|
|
PDF RT8251 Data sheet ( Hoja de datos )
| Número de pieza | RT8251 | |
| Descripción | 570kHz Step-Down Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de RT8251 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
®
RT8251
5A, 24V, 570kHz Step-Down Converter
General Description
The RT8251 is a monolithic step-down switch mode
converter with a built-in internal power MOSFET. It achieves
5A continuous output current over a wide input supply
range with excellent load and line regulation. Current mode
operation provides fast transient response and eases loop
stabilization.
The RT8251 provides protection functions such as
cycle-by-cycle current limiting and thermal shutdown. In
shutdown mode, the regulator draws 25μA of supply
current. Programmable soft-start minimizes the inrush
supply current and the output overshoot at initial startup.
The RT8251 requires a minimum number of external
components. The RT8251 is available in WQFN-16L 3x3
and SOP-8 (Exposed Pad) packages.
Pin Configurations
(TOP VIEW)
Features
z Wide Operating Input Voltage Range : 4.75V to 24V
z Adjustable Output Voltage Range : 0.8V to 15V
z Output Current up to 5A
z 25μA Low Shutdown Current
z Internal Power MOSFET : 70mΩ
z High Efficiency up to 95%
z 570kHz 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 Distributed Power Systems
z Battery Charger
z DSL Modems
z Pre-regulator for Linear Regulators
16 15 14 13
VIN
VIN
VIN
GND
1
2
3
4
GND
17
12 SW
11 SW
10 SW
9 BOOT
5678
WQFN-16L 3x3
BOOT
VIN
SW
GND
8
27
GND
36
9
45
SS
EN
COMP
FB
SOP-8 (Exposed Pad)
Ordering Information
RT8251
Package Type
QW : WQFN-16L 3x3 (W-Type)
SP : SOP-8 (Exposed Pad-Option 1)
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.
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8251-04 February 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT8251
Electrical Characteristics
(VIN = 12V, TA = 25°C unless otherwise specified)
Parameter
Symbol
Feedback Reference Voltage
High-Side Switch-On Resistance
VFB
RDS(ON)1
Low-Side Switch-On Resistance
High-Side Switch Leakage
RDS(ON)2
Current Limit
ILIM
Current Sense Transconductance GCS
Error Amplifier Tansconductance gm
Oscillator Frequency
fSW
Short Circuit Oscillation Frequency
Maximum Duty Cycle
DMAX
Minimum On-Time
UVLO Threshold Rising
tON
UVLO Threshold Hysteresis
EN Input Voltage
Logic Low VIL
Logic High VIH
Enable Pull Up Current
Shutdown Current
Quiescent Current
Soft-Start Current
ISHDN
IQ
ISS
Soft-Start Period
Thermal Shutdown
TSD
Test Conditions
4.75V ≦ VIN ≦ 24V
VEN = 0V, VSW = 0V
Duty = 85%; VBOOT−SW = 4.8V
Output Current to VCOMP
ΔIC = ±10μA
VFB = 0V
VFB = 0.7V
VEN = 0V
VEN = 0V
VEN = 2V, VFB = 1V
VSS = 0V
CSS = 10nF
Min Typ Max Unit
0.784 0.8 0.816 V
-- 70 -- mΩ
-- 15 -- Ω
-- -- 10 μA
-- 6.8 --
A
-- 4.6 -- A/V
-- 920 -- μA/V
420 570 720 kHz
-- 185 -- kHz
-- 85 -- %
-- 100 --
-- 4.1 --
ns
V
-- 200 -- mV
-- -- 0.4
V
1.4 -- 5.5
-- 1 -- μA
-- 25 -- μA
-- 0.8 1 mA
-- 10 -- μA
-- 1 -- ms
-- 150 --
°C
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8251-04 February 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
RT8251
to return VOUT to its steady-state value. During this
recovery time, VOUT can be monitored for overshoot or
ringing that would indicate a stability problem.
snubber between SW and GND and make them as close
as possible to the SW pin (see Figure 5). Another method
is to add a resistor in series with the bootstrap capacitor,
EMI Consideration
Since parasitic inductance and capacitance effects in PCB
circuitry would cause a spike voltage on the SW pin when
high-side MOSFET is turned-on/off, this spike voltage on
SW may impact on EMI performance in the system. In
order to enhance EMI performance, there are two methods
to suppress the spike voltage. One is to place an R-C
CBOOT. But this method will decrease the driving capability
to the high-side MOSFET. It is strongly recommended to
reserve the R-C snubber during PCB layout for EMI
improvement. Moreover, reducing the SW trace area and
keeping the main power in a small loop will be helpful on
EMI performance. For detailed PCB layout guide, please
refer to the section of Layout Consideration.
VIN
4.75V to 24V
Chip Enable
REN*
CEN*
2 VIN
CIN
10µF x 2
7 EN
BOOT 1
RT8251
SW 3
CSS
10nF
8 SS
4,
Exposed Pad(9)
GND
FB 5
COMP 6
RBOOT*
CBOOT L
100nF 4.7µH
RS*
D
B540C
CS*
CC
2.2nF
RC
22k
R1
30.9k
VOUT
3.3V/5A
COUT
22µF x 2
R2
10k
* : Optional
CP
NC
Figure 5. Reference Circuit with Snubber and Enable Timing Control
Thermal Considerations
For continuous operation, do not exceed the maximum
operation junction temperature 125°C. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
The maximum power dissipation can be calculated by
following formula :
PD(MAX) = (TJ(MAX) − TA ) / θJA
Where TJ(MAX) is the maximum operation junction
temperature , TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
For recommended operating conditions specification of
RT8251, the maximum junction temperature is 125°C. The
junction to ambient thermal resistance θJA is layout
dependent. For PSOP-8 and WQFN packages, the thermal
resistance θJA are 75°C/W and 68°C/W on the standard
JEDEC 51-7 four-layers thermal test board. The maximum
power dissipation at TA = 25°C can be calculated by
following formula :
PD(MAX) = (125°C − 25°C) / (75°C/W) = 1.333W for
PSOP-8
PD(MAX) = (125°C − 25°C) / (68°C/W) = 1.471W for
WQFN
(min.copper area PCB layout)
PD(MAX) = (125°C − 25°C) / (49°C/W) = 2.04W for
PSOP-8 (70mm2copper area PCB layout)
The thermal resistance θJA of SOP-8 (Exposed Pad) is
determined by the package architecture design and the
PCB layout design. However, the package architecture
design had been designed. If possible, it's useful to
increase thermal performance by the PCB layout copper
design. The thermal resistance θJA can be decreased by
adding copper area under the exposed pad of SOP-8
(Exposed Pad) package.
As shown in Figure 6, the amount of copper area to which
the SOP-8 (Exposed Pad) is mounted affects thermal
performance. When mounted to the standard
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8251-04 February 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet RT8251.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| RT8250 | 340kHz Synchronous Step-Down Converter | Richtek |
| RT8250N | 340kHz Synchronous Step-Down Converter | Richtek |
| RT8251 | 570kHz Step-Down Converter | Richtek |
| RT8253A | 340kHz Synchronous Step-Down Converter | Richtek |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |