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PDF RT8202L Data sheet ( Hoja de datos )
| Número de pieza | RT8202L | |
| Descripción | (RT8202L/M) Single Synchronous Buck Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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RT8202L/M
Single Synchronous Buck Controller
General Description
The RT8202L/M PWM controller provides the high
efficiency, excellent transient response, and high DC output
accuracy needed for stepping down high voltage batteries
to generate low voltage CPU core, I/O, and chipset RAM
supplies in notebook computers.
The constant-on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides 100ns
“instant-on” response to load transients while maintaining
a relatively constant switching frequency.
The RT8202L/M achieves high efficiency at a reduced cost
by eliminating the current-sense resistor found in
traditional current mode PWMs. Efficiency is further
enhanced by its ability to drive very large synchronous
rectifier MOSFETs. The RT8202L is available in a
WQFN-16L 4x4 package and the RT8202M is available in
a WQFN-16L 3x3 package.
Ordering Information
RT8202L/M
Package Type
QW : WQFN-16L 4x4 (W-Type)
QW : WQFN-16L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
L : WQFN-16L 4x4
M : WQFN-16L 3x3
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 Ultra-High Efficiency
z Resistor Programmable Current Limit by Low Side
RDS(ON) Sense (Lossless Limit)
z 4700ppm/°C RDS(ON) Current Sensing
z Quick Load Step Response within 100ns
z 1% VFB Accuracy over Line and Load
z Adjustable 0.75V to 3.3V Output Voltage Range
z 3V to 26V Battery Input Voltage Range
z Resistor Programmable Frequency
z Integrated Bootstrap Switch
z Over Voltage Protection
z Under Voltage Protection
z Voltage Ramp Soft-Start
z Built In Soft Discharge Output
z Power Good Indicator
z RoHS Compliant and 100% Halogen Free
Applications
z Notebook Computers
z CPU Core Supply
z Chipset/RAM Supply as Low as 0.75V
Pin Configurations
(TOP VIEW)
16 15 14 13
VOUT 1
12 UGATE
VDD 2
FB 3
PGOOD 4
GND
17
11 PHASE
10 OC
9 VDDP
56 78
WQFN-16L 4x4 (RT8202L)/
WQFN-16L 3x3 (RT8202M)
DS8202L/M-04 April 2011
www.richtek.com
1
Free Datasheet http://www.Datasheet4U.com
1 page  
RT8202L/M
Absolute Maximum Ratings (Note 1)
z Input Voltage, TON to GND ------------------------------------------------------------------------------------------------ –0.3V to 32V
z BOOT to PHASE ------------------------------------------------------------------------------------------------------------ –0.3V to 6V
z UGATE to PHASE
DC ------------------------------------------------------------------------------------------------------------------------------- –0.3V to 6V
< 20ns ------------------------------------------------------------------------------------------------------------------------- −5V to 7.5V
z LGATEx to GND
DC ------------------------------------------------------------------------------------------------------------------------------- –0.3V to 6V
< 20ns ------------------------------------------------------------------------------------------------------------------------- −2.5V to 7.5V
z PHASE to GND
DC ------------------------------------------------------------------------------------------------------------------------------- –0.3V to 32V
< 20ns ------------------------------------------------------------------------------------------------------------------------- −8V to 38V
z PGND to GND ---------------------------------------------------------------------------------------------------------------- –0.3V to 0.3V
z VDD, VDDP, VOUT, EN/DEM, FB, PGOOD to GND ---------------------------------------------------------------- –0.3V to 6V
z OC to GND -------------------------------------------------------------------------------------------------------------------- –0.3V to 28V
z Power Dissipation, PD @ TA = 25°C
WQFN-16L 3x3 -------------------------------------------------------------------------------------------------------------- 1.471W
WQFN-16L 4x4 -------------------------------------------------------------------------------------------------------------- 1.852W
z Package Thermal Resistance (Note 2)
WQFN-16L 3x3, θJA --------------------------------------------------------------------------------------------------------- 68°C/W
WQFN-16L 3x3, θJC -------------------------------------------------------------------------------------------------------- 7.5°C/W
WQFN-16L 4x4, θJA --------------------------------------------------------------------------------------------------------- 54°C/W
WQFN-16L 4x4, θJC -------------------------------------------------------------------------------------------------------- 7°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 Mode) ------------------------------------------------------------------------------------------------ 2kV
MM (Machine Mode) -------------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 4)
z Input Voltage, VIN ------------------------------------------------------------------------------------------------------------ 3V to 26V
z Supply Voltage, VDD, VDDP ------------------------------------------------------------------------------------------------ 4.5V to 5.5V
z Junction Temperature Range --------------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range --------------------------------------------------------------------------------------------- −40°C to 85°C
DS8202L/M-04 April 2011
www.richtek.com
5
Free Datasheet http://www.Datasheet4U.com
5 Page 
Applications Information
The RT8202L/M PWM controller provides the high
efficiency, excellent transient response, and high DC output
accuracy needed for stepping down high voltage batteries
to generate low voltage CPU core, I/O, and chipset RAM
supplies in notebook computers. RichTek's Mach
ResponseTM technology is specifically designed for
providing 100ns “instant-on” response to load steps while
maintaining a relatively constant operating frequency and
inductor operating point over a wide range of input voltages.
