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PDF RT8008 Data sheet ( Hoja de datos )
| Número de pieza | RT8008 | |
| Descripción | High Efficiency PWM Step-Down DC/DC Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT8008 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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RT8008
1.5MHz, 600mA, High Efficiency PWM Step-Down DC/DC
Converter
General Description
Features
The RT8008 is a high-efficiency pulse-width-modulated
(PWM) step-down DC-DC converter. Capable of delivering
600mA output current over a wide input voltage range from
2.5V to 5.5V, the RT8008 is ideally suited for portable
electronic devices that are powered from 1-cell Li-ion
www.DataSbhaetetet4rUy.ocor mfrom other power sources within the range such
as cellular phones, PDAs and handy-terminals.
Internal synchronous rectifier with low RDS(ON) dramatically
reduces conduction loss at PWM mode. No external
Schottky diode is required in practical application. The
RT8008 automatically turns off the synchronous rectifier
while the inductor current is low and enters discontinuous
PWM mode. This can increase efficiency at light load
condition.
The RT8008 enters Low-Dropout mode when normal PWM
cannot provide regulated output voltage by continuously
turning on the upper P-MOSFET. RT8008 enter shutdown
mode and consumes less than 0.1µA when EN pin is pulled
low.
The switching ripple is easily smoothed-out by small
package filtering elements due to a fixed operation
frequency of 1.5MHz. This along with small SOT-23-5 and
TSOT-23-5 package provides small PCB area application.
Other features include soft start, lower internal reference
voltage with 2% accuracy, over temperature protection,
and over current protection.
Pin Configurations
(TOP VIEW)
EN 1 5 FB/VOUT
GND 2
LX 3 4 VIN
SOT-23-5/TSOT-23-5
l +2.5V to +5.5V Input Range
l Adjustable Output From 0.6V to VIN
l 1.0V, 1.2V, 1.5V, 1.8V, 2.5V and 3.3V Fixed/
Adjustable Output Voltage
l 600mA Output Current, 1A Peak Current
l 95% Efficiency
l No Schottky Diode Required
l 1.5MHz Fixed-Frequency PWM Operation
l Small SOT-23-5 and TSOT-23-5 Package
l RoHS Compliant and 100% Lead (Pb)-Free
Applications
l Cellular Telephones
l Personal Information Appliances
l Wireless and DSL Modems
l MP3 Players
l Portable Instruments
Ordering Information
RT8008(- )
Package Type
B : SOT-23-5
J5 : TSOT-23-5
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Note :
Output Voltage
Default : Adjustable
10 : 1.0V
12 : 1.2V
15 : 1.5V
18 : 1.8V
25 : 2.5V
33 : 3.3V
RichTek Pb-free and Green 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.
}100% matte tin (Sn) plating.
DS8008-04 March 2007
www.richtek.com
1
1 page  
RT8008
Parameter
Symbol
Test Conditions
FB Input Current
PMOSFET RON
NMOSFET RON
P-Channel Current Limit
IFB VFB = VIN
PRDS(ON) IOUT = 200mA
VIN = 3.6V
VIN = 2.5V
NRDS(ON) IOUT = 200mA
VIN = 3.6V
VIN = 2.5V
IP(LM)
VIN = 2.5V to 5.5 V
EN High-Level Input Voltage
www.DataSheet4U.com
EN Low-Level Input Voltage
VENH
VENL
VIN = 2.5V to 5.5V
VIN = 2.5V to 5.5V
Undervoltage Lock Out threshold
Min Typ Max Units
−50 --
50 nA
-- 0.3 --
-- 0.4 --
Ω
-- 0.25 --
-- 0.35 --
Ω
1 -- 1.8 A
1.5 -- -- V
-- -- 0.4 V
-- 1.8 --
V
Hysteresis
-- 0.1 --
V
Oscillator Frequency
Thermal Shutdown Temperature
Min. On Time
fOSC
TSD
VIN = 3.6V, IOUT = 100mA
1.2 1.5 1.8 MHz
-- 160 --
°C
-- 50 -- ns
Max. Duty Cycle
100 -- -- %
LX Leakage Current
VIN = 3.6V, VLX = 0V or VLX = 3.6V −1 --
1 µA
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. Devices are ESD sensitive. Handling precaution recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of
JEDEC 51-3 thermal measurement standard. Pin 2 of SOT-23-5/TSOT-23-5 packages is the case position for θJC
measurement.
DS8008-04 March 2007
www.richtek.com
5
5 Page 
RT8008
curves. Thus, to obtain I2R losses, simply add RSW to RL
and multiply the result by the square of the average output
current.
Other losses including CIN and COUT ESR dissipative
losses and inductor core losses generally account for less
than 2% of the total loss.
Thermal Considerations
The maximum power dissipation depends on the thermal
www.DataShreeest4isUt.aconmce of IC package, PCB layout, the rate of
surroundings airflow and temperature difference between
junction to ambient. The maximum power dissipation can
be calculated by following formula :
PD(MAX) = ( TJ(MAX) - TA ) / θJA
Where TJ(MAX) is the maximum operation junction
temperature 125°C, TA is the ambient temperature and the
θJA is the junction to ambient thermal resistance.
For recommended operating conditions specification of
RT8008 DC/DC converter, where TJ (MAX) is the maximum
junction temperature of the die (125°C) and TA is the
maximum ambient temperature. The junction to ambient
thermal resistance θJA is layout dependent. For
SOT-23-5/TSOT-23-5 packages, the thermal resistance θJA
is 250°C/W on the standard JEDEC 51-3 single-layer
thermal test board. The maximum power dissipation at
TA= 25°C can be calculated by following formula :
PD(MAX) = ( 125°C - 25°C ) / 250 = 0.4 W for SOT-23-5/
TSOT-23-5 packages
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA. For RT8008 packages, the Figure 5 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
The value of junction to case thermal resistance θJC is
popular for users. This thermal parameter is convenient
for users to estimate the internal junction operated
temperature of packages while IC operating. It's
independent of PCB layout, the surroundings airflow effects
and temperature difference between junction to ambient.
The operated junction temperature can be calculated by
following formula :
TJ = TC + PD x θJC
DS8008-04 March 2007
Where TC is the package case (Pin 2 of package leads)
temperature measured by thermal sensor, PD is the power
dissipation defined by user's function and the θJC is the
junction to case thermal resistance provided by IC
manufacturer. Therefore it's easy to estimate the junction
temperature by any condition.
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, VOUT immediately shifts by an amount
equal to ∆ILOAD (ESR), where ESR is the effective series
resistance of COUT. ∆ILOAD also begins to charge or
discharge COUT generating a feedback error signal used
by the regulator to return VOUT to its steady-state value.
During this recovery time, VOUT can be monitored for
overshoot or ringing that would indicate a stability problem.
450
Single Layer PCB
400
350 SOT-23-5, TSOT-23-5 Packages
300
250
200
150
100
50
0
0 20 40 60 80 100 120 140
Ambient Temperature (°C)
Figure 5. Derating Curves for RT8008 Package
Layout Considerations
Follow the PCB layout guidelines for optimal performance
of RT8008.
} For the main current paths as indicated in bold lines in
Figure 6, keep their traces short and wide.
} Put the input capacitor as close as possible to the device
pins (VIN and GND).
} LX node is with high frequency voltage swing and should
be kept small area. Keep analog components away from
LX node to prevent stray capacitive noise pick-up.
www.richtek.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet RT8008.PDF ] | |
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