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参数资料
| 型号： | RT9205ACS |
| 厂商： | Richtek Technology Corporation |
| 英文描述： | Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| 中文描述： | 双稳压器-同步降压PWM型DC - DC和线性控制器 |
| 文件页数： | 4/16页 |
| 文件大小： | 316K |
| 代理商： | RT9205ACS |
RT9205/A
Preliminary
www.richtek.com
DS9205/A-03 May 2003
12
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 manufacturer 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 fast load transient
requirement. Also high ESR usually induces ripple
that may trigger UV or OV protections. So High
frequency capacitors with low ESR/ESL capacitors
are recommended here.
Linear Regulator Driver
The linear controller of RT9205/A was designed to
drive an external bipolar NPN transistor or a N-
channel MOSFET. For a N-channel MOSFET,
normally
DRV
need
to
provide
minimum
VOUT2+VT+gate-drive voltage to keep VOUT2 as the
set voltage. When driving MOSFET operating at a 5V
power supply, the gate-drive will be limited at 5V. At
this situation, as shown in Fig.7, a MOSFET with low
VT threshold (VT = 1V) and set Vout2 below 2.5V are
suggested. In VBOOT = 12V operation condition, as
Fig.8 shown, VCC is regulated higher than 6V, which
providing higher gate-drive capability for driving the
MOSFET, VOUT2 can be set as VOUT2 ≤ 3.3V.
Fig. 7
Fig. 8
PWM Loop Stability
The RT9205/A is a voltage mode buck controller
designed for 5V step-down applications. The gain of
error amplifier is fixed at 35dB for simplifying design.
The output amplitude of ramp oscillator is 1.6V, the
loop gain and loop pole/zero are calculated as
follows:
DC loop gain GA = 35dB ×
×
LC filter pole PO =
Error Amp pole PA = 300kHz
ESR zero ZO =
The RT9205/A Bode plot is as shown in Fig.9. It is
stable in most of application conditions.
Loop Gain
VOUT = 1.5V
VOUT = 2.5V
VOUT = 3.3V
ZO = 3.2kHz
PO = 2.9kHz
L=2
H
COUT = 1500F(33m)
VOUT = 3.3V
40
30
20
10
1M
100k
10k
1k
100
Fig. 9
75
.
1
5
VOUT
8
.
0
+
FBL
VCC
RT9205/A
VOUT2 ≤ 3.3V
R3
BOOT
DRV
VBOOT = 12V
R4
< 1K
6V
Max. 6V
Suggest Low
VT MOSFET
+
FBL
VCC
RT9205/A
VOUT2 ≤ 2.5V
R3
BOOT
DRV
VCC = 5V
R4
< 1K
Max. 5V
Suggest Low
VT MOSFET
LC
2π
1
C
ESR
2π
1
×
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相关代理商/技术参数 |
参数描述 |
|---|---|
| RT9205-ACS | 制造商:RICHTEK 制造商全称:Richtek Technology Corporation 功能描述:Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9205AGS | 制造商:RICHTEK 制造商全称:Richtek Technology Corporation 功能描述:Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9205APS | 制造商:RICHTEK 制造商全称:Richtek Technology Corporation 功能描述:Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9205GS | 制造商:RICHTEK 制造商全称:Richtek Technology Corporation 功能描述:Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
| RT9205PS | 制造商:RICHTEK 制造商全称:Richtek Technology Corporation 功能描述:Dual Regulators - Synchronous Buck PWM DC-DC and Linear Controller |
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