Datasheet

8
LTC4221
4221fa
UU
U
PI FU CTIO S
ON1 (Pin 1): System/Channel 1 On Input. Both GATE pins
are pulled low by internal 100μA pull-downs and the
FAULT latch is reset when V
ON1
< 0.4V. When 0.425V <
V
ON1
< 0.821V, the FAULT latch is released from reset.
When V
ON1
> 0.851V, GATE1 ramps up after an initial
timing cycle.
V
CC1
(Pin 2): Channel 1 Positive Supply Input. It powers
all the internal circuitry. V
CC1
can range from 2.7V to 13.5V
for normal operation but it must be ≥V
CC2
. An undervolt-
age lockout circuit disables both channels whenever the
voltage at V
CC1
is less than 2.5V.
SENSE1 (Pin 3): Channel 1 Current Sense Input. A sense
resistor R
SENSE1
is placed in the supply path between V
CC1
and SENSE1 to sense channel 1 load current. If V
RSENSE1
exceeds 100mV for more than 1μs or 25mV for an adjust-
able time (set by the C
FILTER
), the FAULT latch is set and
fast pull-down circuits are triggered to discharge both
GATEs low. During the start-up cycle, GATE1 ramp-up is
controlled to servo V
RSENSE1
≤ V
SENSE(ACL)
. V
SENSE(ACL)
increases from 9mV to 25mV as V
FB1
ramps from 0V to
0.5V. To disable the current limit and circuit breaker
function for channel 1, tie SENSE1 to V
CC1
.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
V
PWRGD(OL)
/V
FAULT(OL)
vs Temperature
tp
(SC-FAULT)
vs Temperature
TEMPERATURE (°C)
–50
V
OL
(V)
0.500
0.450
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0
0
50
75
4221 G37
–25
25
100
125
V
CC1
= 2.7V
V
CC1
= 5V
V
CC1
= 13.5V
V
CC2
= 1V, I
PWRGD
/I
FAULT
= 1.6mA
tp
(FC-GATE)
vs Temperature
TEMPERATURE (°C)
–50
tp
(SC-FAULT)
(μS)
16
17
18
25 75
4221 G38
15
14
–25 0
50 100 125
13
12
V
CC1
= 2.7V
V
CC1
= 5V
V
CC1
= 13.5V
V
CC2
= 1V
TIMER = 0.5V
TEMPERATURE (°C)
–50
tp
(FC-GATE)
(μS)
1.4
1.6
1.8
25 75
4221 G39
1.2
1.0
–25 0
50 100 125
0.8
0.6
V
CC1
= 2.7V
V
CC1
= 5V
V
CC1
= 13.5V
V
CC2
= 1V
TIMER = 0.5V
I
FAULT(UP)
vs Temperature
V
FAULT(TH)
vs V
CC1
V
FAULT(TH)
vs Temperature
TEMPERATURE (°C)
–50
–3.7
–3.5
–3.1
25 75
4221 G34
–3.9
–4.1
–25 0
50 100 125
–4.3
–4.5
–3.3
I
FAULT(UP)
(μA)
V
CC1
= 2.7V
V
CC1
= 5V
V
CC1
= 13.5V
V
CC2
= 1V
V
FAULT
= 1.5V
V
CC1
(V)
0
0.810
V
FAULT(TH)
(V)
0.815
0.825
0.830
0.835
0.860
0.845
4
8
10
4221 G35
0.820
0.850
0.855
0.840
26
12
14
16
V
CC2
= 1V
T
A
= 25°C
RISING
FALLING
TEMPERATURE (°C)
–50
0.84
0.85
0.87
25 75
4221 G36
0.83
0.82
–25 0
50 100 125
0.81
0.80
0.86
V
FAULT(TH)
(V)
V
CC1
= 5V
V
CC2
= 3.3V
RISING
FALLING