LT1930 데이터 시트보기 (PDF) - Linear Technology
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LT1930 Datasheet PDF : 12 Pages
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LT1930/LT1930A
APPLICATIONS INFORMATION
VOUT
0.2V/DIV
AC COUPLED
ILI
0.5A/DIV
AC COUPLED
LOAD 250mA
CURRENT 150mA
200µs/DIV
1930 F04
Figure 5. Transient Response of Step-Up Converter with 33µF
Tantalum Output Capacitor and No Phase Lead Capacitor
DIODE SELECTION
A Schottky diode is recommended for use with the LT1930/
LT1930A. The Motorola MBR0520 is a very good choice.
Where the switch voltage exceeds 20V, use the MBR0530
(a 30V diode). Where the switch voltage exceeds 30V, use
the MBR0540 (a 40V diode). These diodes are rated to
handle an average forward current of 0.5A. In applications
where the average forward current of the diode exceeds
0.5A, a Microsemi UPS5817 rated at 1A is recommended.
SETTING OUTPUT VOLTAGE
To set the output voltage, select the values of R1 and R2
(see Figure 1) according to the following equation.
R1 =
R2
VOUT
1.255V
–
1
A good value for R2 is 13.3k which sets the current in the
resistor divider chain to 1.255V/13.3k = 94.7µA.
LAYOUT HINTS
The high speed operation of the LT1930/LT1930A
demands careful attention to board layout. You will not get
advertised performance with careless layout. Figure 6
shows the recommended component placement.
L1
D1
C1
VOUT
+
C2
R2
VIN
SHUTDOWN
GND
R1
C3
1930 F06
Figure 6. Suggested Layout
Driving SHDN Above 10V
The maximum voltage allowed on the SHDN pin is 10V. If
you wish to use a higher voltage, you must place a resistor
in series with SHDN. A good value is 121k. Figure 7 shows
a circuit where VIN = 16V and SHDN is obtained from VIN.
The voltage on the SHDN pin is kept below 10V.
VIN
16V
C1
L1
D1
5
1
121k VIN
SW
R1
LT1930
4
SHDN
3
FB
GND
R2
2
VOUT
C2
1930 F07
Figure 7. Keeping SHDN Below 10V
7
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