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PDF FR9801 Data sheet ( Hoja de datos )
| Número de pieza | FR9801 | |
| Descripción | 600KHz Synchronous Step-Down DC/DC Converter | |
| Fabricantes | Fiti | |
| Logotipo |  |
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fitipower integrated technology lnc.
FR9801
21V, 2A, 600KHz Synchronous Step-Dow85nT
DC/DC Converter
Description
The FR9801 is a synchronous step-down DC/DC
converter that provides wide 4.5V to 21V input
voltage range and 2A continuous load current
capability.
The FR9801 fault protection includes cycle-by-cycle
current limit, UVLO, output overvoltage protection
and thermal shutdown. The 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 FR9801 is available in SOT-23-6 package and
provides good thermal conductance.
Features
High Efficiency up to 94%
Low RDS(ON) Integrated Power MOSFET
Internal Compensation Function
Wide Input Voltage Range: 4.5V to 21V
Adjustable Output Voltage from 0.8V to 17.85V
2A Output Current
Fixed 600KHz Switching Frequency
Current Mode Operation
Cycle-by-Cycle Current Limit
Over-Temperature Protection with Auto Recovery
Output Overvoltage Protection
Under Voltage Lockout
<1μA Shutdown Current
SOT-23-6 Package
Applications
STB (Set-Top-Box)
LCD Display, TV
Distributed Power System
Networking, XDSL Modem
Pin Assignments
S6 Package (SOT-23-6)
LX VIN SHDN
654
(Marking)
123
BST GND FB
Figure 1. Pin Assignment of FR9801
Ordering Information
FR9801□□□
TR: Tape/Reel
C: Green
Package Type
S6: SOT-23-6
SOT-23-6 Marking
Part Number
FR9801S6CTR
Product Code
B1G
FR9801-0.5-JUL-2013
1
1 page  
fitipower integrated technology lnc.
FR9801
Electrical Characteristics
(VIN=12V, TA=25°C, unless otherwise specified.)
Parameter
Symbol
Conditions
85T
Min Typ Max Unit
VIN Input Supply Voltage
VIN
4.5 21 V
VIN Quiescent Current
VIN Shutdown Supply Current
IDDQ
ISD
SH =1.8V, VFB=1.0V
SH =0V
2.5 mA
1 μA
Feedback Voltage
VFB 4.5V≦VIN≦21V
0.78 0.8 0.82
V
Feedback OVP Threshold Voltage
VOVP
1.4 V
High-Side MOSFET RDS(ON)
(Note 2)
RDS(ON)
120 mΩ
Low-Side MOSFET RDS(ON)
(Note 2)
RDS(ON)
110 mΩ
High-Side MOSFET Leakage
Current
ILX(leak)
SH =0V, VLX=0V
10 μA
High-Side MOSFET Current Limit
(Note 2)
ILIMIT(HS) Minimum Duty
2.5 3
A
Low-Side MOSFET Current Limit
(Note 2)
ILIMIT(LS) From Drain to Source
1.5
A
Error Amplifier Voltage Gain
(Note 2)
400 V/V
Oscillation Frequency
FOSC
480 600 720 KHz
Short Circuit Oscillation Frequency
FOSC(short) VFB=0V
160 KHz
Maximum Duty Cycle
DMAX
VFB=0.6V
85 %
Minimum On Time (Note 2)
Input UVLO Threshold
Under Voltage Lockout Threshold
Hysteresis
SH Input Low Voltage
SH Input High Voltage
SH Input Current
Thermal Shutdown Threshold
(Note 2)
Note 2：Not production tested.
TMIN
VUVLO(Vth) VIN Rising
VUVLO(HYS)
SH (L
SH (H
SH
TSD
VIN =2V
100 ns
4.3 V
400 mV
0.4 V
2
2
V
μA
160 °C
FR9801-0.5-JUL-2013
5
5 Page 
fitipower integrated technology lnc.
Application Information
FR9801
85T
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 0.8V. Thus the output voltage is:
T=0.
1+
R1
R2
Table 2 lists recommended values of R1 and R2 for
most used output voltage.
Table 2 Recommended Resistance Values
VOUT
5V
3.3V
2.5V
1.8V
1.2V
R1
30.9kΩ
30.9kΩ
4.99kΩ
4.99kΩ
4.99kΩ
R2
5.76kΩ
9.76kΩ
2.32kΩ
3.92kΩ
10kΩ
Place resistors R1 and R2 close to FB pin to prevent
stray pickup.
Input Capacitor Selection
The use of the input capacitor is filtering the input
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. The
capacitor voltage rating should be 1.25 to 1.5 times
greater than the maximum input voltage. The input
capacitor ripple current RMS value is calculated as:
(RMS = T
1
=T
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 IOUT/2.
The following diagram is the graphical representation
of above equation.
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:
R PPLE t = R PPLE C t + R PPLE ESR t
+ R PPLE(ESL t +
SE t
The following figures show the form of the ripple
contributions.
VRIPPLE(ESR)(t)
+
VRIPPLE(ESL) (t)
(t)
+
VRIPPLE(C) (t)
+
VNOISE (t)
(t)
(t)
=
VRIPPLE(t)
2A
1.5A
1A
(t)
FR9801-0.5-JUL-2013
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet FR9801.PDF ] | |
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