DEMO CIRCUIT 1355
LTC4221
QUICK START GUIDE
LTC4221 Dual Hot Swap Controller/Power Se-
quencer w/ Dual Speed, Dual Level Fault Pro-
tection
DESCRIPTION
Demonstration circuit DC1355 is a dual hot swap
circuit featuring the LTC4221 Dual Hot Swap
Controller / Power Sequencer with Dual Speed,
Dual Level Fault Protection
DC1355 facilitates evaluation of the LTC4221
performance characteristics including supply
ramp-up transients, steady state operation, and
overcurrent fault conditions. On board LEDs in-
dicate input supply presence, output state, and
power good conditions.
The first LTC4221 channel controls a rail from
2.7V to 13.5V and the second one from 1V to
13.5V with condition that V
CC2
≤
V
CC1.
DC1355 is assembled to operate with a +12V rail
with 6A maximum current and a +3.3V rail with
3.0A maximum current.
Design files for this circuit board are avail-
able. Call the LTC factory.
, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are
registered trademarks of Linear Technology Corporation. Adaptive Power, C-
Load, DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, µModule,
Micropower SwitcherCAD, Multimode Dimming, No Latency , No Latency
Delta-Sigma, No R
SENSE
, Operational Filter, PanelProtect, PowerPath, Power-
SOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast
and VLDO are trademarks of Linear Technology Corporation. Other product
names may be trademarks of the companies that manufacture the products.
PERFORMANCE SUMMARY
SYMBOL
V
CC1
V
CC2
V
CC1(UVL)
V
CC2(UVL)
V
SENSE(FC)
V
SENSE(SC)
V
SENSE(ACL)
I
GATE(UP)
I
GATE(DN)
I
GATE(FSTDN)
∆
VGATE
Specifications are at TA = 25°
C
CONDITIONS
V
CC2
≤
V
CC1
V
CC1
Rising
V
CC2
Rising
Channeln Fast Comparator Threshold
Channeln Slow Comparator Threshold
V
FBn
=0V
V
FBn
=0.65V
V
ON1
= V
ON1
=2V,
V
GATEn
=0V
V
ON1
= V
ON1
=0.6V, V
GATEn
=3.3V
UNLO with V
GATEn
=3.3V or
FAULT
latched with
V
GATEn
=3.3V
VGATEn
-V
CC1
for V
CC1
=2.7V, V
CC2
=1V
VGATEn
-V
CC1
for V
CC1
=3.3V, V
CC2
=2.5V
MIN
2.7
1.0
2.1
0.65
85
20.5
4
20.5
-7
75
PARAMETER
Supply Voltage Channel 1
Supply Voltage Channel 2
Undervoltage Lockout for Chan-
nel 1
Undervoltage Lockout for Chan-
nel 2
SENSEn Threshold Voltage
SENSEn Threshold Voltage
SENSEn Voltage at Active Cur-
rent Limit
GATEn Output Current
GATEn Output Current
GATEn Output Current
External N-Channel Gate Drive
TYP
2.5
0.8
100
25
9
25
-9.5
100
16
MAX
13.5
13.5
2.675
0.975
115
29.5
16
29.5
-120
125
UNITS
V
V
V
V
mV
mV
mV
mV
uA
uA
mA
V
V
4.5
5
13
16
1
LTC4221
PERFORMANCE SUMMARY
SYMBOL
PARAMETER
Specifications are at TA = 25°
C
CONDITIONS
VGATEn
-V
CC1
for V
CC1
=5.0V, V
CC2
=3.3V
VGATEn
-V
CC1
for V
CC1
=12V, V
CC2
=12V
High to Low , GATEn Turns Off by 100uA Pull-
Down
V
ON1
Falling
MIN
8
7
TYP
MAX
16
18
0.846
UNITS
V
V
V
mV
V
mV
V
V
µA
µA
V
mV
µA
µA
mA
V
V
V
ON(OFF)
∆V
ON(OFFHYST)
ONn Off Threshold
ONn Off Threshold Hysteresis
ON1 Reset Threshold
ON1 Reset Threshold Hysteresis
FBn Undervoltage Threshold
FBn Overvoltage Threshold
FILTER Pull-Up Current
FILTER Pull-Down Current
FILTER Threshold
FILTER Threshold Hysteresis
TIMER Pull-Up Current 1
TIMER Pull-Up Current 2
TIMER Pull-Down Current
TIMER High Threshold
TIMER Low Threshold
0.796 0.821
30
0.4
25
V
ON(RESET)
∆
V
ON(RESETHYST)
V
FB(UV)
V
FB(OV)
I
FILTER (UP)
I
FILTER (DN)
V
FILTER(TH)
∆V
FILTER(HYST)
I
TMR(UP1)
I
TMR(UP2)
I
TMR(FSTDN)
V
TMR(H)
V
TMR(L)
0.375
0.425
FBn Falling
FBn Rising
During Current Fault Condition
During Normal Cycle
Latched Off Threshold, FILTER Rising
Initial Timing Cycle
Start-Up cycle
V
TMR
=1.5V, End of Initial Timing Cycle
TMER Rising
TIMER Falling
0.605 0.617
0.805 0.822
-80
-105
1.15
1.8
1.18 1.24
105
-1.2
1.9
-15
-20
9
1.172 1.234
0.1
0.4
0.629
0.838
-132
2.45
1.30
-2.6
-25
1.27
0.5
OPERATING PRINCIPLES
The LTC4221 controls two rails with external N-
channel MOSFETs.
