LTC1871IMS-1#TRPBF Linear Technology, LTC1871IMS-1#TRPBF Datasheet - Page 30

• Manufacturer Part Number: LTC1871IMS-1#TRPBF
• Description: IC CONTRLR CURRENT MODE 10-MSOP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost), Flyback, Sepicr

Specifications of LTC1871IMS-1#TRPBF

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.23 ~ 72 V
• Current - Output: 50mA
• Frequency - Switching: 50kHz ~ 1MHz
• Voltage - Input: 2.5 ~ 36 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

LTC1871-1
APPLICATIONS INFORMATION
6. The diode for this design must handle a maximum
7. The output capacitor usually consists of a high valued
30
DC output current of 2A and be rated for a minimum
reverse voltage of V
from International Rectifi er (30BQ040) is chosen for its
small size, relatively low forward drop and acceptable
reverse leakage at high temp.
bulk C connected in parallel with a lower valued, low ESR
ceramic. Based on a maximum output ripple voltage of
1%, or 120mV, the bulk C needs to be greater than:
The RMS ripple current rating for this capacitor needs
to exceed:
To satisfy this high RMS current demand, two 47μF
Kemet capacitors (T495X476K020AS) are required. As a
result, the output ripple voltage is a low 50mV to 60mV.
In parallel with these tantalums, two 10μF , low ESR (X5R)
Taiyo Yuden ceramic capacitors (TMK432BJ106MM) are
added for HF noise reduction. Check the output ripple
I
C
1.5A •
0.01• 12V • 300kHz
RMS(COUT)
OUT
200mV/DIV
V
0.5A/DIV
OUT
(AC)
I
OUT
1.5A
0.01• V
12V
5V
I
OUT(MAX)
V
V
IN
OUT
= 4.5V
I
O(MAX)
= 12V
= 2.3A
OUT
IN
+ V
• f
= 41μF
•
=
OUT
50μs/DIV
V
IN(MIN)
, or 27V. A 3A, 40V diode
V
Figure 19. LTC1871-1 SEPIC Converter Load Step Response
O
=
8. The choice of an input capacitor for a SEPIC converter
9. The DC coupling capacitor in a SEPIC converter is cho-
200mV/DIV
V
OUT
0.5A/DIV
with a single oscilloscope probe connected directly
across the output capacitor terminals, where the HF
switching currents fl ow.
depends on the impedance of the source supply and the
amount of input ripple the converter will safely toler-
ate. For this particular design and lab setup, a single
47μF Kemet tantalum capacitor (T495X476K020AS) is
adequate. As with the output node, check the input ripple
with a single oscilloscope probe connected across the
input capacitor terminals. If any HF switching noise is
observed it is a good idea to decouple the input with
a low ESR, X5R ceramic capacitor as close to the V
and GND pins as possible.
sen based on its RMS current requirement and must be
rated for a minimum voltage of V
voltage. Start with the minimum value which satisfi es
the RMS current requirement and then check the ripple
voltage to ensure that it doesn’t exceed the DC rating.
For this design a single 10μF , low ESR (X5R) Taiyo
Yuden ceramic capacitor (TMK432BJ106MM) is
adequate.
(AC)
I
OUT
I
RMS(CI)
V
V
IN
OUT
= 15V
= 12V
I
O(MAX)
= 1.5A •
50μs/DIV
•
12V + 0.5V
V
V
IN(MIN)
O
+ V
5V
D
IN
18711 F19
plus the AC ripple
= 2.4A
18711fb
IN