FR9889
23V, 3A, 340KHz Synchronous Step-Down
DC/DC Converter
Description
The FR9889 is a synchronous step-down DC/DC
converter that provides wide 4.5V to 23V input
voltage range and 3A continuous load current
capability. At light load condition, the FR9889 can
operate at power saving mode to support high
efficiency and reduce power lose.
The FR9889 fault protection includes cycle-by-cycle
current limit, UVLO, output overvoltage protection
and thermal shutdown. The 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 about 1µA.
The FR9889 is available in a SOP-8 exposed pad
package,
which
provides
good
thermal
conductance.
Features
Low
R
DS(ON)
Integrated Power MOSFET
(120mΩ /100mΩ)
Internal Compensation Function
Internal Power Good Function
Wide Input Voltage Range: 4.5V to 23V
Adjustable Output Voltage Down to 0.925V
3A Output Current
340kHz Switching Frequency
External Programmable Soft-Start or Internal
600µs Soft-Start
Cycle-by-Cycle Current Limit
Over-Temperature Protection with Auto Recovery
OVP, UVLO
Hiccup Short Circuit Protection
SOP-8 Exposed Pad Package
Applications
STB (Set-Top-Box)
LCD Display, TV
Distributed Power System
Networking, XDSL Modem
Pin Assignments
SP Package (SOP-8 Exposed Pad)
Ordering Information
FR9889
□□□
TR: Tape/Reel
C: Green
Package Type
SP: SOP-8 (Exposed Pad)
Figure 1. Pin Assignment of FR9889
FR9889-1.1-MAY-2016
1
FR9889
Typical Application Circuit
Figure 2. C
IN
/C
OUT
use Ceramic Capacitors Application Circuit
Figure 3. C
IN
/C
OUT
use Electrolytic Capacitors Application Circuit
V
IN
=12V, the recommended BOM list is as below.
V
OUT
1.2V
1.8V
2.5V
3.3V
5V
1.2V
1.8V
2.5V
3.3V
5V
R1
3kΩ
9.53kΩ
16.9kΩ
26.1kΩ
44.2kΩ
3kΩ
9.53kΩ
16.9kΩ
26.1kΩ
44.2kΩ
R2
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
C6
10pF~10nF
10pF~10nF
10pF~10nF
10pF~10nF
10pF~10nF
--
--
--
--
--
L1
4.7µH
4.7µH
6.8µH
10µH
10µH
4.7µH
4.7µH
6.8µH
10µH
10µH
C2
22µF MLCC x2
22µF MLCC x2
22µF MLCC x2
22µF MLCC x2
22µF MLCC x2
100µF EC x1
100µF EC x1
100µF EC x1
100µF EC x1
100µF EC x1
Table 1. Recommended Component Values
FR9889-1.1-MAY-2016
2
FR9889
Functional Pin Description
Pin Name
BST
VIN
LX
GND
FB
PG
SHDN
SS
Exposed Pad
Pin No.
1
2
3
4
5
6
7
8
9
Pin Function
High Side Gate Drive Boost Pin. A capacitor rating between 10nF~100nF must be connected from
this pin to LX. It can boost the gate drive to fully turn on the internal high side NMOS.
Power Supply Input Pin. Placed input capacitors as close as possible from VIN to GND to avoid
noise influence.
Power Switching Node. Connect an external inductor to this switching node.
Ground Pin. Connect GND to exposed pad.
Voltage Feedback Input Pin. Connect FB and VOUT with a resistive voltage divider. This IC
senses feedback voltage via FB and regulates it at 0.925V.
Open Drain Power Good Output Pin.
Enable Input Pin. Pull high to turn on IC, and pull low to turn off IC. Connect VIN with a 100kΩ
resistor for self-startup.
Soft-start Pin. This pin controls the soft-start period. Connect a capacitor from SS to GND to set the
soft-start period. If disconnect capacitor from SS to GND, the internal soft-start time will be 600µs.
Ground Pin. The exposed pad must be soldered to a large PCB area and connected to GND for
maximum power dissipation.
