LT1910IS8 [Linear]
LT1910 - Protected High Side MOSFET Driver; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C;
| 型号： | LT1910IS8 |
| 厂家： | 
Linear |
| 描述： | LT1910 - Protected High Side MOSFET Driver; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C 驱动 光电二极管 接口集成电路 驱动器 |
| 文件： | 总14页 (文件大小：203K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1910
Protected High Side
MOSFET Driver
FEATURES
DESCRIPTION
TheLT®1910isahighsidegatedriverthatallowstheuseof
lowcostN-channelpowerMOSFETsforhighsideswitching
applications.Itcontainsacompletelyself-containedcharge
pump to fully enhance an N-channel MOSFET switch with
no external components.
n
8V to 48V Power Supply Range
n
Protected from –15V to 60V Supply Transients
n
Short-Circuit Protected
n
Automatic Restart Timer
n
Open-Collector Fault Flag
n
Fully Enhances N-Channel MOSFET Switches
Whentheinternaldraincomparatorsensesthattheswitch
current has exceeded the preset level, the switch is turned
off and a fault flag is asserted. The switch remains off for
a period of time set by an external timing capacitor and
then automatically attempts to restart. If the fault still
exists, this cycle repeats until the fault is removed, thus
protecting the MOSFET. The fault flag becomes inactive
once the switch restarts successfully.
n
Programmable Current Limit, Delay Time and
Autorestart Period
Voltage Limited Gate Drive
Defaults to Off State with Open Input
Available in SO-8 Package
n
n
n
APPLICATIONS
The LT1910 has been specifically designed for harsh
operating environments such as industrial, avionics and
automotiveapplicationswherepoorsupplyregulationand/
or transients may be present. The device will not sustain
damage from supply transients of –15V to 60V.
n
Industrial Control
n
Avionics Systems
n
Automotive Switches
n
Stepper Motor and DC Motor Control
n
Electronic Circuit Breaker
The LT1910 is available in the SO-8 package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
TYPICAL APPLICATION
Fault Protected High Side Switch
Switch Drop vs Load Current
5V
24V
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
5.1k
LT1910
FAULT
+
0.01Ω
FAULT OUTPUT
V
IN
SENSE
OFF ON
IRFZ34
TIMER GATE
GND
+
10µF
50V
0.1µF
LOAD
1910 TA01
0
1
2
3
4
5
LOAD CURRENT (A)
1910 TA02
1910fc
1
For more information www.linear.com/LT1910
LT1910
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
Supply Voltage (Pin 8) ............................... –15V to 60V
Input Voltage (Pin 4)..................... (GND – 0.3V) to 15V
GATE Voltage (Pin 5)................................................ 75V
+
GND
TIMER
FAULT
IN
1
2
3
4
8
7
6
5
V
NC
+
SENSE Voltage (Pin 6) ........................................ V 5V
SENSE
GATE
FAULT Voltage (Pin 3) .............................................. 36V
Current (Pins 1, 2, 4, 5, 6, 8) ................................ 40mA
Operating Temperature Range (Note 2)
LT1910E............................................... –40°C to 85°C
LT1910I.............................................. –40°C to 125°C
Junction Temperature Range ................ –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
