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fitipower integrated technology lnc.
FR9884
85T 18V, 3A, 340KHz Synchronous Step-Down DC/DC Converter
Description
The FR9884 is a synchronous step-down DC/DC converter that provides wide 4.5V to 18V input voltage range and 3A continuous load current capability. 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 that provides fast transient response. In shutdown mode, the supply current is about 10μA. The FR9884 is available in an 8-pin SOIC package, which provides a very compact system solution and good thermal conductance.
Features
● Wide Input Voltage from 4.5V to 18V ● 3A Output Current ● Adjustable Output Voltage from 0.925V to 14V ● Low Rds(on) Integrated Power MOSFET ● High Efficiency up to 93% ● 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 ● 10μA Shutdown Current ● Thermal Enhanced SOP-8 (Exposed Pad) Package ● RoHS Compliant
Applications
● Set-Top-Box ● DVD,LCD Display ● OLPC, Netbook ● Distributed Power System ● Datacom, XDSL
Pin Assignments
SP Package (SOP-8 Exposed Pad)
Ordering Information
FR9884□□□
TR: Tape / Reel
BS VIN SW GND
1 2 3 4
8 7 6 5
SS EN COMP FB
G: Green Package Type SP: SOP-8 (Exposed Pad)
Figure 1. Pin Assignment of FR9884
FR9884-1.7-DEC-2011
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fitipower integrated technology lnc.
FR9884
85T
Typical Application Circuit
R3 100KΩ C4 10nF
7 EN VIN 5V to 12V
C6 100μF/25V EC x1 C1 10μF/25V CERAMIC x 1
1
BS
SW 3
2
L1 10μH
VIN
VOUT 3.3V
R1 26.1KΩ/1%
(optional)
FR9884
6 COMP GND 4 FB 5 SS
C8
C2 22μF/6.3V CERAMIC x 2
C7 (optional)
C5 10nF
R4 5.6KΩ
8
C3 0.1μF
R2 10KΩ/1%
Figure 2. Output 3.3V Application Circuit
R3 100KΩ
D1 1N4148
C4 10nF
7 EN
VIN
1 BS SW 3
2 VIN
C1 10μF/25V CERAMIC x 2 C5 10nF R4 5.6KΩ
L1 10μH
4.5V to 5V
1.8V
R1 9.53KΩ/1% C8
(optional)
VOUT
FR9884
6 COMP GND 4 FB SS 8
C3 0.1μF
5
C2 22μF/6.3V CERAMIC x 2
(optional)
C7
R2 10KΩ/1%
Figure 3. Low Input Voltage Application Circuit
R3 100KΩ
C4 10nF
7 EN VIN 12V to 18V
C6 330uF/25V EC x1 C1 10uF/25V CERAMIC x 1
1
BS
SW 3
2
L1 10uH
VIN
VOUT 3.3V
R1 26.1KΩ/1%
(optional)
FR9884
6 COMP GND 4 FB 5 SS
C8
C2 22uF/6.3V CERAMIC x 2
C5 10nF C7 (optional)
R4 5.6KΩ
8
C3 0.1uF
R2 10KΩ/1%
Figure 4. High Input Voltage Application Circuit
FR9884-1.7-DEC-2011
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fitipower integrated technology lnc.
FR9884
85T
Functional Pin Description
Pin Name BS VIN SW GND FB COMP EN SS Pin Function High Side Gate Drive Boost Input. A 10nF or greater capacitor must be connected from this pin to SW. boost the gate drive to fully turn on the internal high side NMOS. Power Supply Input Pin. Drive 4.5V to 18V voltage to this pin to power on this chip. Power Switching Output.
It can
It is the output pin of internal high side NMOS which is the switch to supply power.
Ground Pin. Connect this pin to exposed pad. Voltage Feedback Input Pin. Connect FB and VOUT with a resistive voltage divider. voltage via FB and regulates it at 0.925V. Compensation Pin. This pin is used to compensate the regulation control loop. from COMP pin to GND. Enable Input Pin. This pin provides a digital control to turn the converter on or off. resistor for self-startup. Soft-Start Input Pin. start period. This IC senses feedback
Connect a series RC network Connect to VIN with a 100KΩ
This pin controls the soft-start period. Connect a capacitor from SS to GND to set the soft
Block Diagram
1 μA 2.5V
6μ A
OVP OTP VIN UVLO
Figure 5. Block Diagram of FR9884
FR9884-1.7-DEC-2011
+
SS
-
1.3V
0.925V
+
Error Amplifier COMP
-
OVP
+
FB +
-
+ COMP +
EN
REGULATOR
1.4V
Slope Compensation
+
Current Sense Amplifier
VIN 5V
High-Side MOSFET Oscillator CLK
S R Q Q
BS
SW Low-Side MOSFET GND
Current Comparator
3
fitipower integrated technology lnc.
FR9884
85T
Absolute Maximum Ratings
● Input Supply Voltage VIN --------------------------------------------------------------------------------- -0.3V to +21V
● SW Voltage VSW -------------------------------------------------------------------------------------------- -1V to VIN +0.3V ● Boost Trap Voltage VBS ----------------------------------------------------------------------------------- Vsw -0.3V to Vsw +6V ● All Other Pins Voltage ------------------------------------------------------------------------------------ -0.3V to +6V ● Maximum Junction Temperature (T J) ----------------------------------------------------------------- +150°C ● Storage Temperature (TS) ------------------------------------------------------------------------------- -65°C to +150°C ● Lead Temperature (Soldering, 10sec.) --------------------------------------------------------------- +260°C ● Power Dissipation @TA=25°C, (PD) SOP-8 (Exposed Pad) ----------.