 •3.3VAUX
IAUX(ACL)(MIN)
150µF •3.3V
165mA
tSTUP(AUX)
=
=
= 3ms
the MOSFET is ΔT = P
• Z where Z is the thermal
AVG
th th
impedance.
For a start-up time of 3ms with a 2x safety margin, the
TIMER capacitance is calculated as:
Under this condition, the Si7336ADP datasheet’s Tran-
sient Thermal Impedance plot indicates that the junction
2• tSTUP(AUX)
6ms
123 ms /µF 123 ms /µF
temperature will increase by 2.4°C using Z
(single pulse).
= 0.8°C/W
thJC
CT =
=
≅ 0.05µF
[
]
[
]
Thedurationandmagnitudeofthepowerpulsethatresults
during a short-circuit condition on the 12V output are a
function of the TIMER capacitance and LTC4223’s analog
current limit. The short-circuit duration is given as 0.1μF
Considering the tolerances for the TIMER charging rate
and capacitance, a value of 0.1μF ( 10%) for C should
T
suffice.
• 6[ms/μF] = 600μs for C = 0.1μF. The maximum short-
Since the TIMER charging rate during fault time-out is
20 times faster for the 12V supply as compared to the
auxiliary supply during start-up, this scheme ensures that
the external MOSFET will not overheat under any output-
short condition. The fault filter delay for the 12V supply
is given by 0.1μF • 6[ms/μF] = 600μs versus 12ms for
the auxiliary supply.
T
circuit current is calculated using the maximum analog
current limit threshold, ΔV
SENSE
and minimum
SENSE(ACL)(MAX)
R
value.
ΔVSENSE(ACL)(MAX)
66mV
5.94mΩ
ISHORT(MAX)
=
=
=11A
RSENSE(MIN)
The next step is to verify that the thermal ratings of the
selected external MOSFET for the 12V supply aren’t ex-
ceeded during power-up or an output-short.
So the maximum power dissipated in the MOSFET is 11A •
12Vor132Wfor600μs. TheSi7336ADPdatasheet’sTran-
sientThermalImpedanceplotindicatesthattheworse-case
increase in junction temperature during the short-circuit
AssumingtheMOSFETdissipatespoweronlyduetoinrush
current charging the load capacitor, the energy dissipated
in the MOSFET during power-up is the same as that stored
into the load capacitor. The average power dissipated in
the MOSFET is given by:
condition is 13.2°C using Z
= 0.1°C/W (single pulse).
thJC
This will not cause the maximum junction temperature to
be exceeded. The SOA curves of the Si7336ADP are also
checked to be safe under this condition.
422312f
19
LTC4223-1/LTC4223-2
TYPICAL APPLICATION
Card Resident Application with 5V Auxiliary Supply
BACKPLANE
CARD
CONNECTOR CONNECTOR
R
Q1
S
4mΩ
Si7336ADP
12V
10A
12V
R1
+
+
C
10Ω
Z1
G
C
R3
L1
R
G
15nF
SMAJ13A
1000μF
C1
100nF
10Ω
47Ω
12V
IN
12V
12V
SENSE GATE
12V
OUT
5V
AUX
150mA
5V
AUXIN
AUXOUT
R2
R7
2.7Ω
C3
100nF
51Ω
C
L2
R6
Z2
V
CC
150μF
10k SMAJ7.0A
C2
330nF
PWRFLT
PWREN
FAULT
AUXON
12ON
EN
5V
5V
R4
10k
R5
10k
LTC4223-1
R8
10k
AUXPGOOD
12PGOOD
BD_SEL
5V
1μF
GND
V
V
REF
CC
LTC1197
GND
12IMON
+IN
–IN
CLK
TO SYSTEM
CONTROLLER
D
OUT
CS
TIMER
GND
422312 TA02
C
T
0.1μF
422312f
20
LTC4223-1/LTC4223-2
TYPICAL APPLICATION
Card Resident Application with 12V Power Up First Followed by 3.3V Auxiliary
BACKPLANE
CARD
CONNECTOR CONNECTOR
R
Q1
S
4mΩ
Si7336ADP
12V
10A
12V
R1
+
C
G
15nF
10Ω
Z1
SMAJ13A
C
R3
10Ω
L1
R
G
1000μF
C1
100nF
47Ω
12V
IN
12V
SENSE
12V
GATE
12V
OUT
3.3V
AUX
150mA
3.3V
AUXIN
AUXOUT
R2
R7
+
51Ω
2.7Ω
C
Z2
L2
V
CC
C3
100nF
150μF
SMAJ5.0A
C2
330nF
PWREN
12ON
3.3V
3.3V
3.3V
R8
10k
R9
10k
