LT1933ES6#PBF Linear Technology, LT1933ES6#PBF Datasheet - Page 12

• Manufacturer Part Number: LT1933ES6#PBF
• Description: IC, STEP-DOWN REGULATOR, 6-TSOT-23
• Manufacturer: Linear Technology

Specifications of LT1933ES6#PBF

• Primary Input Voltage: 36V
• No. Of Outputs: 1
• Output Current: 600mA
• No. Of Pins: 6
• Operating Temperature Range: -40°C To +85°C
• Supply Voltage Range: 3.6V To 36V
• Switching Frequency Max: 600kHz
• Msl: MSL 1 - Unlimited
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LT1933
cases the discharged output capacitor will present a load
to the switcher which will allow it to start. The plots show
the worst-case situation where V
For lower start-up voltage, the boost diode can be tied to
V
the absolute maximum rating of the BOOST pin.
At light loads, the inductor current becomes discontinu-
ous and the effective duty cycle can be very high. This
reduces the minimum input voltage to approximately
300mV above V
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT1933, requiring a higher
input voltage to maintain regulation.
12
IN
; however, this restricts the input range to one-half of
OUT
. At higher load currents, the inductor
0.1μF
RUN
15k
RUN
Figure 4. To Soft-Start the LT1933, Add a Resistor and Capacitor to
the SHDN Pin. V
IN
SHDN
SHDN
is ramping very slowly.
GND
GND
1933 F04a
1933 F04b
INI
= 12V, V
100mA/DIV
100mA/DIV
5V/DIV
5V/DIV
5V/DIV
5V/DIV
OUT
V
V
RUN
RUN
OUT
OUT
I
I
IN
IN
= 3.3V, C
Soft-Start
The SHDN pin can be used to soft-start the LT1933, reducing
the maximum input current during start up. The SHDN pin
is driven through an external RC fi lter to create a voltage
ramp at this pin. Figure 4 shows the start up waveforms
with and without the soft-start circuit. By choosing a large
RC time constant, the peak start up current can be reduced
to the current that is required to regulate the output, with
no overshoot. Choose the value of the resistor so that it
can supply 60μA when the SHDN pin reaches 2.3V.
OUT
= 22μF , R
0.5ms/DIV
50μs/DIV
LOAD
= 10Ω
1933fe