LT1158ISW#TR Linear Technology, LT1158ISW#TR Datasheet - Page 15

• Manufacturer Part Number: LT1158ISW#TR
• Description: IC DRIVER PWR MOSFET N-CH 16SOIC
• Manufacturer: Linear Technology

Specifications of LT1158ISW#TR

• Configuration: Half Bridge
• Input Type: PWM
• Current - Peak: 500mA
• Number Of Configurations: 1
• Number Of Outputs: 2
• High Side Voltage - Max (bootstrap): 56V
• Voltage - Supply: 5 V ~ 30 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Delay Time: -

APPLICATIONS INFORMATION
Note that for the fi rst event only, t
twice the above value since C
the way from its quiescent voltage. Allowable values for
R
t
output is shorted with a PWM input. This is because the
FAULT pin only conducts when fault currents are actually
present in the MOSFET. FAULT does not conduct while the
input is low in Figures 6 and 7 or during the interval I
0 in Figure 8. Thus t
the duty cycle of the current in the top MOSFET is low,
maintaining the average MOSFET current at a relatively
constant level.
The length of time following shutdown before restart is
attempted is given by:
In Figure 9, the top MOSFET would shut down after being
in DC current limit for 0.9ms and try to restart at 60ms
intervals, thus producing a duty cyle of 1.5% in short
circuit. The resulting average top MOSFET dissipation
during a short is easily measured by taking the product of
the supply voltage and the average supply current.
Starting High In-Rush Current Loads
The LT1158 has a V
than I
SHUTDOWN
F
are from zero to 10k.
t
RESTART
SC
1.15V
7.5V
to fl ow in the top MOSFET providing that the
Figure 9. Self-Protection with Auto Restart
OPTIONAL THERMOSTAT
CLOSE ON RISE
AIRPAX #67FXXX
becomes more diffi cult to analyze when the
=
C
1μF
EN
⎛
⎝ ⎜
25
+
1 5
DS
.
μ
SHUTDOWN
V
sensing function which allows more
A
⎞
⎠ ⎟
R
1k
C
F
EN
ENABLE
FAULT
=
EN
SHUTDOWN
will safely increase when
(
6 10
is being discharged all
×
25μA
7.5V
4
LT1158
is approximately
)
C
EN
1158 F09
DS
=
SENSE
tions the current is limited only by the R
with R
by R
(see Figure 7). Again adjusting R
the worst-case start currents are:
Properly sizing the MOSFET for I
loads with long time constants, such as motors with high
mechanical inertia, to be started.
Returning to the example used in Power MOSFET Selec-
tion, an IRFZ34 (R
operation at 5A. If the short-circuit current is also set at 5A,
what start current can be supported? From the equation
for R
the worst-case start current to be calculated:
This calculation gives the minimum current which could
be delivered with the IRFZ34 at T
ing the FAULT pin on the LT1158. If more start current is
required, using an IRFZ44 (R
increase I
the short-circuit current remains at 5A.
In order for the V
supply pins for the LT1158 must be connected at the drain
of the top MOSFET, which must be properly decoupled
(see Ugly Transient Issues).
Driving Lamps
Incandescent lamps represent a challenging load because
they have much in common with a short circuit when cold.
The top gate driver in the LT1158 can be confi gured to turn
on large lamps while still protecting the power MOSFET
I
I I
I
START
START
START
DS(ON)
SENSE
SENSE
–
pin is within 1.2V of supply. Under these condi-
=
=
START
=
, a 0.03Ω shunt would be required, allowing
(
(
alone, since R
( )
. For a 5-lead MOSFET the current is limited
1
1
1 7 0 05
+
+
.
∂
∂
to over 15A at T
1 2
DS
)
)
.
R
R
DS(ON)
.
sensing function to work properly, the
DS ON
V
DS ON
1 2
1 2
.
( )
( )
.
Ω
V
V
+
= 0.05Ω max) was selected for
SENSE
+
0 03
.
R
DS(ON)
SENSE
Ω
J
is not in the output path
J
= 125°C without activat-
DS(ON)
=
START
= 110°C, even though
= 0.028Ω max) would
10
A
for temperature,
allows inductive
3-Lead MOSFET
5-Lead MOSFET
DS(ON)
LT1158
in series
15
1158fb