Electronic Components Datasheet Search
  English  ▼
ALLDATASHEET.NET

X  

MIC2171BT Datasheet(PDF) 8 Page - Micrel Semiconductor

Part # MIC2171BT
Description  100kHz 2.5A Switching Regulator Preliminary Information
Download  10 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  MICREL [Micrel Semiconductor]
Direct Link  http://www.micrel.com
Logo MICREL - Micrel Semiconductor

MIC2171BT Datasheet(HTML) 8 Page - Micrel Semiconductor

Back Button MIC2171BT Datasheet HTML 2Page - Micrel Semiconductor MIC2171BT Datasheet HTML 3Page - Micrel Semiconductor MIC2171BT Datasheet HTML 4Page - Micrel Semiconductor MIC2171BT Datasheet HTML 5Page - Micrel Semiconductor MIC2171BT Datasheet HTML 6Page - Micrel Semiconductor MIC2171BT Datasheet HTML 7Page - Micrel Semiconductor MIC2171BT Datasheet HTML 8Page - Micrel Semiconductor MIC2171BT Datasheet HTML 9Page - Micrel Semiconductor MIC2171BT Datasheet HTML 10Page - Micrel Semiconductor  
Zoom Inzoom in Zoom Outzoom out
 8 / 10 page
background image
MIC2171
Micrel
4-10
1997
For our practical example:
L1
4.178
.662
3.0
1 105
×
()
×× ×
0
2
2
L1
≥ 12.4µH (use 15µH)
Equation (3) solves for L1’s maximum current value.
(3)
I
L1(peak) =
V
IN TON
L1
Where:
T
ON = δ / fSW = 6.62×10
-6 sec
I
4.178
6.62 10
15 10
L1(peak)
-6
-6
=
××
×
I
L1(peak) = 1.84A
Use a 15
µH inductor with a peak current rating of at least 2A.
Flyback Conversion
Flyback converter topology may be used in low power appli-
cations where voltage isolation is required or whenever the
input voltage can be less than or greater than the output
voltage. As with the step-up converter the inductor (trans-
former primary) current can be continuous or discontinuous.
Discontinuous operation is recommended.
Figure 2 shows a practical flyback converter design using the
MIC2171.
Switch Operation
During Q1’s on time (Q1 is the internal NPN transistor—see
block diagrams), energy is stored in T1’s primary inductance.
During Q1’s off time, stored energy is partially discharged into
C4 (output filter capacitor). Careful selection of a low ESR
capacitor for C4 may provide satisfactory output ripple volt-
age making additional filter stages unnecessary.
C1 (input capacitor) may be reduced or eliminated if the
MIC2171 is located near a low impedance voltage source.
Output Diode
The output diode allows T1 to store energy in its primary
inductance (D2 nonconducting) and release energy into C4
(D2 conducting). The low forward voltage drop of a Schottky
diode minimizes power loss in D2.
Frequency Compensation
A simple frequency compensation network consisting of R3
and C2 prevents output oscillations.
High impedance output stages (transconductance type) in
the MIC2171 often permit simplified loop-stability solutions to
be connected to circuit ground, although a more conventional
technique of connecting the components from the error
amplifier output to its inverting input is also possible.
Voltage Clipper
Care must be taken to minimize T1’s leakage inductance,
otherwise it may be necessary to incorporate the voltage
clipper consisting of D1, R4, and C3 to avoid second break-
down (failure) of the MIC2171’s internal power switch.
Discontinuous Mode Design
When designing a discontinuous flyback converter, first de-
termine whether the device can safely handle the peak
primary current demand placed on it by the output power.
Equation (8) finds the maximum duty cycle required for a
given input voltage and output power. If the duty cycle is
greater than 0.8, discontinuous operation cannot be used.
(8)
δ
2 P
I
V
– V
OUT
CL
IN(min)
SW
()
For a practical example let: (see Figure 2)
P
OUT = 5.0V × 0.5A = 2.5W
V
IN = 4.0V to 6.0V
I
CL = 2.5A when δ < 50%
1.67 (2 –
δ) when δ ≥ 50%
Then:
V
= V
– I
R
IN min
IN
CL
SW
()
×
()
V
IN(min) = 4 – 0.78V
V
IN(min) = 3.22V
δ ≥ 0.74 (74%), less than 0.8 so discontinous is
permitted.
A few iterations of equation (8) may be required if the duty
cycle is found to be greater than 50%.
Calculate the maximum transformer turns ratio a, or
N
PRI/NSEC, that will guarantee safe operation of the MIC2171
power switch.
(9)
a
V
CE FCE – VIN(max)
V
SEC
Where:
a = transformer maximum turns ratio
V
CE = power switch collector to emitter
maximum voltage
F
CE = safety derating factor (0.8 for most
commercial and industrial applications)
V
IN(max) = maximum input voltage
V
SEC = transformer secondary voltage (VOUT + VF)
For the practical example:
V
CE = 65V max. for the MIC2171
F
CE = 0.8
V
SEC = 5.6V
Then:
a
65
× 0.8 – 6.0
5.6
a
≤ 8.2 (N
PRI/NSEC)
Next, calculate the maximum primary inductance required to
store the needed output energy with a power switch duty
cycle of 55%.


Similar Part No. - MIC2171BT

ManufacturerPart #DatasheetDescription
logo
Micrel Semiconductor
MIC2171BT MICREL-MIC2171BT Datasheet
191Kb / 12P
   100kHz 2.5A Switching Regulator
More results

Similar Description - MIC2171BT

ManufacturerPart #DatasheetDescription
logo
Micrel Semiconductor
MIC2171 MICREL-MIC2171_07 Datasheet
191Kb / 12P
   100kHz 2.5A Switching Regulator
MIC2172 MICREL-MIC2172 Datasheet
129Kb / 16P
   100kHz 1.25A Switching Regulators Preliminary Information
MIC2570 MICREL-MIC2570 Datasheet
178Kb / 14P
   Two-Cell Switching Regulator Preliminary Information
MIC2571 MICREL-MIC2571 Datasheet
126Kb / 11P
   Single-Cell Switching Regulator Preliminary Information
MIC5210 MICREL-MIC5210 Datasheet
60Kb / 8P
   Dual 150mA LDO Regulator Preliminary Information
MIC5237 MICREL-MIC5237 Datasheet
41Kb / 8P
   500mA Low-Dropout Regulator Preliminary Information
logo
Linear Technology
LT1170 LINER-LT1170_15 Datasheet
236Kb / 24P
   100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators
logo
List of Unclassifed Man...
PS12000 ETC1-PS12000 Datasheet
1Mb / 24P
   PRELIMINARY INFORMATION
logo
Xicor Inc.
X98027 XICOR-X98027 Datasheet
105Kb / 1P
   PRELIMINARY INFORMATION
logo
Linear Technology
LT1171 LINER-LT1171_15 Datasheet
236Kb / 24P
   100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators
More results


Html Pages

1 2 3 4 5 6 7 8 9 10


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.NET
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com