LINER LTC4252A-1 Dual supply hot swap controller for advanced mezzanine card Datasheet

LTC4223-1/LTC4223-2
Dual Supply Hot Swap
Controller for Advanced
Mezzanine Card
DESCRIPTION
FEATURES
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■
■
■
■
■
■
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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
APPLICATIONS
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Advanced Mezzanine Card, MicroTCA Systems
Workstations and Server I/O
Telecom Networks
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.
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 supply outputs. The LTC4223-1 features a latch-off circuit
breaker, while the LTC4223-2 provides automatic retry
after a fault.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Advanced Mezzanine Card Application
6mΩ
Si7336ADP
12V
7.4A
12V
10Ω
12VIN
3.3V
Normal Power-Up Waveform
47Ω
15nF
12VSENSE 12VGATE
12VOUT
5V/DIV
12VOUT
AUXIN
AUXOUT
3.3V
150mA
AUXPGOOD
5V/DIV
12PGOOD
5V/DIV
51Ω
VCC
330nF
AUXON
12ON
AUXPGOOD
12PGOOD
FAULT
IPMC
ADC
EN
5V/DIV
AUXOUT
5V/DIV
LTC4223-1/LTC4223-2
20ms/DIV
12IMON
422312 TA01b
EN
GND
TIMER
0.1μF
422312 TA01a
CARRIER MODULE
CONNECTOR CONNECTOR
422312f
1
LTC4223-1/LTC4223-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltages
12VIN ..................................................... –0.3V to 20V
AUXIN .................................................... –0.3V to 10V
VCC........................................................... –0.3V to 7V
Input Voltages
12ON, AUXON, ⎯E⎯N ................................... –0.3V to 7V
TIMER..........................................–0.3V to VCC + 0.3V
12VSENSE ............................................... –0.3V to 20V
Output Voltages
⎯F⎯A⎯U⎯L⎯T, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D, ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D,
12IMON ................................................... –0.3V to 7V
12VGATE ................................................. –0.3V to 25V
12VOUT - 12VGATE (Note 3) ................... –4.5V to 0.3V
AUXOUT................................................. –0.3V to 10V
Operating Temperature Range
LTC4223-1C/ LTC4223-2C ....................... 0°C to 70°C
LTC4223-1I/ LTC4223-2I ..................... –40°C to 85°C
Storage Temperature Range
GN Package ....................................... –65°C to 150°C
DHD Package ..................................... –65°C to 125°C
Lead Temperature (Soldering, 10sec)
GN Package ...................................................... 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
12VSENSE
1
16 12VGATE
12VIN
2
15 12VOUT
12IMON
3
14 12PGOOD
12ON
4
13 FAULT
AUXIN
5
12 AUXOUT
VCC
6
11 AUXPGOOD
AUXON
7
10 EN
GND
8
9
12VSENSE
1
16 12VGATE
12VIN
2
15 12VOUT
12IMON
3
14 12PGOOD
12ON
4
AUXIN
5
12 AUXOUT
VCC
6
11 AUXPGOOD
AUXON
7
10 EN
GND
8
9
17
13 FAULT
TIMER
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
θJA = 43°C/W, OTHERWISE θJA = 140°C/W, TJMAX = 125°C
TJMAX = 125°C, θJA = 110°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4223CDHD-1#PBF
LTC4223CDHD-1#TRPBF
42231
16-Lead (5mm × 4mm) Plastic DFN
0°C to 70°C
LTC4223CDHD-2#PBF
LTC4223CDHD-2#TRPBF
42232
16-Lead (5mm × 4mm) Plastic DFN
0°C to 70°C
LTC4223IDHD-1#PBF
LTC4223IDHD-1#TRPBF
42231
16-Lead (5mm × 4mm) Plastic DFN
–40°C to 85°C
LTC4223IDHD-2#PBF
LTC4223IDHD-2#TRPBF
42232
16-Lead (5mm × 4mm) Plastic DFN
–40°C to 85°C
LTC4223CGN-1#PBF
LTC4223CGN-1#TRPBF
42231
16-Lead Plastic SSOP
0°C to 70°C
LTC4223CGN-2#PBF
LTC4223CGN-2#TRPBF
42232
16-Lead Plastic SSOP
0°C to 70°C
LTC4223IGN-1#PBF
LTC4223IGN-1#TRPBF
4223I1
16-Lead Plastic SSOP
–40°C to 85°C
LTC4223IGN-2#PBF
LTC4223IGN-2#TRPBF
4223I2
16-Lead Plastic SSOP
–40°C to 85°C
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
PARAMETER
CONDITIONS
MIN
VDD
Input Supply Range
VCC
AUXIN
12VIN
●
●
●
IDD
Input Supply Current
VCC
AUXIN
12VIN
●
●
●
VDD(UVLO)
Input Supply Undervoltage Lockout
VCC Rising
VAUXIN Rising
V12VIN Rising
●
●
●
ΔVDD(UVLO,
HYST)
Input Supply Undervoltage Lockout
Hysteresis
VCC
AUXIN
12VIN
TYP
MAX
UNITS
Supplies
2.7
2.7
10
6
6
14
V
V
V
0.8
0.4
0.6
2
1
1
mA
mA
mA
2.3
2.4
9.4
2.45
2.5
9.7
2.6
2.6
10
V
V
V
●
●
●
40
70
70
110
110
110
180
150
150
mV
mV
mV
Circuit Breaker Trip Sense Voltage,
(V12VIN – V12VSENSE)
●
47.5
50
52.5
mV
ΔVSENSE(ACL)