R5
10k
R4
10k
LTC4223-1
AUXON
AUXPGOOD
Q2
2N7002K
3.3V
R6
12PGOOD
3.3V
10k
PWRFLT
BD_SEL
FAULT
EN
1μF
V
V
REF
GND
CC
LTC1197L
GND
12IMON
+IN
–IN
CLK
TO SYSTEM
CONTROLLER
D
OUT
CS
TIMER
GND
422312 TA03
C
T
0.1μF
422312f
21
LTC4223-1/LTC4223-2
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
.150 – .157**
(5.817 – 6.198)
(3.810 – 3.988)
.0165 .0015
.0250 BSC
RECOMMENDED SOLDER PAD LAYOUT
1
2
3
4
5
6
7
8
.015 .004
(0.38 0.10)
× 45°
.0532 – .0688
(1.35 – 1.75)
.004 – .0098
(0.102 – 0.249)
.007 – .0098
(0.178 – 0.249)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
.0250
(0.635)
BSC
.008 – .012
GN16 (SSOP) 0204
(0.203 – 0.305)
TYP
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
422312f
22
LTC4223-1/LTC4223-2
PACKAGE DESCRIPTION
DHD Package
16-Lead Plastic DFN (5mm × 4mm)
(Reference LTC DWG # 05-08-1707)
0.70 0.05
4.50 0.05
3.10 0.05
2.44 0.05
(2 SIDES)
PACKAGE
OUTLINE
0.25 0.05
0.50 BSC
4.34 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
0.40 0.10
5.00 0.10
(2 SIDES)
TYP
9
16
R = 0.20
TYP
4.00 0.10 2.44 0.10
(2 SIDES)
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PIN 1
NOTCH
(DHD16) DFN 0504
8
1
0.25 0.05
0.50 BSC
0.75 0.05
0.200 REF
4.34 0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJGD-2) IN JEDEC
PACKAGE OUTLINE MO-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
422312f
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC4223-1/LTC4223-2
TYPICAL APPLICATION
12V/18A Card Resident Application
BACKPLANE
CARD
CONNECTOR CONNECTOR
R
Q1
HAT2160H
S
2.5m
12V
18A
12V
R1
+
+
C
10Ω
Z1
G
C
R3
L1
R
G
15nF
SMAJ13A
1000μF
C1
100nF
10Ω
47Ω
12V
IN
12V
12V
GATE
SENSE
12V
OUT
3.3V
150mA
AUX
3.3V
AUXIN
AUXOUT
R2
R7
2.7Ω
C3
100nF
51Ω
C
L2
Z2
V
CC
150μF
SMAJ5.0A
C2
330nF
3.3V
R9
10k
AUXON
12ON
EN
R4
10k
R5
10k
R6
10k
LTC4223-1
R8
10k
AUXPGOOD
12PGOOD
FAULT
BD_SEL
3..3V
1μF
V
V
REF
CC
LTC1197L
GND
12IMON
+IN
–IN
CLK
TO
D
OUT
CS
CONTROLLER
TIMER
GND
422312 TA04
C
T
0.1μF
RELATED PARTS
PART NUMBER
LTC1421
DESCRIPTION
COMMENTS
Operates from 3V to 12V, Supports –12V, SSOP-24
Dual Channel, Hot Swap Controller
Dual Channel, Hot Swap Controller
LTC1645
Operates from 3V to 12V, Power Sequencing, SO-8 or SO14
Operates from 2.7V to 16.5V, SO-8 or SSOP-16
LTC1647-1/LTC1647-2/ Dual Channel, Hot Swap Controller
LTC1647-3
LTC4210
LTC4211
LTC4215
Single Channel, Hot Swap Controller
Single Channel, Hot Swap Controller
Single Channel, Hot Swap Controller
Operates from 2.7V to 16.5V, Active Current Limiting, SOT23-6
Operates from 2.7V to 16.5V, Multifunction Current Control, MSOP-8 or MSOP-10
2
Operates from 2.9V to 15V, I C Compatible Monitoring, SSOP-16 or QFN-24
(4mm × 5mm)
LTC4216
LTC4221
LTC4245
Single Channel, Hot Swap Controller
Dual Channel, Hot Swap Controller
Operates from 0V to 6V, MSOP-10 or DFN-12 (4mm × 3mm)
Operates from 1V to 13.5V, Multifunction Current Control, SSOP-16
2
Multiple Channel, Hot Swap Controller 3.3V, 5V, 12V Supplies, I C Compatible Monitoring, SSOP-36 or QFN-38
(5mm × 7mm)
LTC4252-1/LTC4252-2/ –48V Hot Swap Controller
LTC4252A-1/
LTC4252A-2
Fast Active Current Limiting with Drain Accelerated Response, Supplies from –15V,
MSOP-8 or MSOP-10
422312f
LT 0807 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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