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LTC4223IDHD-2#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24
LTC4223-1/LTC4223-2
10
422312f
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.
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.
APPLICATIONS INFORMATION
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
S
monitors the
12V load current for fault detection and current sensing
information. GATE capacitor C
G
provides gate slew rate
control to limit the inrush current. Resistor R
G
with C
G
compensates the current control loop while R3 prevents
parasitic oscillations in Q1.
422312 F01
12V
OUT
12V
SENSE
12V
GATE
12V
IN
V
CC
AUXIN
AUXOUT
EN
AUXON
12ON
AUXPGOOD
12PGOOD
FAULT
12V
5
21 16
15
12
10
89
6
7
4
11
13
3
58
2
3
4
7
6
1
14
3.3V
R
S
6mΩ
Q1
Si7336ADP
PWR
MP
PS1
PS0
CARRIER AMC
CONNECTOR
MODULE AMC
CONNECTOR
TIMER
LTC4223-1
GND
12V
7.4A
3.3V
150mA
R3
10Ω
R2
51Ω
MP ENABLE
PWR ENABLE
MP GOOD
PWR GOOD
FAULT
C2
330nF
BULK SUPPLY
BYPASS CAPACITOR
C
T
0.1μF
1μF
R
G
47Ω
C
G
15nF
3.3V
3.3V
INTELLIGENT
PLATFORM
MANAGEMENT
CONTROLLER
ENABLE
PRESENCE
RESET
12IMON
R4*
10k
2.2k
*OPTIONAL
3.3V
10k
R5*
10k
R6*
10k
3.3V 3.3V 3.3V
BULK SUPPLY
BYPASS CAPACITOR
LTC1197L
V
REF
CLK
D
OUT
CS
+IN
–IN
V
CC
GND
3
Figure 1. Advanced Mezzanine Card/MicroTCA Application
LTC4223-1/LTC4223-2
11
422312f
APPLICATIONS INFORMATION
Several conditions must be met before the external and
internal switches are allowed to turn on. First V
CC
and
the input supplies (12V
IN
, 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 fi rst 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 fi rst if
both ON pins are high and start-up conditions met. The
output is current limited at 240mA by its internal ACL
amplifi er 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
⎯
A
⎯
U
⎯
X
⎯
P
⎯
G
⎯
O
⎯
O
⎯
D pulls low.
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/C
G
and the supply inrush current fl owing
into the load capacitor C
L1
(see Figure 14) is limited to:
I
C
C
µA
INRUSH
L
G
=
1
10•
The 12V output follows the GATE voltage when the MOSFET
turns on. If the voltage across the current sense resistor
R
S
becomes too high, the inrush current is limited by the
internal current limit circuitry. Once the output, 12V
OUT
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 fi rst. After that, if AUXON
pulls high, the internal switch turns on only after the 12V
output signals power is good and TIMER <0.2V.
Figure 2. Normal Power-Up Sequence
Table 1. 12V and Auxiliary Supply Turn-Off Conditions
CONDITION RESULT CLEARED BY
AUX 12V
AUXON Goes
Low
Turns Off No Effect AUXON High
12ON Goes Low No Effect Turns Off 12ON High
⎯
E
⎯
N Goes High Turns Off Turns Off
⎯
E
⎯
N Low
UVLO on V
CC
Turns Off Turns Off V
CC
> UVLO
UVLO on AUXIN Turns Off No Effect AUXIN > UVLO
UVLO on 12V
IN
No Effect Turns Off 12V
IN
> UVLO
AUX Overcurrent
Fault
Turns Off Turns Off AUXON and 12ON Low,
⎯
E
⎯
N High-to-Low, UVLO
on V
CC
12V Overcurrent
Fault
No Effect Turns Off 12ON Low,
⎯
E
⎯
N High-to-
Low, UVLO on V
CC
Thermal
Shutdown
Turns Off Turns Off AUXON and 12ON Low,
⎯
E
⎯
N High-to-Low, UVLO
on V
CC
, Temperature <
120°C
20ms/DIV
12PGOOD
5V/DIV
EN
5V/DIV
AUXOUT
5V/DIV
TIMER
2V/DIV
12V
OUT
5V/DIV
AUXPGOOD
5V/DIV
422312 F02
LTC4223-1/LTC4223-2
12
422312f
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 dis-
charges 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 fi nally
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
the bounces internally with a TIMER ramp up period given
by C
T
• 123[ms/μF] as shown in Figure 4.
Timer Functions
An external capacitor C
T
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 C
T
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 C
T
• 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 C
T
• 123[ms/μF].
3. Fault fi ltering during auxiliary supply power-up in analog
current limit. TIMER pulls up with 10μA and pulls down
with 2μA. The fi lter time is given by C
T
• 123[ms/μF].
4. 12V supply fault fi ltering during and after power-up
in analog current limit. TIMER pulls up with 200μA
and pulls down with 2μA. The fi lter time is given by
C
T
• 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 C
T
• 1482
[ms/μF] after an auxiliary supply fault and C
T
• 1358[ms/
μF] after a 12V supply fault.
Figure 3. Normal Power-Down Sequence Figure 4. Debouncing by TIMER during Card Removal
100ms/DIV
12PGOOD
5V/DIV
EN
5V/DIV
AUXOUT
5V/DIV
12V
OUT
5V/DIV
AUXPGOOD
5V/DIV
422312 F03
5ms/DIV
FAULT
2V/DIV
EN
2V/DIV
TIMER
1V/DIV
422312 F04
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24

LTC4223IDHD-2#TRPBF

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Buy LTC4223IDHD-2#TRPBF
Manufacturer:
Analog Devices Inc.
Description:
Hot Swap Voltage Controllers 2x S Hot Swap Cntr for Advanced Mezzanin
Lifecycle:
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