Active Current Limit Sense Voltage,
(V12VIN – V12VSENSE)
●
54
60
66
mV
IAUX(ACL)
AUXOUT Active Current Limit
VAUXOUT = 0V
●
165
240
330
mA
Switch Resistance
(VAUXIN – VAUXOUT)/IAUXOUT
IAUXOUT = 150mA (Note 4)
●
0.3
0.5
Ω
ΔVGATE
External N-Channel Gate Drive
(V12VGATE – V12VOUT)
(Note 3)
●
4.5
6.2
7.9
V
IGATE(UP)
External N-Channel Gate Pull-Up Current
Gate Drive On, V12VGATE = 0V
●
–7
–10
–14
μA
0.5
1
2
mA
Current Limit
ΔVSENSE(CB)
Integrated Switch
RDS(ON)
Gate Drive
IGATE(DN)
External N-Channel Gate Pull-Down Current
Gate Drive Off
V12VGATE = 17V, V12VOUT = 12V
●
IGATE(FPD)
External N-Channel Gate Fast Pull-Down
Current
Fast Turn Off
V12VGATE = 17V, V12VOUT = 12V
●
90
160
250
mA
G12IMON
12IMON Pin Gain Ratio
ΔV12IMON/Δ(V12VIN – V12VSENSE)
(V12VIN – V12VSENSE) = (75mV, 25mV)
●
30
33
36
V/V
V12IMON
12IMON Pin Output Voltage
(V12VIN – V12VSENSE) = 75mV, VCC = 2.7V
●
2.25
2.475
2.7
V
●
82.5
Current Sense
ΔVSENSE(MAX)
12IMON Pin Maximum Input Sense Voltage
V12IMON(CLP)
12IMON Pin Clamp Voltage
(V12VIN – V12VSENSE) = 150mV, VCC = 2.7V
●
2.9
3.2
3.5
mV
V
R12IMON
12IMON Pin Output Resistance
(V12VIN – V12VSENSE) = 0V
●
115
165
215
kΩ
V12IMON(MIN)
12IMON Pin Minimum Output Voltage
(V12VIN – V12VSENSE) = 0V
●
0
130
mV
Comparator Inputs
VPG(TH)
Power Good Threshold Voltage
V12VOUT Falling
VAUXOUT Falling
●
●
10
2.8
10.3
2.885
10.6
2.97
V
V
VPG(HYST)
Power Good Hysteresis
V12VOUT
VAUXOUT
●
●
20
5
60
16
110
30
mV
mV
VTMR(TH)
TIMER Pin Threshold Voltage
VTIMER Rising
VTIMER 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
ITMR(UP)
TIMER Pull-Up Current
VTIMER = 1V, Initial Timing Cycle
VTIMER = 0V, In AUX Fault Mode
VTIMER = 0V, In 12V Fault Mode
●
●
●
–7
–7
–140
–10
–10
–200
–13
–13
–260
μA
μA
μA
ITMR(DN)
TIMER Pull-Down Current
VTIMER = 2V, No Faults
VTIMER = 2V, In Reset Mode
●
●
1.3
2
2
8
2.6
16
μA
mA
IOL = 3mA
●
0.15
0.4
V
(Note 5)
●
VCC – 1
VPU = 1.5V
●
–6
●
0.8
Open Drain Outputs
VOL
VOH
IPU
Output Low Voltage (⎯F⎯A⎯U⎯L⎯T, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D,
⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D)
⎯ U
⎯ L⎯ T⎯ , 1⎯ 2⎯ P
⎯ G
⎯ O
⎯ O
⎯ D
⎯ ,
Output High Voltage (F⎯ A
⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D)
⎯ U
⎯ L⎯ T⎯ ,
Output Pin Pull-Up Current (F⎯ A
⎯1⎯2⎯P⎯G⎯O⎯O⎯D, ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D)
V
–10
–14
μA
2
V
±1
μA
Logic Inputs
VIN(TH)
Logic Input Threshold (12ON, AUXON, ⎯E⎯N)
IIN(LEAK)
Input Leakage Current (12ON, AUXON)
RPU
⎯E⎯N Pin Pull-Up Resistance
●
VIN = VCC
●
60
100
140
kΩ
Other Pin Functions
I12VSENSE
12VSENSE Pin Input Current
V12VSENSE = 12V
●
10
50
100
μA
I12VOUT
12VOUT Pin Input Current
Gate Drive On, V12VOUT = 12V
●
20
50
100
μA
ROUT(DIS)
OUT Pin Discharge Resistance
12VOUT
AUXOUT
Gate Drive Off
V12VOUT = 6V
VAUXVOUT = 2V
●
●
400
375
800
750
1600
1500
Ω
Ω
12
Propagation Delays
tCB
AUX Circuit Breaker Trip Delay
After Power Up
●
25
50
μs
tPHL(SENSE)
Sense Voltage, (12VIN – 12VSENSE)
High to 12VGATE Low
ΔVSENSE = 300mV, C12VGATE = 10nF
ΔVSENSE = 100mV, C12VGATE = 10nF
●
●
0.5
5
1
12
μs
μs
tPHH(AUXON)
AUXON High to AUXOUT High
●
15
30
μs
tPHH(12ON)
12ON High to 12VGATE High
●
30
60
μs
tRST(ON)
Input Low (12ON, AUXON) to ⎯F⎯A⎯U⎯L⎯T High
●
20
40
μs
tRST(VCC)
VCC Low to ⎯F⎯A⎯U⎯L⎯T High
●
80
150
μs
tPLL(UVLO)
12VIN Low to 12VGATE Low
●
6
12
18
μs
AUXIN Low to ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D High
●
6
12
18
μs
tPHL(GATE)
⎯E⎯N High to 12VGATE Low
●
20
40
μs
tPLH(PG)
12VOUT Low to ⎯1⎯2⎯P⎯G⎯O⎯O⎯D High
●
20
40
μs
AUXOUT Low to ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D High
●
20
40
μs
●
2
6
μs
tP(12IMON)
Input Sense Voltage Step to 12IMON
Propagation Delay
ΔVSENSE = 100mV
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 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.
Note 3: An internal clamp limits the 12VGATE pin to a minimum of 4.5V
above 12VOUT. Driving this pin to voltages beyond the clamp may damage
the device.
Note 4: For the DFN package, the AUX switch on resistance, RDS(ON) limit
is guaranteed by correlation to wafer test measurements.
⎯ U
⎯ L⎯ T⎯ , 1⎯ 2⎯ P
⎯ G
⎯ O
⎯ O
⎯ D
⎯ and A
⎯ U
⎯ X
⎯ P
⎯ G
⎯ O
⎯ O
⎯ D
⎯ have an internal
Note 5: The output pins F⎯ A
pull-up to VCC of 10μA. However, an external pull-up resistor may be used
when faster rise time is required or for VOH voltages greater than VCC.
