RT8256 반도체 회로 부품 판매점
400kHz Step-Down Converter
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 Richtek |
RT8256
2A, 22V, 400kHz Step-Down Converter
General Description
The RT8256 is an as high voltage buck converter that can
support the input voltage range from 4.75V to 22V and the
output current can be up to 2A. Current Mode operation
provides fast transient response and eases loop
stabilization.
The chip provides protection functions such as cycle-by-
cycle current limiting and thermal shutdown protection.
In shutdown mode, the regulator draws 25uA of supply
current. The RT8256 is available in a SOP-8 surface mount
package.
Ordering Information
RT8256
Package Type
S : SOP-8
Lead Plating System
G : Green (Halogen Free and Pb Free)
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.
Typical Application Circuit
Features
z Wide Operating Input Range : 4.75V to 22V
z Adjustable Output Voltage Range : 1.22V to 16V
z Output Current up to 2A
z 25uA Low Shutdown Current
z Power MOSFET : 0.18Ω
z High Efficiency up to 95%
z 400kHz Fixed Switching Frequency
z Stable with Low ESR Output Ceramic Capacitors
z Thermal Shutdown Protection
z Cycle-By-Cycle Over Current Protection
z RoHS Compliant and Halogen Free
Applications
z Distributive Power Systems
z Battery Charger
z DSL Modems
z Pre-regulator for Linear Regulators
Pin Configurations
http://www.DataSheet4U.net/
(TOP VIEW)
NC
BOOT
VIN
SW
8
27
36
45
SOP-8
EN
COMP
FB
GND
VIN
4.75V to 22V
Chip Enable
CIN
10µF
3 VIN
BOOT 2
RT8256
SW 4
8 EN
FB 6
5 GND
COMP 7
CB L1
10nF 15µH
D1
B230
RC
10k
CC
1.5nF
R1
17k
R2
10k
VOUT
3.3V/2A
COUT
22µF
CP
NC
DS8256-01 March 2011
www.richtek.com
1
datasheet pdf - http://www.DataSheet4U.net/
RT8256
Table 1. Recommended Component Selection
VOUT (V) R1 (kΩ) R2 (kΩ) RC (kΩ) CC (nF)
12
88.7
10
62 0.82
5 30 10 20 2.2
3.3 17 10 10 1.5
2.5 10.45 10
7.5 1.5
1.8 4.75 10
6 1.5
1.222
0
10
6 3.9
L1 (μH)
33
22
15
10
10
6.8
C OUT (μF)
22
22
22
22
22
22
Functional Pin Description
Pin No.
1
2
3
4
Pin Name
NC
BOOT
VIN
SW
Pin Function
No Internal Connection.
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
swi tc h.
Power Input. VIN 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.
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.
5 GND
Ground.
6 FB
Feedback Input. FB senses the output voltage to regulate said voltage. The feedback
reference voltage is 1.222V typically.
Compensation Node. COMP is used to compensate the regulation control loop. Connect
http://www.DataSheet4U.net/
7 COMP 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.
8 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.
Function Block Diagram
VIN
1µA
Internal
Regulator
Oscillator
400kHz/120kHz
Current Sense
Slope Comp Amplifier
+
-
10k
EN
VA
-
Foldback
Control
1V +
0.6V +
3V Shutdown
Comparator
-
UV
Comparator
1.222V
+
EA
-
S
+
R
-
Current
Comparator
Q
Q
Gm = 780µA/V
VA
BOOT
SW
GND
www.richtek.com
2
FB COMP
DS8256-01 March 2011
datasheet pdf - http://www.DataSheet4U.net/
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PDF 파일 내의 페이지 : 총 12 페이지
제조업체: Richtek
( richtek )
RT8256 converter
데이터시트 다운로드 :
[ RT8256.PDF ]
[ RT8256 다른 제조사 검색 ]
국내 전력반도체 판매점
상호 : 아이지 인터내셔날
전화번호 : 051-319-2877
[ 홈페이지 ]
IGBT, TR 모듈, SCR, 다이오드모듈, 각종 전력 휴즈
( IYXS, Powerex, Toshiba, Fuji, Bussmann, Eaton )
전력반도체 문의 : 010-3582-2743
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