Block Diagram
Figure 4. Block Diagram of FR9889
FR9889-1.1-MAY-2016
3
FR9889
Absolute Maximum Ratings
(Note 1)
● Supply Voltage V
IN
----------------------------------------------------------------------------------------- -0.3V to +25V
● Enable Voltage V
SHDN
----------------------------------------------------------------------------------- -0.3V to +25V
● LX Voltage V
LX
---------------------------------------------------------------------------------------------- -1V to V
IN
+0.3V
● BST Pin Voltage V
BST
------------------------------------------------------------------------------------- V
LX
-0.3V to V
LX
+6.5V
● All Other Pins Voltage ------------------------------------------------------------------------------------ -0.3V to +6V
● Maximum Junction Temperature (T
J
) ----------------------------------------------------------------- +150°C
● Storage Temperature (T
S
) ------------------------------------------------------------------------------- -65°C to +150°C
● Lead Temperature (Soldering, 10sec.) --------------------------------------------------------------- +260°C
● Power Dissipation @T
A
=25°C, (P
D
)
(Note 2)
SOP-8 (Exposed Pad) ------------------------------------------------------------------------ 2.08W
● Package Thermal Resistance, (θ
JA
)
SOP-8 (Exposed Pad) ------------------------------------------------------------------------ 60°C/W
● Package Thermal Resistance, (θ
JC
)
SOP-8 (Exposed Pad) ------------------------------------------------------------------------ 15°C/W
Note 1：Stresses beyond this listed under “Absolute Maximum Ratings" may cause permanent damage to the device.
2
Note 2：PCB heat sink copper area = 10mm .
Recommended Operating Conditions
● Supply Voltage V
IN
----------------------------------------------------------------------------------------- +4.5V to +23V
● Operation Temperature Range ------------------------------------------------------------------------- -40°C to +85°C
FR9889-1.1-MAY-2016
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FR9889
Electrical Characteristics
(V
IN
=12V, T
A
=25°C, unless otherwise specified.)
Parameter
V
IN
Quiescent Current
V
IN
Shutdown Supply Current
Feedback Voltage
Feedback OVP Threshold Voltage
High-Side MOSFET R
DS(ON)
Low-Side MOSFET R
DS(ON)
(Note 3)
Symbol
I
DDQ
I
SD
V
FB
V
OVP
R
DS(ON)
R
DS(ON)
I
LX(leak)
I
LIMIT(HS)
F
OSC
F
OSC(short)
D
MAX
T
MIN
V
UVLO(Vth)
V
UVLO(HYS)
I
SS
T
SS
V
PG (H)
V
PG (L)
I
PG
V
SHDN(L)
V
SHDN(H)
I
SHDN
(Note 3)
Conditions
V
SHDN
=2V, V
FB
=1.0V
V
SHDN
=0V
4.5V
≦
V
IN
≦
23V
Min
Typ
0.8
1
Max
1
10
0.944
Unit
mA
µA
V
V
mΩ
mΩ
0.906
0.925
1.25
120
100
(Note 3)
High-Side MOSFET Leakage Current
High-Side MOSFET Current Limit
Oscillation Frequency
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On Time
(Note 3)
(Note 3)
V
SHDN
=0V, V
LX
=0V
Minimum Duty
4
280
V
FB
=0V
V
FB
=0.8V
4.7
340
110
88
110
V
IN
Rising
4.2
400
V
SS
=0V
6
600
V
FB
Rising
V
FB
Falling
V
PG
=0.3V
92
82
1
10
µA
A
400
kHz
kHz
%
ns
V
mV
µA
µs
%
%
mA
Input Supply Voltage UVLO Threshold
Input Supply Voltage UVLO Threshold
Hysteresis
Soft-Start Current
Internal Soft-Start Period
PG High Threshold
PG Low Threshold
PG Sink Current
SHDN Input Low Voltage
SHDN Input High Voltage
SHDN Input Current
Thermal Shutdown Threshold
Note 3：Not production tested.
0.4
2
V
SHDN
=2V
2
165
V
V
µA
°C
T
SD
FR9889-1.1-MAY-2016
5
嵌入式系统
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