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.
ICC vs VCC
1.0
SUPPLY CURRENT (mA)
1.2
0.8
0.4
35
0.8
VCC
0.6
12VIN
12IMON GAIN RATIO (V/V)
1.6
ICC (mA)
12IMON Gain Ratio vs
Temperature
Supply Current vs Temperature
AUXIN
0.4
34
33
32
0.2
0
– 50
0
2.5
3.0
3.5
4.0 4.5
VCC (V)
5.0
5.5
6.0
– 25
0
25
50
TEMPERATURE (°C)
AUXOUT POWER-GOOD THRESHOLD (V)
12VOUT POWER-GOOD THRESHOLD (V)
RISING
FALLING
10.2
10.1
1
10.0
–50
0
0
20
40
60
80 100
SENSE VOLTAGE (mV)
120
140
–25
0
25
50
TEMPERATURE (°C)
Circuit Breaker Trip Voltage vs
Temperature
49
–25
0
25
50
TEMPERATURE (°C)
75
100
422312 G07
RISING
FALLING
2.86
2.84
–50
100
–25
0
25
50
TEMPERATURE (°C)
75
AUX Active Current Limit vs
Temperature
250
62
61
60
59
58
–50
100
422312 G06
AUX ACTIVE CURRENT LIMIT (mA)
ACTIVE CURRENT LIMIT SENSE VOLTAGE (mV)
50
100
2.88
Active Current Limit Sense
Voltage vs Temperature
51
48
–50
75
2.90
422312 G05
422312 G04
52
70
2.92
10.3
2
0
25
50
TEMPERATURE (°C)
AUXOUT Power-Good Threshold
vs Temperature
10.4
4
3
–25
422312 G03
12VOUT Power-Good Threshold vs
Temperature
12IMON Output Voltage vs Sense
Voltage
12IMON OUTPUT VOLTAGE (V)
31
–50
100
422312 G02
422312 G01
CIRCUIT BREAKER TRIP VOLTAGE (mV)
75
–25
0
25
50
TEMPERATURE (°C)
75
100
422312 G08
240
230
220
210
200
– 50
– 25
0
25
50
TEMPERATURE (°C)
75
100
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
0.3
0.2
GATE DRIVE (ΔVGATE) (V)
6
0.4
6.2
6.1
6.0
–25
0
25
50
TEMPERATURE (°C)
75
5.9
–50
100
4
3
2
0
–25
0
25
50
TEMPERATURE (°C)
422312 G10
75
0
100
–25
0
25
50
TEMPERATURE (°C)
75
25
20
15
– 50
100
0
25
50
TEMPERATURE (°C)
422312 G13
75
100
OUTPUT DISCHARGE RESISTANCE (Ω)
200
150
100
0
25
50
TEMPERATURE (°C)
75
0.1
50
100
422312 G16
100
150
200
250
SENSE VOLTAGE (mV)
Logic Input Threshold vs VCC
3.0
1000
12VOUT
800
AUXOUT
600
400
200
– 50
300
422312 G15
1200
–25
1
Output Discharge Resistance vs
Temperature
250
50
–50
10
422312 G14
Gate Fast Pull-Down Current vs
Temperature
–12
0.01
– 25
LOGIC INPUT THRESHOLD (V)
–9.0
–50
–10
100
ACTIVE CURRENT LIMIT DELAY (µs)
AUX CIRCUIT BREAKER TRIP DELAY (µs)
–9.5
–8
–6
IGATE (μA)
Active Current Limit Delay vs
Sense Voltage
30
–11.0
–10.0
–4
422312 G12
AUX Circuit Breaker Trip Delay vs
Temperature
–10.5
–2
422312 G11
Gate Pull-Up Current vs
Temperature
GATE PULL-UP CURRENT (µA)
5
1
0.1
–50
GATE FAST PULL-DOWN CURRENT (mA)
Gate Drive vs IGATE
7
6.3
GATE DRIVE (ΔVGATE) (V)
AUX SWITCH-ON RESISTANCE (Ω)
0.5
– 25
0
25
50
TEMPERATURE (°C)
75
100
422312 G17
2.5
HIGH
2.0
LOW
1.5
1.0
0.5
0
2.5
3.0
3.5
4.0 4.5
VCC (V)
5.0
5.5
6.0
422312 G18
422312f
6
LTC4223-1/LTC4223-2
PIN FUNCTIONS
12VSENSE (Pin 1): 12V Current Sense Input. Connect this
pin to the output of the current sense resistor. The electronic
circuit breaker trips if the voltage across the sense resistor
exceeds 50mV for more than a fault filter delay.
12VIN (Pin 2): 12V Supply Input. Undervoltage lockout
disables the 12V supply until the input at 12VIN exceeds
9.7V.
12IMON (Pin 3): 12V Current Sense Monitoring Output.
This pin monitors the sense voltage between 12VIN and
12VSENSE. The gain ratio between this pin’s voltage and
the sense voltage is 33.
12ON (Pin 4): 12V Supply On Control Digital Input. A rising edge turns on the external N-channel MOSFET if ⎯E⎯N
is pulled low and a falling edge turns it off. A high-to-low
transition on this pin will clear the 12V supply faults.
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.
VCC (Pin 6): Bias Supply Input. This pin provides power
to the device’s internal circuitry and operates from 2.7V to
6V. Undervoltage lockout circuit disables the device until
the input at VCC exceeds 2.45V. Bypass with 330nF.
AUXON (Pin 7): Auxiliary Supply On Control Digital Input.
A rising edge turns on the internal switch if ⎯E⎯N is pulled
low and a falling edge turns it off. A high-to-low transition on both this pin and 12ON pin will clear the auxiliary
supply faults.
GND (Pin 8): Device Ground.
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
limit during power-up and 6ms/μF duration for 12V current
limit before the external MOSFET is turned off.
⎯E⎯N (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.
⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D (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
resistor to VCC. It pulls low when the AUXOUT pin voltage
exceeds the power-good threshold of 2.901V.
AUXOUT (Pin 12): Auxiliary Supply Output. This pin is
the output from the internal switch connected between
AUXIN and AUXOUT pins. It signals ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D low when
it exceeds 2.901V. A 750Ω active pull-down discharges
AUXOUT to ground when the internal switch is turned
off.
⎯F⎯A⎯U⎯L⎯T (Pin 13): Auxiliary and 12V Supply Fault Status
Output. Open drain output that is normally pulled high by an
internal 10μA current source or an external pull-up resistor
to VCC. It pulls low when the circuit breaker is tripped due
to an overcurrent fault on auxiliary or 12V supply.
1⎯ ⎯2⎯P⎯G⎯O⎯O⎯D (Pin 14): 12V Supply Power Status Output.
Open drain output that is normally pulled high by an internal 10μA current source or an external pull-up resistor
to VCC. It pulls low when the 12VOUT pin voltage exceeds
the power-good threshold of 10.36V.
12VOUT (Pin 15): 12V Gate Drive Return and Power-Good
Input. Connect this pin to the source of the external Nchannel MOSFET for gate drive return. This pin signals
⎯1⎯2⎯P⎯G⎯O⎯O⎯D low when it exceeds 10.36V. When the external
MOSFET is turned off, 12VOUT is discharged to ground
through a 800Ω active pull-down.
12VGATE (Pin 16): Gate Drive for 12V Supply External NChannel MOSFET. An internal 10μA current source charges
the gate of the external N-channel MOSFET. An internal
clamp limits the gate voltage to 6.2V above 12VOUT. A
resistor and capacitor network from this pin to ground
sets the turn-on rate and compensates the active current
limit. During turn-off, a 1mA pull-down current discharges
12VGATE to ground. During short circuit or undervoltage
lockout, a 160mA pull-down current between 12VGATE and
12VOUT is activated.
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
RIN
5k
+
–
A1
12IMON
ROUT
165k
10μA
CHARGE
PUMP
12VGATE
60mV
12VIN
+–
12VSENSE
+
–
50mV
+–
+
–
6.2V
ACL
1mA
12VOUT
GATE
DRIVER
ECB
12V PWRGD
PG2
10.3V
VCC
12V SUPPLY
CONTROL
12ON
+
–
10μA
12V FET ON
12PGOOD
VCC
R2
EN
CARD PRESENCE
VCC
9.7V
+
–
2.45V
+
–
12VIN
VCC
VCC
VCC
AUXIN
200μA
10μA
2.5V
0.2V
TIMER
1.235V
+
–
+
–
+
–
UVLO3
10μA
FAULT
UVLO2
12V FAULT
SYSTEM
CONTROL
UVLO1
CP2
AUX FAULT
CP1
VCC
2μA
10μA
AUXPGOOD
AUXON
AUX FET ON
AUX SUPPLY
CONTROL
GND
AUX PWRGD
THERMAL
SHUTDOWN
PG1
+
–
2.885V
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 Advanced Mezzanine Card (AMC) or MicroTCA backplane,
allowing boards to be safely inserted and removed. It
controls the 12V main and 3.3V auxiliary power through an
external N-channel MOSFET and integrated pass transistor.
These two supplies can be turned on and off independently
by their respective ON control pins.
If either AUXON or 12ON is pulled high, an initial timing 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 ⎯E⎯N 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,
⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D pulls low indicating that power is good.
Otherwise the internal switch turns off and ⎯F⎯A⎯U⎯L⎯T pulls
low when TIMER reaches 1.235V.
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 capacitor. If the inrush current exceeds its limited current
value, an internal analog current limit (ACL) amplifier
servos the gate to force 60mV across the external sense
resistor connected between 12VIN and 12VSENSE pins.
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, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D
pulls low. Otherwise 12V shuts off and ⎯F⎯A⎯U⎯L⎯T pulls low
when TIMER reaches 1.235V.
If an overcurrent fault occurs on the auxiliary supply after
power-up, the current is limited to 240mA and after a 25μs
delay, the circuit breaker trips and ⎯F⎯A⎯U⎯L⎯T pulls low. Thermal 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/RSENSE. After a timing cycle delay set by 200μA
charging the TIMER capacitor, the circuit breaker trips
and ⎯F⎯A⎯U⎯L⎯T 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 information 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.
In the off condition, 12VOUT and AUXOUT are discharged
to ground by internal N-channel pull downs.
422312f
9
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
RS
6mΩ
CARRIER AMC MODULE AMC
CONNECTOR CONNECTOR
Q1
Si7336ADP
PWR
12V
BULK SUPPLY
BYPASS CAPACITOR
2
5
3.3V
R2
51Ω
BULK SUPPLY
BYPASS CAPACITOR
6
C2
330nF
7
PWR ENABLE
4
3.3V
R6*
10k
MP GOOD
3.3V
R5*
10k
R4*
10k
PWR GOOD
FAULT
1
16
12VSENSE 12VGATE
AUXIN
12VOUT
AUXOUT
MP ENABLE
3.3V
CG
RG 15nF
47Ω
R3
10Ω
12VIN
12V
7.4A
15
12
MP
10
PS1
3.3V
150mA
VCC
AUXON
12ON
LTC4223-1
11
14
13
AUXPGOOD
12PGOOD
FAULT
3.3V
INTELLIGENT
PLATFORM
MANAGEMENT
CONTROLLER
1μF
3
7
6
1
CLK
5
8
VREF
VCC
+IN
2
3
EN
12IMON
PS0
DOUT LTC1197L
CS
3.3V
–IN
GND
4
3
GND
8
TIMER
9
2.2k
CT
0.1μF
422312 F01
3.3V
PRESENCE
ENABLE
RESET
10k
*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 controller on the Carrier board sequences the turn-on of power
supplies and manages the fault and power-good reports
from the LTC4223.
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.
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 RS monitors the
12V load current for fault detection and current sensing
information. GATE capacitor CG provides gate slew rate
control to limit the inrush current. Resistor RG with CG
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
internal switches are allowed to turn on. First VCC and
the input supplies (12VIN, AUXIN) must exceed their
undervoltage lockout thresholds. Next TIMER must be
<0.2V and ⎯E⎯N must be pulled low.
