參數(shù)資料
型號： RT9201GQV
廠商： Richtek Technology Corporation
元件分類： DC/DC變換器
英文描述： High Efficiency PWM Step-Down DC-DC Converter
中文描述： 高效PWM降壓型DC - DC轉(zhuǎn)換器
文件頁數(shù)： 11/13頁
文件大?。?/td> 206K
代理商： RT9201GQV
RT9201
11
DS9201-12 August 2007
www.richtek.com
Over Current Protection
The RT9201 continuously monitors the inductor current
by sensing the voltage across the PMOSFET when it
turns on. When the inductor current is higher than current
limit threshold (1A typical), OCP activates and forces the
PMOSFET turning off to limit inductor current cycle by
cycle.
The current limit is set to 50% level of normal condition
when the output voltage is lower than its 50% normal
level. This can minimize the power loss and protect the
device when over current or output short circuit occurs.
Once output voltage drops below to its 50% normal level
Figure 2
Inductor Selection
The output inductor is suggested as the above table for
optimal performance. Make sure that the inductor will
not saturate over the operation conditions including
temperature range, input voltage range, and maximum
output current. If possible, choose an inductor with rated
current higher than 1A so that it will not saturate even
under circuit condition.
V
OUT
(V)
0.85
R
F1
(
)
24k
C
F1
(pF)
330
R
F2
(
)
390k
C
F2
(pF)
10
L
X
(
μ
H)
4.7
C
SS
(pF)
330
1.5
343k
22
390k
10
6.8
470
2.5
820k
10
390k
10
10
680
3.3
1.2M
5.6
390k
10
10
1000
Table 1. Component Selection for Typical Application
F2
F2
F1
REF
V
OUT
V
R
R
R
+
×
=
The internal V
REF
is 0.8V with 1% accuracy. In practical
application, keep R
F2
= 390k
and C
F2
= 10pF
respectively and choose appropriate R
F1
and C
F1
according to the required output voltage. Make sure that
the product of R
F1
and C
F1
is about 8200k
-pF. The
following table shows recommended feedback network
as well as inductor for some typical output voltages.
Input Capacitor Selection
The input capacitor can filter the input peak current and
noise at input voltage source. The capacitor with low ESR
(effective series resistance) provides the small drop
voltage to stabilize the input voltage during the transient
loading. For input capacitor selection, the ceramic
capacitors larger than 10
μ
F is recommend. The capacitor
must conform to the RMS current requirement. The
maximum RMS ripple current is calculated as :
IN
OUT
V
IN
OUT
V
OUT(MAX)
I
RMS
I
V
)
(V
=
due to over current or short circuit, it can build up only
when output current is lower 50% of normal current limit
threshold.
Output Voltage Setting and Feedback Network
The output voltage can be set from V
REF
to V
IN
by a voltage
divider as:
V
LX
(V)
V
OUT
(mV)
0
4
2
0
-100
100
Time (10
μ
s/Div)
Sub-Harmonic at Boundary
Condition
V
IN
= 3.8V, V
= 3.3V
I
OUT
= 600mA, C
OUT
= 100uF
Figure 1
Boundary of PWM and Low-Dropout Mode
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
0
100
200
300
400
500
600
700
Output Current (mA)
M
V
I
(
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
PWM Mode
Low Dropout Mode
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
RT9201PQV 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:High Efficiency PWM Step-Down DC-DC Converter
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RT9202_07 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Single Synchronous Buck PWM DC-DC Controller
RT9202B 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Single Synchronous Buck PWM DC-DC Controller
RT9202BGS 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Single Synchronous Buck PWM DC-DC Controller
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