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PDF RT7259 Data sheet ( Hoja de datos )
| Número de pieza | RT7259 | |
| Descripción | Synchronous Step-Down Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT7259 (archivo pdf) en la parte inferior de esta página. Total 15 Páginas | ||
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®
RT7259
10A, 24V, 600kHz Step-Down Converter with Synchronous
Gate Driver
General Description
The RT7259 is a synchronous step-down DC/DC converter
with an integrated high side internal power MOSFET and
a gate driver for a low side external power MOSFET. It
can deliver up to 10A output current from a 4.5V to 24V
input supply. The RT7259's current mode architecture
allows the transient response to be optimized over a wider
input voltage and load range. Cycle-by-cycle current limit
provides protection against shorted outputs and soft-start
eliminates input current surge during start-up. The RT7259
is synchronizable to an external clock with frequency
ranging from 300kHz to 1.5MHz.
The RT7259 is available in WDFN-14L 4x3package.
Applications
z Point of Load Regulator in Distributed Power System
z Digital Set top Boxes
z Personal Digital Recorders
z Broadband Communications
z Flat Panel TVs and Monitors
Features
z 4.5V to 24V Input Voltage Range
z 10A Output Current
z 45mΩ Internal High Side N-MOSFET
z Current Mode Control
z 600kHz Switching Frequency
z Adjustable Output from 0.808V to 15V
z Up to 95% Efficiency
z Internal Compensation
z Stable with Ceramic Capacitors
z Synchronous External Clock : 300kHz to 1.5MHz
z Cycle-by-Cycle Current Limit
z Input Under Voltage Lockout
z Output Under Voltage Protection
z Power Good Indicator
z Thermal Shutdown Protection
z RoHS Compliant and Halogen Free
Simplified Application Circuit
RT7259
VIN VIN BOOT
CIN
SW
Power Good
VCC
CVCC
PGOOD
BG
FB
Chip Enable
EN/SYNC
GND
CBOOT
L
Q1
VOUT
R1
COUT
R2
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS7259-00 January 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
Free Datasheet http://www.datasheet4u.com/
1 page  
RT7259
Parameter
EN Pull Low Current
Thermal Shutdown
Thermal Shutdown Hysteresis
Power Good Threshold Rising
Power Good Threshold Hysteresis
Power Good Pin Level
BG Driver Bias Supply Voltage
Gate Driver Sink Impedance
Gate Driver Source Impedance
Symbol
TSD
ΔTSD
Test Conditions
VEN = 2V
VC C
RS in k
RSource
PGOOD Sink 10mA
Min Typ Max Unit
-- 1 -- μA
-- 150 --
°C
-- 20 -- °C
-- 0.75 --
V
-- 40 -- mV
-- -- 0.125 V
4.5 5 -- V
-- 0.9 --
Ω
-- 3.3 --
Ω
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.
DS7259-00 January 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
RT7259
Soft-Start
The RT7259 provides soft-start function. The soft-start
function is used to prevent large inrush current while
converter is being powered-up. An internal current source
charges an internal capacitor to build a soft-start ramp
voltage. The VFB voltage will track the internal ramp voltage
during soft-start interval. The typical soft-start time is 2ms.
Operating Frequency and Synchronization
The internal oscillator runs at 600kHz (typ.) when the EN/
SYNC pin is at logic-high level (>2V). If the EN pin is
pulled to low-level for 10μs above, the IC will shut down.
The RT7259 can be synchronized with an external clock
ranging from 300kHz to 1.5MHz applied to the EN/SYNC
pin. The external clock duty cycle must be from 10% to
90%.
3.5ms (Start-up period)
10µs
EN/SYNC
Over Temperature Protection
The RT7259 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.
Under Voltage Protection
For the RT7259, 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 UV condition remains for a period, the
RT7259 will retry every 2ms. When the UV condition is
removed, the converter will resume operation. The UVP
is disabled during soft-start period.
Hiccup Mode
VFB
CLK
Foldback
600kHz
External CLK
Figure 6. Startup Sequence Using External Sync Clock
Figure 6 shows the synchronization operation in startup
period. When the EN/SYNC is triggered by an external
clock, the RT7259 enters soft-start phase and the output
voltage starts to rise. When VFB is lower than 0.7V, the
oscillation frequency will be proportional to the feedback
voltage. With higher VFB, the switching frequency is
relatively higher. After startup period about 3.5ms, the IC
operates with the same frequency as the external clock.
VOUT
(1V/Div)
IL
(10A/Div)
VIN = 12V, IOUT = Short
Time (2.5ms/Div)
Figure 7. Hiccup Mode Under Voltage Protection
Duty Cycle Limitation
The RT7259 has a maximum duty cycle 90%. The
minimum input voltage is determined by the maximum
duty cycle and its minimum operating voltage 4.5V. The
voltage drops of high side MOSFET and low side MOSFET
also must be considered for the minimum input voltage.
The minimum duty cycle can be calculated by the following
equation :
Duty Cycle(min) = fSW x tON(min)
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS7259-00 January 2012
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 RT7259.PDF ] | |
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