LT1610 Linear Technology, LT1610 Datasheet - Page 9

• Manufacturer Part Number: LT1610
• Description: Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter
• Manufacturer: Linear Technology

APPLICATIONS
It is best to choose the compensation components empiri-
cally. Once the power components have been chosen
(based on size, efficiency, cost and space requirements),
a working circuit is built using conservative (or merely
guessed) values of R
circuit is observed under a transient load, and the compen-
Figure 7. Switching Waveforms Without Ceramic Capacitor C5
Figure 8. Switching Waveforms with Ceramic Capacitor C5.
Note the 50mV/DIV Scale for V
200mV/DIV
500mA/DIV
500mA/DIV
50mV/DIV
VOLTAGE
VOLTAGE
SWITCH
10V/DIV
SWITCH
10V/DIV
I
I
DIODE
DIODE
V
V
OUT
OUT
V
LOAD = 100mA
IN
= 4.1V
4 CELLS
U
C
and C
INFORMATION
C1, C2: ALUMINUM ELECTROLYTIC
C3 TO C5: CERAMIC X7R OR X5R
D1: MBR0520
L1, L2: MURATA LQH3C220 OR SUMIDA CLS62-220
100ns/DIV
100ns/DIV
U
+
C
OUT
. Then the response of the
Figure 6. 4-Cell Alkaline to 5V/120mA SEPIC DC/DC Converter
C1
22 F
6.3V
W
C4
1 F
CERAMIC
1610 F07
1610 F08
U
1
8
COMP
V
C
V
GND
IN
7
6
LT1610
22 H
L1
PGND
•
sation network is modified to achieve stable operation.
Linear Technology’s Application Note 19 contains a de-
tailed description of the method. A good starting point for
the LT1610 is C
All Ceramic, Low Profile Design
Large value ceramic capacitors that are suitable for use as
the main output capacitor of an LT1610 regulator are now
available. These capacitors have very low ESR and there-
fore offer very low output ripple in a small package.
However, you should approach their use with some
caution.
Ceramic capacitors are manufactured using a number of
dielectrics, each with different behavior across tempera-
ture and applied voltage. Y5V is a common dielectric used
for high value capacitors, but it can lose more than 80% of
the original capacitance with applied voltage and extreme
temperatures. The transient behavior and loop stability of
the switching regulator depend on the value of the output
capacitor, so you may not be able to afford this loss. Other
dielectrics (X7R and X5R) result in more stable character-
istics and are suitable for use as the output capacitor. The
X7R type has better stability across temperature, whereas
the X5R is less expensive and is available in higher values.
The second concern in using ceramic capacitors is that
many switching regulators benefit from the ESR of the
SW
SHDN
4
5
FB
SHUTDOWN
CERAMIC
2
3
1 F
C3
1M
324k
C
•
L2
22 H
~ 220pF and R
D1
+
C2
22 F
6.3V
1610 F06
C
C5
1 F
CERAMIC
~ 220k.
V
5V
120mA
OUT
LT1610
9