S8 PACKAGE
8-LEAD PLASTIC SO
T
= 125°C, θ = 150°C/W
JA
JMAX
ORDER INFORMATION
LEAD FREE FINISH
LT1910ES8#PBF
LT1910IS8#PBF
LEAD BASED FINISH
LT1910ES8
TAPE AND REEL
LT1910ES8#TRPBF
LT1910IS8#TRPBF
TAPE AND REEL
LT1910ES8#TR
LT1910IS8#TR
PART MARKING
1910
PACKAGE DESCRIPTION
8-Lead Plastic SO
TEMPERATURE RANGE
–40°C to 85°C
1910
8-Lead Plastic SO
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 85°C
PART MARKING
1910
PACKAGE DESCRIPTION
8-Lead Plastic SO
LT1910IS8
1910
8-Lead Plastic SO
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V+ = 12V to 48V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
1.9
0.8
MAX
2.5
UNITS
mA
+
I
Supply Current (Off State)
Delta Supply Current (On State)
Input High Voltage
V = 48V, V = 0.8V
1.2
S
IN
V
= 2V, Measure Increase in I
1.2
mA
∆I
S(ON)
IN
S
l
l
V
E-Grade
I-Grade
2
3.5
V
V
INH
l
l
V
Input Low Voltage
Input Current
E-Grade
I-Grade
0.8
0.7
V
V
INL
l
l
I
V
IN
V
IN
= 2V
= 5V
15
55
30
110
50
185
µA
µA
IN
C
V
V
Input Capacitance (Note 3)
Timer Threshold Voltage
Timer Clamp Voltage
5
pF
V
IN
l
V
V
V
= 2V, Adjust V
= 0.8V
2.6
3.2
9
2.9
3.5
14
3.2
3.8
20
T(TH)
T(CL)
IN
IN
IN
T
V
I
Timer Charge Current
= V = 2V
µA
T
T
V
Drain-Sense Threshold Voltage Temperature
Coefficient (Note 3)
50
65
0.33
80
mV
%/°C
SENSE
1910fc
2
For more information www.linear.com/LT1910
LT1910
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V+ = 12V to 48V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
+
I
Drain Sense Input Current
V = 48V, V
= 65mV
SENSE
0.5
1.5
µA
SENSE
+
+
V
– V Gate Voltage Above Supply
V = 8V
4
7
4.5
8.5
6
10
V
V
GATE
+
l
V = 12V
+
V = 24V
E-Grade
I-Grade
l
l
10
10
12
12
14
15
V
V
+
V = 48V
E-Grade
I-Grade
l
l
10
10
12
12
14
15
V
V
V
V
FAULT Output High Threshold Voltage
FAULT Output Low Threshold Voltage
V
= 2V, I = 1mA, Adjust V
T
3.1
3.0
3.4
3.3
3.7
3.6
V
V
F(TH)
FOL
IN
F
l
FAULT Output Low Voltage
Turn-On Time
I = 1mA
F
0.07
220
25
0.4
400
100
50
V
µs
µs
µs
+
t
t
t
V = 24V, V
= 32V, C = 1nF
GATE
100
ON
OFF
OFF(CL)
GATE
+
Turn-Off Time
V = 24V, V
= 2V, C
= 1nF
GATE
GATE
+
+
Current Limit Turn-Off Time
20
V = 24V, (V – V
)→0.1V, C
SENSE
= 1nF
GATE
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
with statistical process controls. The LT1910I is guaranteed to meet
performance specifications over the full –40°C to 125°C operating
temperature range.
Note 3: Guaranteed but not tested.
Note 2: The LT1910E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
Supply Current vs Temperature
Input Voltage vs Temperature
2.0
1.8
1.6
1.4
1.2
1.0
0.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
+
V
= 48V
T
= 25°C
A
ON STATE
OFF STATE
V
INH
ON STATE
OFF STATE
V
INL
–50
0
25
50
75 100 125
–50 –25
25
50
75 100 125
–25
0
0
10
20
30
40
50
TEMPERATURE (°C)
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
1910 G03
1910 G02
1910 G01
1910fc
3
For more information www.linear.com/LT1910
LT1910
TYPICAL PERFORMANCE CHARACTERISTICS
Timer Threshold Voltage
vs Temperature
Timer Clamp Voltage
vs Temperature
Input Current vs Temperature
200
180
160
140
120
100
