RT9204CS Ver la hoja de datos (PDF) - Richtek Technology
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RT9204CS Datasheet PDF : 14 Pages
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RT9204
Preliminary
Functional Description
The RT9204 operates at either single 5V power
supply with a bootstrap UGATE driver or 5V/12V
dual-power supply form the ATX SMPS. The dual-
power supply is recommended for high current
application, the RT9204 can deliver higher gate
driving current while operating with ATX SMPS based
on dual-power supply.
The Bootstrap Operation
In a single power supply system, the UGATE driver of
RT9204 is powered by an external bootstrap circuit,
as the Fig.1. The boot capacitor, CBOOT, generates a
floating reference at the PHASE node. Typically a
0.1µF CBOOT is enough for most of MOSFETs used
with the RT9204. The voltage drop between BOOT
and PHASE node is refreshed to a voltage of VCC –
diode drop (VD) while the low side MOSFET turning
on.
R1
C2
VCC
BOOT
D1
1µF
UGATE
0.1µF
PHASE
RT9204
5V
+
Fig.1 Single 5V power Supply Operation
Dual Power Operation
The RT9204 was designed to regulate a 6.0V at VCC
pin automatically when BOOT pin is powered by 12V.
In a system with ATX 5V/12V power supply, the
RT9204 is ideal for higher current application due to
the higher gate driving capability, VUGATE = 7V. A RC
(10Ω/1µF) filter is also recommended at BOOT pin to
prevent the ringing induced from fast power on, as
shown in Fig.2.
VCC
C2
1µF
6.0V
Regulator
RT9204
BOOT
R1
12V
10
C1
1µF
UGATE
5V
+
Fig.2 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
4.1V with 0.5V hysteresis and the normal level at
OCSET pin is 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 power on. The soft-
start voltage is controlled by an internal digital
counter. It clamps the ramping of reference voltage at
the input of error amplifier and the pulse-width of the
output driver slowly. The typical soft-start duration is
2mS.
Under Voltage and Over Voltage Protection
The voltage 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/OV detection have 30µS
triggered delay. When OC or UV trigged, a hiccup re-
start sequence will be initialized, as shown in Fig.3.
Only 3 times of trigger are allowed to latch off. Hiccup
is disabled during soft-start interval.
www.richtek-ic.com.tw
8
DS9204-00 February 2002
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