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PDF RT9203A Data sheet ( Hoja de datos )
| Número de pieza | RT9203A | |
| Descripción | Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Preliminary
RT9203/A
Dual Regulators - Synchronous Buck PWM DC-DC and
Linear Controller
General Description
The RT9203/A is a dual-output power controllers designed
for high performance graphics cards and personal
computers. The IC integrates a synchronous buck
controller, a linear controller and protection functions into
a small 8-pin package.
The RT9203/A uses an internal compensated voltage
mode PWM control for simplying design. An internal 0.8V
reference allows the output voltage to be precisely
regulated to meet low output voltage requirement. A fixed
300kHz oscillation frequency reduces the component size
for saving board area.
The RT9203/A also features over voltage protection
(OVP) and under voltage lock-out (UVLO).
Ordering Information
RT9203/A
Package Type
S : SOP-8
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
UVP : Hiccup Mode
UVP : Latch Mode
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 Operates at 5V
l 0.8V Internal Reference
l Drives Two N-MOSFET
l Voltage Mode PWM Control
l Fast Transient Response
l Fixed 300kHz Oscillator Frequency
l Dynamic 0 to 100% Duty Cycle
l Internal PWM Loop Compensation
l Internal Soft-Start
l Adaptive Non-Overlapping Gate Driver
l Over-Voltage Protection Uses Lower MOSFET
l RoHS Compliant and 100% Lead (Pb)-Free
Applications
l PC Motherboard
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
l Graphic Cards
Pin Configurations
(TOP VIEW)
BOOT
UGATE
GND
LGATE
2
3
4
8 FB
7 FBL
6 DRV
5 VCC
SOP-8
DS9203/A-10 March 2007
www.richtek.com
1
Free Datasheet http://www.datasheet4u.
1 page  
Preliminary
RT9203/A
Functional Pin Description
BOOT (Pin 1)
This pin provides ground referenced bias voltage to the
upper MOSFET driver. A bootstrap circuit is used to create
a voltage that is suitable for driving a logic-level N-MOSFET
when operating at a single 5V power supply. This pin also
could be powered from ATX 12V, in this situation, an internal
6.0V regulator will supply to VCC pin for generating bias
required inside the IC.
FB (Pin 8)
This pin is connected to the PWM converter's output-divider
for regulating and monitoring the output voltage of buck
converter. This pin also connects to the protection monitor
and the inverting input of internal PWM error amplifier inside
the IC.
UGATE (Pin 2)
Connect the UGATE pin to the gate of upper MOSFET.
This pin provides the gate drive for the upper MOSFET.
GND (Pin 3)
Signal and power ground for the IC. All voltage levels are
measured with respect to this pin.
LGATE (Pin 4)
Connect the LGATE pin to the gate of lower MOSFET.
This pin provides the gate drive for the lower MOSFET.
VCC (Pin 5)
This is the main bias supply for the RT9203/A. This pin
also provides the gate bias charge for the gate of lower
MOSFET. The voltage at this pin is monitored for ensuring
a proper power-on reset (POR). This pin is also the out
of an internal 6.0V regulator that powered from the BOOT
pin when the BOOT pin is directly powered from ATX
12V.
DRV (Pin 6)
This pin is the output of a linear controller. It should be
connected to the base of an external bypass NPN
transistor or the gate of a N-MOSFET to form a linear low
dropout regulator.
FBL (Pin 7)
This pin is connected to the output resistor-divider of an
external power transistor or a N-MOSFET based low
dropout regulator for regulating and monitoring the output
voltage. This pin is also connected to the protection
monitor and the invertering input of error amplifier of
internal linear regulator inside the IC.
DS9203/A-10 March 2007
www.richtek.com
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
Preliminary
RT9203/A
Application Information
The RT9203/A operates at either single 5V power supply
with a bootstrap UGATE driver or a 5V/12V dual-power
supply form the ATX SMPS. The dual- power supply is
recommended for high current applications, the RT9203/
A can deliver higher gate driving current while operating
with ATX SMPS based on a dual-power supply.
VCC
6.0V
Regulation
BOOT
UGATE
R
C 10
1uF
12V
5V
The Bootstrap Operation
In a single power supply system, the UGATE driver of
RT9203/A is powered by an external bootstrap circuit, as
shown in the Figure 3. The boot capacitor, CBOOT,
generates a floating reference at the PHASE pin. Typically
a 0.1µF CBOOT is enough for most of MOSFETs used
with the RT9203/A. The voltage drop between BOOT and
PHASE is refreshed to a voltage of VCC - diode drop
(VD) while the lower MOSFET turning on.
R1
VCC
BOOT
C2
1uF UGATE
D1
0.1uF
PHASE
VCC
LGATE
5V
RT9203/A
Figure 3. Single 5V power Supply Operation
VCC
LGATE
C2
1uF
RT9203/A
Figure 4. Dual Power Supply Operation
Power On Reset
The Power-On Reset (POR) monitors the supply voltage
(normal +5V) at the VCC pin and the input voltage at the
OCSET pin. The VCC POR level is set to 4.1V with 0.5V
hysteresis and the normal level at OCSET pin is set to
1.5V (see over-current protection). The POR function
initiates soft-start operation after all supply voltages
exceed their POR thresholds.
Soft Start
A built-in soft-start is used to prevent surge current from
power supply input during powering on. The soft-start
voltage is controlled by an internal digital counter. It slows
down and clamps the ramping of reference voltage at the
input of error amplifier and the pulse-width of the output
driver. The typical soft-start duration is 2.5ms.
Dual Power Operation
The RT9203/A was designed to supply a regulated 6.0V
at VCC pin automatically when BOOT pin is powered by
a 12V. In a system with ATX 5V/12V power supply, the
RT9203/A is ideal for higher current applications due to
the higher gate driving capability, VUGATE = 12V and VLGATE
= 6.0V. A RC (10Ω/1µF) filter is also recommended at
BOOT pin to prevent the ringing induced from fast power-
on, as shown in Figure 4.
Under Voltage and Over Voltage Protection
The voltage presents at FB pin is monitored and protected
against OC (over current), UV (under voltage), and OV
(over voltage). The UV threshold is 0.5V and OV threshold
is 1.0V. Both UV and OV detection are with 30ms delay
after triggered. When OC or UV trigged, a hiccup re-start
sequence will be initialized, as shown in Figure 5. For
RT9203, Only 3 times of trigger are allowed before
latching off. But for RT9203A, UVP will be kept in hiccup
mode. Hiccup is disabled during soft-start interval.
DS9203/A-10 March 2007
www.richtek.com
11
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet RT9203A.PDF ] | |
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