LT1316 LINER [Linear Technology], LT1316 Datasheet - Page 9

• Manufacturer Part Number: LT1316
• Description: Micropower DC/DC Converter with Programmable Peak Current Limit
• Manufacturer: LINER [Linear Technology]

4. Find I
5. Find R
Find R
These discontinuous mode equations are designed to
minimize peak current at the expense of inductor size. If
smaller inductors are desired peak current must be
increased.
Capacitor Selection
Low ESR (Equivalent Series Resistance) capacitors should
be used at the output of the LT1316 to minimize output
ripple voltage. High quality input bypassing is also
required. For surface mount applications AVX TPS series
tantalum capacitors are recommended. These have been
specifically designed for switch mode power supplies and
have low ESR along with high surge current ratings.
APPLICATIONS
R
Overshoot =
I
PEAK
SET
SET
PEAK
SET
=
= 0.202A
13k
from Figure 3 for 0.202A – 19mA = 0.183A
t
ON
resistor
for 3.4 s on-time
=
(V
IN
52 H
V
3.3
L
L
IN
U
– V
300ns
SAT
300ns = 19mA
INFORMATION
U
)
=
3.4 s(3.3 – 0.2)
W
2
CELLS
52 H
+
Figure 6. 2-Cell to 5V Step-Up Converter
with Reduced Output Ripple Voltage
SHUTDOWN
47 F
U
SHDN
R
V
SET
IN
10k
LT1316
47 H
L1
For through-hole applications Sanyo OS-CON capacitors
offer extremely low ESR in a small package size. If peak
switch current is reduced using the R
requirements can be eased and smaller, higher ESR units
can be used. Ordinary generic capacitors can generally be
used when peak switch current is less than 100mA,
although output voltage ripple may increase.
Diodes
Most of the application circuits on this data sheet specify
the Motorola MBR0520L surface mount Schottky diode.
This 0.5A, low drop diode suits the LT1316 well. In lower
current applications, a 1N4148 can be used although
efficiency will suffer due to the higher forward drop. This
effect is particularly noticeable at low output voltages. For
higher output voltage applications, such as LCD bias
generators, the extra drop is a small percentage of the
output voltage so the efficiency penalty is small. The low
cost of the 1N4148 makes it attractive wherever it can be
used. In through-hole applications the 1N5818 is the all
around best choice.
Lowering Output Ripple Voltage
To obtain lower output ripple voltage, a small feedforward
capacitor of about 50pF to 100pF may be placed from
V
and without the added capacitor are pictured in Figures
7 and 8.
GND
SW
OUT
FB
D1
to FB as detailed in Figure 6. Ripple voltages with
R1
1M
1%
R2
324k
1%
1316 F06
C1
100pF
+
47 F
V
OUT
SET
pin, capacitor
LT1316
9