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RT8271GFP

P1-P3P4-P6P7-P9P10-P12P13-P15
RT8271
1
DS8271-02 March 2011 www.richtek.com
Ordering Information
Pin Configurations
(TOP VIEW)
MSOP-10 (Exposed Pad)
Note :
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
2A, 24V, 1.2MHz Step-Down Converter
Applications
z Distributive Power Systems
z Battery Charger
z DSL Modems
z Pre-regulator for Linear Regulators
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area, otherwise visit our website for detail.
General Description
The RT8271 is a high voltage buck converter that can
support the input voltage range from 4.75V to 24V and the
output current can be up to 2A. Current Mode operation
provides fast transient response and eases loop
stabilization. The RT8271 also provides adjustable soft-
start to be a flexible solution for customers.
The chip provides protection functions such as cycle-by-
cycle current limiting and thermal shutdown protection.
In shutdown mode, the regulator draws 22μA of supply
current. The RT8271 is available in the SOP-8 and
MSOP-10 (Exposed Pad) surface mount package.
Features
zz
zz
z
Wide Operating Input Range : 4.75V to 24V
zz
zz
z Adjustable Output Voltage Range : 0.92V to 16V
zz
zz
z Output Current up to 2A
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z 22
μμ
μμ
μA Low Shutdown Current
zz
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z Power MOSFET : 0.18
ΩΩ
ΩΩ
Ω
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z High Efficiency up to 92%
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z 1.2MHz Fixed Switching Frequency
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z Stable with Low ESR Output Ceramic Capacitors
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z Programmable Soft-Start
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z Thermal Shutdown Protection
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z Cycle-By-Cycle Over Current Protection
zz
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z RoHS Compliant and Halogen Free
SS
FB
NC
VIN
NC
EN
COMP
SW
GND
BOOT
5
6
7
8
4
3
2
10
9
GND
11
BOOT
VIN
SW
GND
SS
EN
FB
COMP
2
3
4
5
6
7
8
SOP-8
Package Type
S : SOP-8
FP : MSOP-10 (Exposed Pad)
RT8271
Lead Plating System
G : Green (Halogen Free and Pb Free)
RT8271
2
DS8271-02 March 2011www.richtek.com
V
OUT
(V) R1 (kΩ) R2 (kΩ) R
C
(kΩ) C
C
(nF) L (μH) C
OUT
(μF)
15 154 10 68 0.56 22 22
10 100 10 49.9 0.82 15 22
8 76.8 10 49.9 1 10 22
5 44.2 10 33 1.2 6.8 22
3.3 25.5 10 22 1.5 4.7 22
2.5 16.9 10 15 1.5 4.7 22
1.8 9.53 10 12 1.5 2.2 22
1.2 3 10 12 1.5 2.2 22
Table 1. Recommended Component Selection
Function Block Diagram
Typical Application Circuit
VIN
EN
GND
BOOT
FB
SW
L1
4.7µH
C
BOOT
10nF
C
OUT
22µF/6.3V
R1
16.9k
R2
10k
V
OUT
2.5V
C
IN
10µF/25V
Chip Enable
V
IN
4.75V to 24V
RT8271
D1
B230A
SS
C
SS
10nF
COMP
C
C
1.5nF
R
C
15k
C
P
NC
VA
+
-
+
-
+
-
UV
Comparator
Oscillator
1.2MHz/440kHz
Foldback
Control
0.5V
Internal
Regulator
+
-
1V
1µA
Shutdown
Comparator
Current Sense
Amplifier
BOOT
VIN
GND
SW
FB
EN
COMP
3V
10k
VA
V
CC
V
CC
Slope Comp
Current
Comparator
SS
10µA
V
CC
+
-
EA
0.92V
Gm = 920µA/V
+
Logic
RT8271
3
DS8271-02 March 2011 www.richtek.com
Functional Pin Description
Pin No.
PMSOP-10 SOP-8
Pin Name Pin Function
1, 3 -- NC No Internal Connection.
2 1 BOOT
High Side Gate Drive Boost Input. BOOT supplies the drive for the
high side N-MOSFET switch. Connect a 10nF or greater capacitor
from SW to BOOT to power the high side switch.
4 2 VIN
Power Input. V
IN
supplies the power to the IC, as well as the
step-down converter switches. Bypass VIN to GND with a suitable
large capacitor to eliminate noise on the input to the IC.
5 3 SW
Power Switching Output. SW is the switching node that supplies
power to the output. Connect the output LC filter from SW to the
output load. Note that a capacitor is required from SW to BOOT to
power the high side switch.
6,
11 (Exposed Pad)
4 GND
Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
7 5 FB
Feedback Input. FB senses the output voltage to regulate said
voltage. The feedback reference voltage is 0.92V typically.
8 6 COMP
Compensation Node. COMP is used to compensate the regulation
control loop. Connect a series RC network from COMP to GND to
compensate the regulation control loop. In some cases, an additional
capacitor from COMP to GND is required.
9 7 EN
Enable Input. EN is a digital input that turns the regulator on or off.
Drive EN higher than 1.4V to turn on the regulator, lower than 0.4V to
turn it off. If the EN pin is open, it will be pulled to high by internal
circuit.
10 8 SS
Soft-Start Control Input. SS controls the soft start period. Connect a
capacitor from SS to GND to set the soft-start period. A 10nF
capacitor sets the soft-start period to 1ms.
P1-P3P4-P6P7-P9P10-P12P13-P15

RT8271GFP

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Description:
IC REG BUCK ADJ 2A 10MSOP
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