The topology circumvents the poor load transient timing
problems of fixed frequency current mode PWMs while
also avoiding the problems caused by widely varying
switching frequencies in conventional constant-on-time and
constant- off-time PWM schemes. The DRVTM mode PWM
modulator is specifically designed to have better noise
immunity for such a single output application.
PWM Operation
The Mach ResponseTM, DRVTM mode controller relies on
the output filter capacitor's effective series resistance
(ESR) to act as a current-sense resistor, so the output
ripple voltage provides the PWM ramp signal. Referring to
the function diagrams of the RT8202L/M, the synchronous
high side MOSFET is turned on at the beginning of each
cycle. After the internal one-shot timer expires, the
MOSFET is turned off. The pulse width of this one shot is
determined by the converter's input and output voltages
to keep the frequency fairly constant over the input voltage
range. Another one-shot sets a minimum off-time (400ns
typ.).
On-Time Control (TON)
The on-time one-shot comparator has two inputs. One
input looks at the output voltage, while the other input
samples the input voltage and converts it to a current.
This input voltage proportional current is used to charge
an internal on-time capacitor. The on-time is the time
required for the voltage on this capacitor to charge from
zero volts to VOUT, thereby making the on-time of the high
side switch directly proportional to the output voltage and
inversely proportional to the input voltage. The
implementation results in a nearly constant switching
frequency without the need of a clock generator.
RT8202L/M
tON
=
3.85p x RTON x VOUT
(VIN − 0.5)
And then the switching frequency is :
Frequency =
VOUT
(VIN x tON )
RTON is a resistor connected from the input supply (VIN)
to the TON pin.
Mode Selection (EN/DEM) Operation
The EN/DEM pin enables the supply. When EN/DEM is
tied to VDD, the controller is enabled and operates in
diode-emulation mode. When the EN/DEM pin is floating,
the RT8202L/M will operate in forced-CCM mode.
Diode-Emulation Mode (EN/DEM = High)
In diode-emulation mode, the RT8202L/M automatically
reduces switching frequency at light load conditions to
maintain high efficiency. This reduction of frequency is
achieved smoothly and without increasing VOUT ripple or
load regulation. As the output current decreases from
heavy-load condition, the inductor current is also reduced,
and eventually comes to the point when its valley touches
zero current, which is the boundary between continuous
conduction and discontinuous conduction modes. By
emulating the behavior of diodes, the low side MOSFET
allows only partial negative current when the inductor
freewheeling current becomes negative. As the load current
is further decreased, it takes longer and longer to discharge
the output capacitor to the level that requires the next
“ON” cycle. The on-time is kept the same as that in the
heavy-load condition. In reverse, when the output current
increases from light load to heavy load, the switching
frequency increases to the preset value as the inductor
current reaches the continuous condition. The transition
load point to the light load operation can be calculated as
follows (Figure 1) :
ILOAD
≈
(VIN − VOUT )
2L
x tON
where tON is the On-time.
DS8202L/M-04 April 2011
www.richtek.com
11
Free Datasheet http://www.Datasheet4U.com
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet RT8202L.PDF ] | |
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