80
3.2
3.1
3.0
2.9
2.8
2.7
2.6
3.8
3.7
3.6
3.5
3.4
3.3
3.2
V
= 2V
V
≤ 0.8V
IN
IN
V
= 5V
= 2V
IN
60
40
V
IN
20
0
–50 –25
25
50
75 100 125
0
–50
0
25
50
75 100 125
–50
0
25
50
100
–25
–25
75
125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
1910 G04
1910 G05
1910 G06
Timer Charge Current
vs Temperature
Drain Sense Threshold Voltage
vs Temperature
MOSFET Gate Voltage Above V+
(VGATE – V+) vs Supply Voltage
16
14
12
10
8
20
18
16
14
12
10
8
90
85
80
75
70
65
60
55
50
45
40
+
V
= 24V
V
IN
= V = 2V
T
T
T
= 125°C
= –40°C
T
A
= 25°C
A
A
6
4
2
0
0
5
10 15 20 25 30 35 40 45 50
SUPPLY VOLTAGE (V)
LTC1266 • F04
–50
0
25
50
75 100 125
–50 –25
25
50
75 100 125
–25
0
TEMPERATURE (°C)
TEMPERATURE (°C)
1910 G07
1910 G08
MOSFET Gate Drive Current
vs VGATE – V+
Fault Threshold Voltage
vs Temperature
Fault Output Low Voltage
vs Temperature
3.7
3.6
3.5
3.4
3.3
3.2
3.1
3.0
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
100
10
I = 1mA
F
V
F
= 2V
T
= 25°C
IN
A
I = 1mA
FAULT HIGH THRESHOLD
+
+
+
V
= 8V
V = 12V V ≥ 24V
1
FAULT LOW THRESHOLD
0.1
–50
0
25
50
75 100 125
–25
–50 –25
25
50
75 100 125
0
0
2
4
6
8
10 12 14 16
+
TEMPERATURE (°C)
TEMPERATURE (°C)
V
– V (V)
GATE
1910 G11
1910 G012
1910 G10
1910fc
4
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LT1910
TYPICAL PERFORMANCE CHARACTERISTICS
Automatic Restart Period
vs Temperature
Turn-On Time vs Temperature
Turn-Off Time vs Temperature
400
350
300
250
200
150
100
100
90
80
70
60
50
40
30
20
10
0
1000
100
10
+
+
+
V
= 24V
V
V
C
= 24V
V
V
C
= 24V
= 2V
= 32V
GATE
GATE
GATE
GATE
= 1nF
C
= 3.3µF
= 1nF
T
C
= 1µF
T
C
= 0.33µF
T
NORMAL
CURRENT LIMIT
C
T
= 0.1µF
–50 –25
25
50
75 100 125
–50
0
25
50
75 100 125
0
–25
–50 –30 –10 10 30 50
TEMPERATURE (°C)
110 130
70 90
TEMPERATURE (°C)
TEMPERATURE (°C)
1910 G014
1910 G13
1910 G15
PIN FUNCTIONS
GND (Pin 1): Common Ground.
pump is activated to pull up the GATE pin. The IN pin can
be pulled as high as 15V regardless of whether the sup-
ply is on or off. If the IN pin is left open, an internal 75k
pull-down resistor pulls the pin below 0.8V to ensure that
the GATE pin is inactive LOW.
TIMER (Pin 2): A timing capacitor, C , from the TIMER
T
pin to ground sets the restart time following overcurrent
detection. Upon detection of an overcurrent condition, C
T
is rapidly discharged to less than 1V and then recharged
by a 14µA nominal current source back to the 2.9V timer
threshold, whereupon the restart is attempted. Whenever
TIMER pulls below 2.9V, the GATE pin pulls low to turn off
theexternalswitch.Thiscyclerepeatsuntiltheovercurrent
condition goes away and the switch restarts successfully.
During normal operation the pin clamps at 3.5V nominal.
GATE (Pin 5): The GATE pin drives the power MOSFET
gate. When the IN pin is greater than 2V, the GATE pin is
pumped approximately 12V above the supply. It has rela-
tively high impedance (the equivalence of a few hundred
kΩ) when pumped above the rail. Care should be taken
to minimize any loading by parasitic resistance to ground
or supply. The GATE pin pulls LOW when the TIMER pin
falls below 2.9V.
