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PDF RT9202B Data sheet ( Hoja de datos )
| Número de pieza | RT9202B | |
| Descripción | Single Synchronous Buck PWM DC-DC Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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RT9202B
Single Synchronous Buck PWM DC-DC Controller
General Description
The RT9202B is a single power supply PWM DC-DC
converter controller designed to drive N-MOSFET in a
synchronous buck topology. The IC integrates the control,
output adjustment, monitoring and protection functions in
a small 8-pin package.
The RT9202B uses a low gain voltage mode PWM control
for simple application design. An internal 0.8V reference
allows the output voltage to be precisely regulated to
low voltage requirement. A fixed 300kHz oscillator
reduces the component size for saving board space.
The RT9202B features over current protection, over voltage
protection, and under voltage lock-out. The output current
is monitored by sensing the voltage drop across the
MOSFET's RDS(ON), which eliminates the need for a current
sensing resistor.
Ordering Information
RT9202B
Package Type
S : SOP-8
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Note :
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.
Features
l Operate From 5V
l 0.8V Internal Reference
l Drive Two N-MOSFETs
l Voltage Mode PWM Control
l Fast Transient Response
l Fixed 300kHz Oscillator Frequency
l Full 0 to 100% Duty Cycle
l Internal Soft Start
l Adaptive Non-Overlapping Gate Driver
l Over-Current Monitor Uses MOSFET RDS(ON)
l Over-Voltage Protection Uses Low-Side MOSFET
l RoHS Compliant and 100% Lead (Pb)-Free
Applications
l Motherboard Power Regulation for Computers
l Subsystems Power Supplies
l Cable Modems, Set Top Box, and DSL Modems
l DSP and Core Communications processor Supplies
l Memory Power Supplies
l Personal Computer Peripherals
l Industrial Power Supplies
l 5V-Input DC-DC Regulators
l Low Voltage Distributed Power Supplies
Pin Configurations
(TOP VIEW)
BOOT
UGATE
GND
LGATE
2
3
4
8 PHASE
7 OCSET
6 FB
5 VCC
SOP-8
DS9202B-03 March 2007
www.richtek.com
1
Free Datasheet http://www.datasheet4u.
1 page  
RT9202B
Absolute Maximum Ratings (Note 1)
l Supply Input Voltage, VCC ----------------------------------------------------------------------------------------- 7V
l BOOT & UGATE to GND -------------------------------------------------------------------------------------------- 15V
l Input, Output or I/O Voltage ---------------------------------------------------------------------------------------- GND − 0.3V to 7V
l Power Dissipation, PD @ TA = 25°C
SOP-8 ------------------------------------------------------------------------------------------------------------------- 0.625W
l Package Thermal Resistance (Note 4)
SOP-8, θJA -------------------------------------------------------------------------------------------------------------- 160°C/W
l Ambient Temperature Range --------------------------------------------------------------------------------------- 0°C to +70°C
l Lead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------- 260°C
l Storage Temperature Range ---------------------------------------------------------------------------------------- −65°C to +150°C
l ESD Susceptibility (Note 2)
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 3)
l Junction Temperature Range --------------------------------------------------------------------------------------- −40°C to +125°C
Electrical Characteristics
(VCC = 5V, TA = 25° C, Unless otherwise specified.)
Parameter
Symbol
VCC Supply Current / Regulated Voltage
Nominal Supply Current
ICC
Regulated Voltage from BOOT
VCC
Power-On Reset
Rising VCC Threshold
VCC Threshold Hysteresis
Rising VOCSET Threshold
Reference
Reference Voltage
Oscillator
Free Running Frequency
Ramp Amplitude
Error Amplifier
∆ VOSC
DC gain
PWM Controller Gate Driver
Upper Drive Source
Upper Drive Sink
Lower Drive Source
Lower Drive Sink
RUGATE
RUGATE
RLGATE
RLGATE
Test Conditions
UGATE, LGATE open
VBOOT = 12V
VOCSET = 4.5V
VOCSET = 4.5V
BOOT= 12V
BOOT-VUGATE = 1V
VUGATE = 1V
VCC - VLGATE = 1V,
VLGATE = 1V
DS9202B-03 March 2007
Min Typ Max Units
-- 3
6 mA
567 V
3.85 4.1 4.35
0.3 0.5 0.7
0.8 1.25 2.0
V
V
V
0.784 0.8 0.816 V
250 300 350 kHz
-- 1.75 -- VP-P
32 35 38 dB
-- 7 11 Ω
-- 5 7.5 Ω
-- 4 6 Ω
-- 2 4 Ω
To be continued
www.richtek.com
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
RT9202B
Table 1
VOUT
Inductor
3.3V
2µH 5µH
2.5V
2µH 5µH
1000µF (ESR=53mΩ) 100mV 40mV 110mV 44mV
1500µF (ESR=33mΩ) 62mV 25mV 68mV 28mV
3000µF (ESR=21mΩ) 40mV 16mV 43mV 18mV
*Refer to Sanyo low ESR series (CE, DX, PX.....)
1.5V
2µH 5µH
93mV 37mV
58mV 23mV
37mV 15mV
The suggested L and C are as follows:
2µH with ≥ 1500µF COUT
5µH with ≥ 1000µF COUT
L
Q
VL
VI D C R VO
C.C.M
TS
TON
TOFF
VI - VO
Input / Output Capacitor
High frequency/long life decoupling capacitors should be
placed as close to the power pins of the load as physically
possible. Be careful not to add inductance to the PCB
trace, as it could eliminate the performance from utilizing
these low inductance components. Consult with the
manuf acturer of the load on specific decoupling
requirements.
The output capacitors are necessary for filtering output
and stabilizing the close loop (see the PWM loop stability).
For powering advanced, high-speed processors, it is
required to meet with the requirement of fast load
transient, high frequency capacitors with low ESR/ESL
capacitors are recommended.
VL
- VO
Another concern is high ESR induced ripple may trigger
UV or OV protections.
PWM Loop Stability
iL
uQ
IL = IO
The RT9202B is a voltage mode buck controller designed
mIL for 5V step-down applications. The gain of error amplifier
is fixed at 35dB for simplified design.
The output amplitude of ramp oscillator is 1.75V, the loop
gain and loop pole/zero are calculated as follows :
iQ
IQ
DC loop gain GA =
35dB
×
5
1.75
×
0.8
VOUT
LC filter pole PO = 1
2π LC
iD Error Amp pole PA = 300kHz
ID
ESR zero ZO =
2π
1
ESRC
The RT9202B Bode plot as shown Figure 6 is stable in
Figure 5
most of application conditions.
DS9202B-03 March 2007
www.richtek.com
11
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet RT9202B.PDF ] | |
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