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PDF FR9886D Data sheet ( Hoja de datos )
| Número de pieza | FR9886D | |
| Descripción | 340KHz Synchronous Step-Down DC/DC Converter | |
| Fabricantes | Fiti | |
| Logotipo |  |
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fitipower integrated technology lnc.
FR9886D
23V, 2A/2.5A, 340KHz Synchronous Step-Do8w5Tn
DC/DC Converter
Description
The FR9886D is a synchronous step-down DC/DC
converter that provides wide 4.5V to 23V input
voltage range. There are two packages (SOP-8 &
SOP-8(EP)) to support 2A/2.5A continuous output
current.
The FR9886D 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.
Internal Compensation function reduces external
compensation components and simplifies the design
process. In shutdown mode, the supply current is
less than 1μA.
The FR9886D is available in SOP-8/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
● Internal Compensation Function
● Wide Input Voltage Range: 4.5V to 23V
● Adjustable Output Voltage from 0.925V to 20V
● 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
● STB (Set-Top-Box)
● LCD Display, TV
● Distributed Power System
● Networking, XDSL Modem
Pin Assignments
SO Package (SOP-8)
BST
VIN
LX
GND
1
2
3
4
8 SS
7 SHDN
6 NC
5 FB
SP Package (SOP-8 Exposed Pad)
BST
VIN
LX
GND
1
2
3
4
8 SS
7 SHDN
6 NC
5 FB
Figure 1. Pin Assignments of FR9886D
FR9886D-1.0-JAN-2012
Ordering Information
FR9886D□□□
TR: Tape / Reel
C: Green
Package Type
SO: SOP-8
SP: SOP-8 (Exposed Pad)
1
1 page  
fitipower integrated technology lnc.
FR9886D
Electrical Characteristics
(VIN=12V, TA=25°C, unless otherwise specified.)
Parameter
Symbol
Conditions
VIN Input Supply Voltage
VIN Quiescent Current
VIN Shutdown Supply Current
Feedback Voltage
Feedback OVP Threshold Voltage
High-Side MOSFET RDS(ON) (Note3)
VIN
IDDQ
ISD
VFB
VOVP
RDS(ON)
VSH N=1.8V, VFB=1.0V
VSH N=0V
4.5V≦VIN≦23V
SOP-8
SOP-8(EP)
Low-Side MOSFET RDS(ON) (Note3)
High-Side MOSFET Leakage Current
High-Side MOSFET Current Limit
(Note3)
Low-Side MOSFET Current Limit
(Note3)
Error Amplifier Voltage Gain (Note3)
RDS(ON)
ILX(leak)
ILIMIT(HS)
VSH N=0V, VLX=0V
Minimum
Duty
SOP-8
SOP-8(EP)
ILIMIT(LS) From Drain to Source
Oscillation frequency
Short Circuit Oscillation Frequency
Maximum Duty Cycle
FOSC
FOSC(short) VFB=0V
DMAX
VFB=0.8V
Minimum On Time (Note3)
TMIN
Input UVLO Threshold
Under Voltage Lockout
Hysteresis
Threshold
VUVLO(Vth)
VUVLO(HYS)
VIN Rising
Soft-Start Current
ISS VSS=0V
Soft-Start Period
TSS CSS=0.1μF
SH N Input Low Voltage
VSH N (L)
SH N Input High Voltage
SH N Input Current
VSH N (H)
I SH N
VSH N=2V
Thermal Shutdown Threshold (Note3)
TSD
Note 3：Not production tested.
Min Typ Max
4.5 23
2
1
0.9 0.925 0.95
1.5
130
120
110
10
2.8 4
3.1 4.5
1.5
400
290 340 420
110
90
100
4.3
250
6
15
0.4
2
0.75
170
85T
Unit
V
mA
μA
V
V
mΩ
mΩ
μA
A
A
V/V
KHz
KHz
%
ns
V
mV
μA
ms
V
V
μA
°C
FR9886D-1.0-JAN-2012
5
5 Page 
fitipower integrated technology lnc.
FR9886D
Application Information
VRIPPLE(ESR,
p
p)
=
VOUT
FOSC
L
1
VOUT
VIN
ESR
VRIPPLE(ESL,
p
p)
=
ESL
L ESL
VIN
VRIPPLE(C, p p)= 8
VOUT
FOSC2 L
COUT
1
VOUT
VIN
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 requirement.
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 eliminating 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.
85T
That will lower ripple current and result in lower
output ripple voltage. The ΔIL is inductor
peak-to-peak ripple current:
IL
=
VOUT
FOSC
L
1
VOUT
VIN
The following diagram is an example to graphically
represent ΔIL 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 ΔIL equal to 30% of the maximum load
current. But setting the peak-to-peak inductor
ripple current ΔIL between 20%~50% of the
maximum load current is also acceptable. Then
the inductance can be calculated with the following
equation:
IL=0.3 IOUT(MAX)
L=
VIN VOUT
VIN FOSC
VOUT
IL
To guarantee sufficient output current, peak
inductor current must be lower than the FR9886
high-side MOSFET current limit. The peak
inductor current is shown as below:
IPEAK=IOUT(MAX)
IL
2
FR9886D-1.0-JAN-2012
11
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| PDF Descargar | [ Datasheet FR9886D.PDF ] | |
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