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PDF RT7248 Data sheet ( Hoja de datos )
| Número de pieza | RT7248 | |
| Descripción | Synchronous Step-Down Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT7248 (archivo pdf) en la parte inferior de esta página. Total 15 Páginas | ||
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®
RT7248
2A, 18V, 340kHz Synchronous Step-Down Converter
General Description
The RT7248 is a high efficiency, monolithic synchronous
step-down DC/DC converter that can deliver up to 2A output
current from a 4.5V to 18V input supply. The RT7248's
current mode architecture and external compensation
allow the transient response to be optimized over a wide
input range and loads. Cycle-by-cycle current limit
provides protection against shorted outputs and soft-start
eliminates input current surge during start up. The RT7248
also provides under voltage protection and thermal
shutdown protection. The low current (< 3μA) shutdown
mode provides output disconnection, enabling easy power
management in battery-powered systems. The RT7248
is available in SOP-8 (Exposed Pad) package.
Marking Information
RT7248x
GSPYMDNN
RT7248xGSP : Product Number
x : H or N
YMDNN : Date Code
Features
±1.5% High Accuracy Feedback Voltage
Input Voltage Range : 4.5V to 18V
2A Output Current
Integrated N-MOSFETs
Current Mode Control
340kHz Fixed Frequency Operation
Output Adjustable Voltage Range : 0.923V to 15V
Efficiency Up to 95%
Programmable Soft-Start
Stable with Low ESR Ceramic Output Capacitors
Cycle-by Cycle Over Current Protection
Input Under Voltage Lockout
Output Under Voltage Protection
Thermal Shutdown Protection
RoHS Compliant and Halogen Free
Applications
Wireless AP/Router
Set-Top-Box
Industrial and Commercial Low Power Systems
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation of High-Performance DSPs
Simplified Application Circuit
VIN
Chip Enable
CIN
CSS
VIN BOOT
RT7248
SW
EN
SS FB
GND
COMP
CBOOT L
CC RC
CP
VOUT
R1
COUT
R2
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS7248-01 September 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
Free Datasheet http://www.datasheet4u.com/
1 page  
RT7248
Parameter
EN Input Threshold
Voltage
Logic High
Logic Low
Input Under Voltage Lockout Threshold
Input Under Voltage Lockout Hysteresis
Soft-Start Current
Soft-Start Period
Thermal Shutdown
Symbol
VIH
VIL
VUVLO
ΔVUVLO
ISS
tSS
TSD
Test Conditions
VIN Rising
VSS = 0V
CSS = 0.1μF
Min Typ Max Unit
2.7 -- 18
V
-- -- 0.4
3.8 4.2 4.5
V
-- 320 -- mV
-- 6 -- μA
-- 15.5 --
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 ©2012 Richtek Technology Corporation. All rights reserved.
DS7248-01 September 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
RT7248
Under Voltage Protection
Hiccup Mode
For the RT7248H, it provides Hiccup Mode Under Voltage
Protection (UVP). When the VFB voltage drops below 0.4V,
the UVP function will be triggered to shut down switching
operation. If the UVP condition remains for a period, the
RT7248H will retry automatically. When the UVP condition
is removed, the converter will resume operation. The UVP
is disabled during soft-start period.
Hiccup Mode
VOUT
(2V/Div)
ILX
(2A/Div)
IOUT = Short
Time (25ms/Div)
Figure 5. Hiccup Mode Under Voltage Protection
Clamp Mode
For the RT7248N, it provides inductor current clamp mode.
Clamp Mode
VOUT
(2V/Div)
ILX
(1A/Div)
Time (1ms/Div)
Figure 6. Clamp Mode
IOUT = Short
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS7248-01 September 2012
Over Temperature Protection
The RT7248 features an Over Temperature Protection
(OTP) circuitry to prevent from overheating due to
excessive power dissipation. The OTP will shut down
switching operation when junction temperature exceeds
150°C. Once the junction temperature cools down by
approximately 20°C, the converter will resume operation.
To maintain continuous operation, the maximum junction
temperature should be lower than 125°C.
Inductor Selection
The inductor value and operating frequency determine the
ripple current according to a specific input and output
voltage. The ripple current ΔIL increases with higher VIN
and decreases with higher inductance.
ΔIL
=
⎡
⎢⎣
VOUT
f ×L
⎤
⎥⎦
×
⎡⎢⎣1−
VOUT
VIN
⎤
⎥⎦
Having a lower ripple current reduces not only the ESR
losses in the output capacitors but also the output voltage
ripple. High frequency with small ripple current can achieve
the highest efficiency operation. However, it requires a
large inductor to achieve this goal.
For the ripple current selection, the value of ΔIL= 0.24(IMAX)
will be a reasonable starting point. The largest ripple
current occurs at the highest VIN. To guarantee that the
ripple current stays below the specified maximum, the
inductor value should be chosen according to the following
equation :
L
=
⎡
⎢⎣
f
×
VOUT
ΔIL(MAX)
⎤
⎥⎦
×
⎡⎢⎣1−
VOUT
VIN(MAX)
⎤
⎥⎦
The inductor's current rating (caused a 40°C temperature
rising from 25°C ambient) should be greater than the
maximum load current and its saturation current should
be greater than the short circuit peak current limit. Please
see Table 2 for the inductor selection reference.
Table 2. Suggested Inductors for Typical
Application Circuit
Component
Supplier
Series
Dimensions
(mm)
TDK
VLF10045 10 x 9.7 x 4.5
TDK
T AIYO
YUDEN
SLF12565
NR8040
12.5 x 12.5 x 6.5
8x8x4
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet RT7248.PDF ] | |
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