FAULT (Pin 3): The FAULT pin monitors the TIMER pin
voltageandindicatestheovercurrentcondition.Whenever
the TIMER pin is pulled below 3.3V at the onset of a cur-
rent limit condition, the FAULT pin pulls active LOW. The
FAULT pin resets HIGH immediately when the TIMER pin
ramps above 3.4V during autorestart. The FAULT pin is an
open-collector output, thus requiring an external pull-up
resistor and is intended for logic interface. The resistor
should be selected with a maximum of 1mA pull-up at
low status.
SENSE (Pin 6): The SENSE pin connects to the input of
a supply-referenced comparator with a 65mV nominal
offset. When the SENSE pin is taken more than 65mV
below supply, the MOSFET gate is driven LOW and the
timing capacitor is discharged. The SENSE pin threshold
hasa0.33%/°Ctemperaturecoefficient(TC),whichclosely
matches the TC of the drain-sense resistor formed from
the copper trace of the PCB.
IN (Pin 4): The IN pin threshold is TTL/CMOS compatible
and has approximately 200mV of hysteresis. When the
IN pin is pulled active HIGH above 2V, an internal charge
Forloadsrequiringhighinrushcurrent,anRCtimingdelay
can be added between the drain-sense resistor and the
SENSE pin to ensure that the current-sense comparator
1910fc
5
For more information www.linear.com/LT1910
LT1910
PIN FUNCTIONS
+
does not false trigger during start-up (see Applications
Information).Amaximumof10kΩcanbeinsertedbetween
adrain-senseresistorandtheSENSEpin.Ifcurrentsensing
is not required, the SENSE pin is tied to supply.
V (Pin 8): In addition to providing the operating cur-
+
rent for the LT1910, the V pin also serves as the Kelvin
connection for the current-sense comparator. The V pin
must be connected to the positive side of the drain-sense
resistor for proper current-sensing operation.
+
BLOCK DIAGRAM
+
V
14µA
FAULT
–
+
3.3V
+
V
TIMER
+
65mV
2.9V
+
–
+
–
SENSE
–
+
–
GATE
1.4V
1.4V
+
OSCILLATOR
AND
CHARGE PUMP
75k
IN
–
75k
250Ω
1910 BD
(Refer to the Block Diagram)
OPERATION
The LT1910 GATE pin has two states, off and on. In the off
state it is held LOW, while in the on state it is pumped to
12V above the supply by a self-contained 750kHz charge
pump. The off state is activated when either the IN pin is
below 0.8V or the TIMER pin is below 2.9V. Conversely,
for the on state to be activated, the IN pin must be above
2V and the TIMER pin must be above 2.9V.
TheSENSEpinnormallyconnectstothedrainofthepower
MOSFET, which returns through a low value drain-sense
resistor to supply. In order for the sense comparator to
+
accurately sense the MOSFET drain current, the V pin
must be connected directly to the positive side of the
drain-sense resistor. When the GATE pin is on and the
MOSFETdraincurrentexceedsthelevelrequiredtogener-
atea65mVdropacrossthedrain-senseresistor, thesense
comparator activates a pull-down NPN which rapidly pulls
the TIMER pin below 2.9V. This in turn causes the timer
comparator to override the IN pin and set the GATE pin
to the off state, thus protecting the power MOSFET. When
the TIMER pin is pulled below 3.3V, the fault comparator
1910fc
The IN pin has approximately 200mV of hysteresis. If it is
left open, the IN pin is held LOW by a 75k resistor. Under
normal conditions, the TIMER pin is held a diode drop
above 2.9V by a 14µA pull-up current source. Thus the
TIMER pin automatically reverts the GATE pin to the on
state if the IN pin is above 2V.
6
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LT1910
OPERATION
also activates the open-collector NPN to pull the FAULT
pin LOW, indicating an overcurrent condition.
OFF NORMAL
OVERCURRENT
NORMAL
IN
0V
When the MOSFET gate voltage is discharged to less than
1.4V, the TIMER pin is released. The 14µA current source
then slowly charges the timing capacitor back to 2.9V
where the charge pump again starts to drive the GATE pin
HIGH. If a fault condition still exists, the sense comparator
threshold will again be exceeded and the timer cycle will
repeat until the fault is removed. The FAULT pin becomes
inactive HIGH if the TIMER pin charges up successfully
above 3.4V (see Figure 1).
