LT1336IS#TR Linear Technology, LT1336IS#TR Datasheet - Page 12

• Manufacturer Part Number: LT1336IS#TR
• Description: IC DRVR MOSF 1/2BRDG N-CH 16SOIC
• Manufacturer: Linear Technology

Specifications of LT1336IS#TR

• Configuration: Half Bridge
• Input Type: Differential
• Delay Time: 250ns
• Current - Peak: 1.5A
• Number Of Configurations: 1
• Number Of Outputs: 2
• High Side Voltage - Max (bootstrap): 60V
• Voltage - Supply: 10 V ~ 15 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

applicaTions inForMaTion
Using the components as shown in Figure 2 the flyback
regulator will run at around 800kHz. To lower the frequency
C
C
C
The flyback regulator works as follows: when switch S is
on, the primary current ramps up as the magnetic field
builds up. The magnetic field in the core induces a voltage
on the secondary winding equal to V
is transferred to V
reverse biased. The energy is stored in the transformer’s
magnetic field. When the primary inductor peak current
is reached, the switch is turned off. Energy is no longer
transferred to the transformer causing the magnetic field
to collapse. The collapsing magnetic field induces a change
in voltage across the transformer’s windings. During this
transition the Switch pin’s voltage flies to 10.6V plus a diode
above V
D2 and the transformer’s energy is transferred to V
Meanwhile the primary inductor current goes to zero and
the voltage at I
threshold with a time constant of (R
completing the cycle.
LT1336
12
FILTER
0.1µF
FILTER
FILTER
* COILTRONICS CTX100-1P
can be decreased.
can be increased and to increase the frequency
+
, the secondary forward biases the rectifier diode
R
2
1/4W
Figure 2. Using the Flyback Regulator
SENSE
SENSE
SV
PV
I
SENSE
+
+
BOOST
decays to the lower inductor current
LT1336
24V
because the rectifier diode D2 is
TSOURCE
1N4148
TGATEDR
TGATEFB
SWITCH
1000pF
SWGND
BOOST
S
1N4148
6.2k
+
V
–
D1
BOOST
+
SENSE
. However, no power
1:1
T1*
)(C
+
D2
1N4148
40V
FILTER
C
1µF
BOOST
BOOST
), thus
60V MAX
HV =
1336 F02
+
.
Power MOSFET Selection
Since the LT1336 inherently protects the top and bottom
MOSFETs from simultaneous conduction, there are no size
or matching constraints. Therefore, selection can be made
based on the operating voltage and R
The MOSFET BV
absolute maximum operating voltage. For a maximum
operating HV supply of 60V, the MOSFET BV
be from 60V to 100V.
The MOSFET R
erally chosen based on the operating efficiency required
as long as the maximum MOSFET junction temperature is
not exceeded. The dissipation in each MOSFET is given by:
where D is the duty cycle and ∂ is the increase in R
at the anticipated MOSFET junction temperature. From this
equation the required R
For example, if the MOSFET loss is to be limited to 2W
when operating at 5A and a 90% duty cycle, the required
R
each MOSFET in the form of a normalized R
temperature curve, but ∂ = 0.007/°C can be used as an
approximation for low voltage MOSFETs. Thus, if T
and the available heat sinking has a thermal resistance of
20°C/W, the MOSFET junction temperature will be 125°C
and ∂ = 0.007(125 – 25) = 0.7. This means that the required
R
which can be satisfied by an IRFZ34 manufactured by
International Rectifier.
Transition losses result from the power dissipated in each
MOSFET during the time it is transitioning from off to on,
or from on to off. These losses are proportional to (f)(HV)
and vary from insignificant to being a limiting factor on
operating frequency in some high voltage applications.
DS(ON)
DS(ON)
P = D I
R
DS ON
( )
( )
of the MOSFET will be 0.089Ω/1.7 = 0.0523Ω,
would be 0.089Ω/(1 + ∂). (1 + ∂) is given for
DS
=
2
D I
DS(ON)
(
( )
1+ ∂
DSS
DS
should be at least equal to the LT1336
P
2
)
is specified at T
R
(
1+ ∂
DS ON
DS(ON)
( )
)
can be derived:
DS(ON)
J
= 25°C and is gen-
requirements.
DSS
DS(ON)
A
should
= 85°C
DS(ON)
1336fa
vs
2