|
|
PDF RT8253A Data sheet ( Hoja de datos )
| Número de pieza | RT8253A | |
| Descripción | 340kHz Synchronous Step-Down Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de RT8253A (archivo pdf) en la parte inferior de esta página. Total 15 Páginas | ||
|
No Preview Available !
RT8253A
3A, 23V, 340kHz Synchronous Step-Down Converter
General Description
Features
The RT8253A is a high efficiency, monolithic synchronous
step-down DC/DC converter that can deliver up to 3A
output current from a 4.5V to 23V input supply. The
RT8253A's current mode architecture and external
compensation allow the transient response to be
optimized over a wide range of loads and output capacitors.
Cycle by cycle current limit provides protection against
shorted outputs and soft-start eliminates input current
surge during start up. Fault conditions also include output
under voltage protection and thermal shutdown. The low
current (<3μA) shutdown mode provides output
disconnect, enabling easy power management in battery
powered systems. The RT8253A is available in a
SOP-8 (Exposed Pad) package.
z ±1.5% High Accuracy Feedback Voltage
z 4.5V to 23V Input Voltage Range
z 3A Output Current
z Integrated N-MOSFET Switches
z Current Mode Control
z Fixed Frequency Operation : 340kHz
z Output Adjustable from 0.8V to 20V
z Up to 95% Efficiency
z Programmable Soft-Start
z Stable with Low ESR Ceramic Output Capacitors
z Cycle by Cycle Over Current Protection
z Input Under Voltage Lockout
z Output Under Voltage Protection
z Thermal Shutdown Protection
z RoHS Compliant and Halogen Free
Ordering Information
RT8253A
Package Type
SP : SOP-8 (Exposed Pad-Option 1)
Applications
z Industrial and Commercial Low Power Systems
z Set Top Box
Lead Plating System
LCD Monitors and TVszhttp://www.DataSheet4U.net/
G : Green (Halogen Free and Pb Free) z Green Electronics/Appliances
Note :
H : UVP Hiccup
L : UVP Latch-Off
z Point of Load Regulation of High Performance DSPs
z Wireless AP/Router
Richtek products are :
` RoHS compliant and compatible with the current require-
Pin Configurations
ments of IPC/JEDEC J-STD-020.
(TOP VIEW)
` Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
RT8253A
GSPYMDNN
RT8253AGSP : Product Number
YMDNN : Date Code
BOOT
VIN
SW
GND
8
27
GND
36
9
45
SS
EN
COMP
FB
SOP-8 (Exposed Pad)
DS8253A-02 March 2011
www.richtek.com
1
datasheet pdf - http://www.DataSheet4U.net/
1 page  
RT8253A
Parameter
Input Under Voltage Lockout
Threshold
Input Under Voltage Lockout
Threshold Hysteresis
EN Threshold Logic-High
Voltage
Logic-Low
Soft-Start Current
Soft-Start Period
Thermal Shutdown
Symbol
VIH
VIL
ISS
tSS
TSD
Test Conditions
VIN Rising
VSS = 0V
CSS = 0.1μF
Min Typ Max Unit
3.8 4.2 4.5
V
-- 320 --
2.7 -- 5.5
-- -- 0.4
-- 6 --
-- 13.5 --
-- 150 --
mV
V
μA
ms
°C
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in natural convection at TA = 25°C on a high effective thermal conductivity four-layer test board of
JEDEC 51-7 thermal measurement standard. The measurement case positions of θJC are on the lead of the SOP
package and the expose pad for the SOP(Exposed Pad) package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
http://www.DataSheet4U.net/
DS8253A-02 March 2011
www.richtek.com
5
datasheet pdf - http://www.DataSheet4U.net/
5 Page 
RT8253A
Input Capacitor Selection
Voltage rating and current rating are the key parameters
in selecting the input capacitor. Generally, the input
capacitor should have a voltage rating 1.5 times greater
than the maximum input voltage to be considered a
conservatively safe design.
The input capacitor is used to supply the input RMS
current, which can be approximately calculated using the
following equation :
IIN_RMS = ILOAD x
VOUT
VIN
x
⎛
⎜1−
⎝
VOUT
VIN
⎞
⎟
⎠
The next step is to select a proper capacitor for RMS
current rating. For a good design use more than one
capacitor with low Equivalent Series Resistance (ESR) in
parallel to form a capacitor bank.
For a given output voltage sag specification, the ESR value
can be determined.
Another parameter that has influence on the output voltage
sag is the equivalent series inductance (ESL). The rapid
change in load current results in di/dt during transient.
Therefore ESL contributes to part of the voltage sag. Use
a capacitor that has low ESL to obtain better transient
performance. Generally, using several capacitors
connected in parallel will have better transient performance
than using one single capacitor for the same total ESR.
Unlike the electrolytic capacitor, the ceramic capacitor has
relatively low ESR and can reduce the voltage deviation
during load transient. However, the ceramic capacitor can
only provide low capacitance value. Therefore, using a
mixed combination of electrolytic capacitor and ceramic
capacitor can also have better transient performance.
Output Capacitor Selection
The output capacitor and inductor form a low pass filter in
the buck topology. In steady state condition, the ripple
current flowing into/out of the capacitor results in ripple
voltage. The output voltage ripple (Vp-p) can be calculated
by the following equation.
VP−P
= LIR x ILOAD(MAX)
x
⎛
⎜ ESR
⎝
+
8
x
1
COUT
x fSW
⎞
⎟
⎠
When load transient occurs, the output capacitor supplies
the load current before the controller can respond.
Therefore, the ESR will dominate the output voltage sag
during load transient. The output voltage undershoot (VSAG)
can be calculated by the following equation :
VSAG = ΔILOAD x ESR
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 EMI performance in the system. In order
to enhance EMI performance, there are two methods to
http://www.DataSheet4U.net/
suppress the spike voltage. One method is to place an R-
C snubber between SW and GND and locate them as close
as possible to the SW pin (see Figure 3). Another way is
adding a resistor in series with the bootstrap capacitor,
CBOOT, but this 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 for EMI
performance. For detailed PCB layout guideline, please
refer to the section on Layout Consideration.
VIN
4.5V to 23V
Chip Enable
REN*
CEN*
CSS
0.1µF
CIN
10µF x 2
2 VIN
BOOT 1 RBOOT*
RT8253A
7 EN
SW 3
CBOOT
0.1µF
Rs*
L
10µH
Cs*
8 SS
4, 9 (Exposed Pad)
GND
FB 5
COMP 6
RC CC
15k 3.3nF
VOUT
3.3V/3A
R1
31.25k
COUT
22µF x 2
R2
10k
CP
NC
Figure 3. Reference Circuit with Snubber and Enable Timing Control
DS8253A-02 March 2011
www.richtek.com
11
datasheet pdf - http://www.DataSheet4U.net/
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet RT8253A.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| RT8253A | 340kHz Synchronous Step-Down Converter | Richtek |
| RT8253B | 1.2MHz 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 |