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PDF LTC4213 Data sheet ( Hoja de datos )
| Número de pieza | LTC4213 | |
| Descripción | Electronic Circuit Breaker | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
■ Fast 1µs Response Circuit Breaker
■ 3 Selectable Circuit Breaker Thresholds
■ No Sense Resistor Required
■ Dual Level Overcurrent Fault Protection
■ Controls Load Voltages from 0V to 6V
■ High Side Drive for External N-Channel FET
■ Undervoltage Lockout
■ READY Pin Signals When Circuit Breaker Armed
■ Small Plastic (3mm x 2mm) DFN Package
U
APPLICATIO S
■ Electronic Circuit Breaker
■ High-Side Switch
■ Hot Board Insertion
TYPICAL APPLICATIO
1.25V Electronic Circuit Breaker
VIN
1.25V
SI4864DY
VOUT
1.25V
3.5A
VBIAS
2.3V TO 6V
OFF ON
SENSEP GATE SENSEN
VCC
LTC4213
VBIAS
10k
ON GND ISEL READY
4213 TA01
LTC4213
No RSENSE™
Electronic Circuit Breaker
DESCRIPTIO
The LTC®4213 is an Electronic Circuit Breaker. An over-
current circuit breaker senses the voltage across the drain
and source terminals of an external N-channel MOSFET
with no need for a sense resistor. The advantages are a
lower cost and reduced voltage and power loss in the
switch path. An internal high-side driver controls the
external MOSFET gate.
Two integrated comparators provide dual level over-
current protection over the bias supply to ground common
mode range. The slow comparator has 16µs response
while the fast comparator trips in 1µs. The circuit breaker
has three selectable trip thresholds: 25mV, 50mV and
100mV. An ON pin controls the ON/OFF and resets circuit
breaker faults. READY signals the MOSFET is conducting
and the circuit breaker is armed. The LTC4213 operates
from VCC = 2.3V to 6V.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Severe Overload Response
IOUT
(50A/DIV)
VOUT
(1V/DIV)
VGATE
(5V/DIV)
VIN
(1V/DIV)
2µs/DIV
4213 TA01b
4213f
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LTC4213
TYPICAL PERFOR A CE CHARACTERISTICS Specifications are at TA = 25°C. VCC = 5V
unless otherwise noted.
∆VGSMAX and ∆VGSARM vs VCC
8
∆VGSMAX
7
∆VGSARM
6
5
4
∆VGSMAX and ∆VGSARM vs
Temperature
8
∆VGSMAX (FOR 5VCC)
7
∆VGSARM (FOR 5VCC)
6
∆VGSMAX (FOR 2.5VCC)
5
∆VGSARM (FOR 2.5VCC)
4
VON(TH) vs VCC
0.90
0.85
HIGH THRESHOLD
0.80
LOW THRESHOLD
0.75
0.70
3
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
BIAS SUPPLY VOLTAGE (V)
4213 G10
3
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4213 G11
0.65
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
BIAS SUPPLY VOLTAGE (V)
4213 G12
VON(TH) vs Temperature
0.90
0.85
HIGH THRESHOLD
0.80
LOW THRESHOLD
0.75
0.70
0.65
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4213 G13
tDEBOUNCE and tREADY vs VCC
100
80
tDEBOUNCE
60
tREADY
40
20
0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
BIAS SUPPLY VOLTAGE (V)
4213 G16
∆VOV vs VCC
0.74
0.72
0.70
0.68
0.66
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
BIAS SUPPLY VOLTAGE (V)
4213 G14
tDEBOUNCE and tREADY vs
Temperature
100
80
60 tDEBOUNCE
40 tREADY
20
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4213 G17
∆VOV vs Temperature
1.0
0.9
0.8
0.7
0.6
0.5
0.4
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4213 G15
tRESET vs VCC
120
100
80
60
40
20
0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
BIAS SUPPLY VOLTAGE (V)
4213 G18
4213f
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LTC4213
APPLICATIO S I FOR ATIO
supply transient dips below 1.97V of less than 80µs are
ignored.
ON Function
When VON is below comparator COMP1’s threshold of
0.4V for 80µs, the device resets. The system leaves reset
mode if the ON pin rises above comparator COMP2’s
threshold of 0.8V and the UVLO condition is met. Leaving
reset mode, the GATE pin starts up after a tDEBOUNCE delay
of 60µs. When ON goes below 0.76V, the GATE shuts off
after a 5µs glitch filter delay. The output is discharged by
the external load when VON is in between 0.4V to 0.8V. At
this state, the ON pin can re-enable the GATE if VON
exceeds 0.8V for more than 8µs. Alternatively, the device
resets if the ON pin is brought below 0.4V for 80µs. Once
reset, the GATE pin restarts only after the tDEBOUNCE 60µs
delay at VON rising above 0.8V. To protect the ON pin from
overvoltage stress due to supply transients, a series
resistor of greater than 10k is recommended when the ON
pin is connected directly to the supply. An external resis-
tive divider at the ON pin can be used with COMP2 to set
a supply undervoltage lockout value higher than the inter-
nal UVLO circuit. An RC filter can be implemented at the
ON pin to increase the powerup delay time beyond the
internal 60µs delay.
Gate Function
The GATE pin is held low in reset mode. 60µs after leaving
reset mode, the GATE pin is charged up by an internal
100µA current source. The circuit breaker arms when
VGATE > VSENSEN + ∆VGSARM. In normal mode operation,
the GATE peak voltage is internally clamped to ∆VGSMAX
above the SENSEN pin. When the circuit breaker trips, an
internal MOSFET shorts the GATE pin to GND, turning off
the external MOSFET.
READY Status
The READY pin is held low during reset and at startup. It
is pulled high by an external pullup resistor 50µs after the
circuit breaker arms. The READY pin pulls low if the circuit
breaker trips or the ON pin is pulled below 0.76V, or VCC
drops below undervoltage lockout.
∆VGSARM and VGSMAX
Each MOSFET has a recommended VGS drive voltage
where the channel is deemed fully enhanced and RDSON is
minimized. Driving beyond this recommended VGS volt-
age yields a marginal decrease in RDSON. At startup, the
gate voltage starts at ground potential. The GATE ramps
past the MOSFET threshold and the load current begins to
flow. When VGS exceeds ∆VGSARM, the circuit breaker is
armed and enabled. The chosen MOSFET should have a
recommended minimum VGS drive level that is lower than
∆VGSARM. Finally, VGS reaches a maximum at ∆VGSMAX.
Trip and Reset Circuit Breaker
Figure 2 shows the timing diagram of VGATE and VREADY
after a fault condition. A tripped circuit breaker can be reset
either by cycling the VCC bias supply below UVLO thresh-
old or pulling ON below 0.4V for >tRESET. Figure 3 shows
the timing diagram for a tripped circuit breaker being reset
by the ON pin.
Calculating Current Limit
The fault current limit is determined by the RDSON of the
MOSFET and the circuit breaker voltage VCB.
ILIMIT
=
VCB
RDSON
(2)
The RDSON value depends on the manufacturer’s distribu-
tion, VGS and junction temperature. Short Kelvin-sense
connections between the MOSFET drain and source to
the LTC4213 SENSEP and SENSEN pins are strongly
recommended.
For a selected MOSFET, the nominal load limit current is
given by:
ILIMIT(NOM)
=
VCB(NOM)
RDSON(NOM)
The minimum load limit current is given by:
(3)
ILIMIT(MIN)
=
VCB(MIN)
RDSON(MAX)
(4)
4213f
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| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC4213.PDF ] | |
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