LT1317BCMS8 Linear Technology, LT1317BCMS8 Datasheet - Page 9

• Manufacturer Part Number: LT1317BCMS8
• Description: IC BOOST ADJ .5A 8MSOP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost)r

Specifications of LT1317BCMS8

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.24 ~ 30 V
• Current - Output: 500mA
• Frequency - Switching: 620kHz
• Voltage - Input: 1.5 ~ 12 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIONS
Table 1. Inductors Suitable for Use with the LT1317
PART
LQH3C100
DO1608-103
CD43-100
CD54-100
CTX32CT-100 10 H
Capacitor Selection
Low ESR (Equivalent Series Resistance) capacitors should
be used at the output of the LT1317. For most applications
a solid tantalum in a C or D case size works well. Accept-
able capacitance values range from 10 F to 330 F with
ESR falling between 0.1 and 0.5 . If component size is
an issue, tantalum capacitors in smaller case sizes can be
used but they have high ESR and output voltage ripple may
reach unacceptable levels.
Ceramic capacitors are an alternative because of their
combination of small size and low ESR. A 10 F ceramic
capacitor will work for some applications but the ex-
tremely low ESR of these capacitors may cause loop
stability problems. Compensation components will need
Figure 4. 2V to 3.3V Converter with a 10 F Ceramic Output
Capacitor. R
Transient Response.
V
2V
IN
D1: MBR0520
L1: SUMIDA CD43-100
VALUE
C1
10 F
10 H
10 H
10 H
10 H
C
and C
U
MAX
DCR
0.57
0.16
0.18
0.10
0.50
C
SHDN
Have Been Adjusted to Give Optimum
V
V
IN
C
R
20k
LT1317B
INFORMATION
C
C
1500pF
10 H
Murata-Erie
U
C
Coiltronics
L1
Coilcraft
Sumida
Sumida
MFR
GND
SW
FB
W
HEIGHT
D1
R2
604k
1%
(mm)
2.0
3.0
3.2
4.5
2.2
1%
1M
R1
COMMENT
Smallest Size,
Limited Current
Handling
Best Efficiency
1210 Footprint
1317 F04
C2
10 F
CERAMIC
U
V
3.3V
OUT
to be adjusted to ensure a stable system for the entire input
voltage range. Figure 4 shows a 2V to 3.3V converter with
new values for R
response for this circuit. Also, ceramic caps are prone to
temperature effects and the designer must check loop
stability over the operating temperature range (see section
on Frequency Compensation).
Input bypass capacitor ESR is less critical and smaller
units may be used. If the input voltage source is physically
near the V
tantalum is adequate.
Diodes
Most of the application circuits on this data sheet specify
the Motorola MBR0520L surface mount Schottky diode.
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 voltage output 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.
AC COUPLED
Figure 5. Transient Response for the Circuit of Figure 4.
200mV/DIV
5mA TO
200mA
I
V
LOAD
OUT
IN
pin (<5mm), a 10 F ceramic or a 10 F A case
C
and C
C
LT1317/LT1317B
. Figure 5 details transient
200 s/DIV
1317 F05
9