12V
+
V
GATE
0V
3.5V
2.9V
3.4V
TIMER
0V
5V
FAULT
0V
1910 F01
Figure 1. Timing Diagram
APPLICATIONS INFORMATION
Input/Supply Sequencing
temperature range. The optoisolator must have less than
20µA of dark current (leakage) at hot in order to maintain
the off state (see Figure 2).
There are no input/supply sequencing requirements for
the LT1910. The IN pin may be taken up to 15V with the
supply at 0V. When the supply is turned on with the IN
pin set HIGH, the MOSFET turn-on will be inhibited until
the timing capacitor charges up to 2.9V (i.e., for one
restart cycle).
Drain-Sense Configuration
The LT1910 uses supply referenced current sensing. One
input of the current-sense comparator is connected to a
drain-sense pin, while the second input is offset 65mV
below the supply inside the device. For this reason, Pin 8
of the LT1910 must be treated not only as a supply pin,
but also as the reference input for the current-sense
comparator.
Isolating the Inputs
Operation in harsh environments may require isolation to
prevent ground transients from damaging control logic.
TheLT1910easilyinterfacestolowcostoptoisolators.The
network shown in Figure 2 ensures that the input will be
pulled above 2V, but not exceed the absolute maximum
rating for supply voltages of 12V to 48V over the entire
Figure 3 shows the proper drain-sense configuration for
the LT1910. Note that the SENSE pin goes to the drain
+
end of the sense resistor, while the V pin is connected
24V
12V TO 48V
2k
5V
R1
LOGIC
INPUT
100k
R
LT1910
FAULT
5.1k
S
3
4
2
8
6
5
+
0.02Ω
(PTC)
FAULT OUTPUT
V
LT1910
INPUT
IN
SENSE
4
Q1
IRFZ34
IN
TIMER GATE
GND
LOGIC GROUND
51k
GND
1
1
24V
2A
SOLENOID
+
1910 F02
C1
100µF
50V
C
T
1µF
POWER GROUND
1910 F03
0V
Figure 2. Isolating the Input
Figure 3. Drain-Sense Configuration
1910fc
7
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LT1910
APPLICATIONS INFORMATION
to the supply at the same point as the positive end of the
sense resistor.
FAULT pin from resetting HIGH until the IN pin has been
recycled. C is used to prevent the FAULT pin from glitch-
T
ing whenever the IN pin recycles to turn on the MOSFET
unsuccessfully under an existing fault condition.
The drain-sense threshold voltage has a positive tempera-
ture coefficient, allowing PTC sense resistors to be used
(see Printed Circuit Board Shunts). The selection of R
should be based on the minimum threshold voltage:
S
Inductive vs Capacitive Loads
Turning on an inductive load produces a relatively benign
ramp in MOSFET current. However, when an inductive
load is turned off, the current stored in the inductor needs
somewhere to decay. A clamp diode connected directly
across each inductive load normally serves this purpose.
Ifadiodeisnotemployed, theLT1910clampstheMOSFET
R = 50mV/I
S
SET
Thus the 0.02Ω drain-sense resistor in Figure 3 will yield
a minimum trip current of 2.5A. This simple configuration
is appropriate for resistive or inductive loads that do not
generate large current transients at turn-on.
gate0.7Vbelowground.ThiscausestheMOSFETtoresume
+
Automatic Restart Period
conductionduringthecurrentdecaywith(V +V +0.7V)
GS
across it, resulting in high dissipation peaks.