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 ⎯E⎯N goes 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 capacitor 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
⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D pulls low.
EN
5V/DIV
TIMER
2V/DIV
AUXOUT
5V/DIV
12VOUT
5V/DIV
AUXPGOOD
5V/DIV
12PGOOD
5V/DIV
20ms/DIV
422312 F02
Figure 2. Normal Power-Up Sequence
Once AUXOUT signals power is good and the TIMER pin
returns to <0.2V, the external MOSFET is then allowed to
turn on by charging up the GATE with a 10μA current source
(Figure 2). The voltage at the GATE pin rises with a slope
equal to 10μA/CG and the supply inrush current flowing
into the load capacitor CL1 (see Figure 14) is limited to:
IINRUSH =
CL1
• 10µA
CG
The 12V output follows the GATE voltage when the MOSFET
turns on. If the voltage across the current sense resistor
RS becomes too high, the inrush current is limited by the
internal current limit circuitry. Once the output, 12VOUT
exceeds its power-good threshold, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D also 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
12ON Goes Low
No Effect
Turns Off
12ON High
AUXON High
⎯E⎯N Goes High
Turns Off
Turns Off
⎯E⎯N Low
UVLO on VCC
Turns Off
Turns Off
VCC > UVLO
UVLO on AUXIN
Turns Off
No Effect
AUXIN > UVLO
UVLO on 12VIN
No Effect
Turns Off
12VIN > UVLO
AUX Overcurrent
Fault
Turns Off
Turns Off
12V Overcurrent
Fault
No Effect
Turns Off
AUXON and 12ON Low,
⎯E⎯N High-to-Low, UVLO
on VCC
⎯ High-to12ON Low, E⎯ N
Low, UVLO on VCC
Thermal
Shutdown
Turns Off
Turns Off
AUXON and 12ON Low,
⎯E⎯N High-to-Low, UVLO
on VCC, Temperature <
120°C
422312f
11
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
Turn-Off Sequence
The switches can be turned off by various conditions and
this is summarized in Table 1.
When the 12ON pin goes low, the external switch is turned
off with the GATE pin pulled to ground by 1mA current
sink. The ⎯1⎯2⎯P⎯G⎯O⎯O⎯D pin pulls high indicating that power is
no longer good, while an internal N-channel transistor discharges the output to ground. Similarly, when the AUXON
pin goes low, the internal switch is turned off, ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D
pulls high while its output is discharged to ground through
an internal N-channel transistor. Figure 3 shows the two
supplies being turned off by ⎯E⎯N going high.
Card Presence Detect
In an AMC system, ⎯P⎯S⎯1 and ⎯P⎯S⎯0 signals are used to
detect the presence of a card upon insertion or removal.
Normally ⎯P⎯S⎯1 is connected to the ⎯E⎯N pin with a pull-up
resistor. If AUXON or 12ON is high when the ⎯E⎯N pin goes
low, indicating a board insertion, a timing cycle for contact
debouncing is initiated. Upon insertion, any bounces on the
⎯E⎯N pin will re-start the timing cycle. When TIMER finally
reaches its threshold during ramp up, the fault latches
will be cleared. If the ⎯E⎯N pin remains low at the end of the
timing cycle, the switches are allowed to turn on.
If the ⎯E⎯N pin is toggled from low to high, indicating board
removal, all the switches will be turned off after a 20μs delay.
Any latched faults will not be cleared. However, removing
the card could cause the ⎯E⎯N pin voltage to bounce, clearing
the fault latches undesirably. This is prevented by blanking
EN
5V/DIV
AUXOUT
5V/DIV
the bounces internally with a TIMER ramp up period given
by CT • 123[ms/μF] as shown in Figure 4.
Timer Functions
An external capacitor CT connected from the TIMER pin
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 CT with 10μA current to TIMER high
threshold (1.235V) and then ramping down with 2μA
current to below TIMER low threshold (0.2V). This gives
an average debounce cycle time of CT • 741[ms/μF].
After that, if any ON pin is pulled high and ⎯E⎯N pin is
low, the switches can be turned on.
2. Blanking contact bounce on the ⎯E⎯N pin that might
trigger unwanted fault clearing during card removal.
The blanking time is given by CT • 123[ms/μF].
3. Fault filtering during auxiliary supply power-up in analog
current limit. TIMER pulls up with 10μA and pulls down
with 2μA. The filter time is given by CT • 123[ms/μF].
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
CT • 6[ms/μF].
5. For cooling off during an auto-retry cycle after
an overcurrent fault on auxiliary or 12V supply
(LTC4223-2). The cool-off time is given by CT • 1482
[ms/μF] after an auxiliary supply fault and CT • 1358[ms/
μF] after a 12V supply fault.
EN
2V/DIV
12VOUT
5V/DIV
TIMER
1V/DIV
AUXPGOOD
5V/DIV
12PGOOD
5V/DIV
FAULT
2V/DIV
100ms/DIV
422312 F03
Figure 3. Normal Power-Down Sequence
5ms/DIV
422312 F04
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.
Whenever both AUXON and 12ON are pulled low, the device 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, the aux switch will shut off immediately and ⎯F⎯A⎯U⎯L⎯T
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.
Overcurrent Fault
The LTC4223 features an adjustable current limit with circuit
breaker function that protects the external MOSFET against
FAULT
5V/DIV
ILOAD
5A/DIV
12VOUT
5V/DIV
12VGATE
5V/DIV
0.1ms/DIV
422312 F05
Figure 5. Overcurrent Fault on 12V Output
short circuits or excessive load current on 12V supply. 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), the ACL amplifier regulates the MOSFET
to prevent any further increase in current. This overcurrent
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 ⎯F⎯A⎯U⎯L⎯T 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
pin threshold, is given by CT • 6[ms/μF].
After the MOSFET turns off, the TIMER pin capacitor discharges 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.
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, the GATE of the MOSFET recovers rapidly
due to the RG/CG compensation network and enters into
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 current 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 recommended if there is no input capacitance.
