LT1930AES5 LINER [Linear Technology], LT1930AES5 Datasheet - Page 7

• Manufacturer Part Number: LT1930AES5
• Description: 1A, 1.2MHz/2.2MHz, Step-Up DC/DC Converters
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
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.
A good value for R2 is 13.3k which sets the current in the
resistor divider chain to 1.255V/13.3k = 94.7 A.
Figure 5. Transient Response of Step-Up Converter with 33 F
Tantalum Output Capacitor and No Phase Lead Capacitor
R
1
CURRENT
LOAD
AC COUPLED
AC COUPLED
R
2
0.2V/DIV
0.5A/DIV
250mA
150mA
1 255
V
V
.
OUT
I
OUT
LI
V
U
–
1
INFORMATION
U
200 s/DIV
W
16V
V
IN
C1
Figure 7. Keeping SHDN Below 10V
U
121k
1930 F04
4
SHDN
V
IN
5
LT1930
GND
L1
2
SW
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.
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 V
The voltage on the SHDN pin is kept below 10V.
FB
1
D1
3
V
OUT
R1
R2
GND
+
1930 F07
C2
D1
Figure 6. Suggested Layout
IN
V
C2
OUT
= 16V and SHDN is obtained from V
R2
R1
L1
LT1930/LT1930A
C3
C1
V
SHUTDOWN
IN
1930 F06
7
IN
.