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PDF FR9886C Data sheet ( Hoja de datos )
| Número de pieza | FR9886C | |
| Descripción | 340KHz Synchronous Step-Down DC/DC Converter | |
| Fabricantes | Fiti | |
| Logotipo |  |
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fitipower integrated technology lnc.
FR9886C
21V, 2A/2.5A, 340KHz Synchronous Step-Dow85nT
DC/DC Converter
Description
The FR9886C is a synchronous step-down DC/DC
converter that provides wide 4.5V to 21V input
voltage range. There are two packages (SOP-8 &
SOP-8(EP)) to support 2A/2.5A continuous output
current.
The FR9886C fault protection includes
cycle-by-cycle current limit, input UVLO, output over
voltage protection and thermal shutdown. Besides,
adjustable soft-start function prevents inrush current
at turn-on. This device uses current mode control
scheme which provides fast transient response.
In shutdown mode, the supply current is less than
1μA.
The FR9886C is available in SOP-8 and SOP-8
exposed pad packages. It is RoHS compliant and
100% lead (Pb) free.
Features
● High Efficiency Synchronous Buck Converter with
Low ISD (<1μA)
● Low Rds(on) Integrated Power MOSFET
● Wide Input Voltage Range: 4.5V to 21V
● Adjustable Output Voltage from 0.925V to 17.85V
● 2A Output Current (Package: SOP-8)
● 2.5A Output Current (Package: SOP-8(EP))
● Fixed 340KHz Switching Frequency
● Current Mode Operation
● Adjustable Soft-Start
● Cycle-by-Cycle Current Limit
● Input Under Voltage Lockout
● Over-Temperature Protection with Auto Recovery
● SOP-8 and SOP-8 Exposed Pad Packages
Applications
● Set-Top-Box
● DVD,LCD Display
● OLPC, Netbook
● Distributed Power System
● Datacom, XDSL
Pin Assignments
SO Package (SOP-8)
BST
VIN
LX
GND
1
2
3
4
8 SS
7 SHDN
6 COMP
5 FB
SP Package (SOP-8 Exposed Pad)
Ordering Information
FR9886C□□□
TR: Tape / Reel
C: Green
Package Type
SO: SOP-8
SP: SOP-8 (Exposed Pad)
BST
VIN
LX
GND
1
2
3
4
8 SS
7 SHDN
6 COMP
5 FB
Figure 1. Pin Assignment of FR9886C
FR9886C-0.4-JUL-2012
1
1 page  
fitipower integrated technology lnc.
FR9886C
Electrical Characteristics
(VIN=12V, TA=25°C, unless otherwise specified.)
Parameter
Symbol
Conditions
85T
Min Typ Max Unit
VIN Input Supply Voltage
VIN Quiescent Current
VIN Shutdown Supply Current
Feedback Voltage
Feedback OVP Threshold Voltage
High-Side MOSFET RDS(ON) (Note3)
Low-Side MOSFET RDS(ON) (Note3)
High-Side MOSFET Leakage Current
High-Side MOSFET Current Limit
(Note3)
Low-Side MOSFET Current Limit
(Note3)
Current sense to COMP
Transconductance (Note3)
Error Amplifier Transconductance
(Note3)
Error Amplifier Voltage Gain (Note3)
VIN
IDDQ
ISD
VFB
VOVP
RDS(ON)
RDS(ON)
ILX(leak)
ILIMIT(HS)
=1.8V, VFB=1.0V
=0V
4.5V≦VIN≦21V
SOP-8
SOP-8 (EP)
=0V, VLX=0V
Minimum
Duty
SOP-8
SOP-8 (EP)
4.5 21
2
1
0.9 0.925 0.95
1.5
130
120
110
10
2.8 4
3.1 4.5
V
mA
μA
V
V
mΩ
mΩ
μA
A
ILIMIT(LS) From Drain to Source
1.5 A
3.5 A/V
Δ ICOMP = ±10μA
1600
μA/V
400 V/V
Oscillation frequency
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On Time (Note3)
Input UVLO Threshold
Under Voltage Lockout Threshold
Hysteresis
Soft-Start Current
Soft-Start Period
FOSC
FOSC(short) VFB=0V
DMAX
VFB=0.8V
TMIN
VUVLO(Vth) VIN Rising
VUVLO(HYS)
ISS VSS=0V
TSS CSS=0.1μF
290 340 420 KHz
110 KHz
90 %
100 ns
4.3 V
400 mV
6 μA
15 ms
Input Low Voltage
(L)
0.4 V
Input High Voltage
Input Current
Thermal Shutdown Threshold (Note3)
Note 3：Not production tested.
()
TSD
=2V
2
2
170
V
μA
°C
FR9886C-0.4-JUL-2012
5
5 Page 
fitipower integrated technology lnc.
Application Information (Continued)
FR9886C
85T
R PPL (
R,
p
p)=
O
FO C
T
L
R PPL ( L, p p)= L
L
L
1 OT
R
R PPL (C, p p)=
OT
FO C2 L CO T
1 OT
Where FOSC is the switching frequency, L is the
inductance value, VIN is the input voltage, ESR is the
equivalent series resistance value of the output
capacitor, ESL is the equivalent series inductance
value of the output capacitor and the COUT is the
output capacitor.
Low ESR capacitors are preferred to use. Ceramic,
tantalum or low ESR electrolytic capacitors can be
used depending on the output ripple requirements.
When using the ceramic capacitors, the ESL
component is usually negligible.
It is important to use the proper method to eliminate
high frequency noise when measuring the output
ripple. The figure shows how to locate the probe
across the capacitor when measuring output ripple.
Removing the scope probe plastic jacket in order to
expose the ground at the tip of the probe. It gives a
very short connection from the probe ground to the
capacitor and eliminates noise.
Probe Ground
VOUT
GND
Ceramic Capacitor
Inductor Selection
The output inductor is used for storing energy and
filtering output ripple current. But the trade-off
condition often happens between maximum energy
storage and the physical size of the inductor. The
first consideration for selecting the output inductor is
to make sure that the inductance is large enough to
keep the converter in the continuous current mode.
That will lower ripple current and result in lower
output ripple voltage. The Δ L is inductor
peak-to-peak ripple current:
=
FO
O
C
T
L
1 OT
The following diagram is an example to graphical
represent Δ L equation.
L=4.7μ
L=6.8μ
L=10μ
VOUT=3.3V, FOSC=340KHz
A good compromise value between size and
efficiency is to set the peak-to-peak inductor ripple
current Δ L equal to 30% of the maximum load
current. But setting the peak-to-peak inductor
ripple current Δ L between 20%~50% of the
maximum load current is also acceptable. Then
the inductance can be calculated with the following
equation:
=0.3 O T(MA )
L=
OT
FO C
OT
L
To guarantee sufficient output current, peak
inductor current must be lower than the FR9886C
high-side MOSFET current limit. The peak
inductor current is as below:
P AK= O T(MA )
L
2
FR9886C-0.4-JUL-2012
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet FR9886C.PDF ] | |
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