RT9205 データシートの表示（PDF） - Richtek Technology
部品番号
コンポーネント説明
メーカー
RT9205 Datasheet PDF : 15 Pages
| |||
RT9205/A
Preliminary
Application Information
The RT9205/A operates at either single 5V power supply VCC
with a bootstrap UGATE driver or a 5V/12V dual-power
supply form the ATX SMPS. The dual- power supply is
6.0V
Regulation
BOOT
R
C 10
1uF
12V
5V
recommended for high current applications, the RT9205/
UGATE
A can deliver higher gate driving current while operating
with ATX SMPS based on a dual-power supply.
VCC
The Bootstrap Operation
C2
In a single power supply system, the UGATE driver of
1uF
LGATE
RT9205/A is powered by an external bootstrap circuit, as
shown in the Figure 3. The boot capacitor, CBOOT,
RT9205/A
generates a floating reference at the PHASE pin. Typically
a 0.1µF CBOOT is enough for most of MOSFETs used
Figure 4. Dual Power Supply Operation
with the RT9205/A. The voltage drop between BOOT and
PHASE is refreshed to a voltage of VCC − diode drop
(VD) while the lower MOSFET turning on.
Power On Reset
The Power-On Reset (POR) monitors the supply voltage
R1
(normal +5V) at the VCC pin and the input voltage at the
VCC
BOOT
C2
1uF
UGATE
D1
0.1uF
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
5V
1.5V (see over-current protection). The POR function
initiates soft-start operation after all supply voltages
PHASE
exceed their POR thresholds.
VCC
LGATE
RT9205/A
Figure 3. Single 5V power Supply Operation
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 RT9205/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
RT9205/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
(ov er v oltage). The UV threshold is 0.56V and
OV-threshold is 1.0V. Both UV and OV detection are with
30µs delay after triggered. When OC or UV trigged, a
hiccup re-start sequence will be initialized, as shown in
Figure 5. For RT9205, only 3 times of trigger are allowed
before latching off. But for RT9205A, UVP will be kept in
hiccup mode. Hiccup is disabled during soft-start interval.
www.richtek.com
10
DS9205/A-08 March 2007
Share Link: 