The timing capacitor, C , shown in Figure 3 determines
T
the length of time the power MOSFET is held off follow-
ing a current limit trip. Curves are given in the Typical
Performance Characteristics to show the restart period
for various values of C . For example, C = 0.33µF yields
Capacitive loads exhibit the opposite behavior. Any load
thatincludesadecouplingcapacitorwillgenerateacurrent
equal to C
• (∂V/∂t) during capacitor in-rush. With
LOAD
large electrolytic capacitors, the resulting current spike
can play havoc with the power supply and false trip the
current-sense comparator.
T
T
a 50ms restart period.
Defeating Automatic Restart
Turn-on ∂V/∂t is controlled by the addition of the simple
networkshowninFigure5.Thisnetworktakesadvantageof
the fact that the MOSFET acts as a source follower during
turn-on. Thus the ∂V/∂t on the source can be controlled
by controlling the ∂V/∂t on the gate.
Some applications are required to remain off after a fault
occurs.WhentheLT1910isbeingdrivenfromCMOSlogic,
this can be easily implemented by connecting resistor R2
between the IN and TIMER pins as shown in Figure 4. R2
supplies the sustaining current for an internal SCR which
latches the TIMER pin LOW under a fault condition. The
FAULTpinissetactiveLOWwhentheTIMERpinfallsbelow
3.3V. This keeps the MOSFET gate from turning on and the
CURRENT LIMIT
DELAY NETWORK
24V
1N4148
R
8
6
S
+
C
D
V
0.01Ω
SENSE
5V
R
D
(≤10k)
R1
5.1k
LT1910
∂V/∂t CONTROL NETWORK
1N4148
3
FAULT OUTPUT
ON = 5V
FAULT
5V
CMOS
LOGIC
4
2
5
IN
LT1910
Q1
GATE
GND
OFF = 0V
IRFZ34
R1
100k
R2
TIMER
15V
1N4744
100k
R2
2k
GND
1
+
C2
50µF
50V
+
1
C1
C
T
C
LOAD
1µF
1910 F05
1910 F04
Figure 4. Latch-Off Configuration (Autorestart Defeated)
Figure 5. Control and Current Limit Delay
1910fc
8
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LT1910
APPLICATIONS INFORMATION
The turn-on current spike into C
is estimated by:
R and C delay the overcurrent trip for drain currents up
D D
LOAD
toapproximately10•I ,abovewhichthediodeconducts
SET
VG – VTH
R1•C1
IPEAK =CLOAD
•
and provides immediate turn-off (see Figure 7). To ensure
proper operation of the timer, C must be ≤C .
D
T
where V is the MOSFET gate threshold voltage. V is
10
TH
G
obtained by plotting the equation:
VGATE
R1
IGATE
=
1
on the graph of Gate Drive Current (I
) vs Gate Voltage
GATE
(V
) as shown in Figure 6. The value of V
at the
0.1
0.01
GATE
GATE
intersection of the curves for a given supply is V . For
G
+
example, if V = 24V and R1 = 100k, then V = 18.3V. For
G
V
PEAK
= 2V, C1 = 0.1µF and C
= 1000µF, the estimated
TH
LOAD
1
10
100
I
= 1.6A. The diode and the second resistor in the
MOSFET DRAIN CURRENT (1 = SET CURRENT)
network ensure fast current limit turn-off.
1910 F07
Figure 7. Current Limit Delay Time
When turning off a capacitive load, the source of the
MOSFET can “hang up” if the load resistance does not
Printed Circuit Board Shunts
discharge C
as fast as the gate is being pulled down.
LOAD
If this is the case, a 15V Zener may be added from gate to
The sheet resistance of 1oz copper clad is approximately
5 • 10 Ω/square with a temperature coefficient of
–4
source to prevent V
from being exceeded.
GS(MAX)
0.39%/°C. Since the LT1910 drain-sense threshold has a
similar temperature coefficient (0.33%/°C), this offers the
possibilityofnearlyzeroTCcurrentsensingusingthe“free”
drain-sense resistor made out of PC trace material.