422312f
13
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
There are two different modes of fault time-out for the 3.3V
auxiliary supply: adjustable delay through TIMER capacitor
during power-up when ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D not asserted; fixed
25μs delay after power-up when ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D asserted
low. Under the situation whereby AUXON toggles low then
high for short duration after power-up while ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D
still pulling low due to output load capacitor, 25μs fault
time-out applies.
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 current. 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
⎯F⎯A⎯U⎯L⎯T pulls low. Thereafter, the TIMER is discharged by
a 2μA pull-down current. The fault filter delay is given by
CT • 123[ms/μF].
After a successful power-up cycle, the ACL amplifier protects the auxiliary supply from overcurrent by pulling down
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, ⎯F⎯A⎯U⎯L⎯T pulls low and the 12V external MOSFET is
also turned off by the 1mA GATE pull-down current.
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 ⎯F⎯A⎯U⎯L⎯T latches low when the
affected channels turn off, and ⎯F⎯A⎯U⎯L⎯T is cleared by toggling 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.
Undervoltage Fault
An undervoltage fault occurs if either AUXIN or 12VIN falls
below its undervoltage threshold for longer than 12μs. 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, VCC falls below its UVLO
threshold for more than 80μs, all supply switches are turned
off and the fault latches are cleared. Operation resumes
from a fresh start-up cycle when VCC is restored.
FAULT
5V/DIV
ΔVSENSE
200mV/DIV
12VOUT
5V/DIV
ILOAD
1A/DIV
12VGATE
5V/DIV
AUXOUT
5V/DIV
5μs/DIV
422312 F06
Figure 6. Short-Circuit Fault on 12V Output
5μs/DIV
422312 F07
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
and 12VOUT. The power-good status is reported via their
⎯ U
⎯ X
⎯ P
⎯ G
⎯ O
⎯ O
⎯ D
⎯ and 1⎯ 2⎯ P
⎯ G
⎯ O
⎯ O
⎯ D
⎯ .
respective open drain outputs, A
Several conditions must be met before the power-good
outputs assert low.
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 ⎯F⎯A⎯U⎯L⎯T 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, ⎯F⎯A⎯U⎯L⎯T 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.
1. The monitored output should be above its powergood threshold and hysteresis.
2. The input supply is above undervoltage lockout.
3. ⎯E⎯N 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.
Resetting Faults (LTC4223-1)
Any supply faults tripping the circuit breaker are latched
and ⎯F⎯A⎯U⎯L⎯T asserts low. For the latched-off version
(LTC4223-1), to reset a fault latch due to overcurrent or
thermal shutdown on auxiliary supply, pull both AUXON and
12ON pins low together for at least 100μs, after which the
⎯FA
⎯ U
⎯ L⎯ T⎯ will go high. Toggling both the ON pins high together
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.
To reset a fault on the 12V supply and re-start the output,
toggle only the 12ON pin low and then high again. Toggling the ⎯E⎯N pin high then low again or bringing the bias
input, VCC below its UVLO threshold for more than 100μs
will initiate the debounce timing cycle and reset all fault
latches before power-up. Bringing AUXIN or 12VIN below its
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.
In Figure 9, a fault latches off the 12V supply at time point
1; a cool-off cycle begins by discharging the TIMER capacitor with 2μA current from 1.235V to 0.2V threshold.
At time point 2 a new debounce timing cycle is initiated
where the fault latch is cleared, and ⎯F⎯A⎯U⎯L⎯T pulls high when
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, ⎯F⎯A⎯U⎯L⎯T 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.
The auto-retry duty cycle is given by:
DutyCycle =
tFILTER • 100%
tCOOL + tDEBOUNCE + tFILTER
For example, if TIMER capacitor, CT = 0.1μF, the auto-retry
duty cycle for auxiliary and 12V supply is 6.5% and 0.5%
respectively.
422312f
15
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
GATE Pin Voltage
The gate drive at 12VGATE is compatible with any logic
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 RG and
gate slew rate control capacitor CG stabilizes the internal
active current limit circuit. The value of CG is selected based
on the inrush current allowed. The suggested value for
RG is 47Ω. The value of CG should be ≤330nF and RG is
between 10Ω and 100Ω for optimum performance.
High Side Current Sense
The 12V load current is monitored via the voltage across an
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
The internal circuitry of the LTC4223 is powered from the
VCC pin. Bypass VCC with at least 330nF to ground. If VCC
is derived from the same supply as is AUXIN, include a
decoupling resistor as shown in Figure 11. This RC network allows the VCC pin to ride out supply glitches caused
by short circuits on the auxiliary output or on adjacent
boards, thus preventing an undervoltage lockout condition on VCC. Since the absolute maximum rating for VCC
is 7V as compared to 10V for AUXIN, select R2 and C2 to
keep the peak voltage seen by VCC below 7V during any
voltage spikes.
START AUX INTERNAL GATE RAMP WHEN STARTUP CONDITIONS ARE MET
AUX OUTPUT IN CURRENT LIMIT
START OF
DEBOUNCE CYCLE
2
VCC Supply Filtering
END OF DEBOUNCE CYCLE
FAULT PULLS LOW DUE TO AUX
OVERCURRENT FAULT AFTER POWER UP
START OF COOL-OFF CYCLE
1
then be fed into an LTC1197L ADC as shown in Figure 10
for data conversion. The current sense information can be
used by the system controller to manage the power budget
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.
