LTC4210-4IS6#PBF Linear Technology, LTC4210-4IS6#PBF Datasheet - Page 12

• Manufacturer Part Number: LTC4210-4IS6#PBF
• Manufacturer: Linear Technology

Specifications of LTC4210-4IS6#PBF

• Linear Misc Type: Positive Low Voltage
• Package Type: TSOT-23
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (max): 7V
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Height (mm): 0.9mm
• Product Length (mm): 2.9mm
• Mounting: Surface Mount
• Pin Count: 6
• Lead Free Status / RoHS Status: Compliant

APPLICATIO S I FOR ATIO
LTC4210-3/LTC4210-4
Circuit Breaker Timer Operation
When a current limit fault is encountered at time point A in
Figure 5, the circuit breaker timing is activated with a 60µA
pull-up. The circuit breaker trips at time point B if the fault
is still present and the TIMER pin voltage reaches the
COMP2 threshold and the LTC4210 shuts down. For a
continuous fault, the circuit breaker delay is:
Intermittent overloads may exceed the current limit as in
Figure 6, but if the duration is sufficiently short, the TIMER
pin may not reach the COMP2 threshold and the LTC4210
will not shut down. To handle this situation, the TIMER
discharges with 2µA whenever (V
below the 50mV limit and the TIMER voltage is between
the COMP1 and COMP2 thresholds. When the TIMER
voltage falls below the COMP1 threshold, the TIMER pin is
discharged with an equivalent 7k resistor (normal mode,
100µA source) when (V
50mV limit. If the TIMER pin does not drop below the
COMP1 threshold, any intermittent overload with an ag-
gregate duty cycle of more than 3.8% will eventually trip
the circuit breaker. Figure 7 shows the circuit breaker
response time in seconds normalized to 1µF. The asym-
metric charging and discharging of TIMER is a fair gauge
of MOSFET heating.
When the circuit breaker trips, the GATE pin is pulled low.
The TIMER enters latchoff mode with a 5µA pull-up for the
LTC4210-4 (latched-off version), while an autoretry “cool-
off” cycle begins with a 2µA pull-down for the LTC4210-3
(autoretry version). An autoretry cool-off delay of the
LTC4210-3 between COMP2 and COMP1 thresholds takes:
12
C
t
C
t
CBDELAY
COOLOFF
LOAD
TIMER
t
•
( /
I
RSENSE
s
=
=
1 1
1 3
µ =
.
.
F
)
V
V
V
IN
U
–
•
•
(
C
I
C
LOAD
60
60
TIMER
2
TIMER
CC
µ
1 3
µ
µ
U
A
.
A D
– SENSE) voltage is below the
A
<
V
•
t
•
CBDELAY
)
1
µ
–
CC
F
2
W
µ
– SENSE) voltage is
A
U
(12)
(13)
(14)
(15)
COMP2
V
V
TIMER
I
LOAD
GATE
V
TIMER
Figure 6. Mulitple Intermittent Overcurrent Conditon
60µA
100µA
NORMAL
0.01
A1
Figure 7. Circuit Breaker Timer Response
for Intermittent Overload
MODE
0.1
FAULT
Figure 5. A Continuous Fault Timing
1
10µA
CB
0
B1
10
A
2µA
60µA
COMP2
OVERLOAD DUTY CYCLE, D (%)
20
FAULT
A2
MODE
COMP1
FAULT
30
10µA
CB
C
TIMER
t
40
B2
B
60µA
60µA
2µA
4210 F05
(s/µF) =
50
CIRCUIT BREAKER
TRIPS
A3
FAULT
CB
60
LATCHED OFF (5µA PULL-UP)
OR RETRY (2µA PULL-DOWN)
B3
60µA • D – 2µA
70
OR RETRY (2µA PULL-DOWN)
1.3V • 1µF
LATCHED OFF (5µA PULL-UP)
COMP1
~50mV/R
CIRCUIT BREAKER
TRIPS
80
4210 F06
90
4210 F07
SENSE
100
421034fa