800
700
600
+
+
V
= 24V
+
V
= 48V
500
A conservative approach is to use 0.02" of width for each
1A of current for 1oz copper. Combining the LT1910 drain
sense threshold with the 1oz copper resistance results in
a simple expression for width and length:
V
= 12V
I
V
=
GATE
GATE
400
300
5
/10
+
V
= 8V
200
100
0
Width (1oz Cu) = 0.02" • I
Length (1oz Cu) = 2"
SET
10
20
40
0
50
60
30
GATE VOLTAGE (V)
1910 F06
The width for 2oz copper would be halved while the length
would remain the same.
Figure 6. Gate Drive Current vs Gate Voltage
Bends may be incorporated into the resistor to reduce
space; each bend is equivalent to approximately 0.6 • the
width of a straight length. Kelvin connection should be
employed by running a separate trace from the ends of
Adding Current Limit Delay
When capacitive loads are being switched or in very noisy
environments, it is desirable to add delay in the drain
current-sense path to prevent false tripping (inductive
loads normally do not need delay). This is accomplished
by the current limit delay network shown in Figure 5.
+
the resistor back to the LT1910’s V and SENSE pins. See
Application Note 53 for further information on printed
circuit board shunts.
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For more information www.linear.com/LT1910
LT1910
APPLICATIONS INFORMATION
Low Voltage/Wide Supply Range Operation
Low Side Driving
When the supply is less than 12V, the LT1910’s charge
pump does not produce sufficient gate voltage to fully
enhance the standard N-channel MOSFET. For these ap-
plications, a logic-level MOSFET can be used to extend
the operating supply down to 8V. If the MOSFET has a
Although the LT1910 is primarily targeted at high side
(grounded load) switch applications, it can also be used
for low side (supply connected load) switch applications.
Figures 8a and 8b illustrate the LT1910 driving low side
power MOSFETs. Because the LT1910 charge pump tries
to pump the gate of the N-channel MOSFET above the
maximum V rating of 15V or greater, then the LT1910
GS
can also operate up to a supply voltage of 60V (absolute
supply, a clamp Zener is required to prevent the V (ab-
GS
+
maximum rating of the V pin).
solute maximum) of the MOSFET from being exceeded.
The LT1910 gate drive is current limited for this purpose
so that no resistance is needed between the GATE pin
and Zener.
Protecting Against Supply Transients
The LT1910 is 100% tested and guaranteed to be safe
+
from damage with 60V applied between the V and GND
Currentsensingforprotectinglowsidedriverscanbedone
in several ways. In the Figure 8a circuit, the supply voltage
for the load is assumed to be within the supply operating
range of the LT1910. This allows the load to be returned
pins. However, when this voltage is exceeded, even for a
few microseconds, the result can be catastrophic. For this
reason it is imperative that the LT1910 is not exposed to
supply transients above 60V. A transient suppressor, such
as Diodes Inc.’s SMAJ48A, should be added between the
to supply through current-sense resistor, R , providing
S
normal operation of the LT1910 protection circuitry.
+
V and GND pins for such applications.
If the load cannot be returned to supply through R , or
S
+
For proper current sense operation, the V pin is required
the load supply voltage is higher than the LT1910 supply,
the current sense must be moved to the source of the
low side MOSFET.
to be connected to the positive side of the drain-sense
resistor (see Drain-Sense Configuration). Therefore, the
supply should be adequately decoupled at the node where
Figure 8b shows an approach to source sensing. An
operational amplifier (must common mode to ground) is
+
the V pin and drain sense resistor meet. Several hundred
microfarads may be required when operating with a high
current switch.
used to level shift the voltage across R up to the drain-
S
sense pin. This approach allows the use of a small sense
resistor which could be made from PC trace material. The
LT1910restarttimerfunctionsthesameasinthehighside
switch application.
When the operating voltage approaches the 60V absolute
maximum rating of the LT1910, local supply decoupling
+
between the V and GND pins is highly recommended. An
RC snubber with a transient suppressor are an absolute
necessity. Note however that resistance should not be
+
added in series with the V pin because it will cause an
error in the current-sense threshold.