3
FAULT PULLS LOW AND RESTART OF
COOL-OFF CYCLE DURING POWER UP
RESET FAULT HIGH
4
5 6 7
8
RESTART OF
DEBOUNCE CYCLE
9
10
FAULT
10μA
VTMR
2μA
10μA
VTMR
2μA
10μA
VTMR
2μA
10μA
VTMR
2μA
10μA
TIMER
FILTER DELAY
COOL-OFF CYCLE
DEBOUNCE CYCLE
COOL-OFF CYCLE
AUX INTERNAL GATE REGULATES
IAUXOUT
12VOUT
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
DEBOUNCE CYCLE
1
2
FAULT PULLS LOW AND
RESTART OF COOL-OFF CYCLE
RESET FAULT HIGH
3
4 5
6
7
RESTART OF
DEBOUNCE CYCLE
8
FAULT
200μA
VTMR
2μA
10μA
VTMR
2μA
200μA
VTMR
2μA
10μA
TIMER
FILTER DELAY
COOL-OFF CYCLE
COOL-OFF CYCLE
DEBOUNCE CYCLE
12VGATE REGULATES
12VGATE
60mV
60mV
12VIN - 12VSENSE
12VOUT
422312 F08
Figure 9. Auto-Retry after 12V Overcurrent Fault
VSENSE
– +
Q1
12V
12VSENSE
12VIN
RIN
5k
LOAD
12VGATE
–
The supply inputs, AUXIN and 12VIN are fed directly from
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
ratings for AUXIN and 12VIN. To minimize such spikes,
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.
ILOAD
+
Supply Transient Protection
1μF
12IMON
ROUT
165k
VOUT
VREF
+IN
VCC
LTC1197L
CLK
DOUT
TO SYSTEM
CONTROLLER
CS
–IN
LTC4223
3.3V
GND
422312 F10
VOUT =
ROUT
RIN
• VSENSE = 33 • VSENSE
Figure 10. High Side Current Sense with LTC1197L ADC
422312f
17
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
CURRENT FLOW
TO LOAD
R2
51Ω
AUXIN
C2
330nF
SENSE
RESISTOR
POWER PAK
SO-8
CURRENT FLOW
TO LOAD
VCC
12VIN
W
12VOUT
W
422312 F11
Figure 11. RC Network for VCC Filtering
TRACK WIDTH W:
0.03" PER AMPERE
ON 1OZ Cu FOIL
R3
12VGATE
•
RG
VIA TO
GND PLANE
CG
PCB Layout Considerations
For proper operation of the LTC4223’s circuit breaker,
Kelvin-connection to the sense resistor is strongly recommended. 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.
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 current applications.
In most applications, it will be necessary to use platedthrough 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.
It is important to place the VCC bypass capacitor C2 as
close as possible between VCC and GND. The transient
voltage suppressors Z1 and Z2 are also placed between
the supply inputs and ground using short wide traces.
Z1
1
C1
2
16
LTC4223CGN*
15
8
CURRENT FLOW
TO SOURCE
VIA TO
GND PLANE
•
GND
W
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
The first step is to select the appropriate value of RSENSE
for the 12V supply. Calculating RSENSE value is based on
the maximum load current and the lower limit for the
circuit breaker threshold, ΔVSENSE(CB)(MIN).
RSENSE =
ΔVSENSE(CB)(MIN)
ILOAD(MAX )
=
47.5mV
= 6mΩ
7.4A
A
If a 1% tolerance is assumed for the 6mΩ sense resistor,
the minimum and maximum circuit breaker trip current is
calculated as follows:
Table 2. AMC Power Supply Requirements
SUPPLY VOLTAGE
MAXIMUM LOAD
CURRENT
MAXIMUM LOAD
CAPACITANCE
12V
7.4A
800μF
3.3VAUX
150mA
150μF
Table 3. MicroTCA Power Supply Requirements
SUPPLY VOLTAGE
MAXIMUM LOAD
CURRENT
MAXIMUM LOAD
CAPACITANCE
12V
7.6A
1600μF
3.3VAUX
150mA
150μF
Design Example
As a design example, consider the AMC Hot Swap application shown earlier in Figure 1 with the power supply
requirements given in Table 2.
R1
422312f
18
LTC4223-1/LTC4223-2
APPLICATIONS INFORMATION
ITRIP(MIN) =
ITRIP(MAX ) =
ΔVSENSE(CB)(MIN)
RSENSE(MAX )
=
ΔVSENSE(CB)(MAX )
RSENSE(MIN)
47.5m
mV
= 7.8 A
6.06mΩ
=
52.5mV
= 8.8 A
5.94mΩ
For proper operation, ITRIP(MIN) must exceed the maximum
load current with margin, so RSENSE = 6mΩ should suffice
for the 12V supply.
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 worstcase start-up time is calculated using the minimum active
current limit value for the auxiliary supply.
tSTUP( AUX ) =
CL2 • 3.3VAUX 150µF • 3.3V
= 3ms
=
165mA
IAUX( ACL)(MIN)
For a start-up time of 3ms with a 2x safety margin, the
TIMER capacitance is calculated as:
CT =
2 • tSTUP( AUX )
123[ms / µF ]
=
6ms
≅ 0.05µF
123[ms / µF ]
Considering the tolerances for the TIMER charging rate
and capacitance, a value of 0.1μF (±10%) for CT should
suffice.
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 outputshort condition. The fault filter delay for the 12V supply
is given by 0.1μF • 6[ms/μF] = 600μs versus 12ms for
the auxiliary supply.
The next step is to verify that the thermal ratings of the
selected external MOSFET for the 12V supply aren’t exceeded during power-up or an output-short.
Assuming the MOSFET dissipates power only due to inrush
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:
CL1 • 12VOUT2
PAVG =
2 • tCHARGE
The inrush current can be limited by using the GATE capacitance (CG) so that the power dissipated in the MOSFET
is well within its safe operating area (SOA). For IGATE =
10μA and CL1 = 800μF, we choose CG = 15nF to set the
inrush current to 0.5A.
IINRUSH =
CL1 • IGATE
= 0.5A
CG
tCHARGE =
CL1 • 12VOUT
= 19ms
IINRUSH
This results in PAVG = 3W and the MOSFET selected must
be able to tolerate 3W for 19ms. The increase in steady
state junction temperature due to power dissipated in
the MOSFET is ΔT = PAVG • Zth where Zth is the thermal
impedance.
Under this condition, the Si7336ADP datasheet’s Transient Thermal Impedance plot indicates that the junction
temperature will increase by 2.4°C using ZthJC = 0.8°C/W
(single pulse).
The duration and magnitude of the power pulse that results
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
• 6[ms/μF] = 600μs for CT = 0.1μF. The maximum shortcircuit current is calculated using the maximum analog
current limit threshold, ΔVSENSE(ACL)(MAX) and minimum
RSENSE value.
