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PDF RT8072 Data sheet ( Hoja de datos )
| Número de pieza | RT8072 | |
| Descripción | High Efficiency Synchronous Step-Down Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT8072
5A, 2MHz, High Efficiency Synchronous Step-Down Converter
General Description
The RT8072 is a high efficiency PWM step-down converter
and capable of delivering 5A output current over a wide
input voltage range from 2.9V to 5.5V.
The RT8072 provides accurate regulation for a variety of
loads with an ±1% reference voltage at room temperature.
For reducing inductor size, it provides up to 2MHz
switching frequency. The efficiency is maximized through
the integrated 50mΩ for high side, 35mΩ for low side
MOSFETs and 250μA typical supply current.
The RT8072 features over current protection, frequency
fold back function in shorted circuit, hiccup mode under
voltage protection and over temperature protection.
The RT8072 is available in SOP-8 (Exposed Pad) and
WDFN-12L 3x3 packages.
Ordering Information
RT8072
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
QW : WDFN-12L 3x3 (W-Type)
Note :
Lead Plating System
G : Green (Halogen Free and Pb Free)
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.
Features
z Integrated 50mΩ and 35mΩ MOSFETs
z 5A Output Current
z High Efficiency Up to 95%
z 2.9V to 5.5V Input Range
z Adjustable PWM Frequency : 300kHz to 2MHz
z 0.8V ±1% Reference Voltage
z Adjustable External Soft-Start
z Power Good Indicator (WDFN-12L 3x3 Only)
z Over Current Protection
z Under Voltage Protection
z Over Temperature Protection
z SOP-8 (Exposed Pad) and 12-Lead WDFN Packages
z RoHS Compliant and Halogen Free
Applications
z Low Voltage, High Density Power Systems
z Distributed Power Systems
z Point-of-Load Conversions
Marking Information
RT8072GSP
RT8072
GSPYMDNN
RT8072GSP : Product Number
YMDNN : Date Code
RT8072GQW
6C=YM
DNN
6C= : Product Code
YMDNN : Date Code
Simplified Application Circuit
VIN VIN BOOT
CIN RT8072
EN
COMP
RC RT
CC RT
GND
LX
FB
CBOOT
L
COUT
VOUT
RFB1
RFB2
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8072-01 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT8072
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- −0.3V to 6.5V
z BOOT to LX ----------------------------------------------------------------------------------------------------------- −0.3V to 6V
z Other Pins ------------------------------------------------------------------------------------------------------------- −0.3V to (VIN + 0.3V)
z Power Dissipation, PD @ TA = 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------- 2.041W
WDFN-12L 3x3 ------------------------------------------------------------------------------------------------------- 1.667W
z Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------- 49°C/W
SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------- 15°C/W
WDFN-12L 3x3, θJA ------------------------------------------------------------------------------------------------- 60°C/W
WDFN-12L 3x3, θJC ------------------------------------------------------------------------------------------------- 7.5°C/W
z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C
z Junction Temperature ----------------------------------------------------------------------------------------------- 150°C
z Storage Temperature Range -------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------- 2kV
Recommended Operating Conditions (Note 4)
z Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 2.9V to 5.5V
z Junction Temperature Range -------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range -------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 5V, CIN = 10μF, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Input Power Supply
Under Voltage Lockout Threshold
Quiescent Current
Shutdown Current
Voltage Reference
VUVLO
IQ
ISHDN
VIN Rising
Active, VFB = 0.9V, Not switching
Voltage Reference
VREF
Enable
Logic-High
EN Input Voltage
Logic-Low
VIH
VIL
Switching Frequency Setting
Switching Frequency
Power Good Range
Minimum On-Time
Minimum Off-Time
fOSC
RT = 28.7kΩ
RT pin is floating
WDFN-12L 3x3 Only
Min Typ Max Unit
-- 2.6 2.8 V
-- 250 -- μA
-- 2 5 μA
0.792 0.8 0.808 V
1.5 -- 5.5
V
-- -- 0.4
300 -- 2000
-- 1400 -- kHz
-- 300 --
-- ±7 -- %
-- 80 -- ns
-- 60 -- ns
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8072-01 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
Application Information
The basic RT8072 application circuit is shown in Typical
Application Circuit. External component selection is
determined by the maximum load current and begins with
the selection of the inductor value and operating frequency
followed by CIN and COUT.
Output Voltage Setting
The output voltage is set by an external resistive divider
according to the following equation :
VOUT
=
VREF
×
⎛
⎜1+
⎝
RFB1
RFB2
⎞
⎟
⎠
where VREF equals to 0.8V (typical)
The resistive divider allows the FB pin to sense a fraction
of the output voltage as shown in Figure 1.
VOUT
FB
RT8072
GND
RFB1
RFB2
Figure 1. Setting the Output Voltage
Soft-Start (SS)
An internal current source charges an external capacitor
to build the soft-start ramp voltage (VSS). The VFB voltage
will track the VSS during soft-start interval. The chip will
use internal soft-start if the SS pin is floating. The nominal
internal soft-start time is 800μs.
With external soft-start, the typical soft-start time can be
calculated as following equation :
tSS (ms) = 0.1 x CSS (nF)
For example, if CSS = 10nF, the soft-start time is 1ms.
Operating Frequency
Selection of the operating frequency is a tradeoff between
efficiency and component size. High frequency operation
allows the use of smaller inductor and capacitor values.
Operation at lower frequency improves efficiency by
reducing internal gate charge and switching losses but
requires larger inductance and/or capacitance to maintain
low output ripple voltage.
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8072-01 November 2012
RT8072
The operating frequency of the RT8072 is determined by
an external resistor that is connected between the SHDN/
RT pin and GND. The value of the resistor sets the ramp
current that is used to charge and discharge an internal
timing capacitor within the oscillator. The RT resistor value
can be determined by examining the frequency vs. RT
curve. Although frequency as high as 2MHz is possible,
the minimum on-time of the RT8072 imposes a minimum
limit on the operating duty cycle. The minimum on-time
is typically 80ns. Therefore, the minimum duty cycle is
equal to 100 x 80ns x f (Hz).
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
20 40 60 80 100 120 140 160 180 200
RT (kΩ)
Figure 2
Chip Enable Operation
The EN pin is the chip enable input. Pulling the EN pin
low (<0.4V) will shut down the device. During shutdown
mode, the RT8072 quiescent current drops to lower than
2μA. Driving the EN pin high (>1.5V, <5.5V) will turn on
the device again. For external timing control, the EN pin
can also be externally pulled high by adding a REN resistor
and CEN capacitor from the VIN pin (see Figure 3).
EN
REN
VIN
CEN
EN
RT8072
GND
Figure 3. Enable Timing Control
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet RT8072.PDF ] | |
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