Electronic Components Datasheet Search
  English  ▼

X  

Preview PDF HTML

FR9889 Datasheet(PDF) 10 Page - Fitipower Integrated Technology Inc.

Part # FR9889
Description  23V, 3A, 340KHz Synchronous Step-Down DC/DC Converterxxxxxxxxxxx
PDF  13 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  FITIPOWER [Fitipower Integrated Technology Inc.]
Direct Link  http://www.fitipower.com/en_US/index.asp
Logo FITIPOWER - Fitipower Integrated Technology Inc.

FR9889 Datasheet(HTML) 10 Page - Fitipower Integrated Technology Inc.

Back Button FR9889 Datasheet HTML 5Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 6Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 7Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 8Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 9Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 10Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 11Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 12Page - Fitipower Integrated Technology Inc. FR9889 Datasheet HTML 13Page - Fitipower Integrated Technology Inc.  
Zoom Inzoom in Zoom Outzoom out
 10 / 13 page
background image
FR9889-1.1-MAY-2016
Application Information
Output Voltage Setting
The output voltage VOUT is set by using a resistive
divider from the output to FB.
The FB pin regulated
voltage is 0.925V.
Thus the output voltage is:
VOUT=0.925V× 1+
R1
R2
Table 2 lists recommended values of R1 and R2 for
most used output voltage.
Table 2
Recommended Resistance Values
VOUT
R1
5V
44.2kΩ
10kΩ
3.3V
26.1kΩ
10kΩ
2.5V
16.9kΩ
10kΩ
1.8V
9.53kΩ
10kΩ
1.2V
3kΩ
10kΩ
Place resistors R1 and R2 close to FB pin to
stray pickup.
Input Capacitor Selection
The use of the input capacitor is filtering
voltage ripple and the MOSFETS switching spike
voltage.
Because
the
input
current
to
the
step-down converter is discontinuous, the input
capacitor is required to supply the current to the
converter to keep the DC input voltage.
capacitor voltage rating should be 1.25 to 1.5 times
greater than the maximum input voltage.
capacitor ripple current RMS value is calculated as:
ICIN(RMS)=IOUT× D× 1-D
D=
VOUT
VIN
Where D is the duty cycle of the power MOSFET.
This function reaches the maximum value at D=0.5
and the equivalent RMS current is equal to I
The
following
diagram
is
the
graphical
representation of above equation.
0
0.25
0.5
0.75
1
1.25
1.5
1.75
10 20 30 40 50 60 70
D (%)
3A
1A
2A
using a resistive
The FB pin regulated
Thus the output voltage is:
1
2
lists recommended values of R1 and R2 for
Recommended Resistance Values
R2
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
Place resistors R1 and R2 close to FB pin to prevent
filtering the input
voltage ripple and the MOSFETS switching spike
Because
the
input
current
to
the
down converter is discontinuous, the input
uired to supply the current to the
converter to keep the DC input voltage.
The
1.25 to 1.5 times
greater than the maximum input voltage.
The input
capacitor ripple current RMS value is calculated as:
D
D is the duty cycle of the power MOSFET.
This function reaches the maximum value at D=0.5,
and the equivalent RMS current is equal to IOUT/2.
The
following
diagram
is
the
graphical
A low ESR capacitor is required to keep the noise
minimum.
Ceramic capacitors are better, but
tantalum or low ESR electrolytic capacitors may also
suffice.
When using tantalum or electrolytic
capacitors, a 0.1µF ceramic capacitor should be
placed as close to the IC as possible.
Output Capacitor Selection
The output capacitor is used to keep the DC output
voltage and supply the load transient current.
When operating in constant current mode, the
output ripple is determined by four components:
VRIPPLE t =VRIPPLE(C) t +VRIPPLE
+VRIPPLE(ESL)(t)+V
The following figures show
contributions.
VRIPPLE(ESR)(t)
+
VRIPPLE(ESL) (t)
+
VRIPPLE(C) (t)
+
VNOISE (t)
=
VRIPPLE(t)
80 90
(t)
(t)
(t)
(t)
10
FR9889
A low ESR capacitor is required to keep the noise
Ceramic capacitors are better, but
tantalum or low ESR electrolytic capacitors may also
When using tantalum or electrolytic
µF ceramic capacitor should be
e to the IC as possible.
Output Capacitor Selection
The output capacitor is used to keep the DC output
voltage and supply the load transient current.
When operating in constant current mode, the
output ripple is determined by four components:
RIPPLE(ESR)(t)
VNOISE(t)
figures show the form of the ripple



Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13


Datasheet Download

Go To PDF Page


Link URL



Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Link to Datasheet    |   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