ISHORT(MAX ) =
ΔVSENSE( ACL)(MAX )
RSENSE(MIN)
=
mV
66m
= 11A
5.94mΩ
So the maximum power dissipated in the MOSFET is 11A •
12V or 132W for 600μs. The Si7336ADP datasheet’s Transient Thermal Impedance plot indicates that the worse-case
increase in junction temperature during the short-circuit
condition is 13.2°C using ZthJC = 0.1°C/W (single pulse).
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
RS
4mΩ
Q1
Si7336ADP
12V
10A
12V
Z1
SMAJ13A
R1
10Ω
R3
10Ω
C1
100nF
12VIN
+
CG
RG 15nF
47Ω
CL1
1000μF
12VSENSE 12VGATE
12VOUT
5V
AUXIN
R6
Z2
10k SMAJ7.0A
R7
2.7Ω
C3
100nF
5VAUX
150mA
AUXOUT
R2
51Ω
C2
330nF
+
PWRFLT
FAULT
PWREN
AUXON
5V
R8
10k
BD_SEL
CL2
150μF
VCC
LTC4223-1
AUXPGOOD
12ON
5V
R4
10k
R5
10k
12PGOOD
EN
5V
1μF
GND
12IMON
+IN
VREF
VCC
LTC1197
TIMER
GND
CT
0.1μF
CLK
DOUT
TO SYSTEM
CONTROLLER
CS
–IN
GND
422312 TA02
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
RS
4mΩ
Q1
Si7336ADP
12V
10A
12V
R1
10Ω
Z1
SMAJ13A
R3
10Ω
C1
100nF
12VIN
+
CG
RG 15nF
47Ω
CL1
1000μF
12VSENSE 12VGATE
12VOUT
3.3V
AUXIN
R7
2.7Ω
C3
100nF
Z2
SMAJ5.0A
3.3VAUX
150mA
AUXOUT
R2
51Ω
C2
330nF
PWREN
+
VCC
CL2
150μF
12ON
R8
10k
3.3V
R9
10k
3.3V
3.3V
R5
10k
3.3V
Q2
2N7002K
R4
10k
LTC4223-1
AUXPGOOD
AUXON
12PGOOD
R6
10k
3.3V
PWRFLT
FAULT
BD_SEL
EN
1μF
GND
12IMON
+IN
VREF
VCC
LTC1197L
TIMER
GND
CT
0.1μF
–IN
CLK
DOUT
TO SYSTEM
CONTROLLER
CS
GND
422312 TA03
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
16 15 14 13 12 11 10 9
.254 MIN
.009
(0.229)
REF
.150 – .165
.229 – .244
(5.817 – 6.198)
.0165 ± .0015
.150 – .157**
(3.810 – 3.988)
.0250 BSC
RECOMMENDED SOLDER PAD LAYOUT
1
.015 ± .004
× 45°
(0.38 ± 0.10)
.007 – .0098
(0.178 – 0.249)
.0532 – .0688
(1.35 – 1.75)
2 3
4
5 6
7
8
.004 – .0098
(0.102 – 0.249)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. CONTROLLING DIMENSION: INCHES
INCHES
2. DIMENSIONS ARE IN
(MILLIMETERS)
.008 – .012
(0.203 – 0.305)
TYP
.0250
(0.635)
BSC
GN16 (SSOP) 0204
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
TYP
5.00 ±0.10
(2 SIDES)
R = 0.20
TYP
4.00 ±0.10
(2 SIDES)
9
0.40 ± 0.10
16
2.44 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PIN 1
NOTCH
(DHD16) DFN 0504
8
0.200 REF
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.00 – 0.05
4.34 ±0.10
(2 SIDES)
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 representation 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
RS
2.5m
Q1
HAT2160H
12V
18A
12V
R1
10Ω
Z1
SMAJ13A
R3
10Ω
C1
100nF
12VIN
+
CG
RG 15nF
47Ω
CL1
1000μF
12VSENSE 12VGATE
12VOUT
3.3V
AUXIN
Z2
SMAJ5.0A
R7
2.7Ω
C3
100nF
3.3VAUX
150mA
AUXOUT
R2
51Ω
+
CL2
150μF
VCC
C2
330nF
3.3V
R9
10k
AUXON
R8
10k
BD_SEL
R4
10k
LTC4223-1
R5
10k
R6
10k
AUXPGOOD
12PGOOD
FAULT
12ON
EN
3..3V
1μF
12IMON
+IN
VREF
VCC
LTC1197L
TIMER
GND
CLK
DOUT
–IN
TO
CONTROLLER
CS
GND
CT
0.1μF
422312 TA04
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1421
Dual Channel, Hot Swap Controller
Operates from 3V to 12V, Supports –12V, SSOP-24
LTC1645
Dual Channel, Hot Swap Controller
Operates from 3V to 12V, Power Sequencing, SO-8 or SO14
LTC1647-1/LTC1647-2/ Dual Channel, Hot Swap Controller
LTC1647-3
Operates from 2.7V to 16.5V, SO-8 or SSOP-16
LTC4210
Single Channel, Hot Swap Controller
Operates from 2.7V to 16.5V, Active Current Limiting, SOT23-6
LTC4211
Single Channel, Hot Swap Controller
Operates from 2.7V to 16.5V, Multifunction Current Control, MSOP-8 or MSOP-10
LTC4215
Single Channel, Hot Swap Controller
Operates from 2.9V to 15V, I2C Compatible Monitoring, SSOP-16 or QFN-24
(4mm × 5mm)
LTC4216
Single Channel, Hot Swap Controller
Operates from 0V to 6V, MSOP-10 or DFN-12 (4mm × 3mm)
LTC4221
Dual Channel, Hot Swap Controller
Operates from 1V to 13.5V, Multifunction Current Control, SSOP-16
LTC4245
Multiple Channel, Hot Swap Controller
3.3V, 5V, ±12V Supplies, I2C 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
24 Linear Technology Corporation
LT 0807 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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© LINEAR TECHNOLOGY CORPORATION 2007