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PDF RT7262E Data sheet ( Hoja de datos )
| Número de pieza | RT7262E | |
| Descripción | Synchronous Step-Down Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT7262E
2A, 21V 500kHz Synchronous Step-Down Converter
General Description
The RT7262E is a synchronous step-down regulator with
integrated power MOSFETs. It achieves 2A of 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.
Fault condition protection includes cycle-by-cycle current
limiting and thermal shutdown. An adjustable soft-start
reduces the stress on the input source at start-up.
The RT7262E requires a minimal number of readily
available external components, providing a compact
solution.
Ordering Information
RT7262E
Package Type
QW : WDFN-14L 4x3 (W-Type)
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
Z : ECO (Ecological Element with
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.
Features
z Wide Input Range : 4.5V to 21V
z Adjustable Output from 0.808V to 15V
z 2A Output Current
z 150mΩ/60mΩ Internal Power MOSFET Switch
z Internal Compensation Minimizes External Parts
z 500kHz Fixed Switching Frequency
z Synchronized External Clock from 300kHz to 2MHz
z Adjustable Soft-Start
z Cycle-by-Cycle Over Current Limit
z Thermal Shutdown Protection
z Available in SOP-8 (Exposed Pad) and 14-Lead
WDFN Packages
z RoHS Compliant and Halogen Free
Applications
z Distributive Power Systems
z Battery Charger
z DSL Modems
z Pre-Regulator for Linear Regulators
Simplified Application Circuit
VIN
Chip Enable
VIN BOOT
CIN RT7262E
SW
EN/SYNC
VCC
FB
CC GND
CBOOT L
RT R1
R2
VOUT
COUT
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS7262E-00 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
Free Datasheet http://www.datasheet4u.com/
1 page  
RT7262E
Absolute Maximum Ratings (Note 1)
z Supply Voltage, VIN ------------------------------------------------------------------------------------------- −0.3V to 26V
z Switch Voltage, SW ------------------------------------------------------------------------------------------- −0.3V to (VIN + 0.3V)
z Boot Voltage, BOOT ------------------------------------------------------------------------------------------- (SW − 0.3V) to (SW + 6V)
z Other Pins -------------------------------------------------------------------------------------------------------- −0.3V to 6V
z Power Dissipation, PD @ TA = 25°C
WDFN-14L 4x3 ------------------------------------------------------------------------------------------------- 3.33W
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------- 1.63W
z Package Thermal Resistance (Note 2)
WDFN-14L 4x3, θJA ------------------------------------------------------------------------------------------- 30°C/W
WDFN-14L 4x3, θJC ------------------------------------------------------------------------------------------- 7.5°C/W
SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------- 61.2°C/W
SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------- 6.5°C/W
z Junction Temperature ----------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------- 260°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 Range, VIN --------------------------------------------------------------------------- 4.5V to 21V
z Junction Temperature Range --------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range --------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 12V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Shutdown Current
ISHDN
Quiescent Current
IQ
Upper Switch On Resistance
RDS(ON)1
Lower Switch On Resistance
RDS(ON)2
Switch Leakage
ILEAK
Current Limit
ILIM
Oscillator Frequency
fSW
SYNC Threshold
Voltage
Logic-High VSYNCH
Logic-Low VSYNCL
SYNC Frequency Range
fSYNC
SYNC Input Current
ISYNC
Power Good Rising Threshold
Power Good Falling Threshold
Power Good Sink Current
Capability
Test Conditions
VEN = 0
VEN = 2V, VFB = 1V
VEN = 0V, VSW = 0V or 12V
VBOOT − VSW = 4.8V
VFB = 0.75V
VSYNC = 6V
Sink 4mA
Min Typ Max Unit
-- 0 1 μA
-- 0.7 -- mA
-- 150 -- mΩ
-- 60 -- mΩ
-- 0 10 μA
3.9 5.5 --
A
425 500 575 kHz
1.8 --
--
V
-- -- 0.4
0.3 --
2 MHz
-- 1.5 2.5 μA
-- 90 -- %
-- 70 -- %
-- -- 0.4 V
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS7262E-00 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
Application Information
The IC is a synchronous high voltage step-down converter
that can support the input voltage range from 4.5V to 21V
and the output current can be up to 2A.
Output Voltage Setting
The output voltage is set by an external resistive divider
according to the following equation :
VOUT
=
VFB
⎛⎜⎝1+
R1
R2
⎞⎟⎠
where VFB is the feedback reference voltage 0.808V
(typical).
The resistive divider allows the FB pin to sense a fraction
of the output voltage as shown in Figure 1.
VOUT
FB
RT7262E
GND
R1
R2
Figure 1. Output Voltage Setting
External Bootstrap Diode
Connect a 100nF low ESR ceramic capacitor between
the BOOT pin and SW pin as shown in Figure 2. This
capacitor provides the gate driver voltage for the high side
MOSFET. It is recommended to add an external bootstrap
diode between an external 5V and BOOT pin for efficiency
improvement when input voltage is lower than 5.5V or duty
ratio is higher than 65% .The bootstrap diode can be a
low cost one such as IN4148 or BAT54. The external 5V
can be a 5V fixed input from system or a 5V output of the
IC. Note that the external boot voltage must be lower than
5.5V.
5V
BOOT
RT7262E
SW
100nF
Figure 2. External Bootstrap Diode
RT7262E
Soft-Start for WDFN-14L Package
The RT7262EZQW (WDFN-14L package) contains an
external soft-start clamp that gradually raises the output
voltage. The soft-start timing is programmed by the
external capacitor between SS pin and GND. The chip
provides an internal 10μA charge current for the external
capacitor. If 47nF capacitor is used to set the soft-start,
the period will be 4.7ms (typ.).
Soft-Start for SOP-8 (Exposed Pad) Package
The RT7262EZSP (SOP-8 (Exposed Pad) package)
contains an internal soft-start function to prevent large
inrush current and output voltage overshoot when the
converter starts up. Soft-start automatically begins once
the chip is enabled. During soft-start, the internal soft-
start capacitor becomes charged and generates a linear
ramping up voltage across the capacitor. This voltage
clamps the voltage at the internal reference, causing the
duty pulse width to increase slowly and in turn reduce the
output surge current. The typical soft-start time for this
IC is set at 2ms.
Under Voltage Lockout Threshold
The IC includes an input Under Voltage Lockout Protection
(UVLO). If the input voltage exceeds the UVLO rising
threshold voltage (4.2V), the converter resets and prepares
the PWM for operation. If the input voltage falls below the
UVLO falling threshold voltage (3.8V) during normal
operation, the device stops switching. The UVLO rising
and falling threshold voltage includes a hysteresis to
prevent noise caused reset.
Chip Enable Operation
The EN pin is the chip enable input. Pulling the EN pin
low (<0.4V) will shutdown the device. During shutdown
mode, the RT7262E quiescent current drops to lower than
1μA. Driving the EN pin high (2V < EN < 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).
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS7262E-00 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet RT7262E.PDF ] | |
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