Two independent ONn comparators allow ramping
rails up and down separately or simultaneously.
Each channel has two current limit comparators
that provide dual level and dual speed overcurrent
circuit breaker protection after the start-up period.
If any current sense voltage exceeds 100mV for
1us or 25mV for the timeout delay, then the
FAULT
latch is set and both GATE pins are pulled low.
The LTC4221 is suited for low voltage applications
such as a hot board insertion and removal and has
a rich set of features to support hot swap applica-
tion including:
Overvoltage protection
FAULT
latch setting and resetting and fault
state indication
Adjustable Inrush Current Control
Adjustable duration for Current Limit be-
fore switch is turned off
Power-good signaling
QUICK START PROCEDURE
Demonstration circuit 1355 is easy to set up to
evaluate the performance of the LTC4221. Refer to
Figure 1. for proper measurement equipment
setup and follow the procedure below:
1.
Place jumpers in the initial position:
JP1
(ON2) Off
JP2
(ON1) Off
2
LTC4221
JP3
(AUTO RETRY) NO
JP4
(FAULT SIGNAL) NO
2.
Adjust +12V supply output voltage between
10.6V and 13.0V. Connect +12V power sup-
ply to the +12V INPUT and GND turrets and
turn it on. Green LED +12V INPUT (D2)
should light.
3.
Adjust +3.3V supply output voltage between
2.89V and 3.67V. Connect +3.3V power sup-
ply to the +3.3V INPUT and GND turrets and
turn it on. Green LED +3.3V INPUT (D6)
should light.
4.
Place jumpers JP1 and JP2 in the ON posi-
tions. Two amber LEDs, PWRGD1 and
PWRGD2, should light.
5.
Connect electronic or resistive loads to the
+12V and +3.3V output turrets.
6.
Activate both loads with lower than 1A for
each rail. Increase load current, use a current
probe or meter and verify circuit breaker
threshold level. For the +12V circuit it should
be between 5A and 7.5A, for the +3.3V circuit,
between 2.5A and 3.8A. After an overcurrent
fault associated power good LED D3 or D4
will be off. To reset
FAULT
latch turn +12V sup-
ply off and then on.
7.
Remove the loads. Turn both +12V and
+3.3V rails off by placing JP1 and JP2 in the
OFF position. Load the +12V output with a
1500uF capacitor and return jumper headers
of the JP1 and JP2 to the ON position. Turn
the +3.3V rail on first and then the +12V rail.
Both rails should be on.
8.
Repeat step 7 with a 6000uF capacitor. In
this case only the +3.3V rail comes up, but
+12V fails.
9.
Place the JP3 (AUTO RETRY) in the YES
position. Use a current probe to display the
+12V rail current and scope probes to display
+12V and +3.3V output voltages. Activate
both channels and overload +12V rail. The
transient should be similar to that shown in
Figure 2.
10.
Place JP4 (FAULT SIGNAL) in the YES posi-
tion and control
FAULT
pin signal on the
FAULT
turret. Activate both channels with no load.
Slowly increase the +12V supply output (not
higher than 16V). Overvoltage protection
should disable both channels when the output
voltage is in a range from 13.6V to 15.0V and
FAULT
turret signal drops to low.
11.
Activate both channels with no load. Slowly
decrease +12V supply output. The PWRGD1
LED goes off when output is in the range of
10.4V to 11.3V.
12.
Place JP4 (FAULT SIGNAL) in the YES po-
sition and control
FAULT
pin signal on the
FAULT
turret. Activate both channels with no
load. Slowly increase +3.3V supply output
(not higher than 16V). Overvoltage protection
should disable both channels, when the out-
put voltage is in the range of 3.7V to 3.9V and
FAULT
turret signal drops to low.
13.
Activate both channels with no load. Slowly
decrease +3.3V supply output. The PWRGD2
LED goes off when output is in a range from
2.76V to 3.0V.
3
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