Datasheet

LT1336
15
1336fa
Typical applicaTions
applicaTions inForMaTion
V
+
V
+
SWITCH
BOOST
TGATEDR
TGATEFB
TSOURCE
BGATEDR
BGATEFB
PGND
LT1336
I
SENSE
D1
1N4148
D2
1N4148
C
BOOST
1µF
1336 F05
HV = 40V MAX
+
+
R
SENSE
2Ω
1/4W
R
DISCHRG
24k
*SUMIDA
RCR-664D-221KC
200µH*
10µF
+
–
+
V
BOOST
current can raise the voltage of the high voltage rail. This
can be avoided by placing a discharge resistor between HV
supply and ground to divert the return current to ground
as shown in Figure 5. For a high voltage rail of 40V, a 26k
resistor or smaller should be used, since the top driver
will return about 1.5mA.
For applications where using a discharge resistor is un-
desirable, use the flyback regulator topology instead of
the boost regulator topology (see Deriving the Floating
Supply with the Flyback Topology).
To drive a DC motor in both directions, two LT1336s
can be used to drive an H-bridge output stage. In this
configuration the motor can be made to run clockwise,
counterclockwise, stop rapidly (“plugging” braking) or free
run (coast) to a stop. A very rapid stop may be achieved
by reversing the current, though this requires more careful
design to stop the motor dead. In practice a closed-loop
control system with tachometric feedback is usually
necessary.
The motor speed in these examples can be controlled by
switching the drivers with pulse width modulated square
waves. This approach is particularly suitable for micro-
computers/DSP control loops.
Figure 6. 90% Efficiency, 40V to 5V, 10A, Low Dropout Voltage Mode Switching Regulator
Figure 5. Driving a Supply Referenced Motor
+
+
++
+
+
2.2nF
27k
0.1µF
1k
1k
5k
2k
5V
5400µF
LOW
ESR
1336 F06
1µF
10µF
1µF
1µF
0.022µF
C1
0.1µF
360Ω
510Ω
4.7k
0.33µF
330k
12V
1N4148
1N4148
IRFZ44
IRFZ44
MBR340
* SUMIDA RCR-664D-221KC
** MAGNETICS CORE #55585-A2 30 TURNS 14GA MAGNET WIRE
†
DALE TYPE LVR-3 ULTRONIX RCS01
IRFZ44
40V
2200µF EA
LOW ESR
R
S
†
0.007Ω
L2**
70µH
f = 25kHz
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
L1*
200µH
R
SENSE
2Ω, 1/4W
SWITCH
SWGND
BOOST
TGATEDR
TGATEFB
TSOURCE
PV
+
BGATEDR
LT1336
I
SENSE
SV
+
INTOP
INBOTTOM
UVOUT
SGND
PGND
BGATEFB
SHUTDOWN
+
2N2222
1N4148
0.1µF
4.7k
1
2
3
4
5
6
7
8
9
18
17
16
15
14
13
12
11
10
LT3526
1N4148