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For more information www.linear.com/LT1910
LT1910
APPLICATIONS INFORMATION
12V TO 48V
5V
R1
R
S
5.1k
3
4
8
6
+
0.01Ω
(PTC)
FAULT OUTPUT
FAULT
V
INPUT
IN
SENSE
LT1910
4A
LOAD
+
C1
100µF
100V
2
5
Q1
IRFZ44
TIMER GATE
GND
15V
1N4744
1
C
T
1µF
1910 F08a
0V
Figure 8a. Low Side Driver with Load Current Sensing
8V TO 24V
HV
5V
R1
5.1k
LT1910
FAULT
HV
3
4
2
8
6
5
+
FAULT OUTPUT
INPUT
V
51Ω
LOAD
IN
SENSE
Q1
IRF630
TIMER GATE
15V
1N4744
GND
1
+
R
S
2N2222
LT1006
0.02Ω
+
C1
10µF
50V
–
C
T
1µF
51Ω
1910 F08b
Figure 8b. Low Side Driver for Source Current Sensing
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11
For more information www.linear.com/LT1910
LT1910
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610 Rev G)
.189 – .197
(4.801 – 5.004)
.045 ±.005
NOTE 3
.050 BSC
7
5
8
6
.245
MIN
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
1
3
4
2
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
(0.254 – 0.508)
× 45°
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
.008 – .010
(0.203 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
INCHES
1. DIMENSIONS IN
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
SO8 REV G 0212
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12
For more information www.linear.com/LT1910
LT1910
REVISION HISTORY (Revision history begins at Rev B)
REV
DATE
7/14
6/15
DESCRIPTION
PAGE NUMBER
B
Updated FAULT pin description
Changed top mark
5
2
C
1910fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
13
LT1910
TYPICAL APPLICATION
Protected 1A Automotive Solenoid Driver with Overvoltage Shutdown
8V TO 24V OPERATING
32V TO 60V SHUTDOWN
5V
R1
5.1k
R
LT1910
FAULT
S
3
4
2
8
6
5
+
0.03Ω
(PTC)
FAULT OUTPUT
V
INPUT
30V
1N6011B
IN
SENSE
Q1
TIMER GATE
MTD3055EL
GND
1
1N4148
2N3904
R2
24V
1A
SOLENOID
10k
+
C1
10µF
100V
C
T
1µF
R3
5.1k
POWER
GROUND
1910 TA03
RELATED PARTS
PART NUMBER
LTC®1153
LTC1155
DESCRIPTION
COMMENTS
Autoreset Electronic Circuit Breaker
Programmable Trip Current, Fault Status Output
Dual High Side Micropower MOSFET Driver
Quad Protected High Side MOSFET Driver
Triple 1.8V to 6V High Side MOSFET Driver
Dual 24V High Side MOSFET Driver
Operates from 4.5V to 18V, 85µA On Current, Short-Circuit Protection
8V to 48V Supply Range, Individual Short-Circuit Protection
0.01µA Standby Current, Triple Driver in SO-8 Package
Operates from 9V to 24V, Short-Circuit Protection
LT1161
LTC1163
LTC1255
LTC1477
Protected Monolithic High Side Switch
SMBus Dual High Side Switch Controller
Low R
0.07Ω Switch, 2A Short-Circuit Protected
DS(ON)
LTC1623
2-Wire SMBus Serial Interface, Built-In Gate Charge Pumps
1.5A Peak Output Current, 4.5V ≤ V ≤ 13.2V, SO-8 Package
LTC1693 Family
High Speed Single/Dual N-Channel/P-Channel
MOSFET Drivers
CC
LTC1710
LTC4412
SMBus Dual Monolithic High Side Switch
Low Loss PowerPath™ Controller
Two Low R
0.4Ω/300mA Switches in 8-Lead MSOP Package
DS(ON)
Implements “Ideal Diode” Function, ThinSOT™ Package
PowerPath and ThinSOT are trademarks of Linear Technology Corporation.
1910fc
LT 0615 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
14
●
●
LINEAR TECHNOLOGY CORPORATION 2009
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LT1910
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