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參數(shù)資料
| 型號(hào)： | RT8803A |
| 廠商： | Richtek Technology Corporation |
| 英文描述： | 2/3-Phase PWM Controller for High-Density Power Supply |
| 中文描述： | 2/3-Phase PWM控制器的高密度電源 |
| 文件頁(yè)數(shù)： | 25/27頁(yè) |
| 文件大?。?/td> | 553K |
| 代理商： | RT8803A |
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RT8803A
25
DS8803A-05 August 2007
www.richtek.com
All brandname or trademark belong to their owner respectively
For example, assuming the negative inductor current is
I
LX_50%
=
5A at no load, then for
R
CSN
330
Ω
, R
ADJ
= 160
Ω,
V
OUT
= 1.300V
R
CSN2
≤
85.8k
Ω
Choose R
CSN2
= 82k
Ω
Figure 10 shows that dead zone of load line at light load
is eliminated by applying this technique.
VR_HOT & VR_FAN Setting
Figure 12
Load Line Setting and Thermal Compensation
V
ADJ
= Sum(I
X
) x R
ADJ
= (DCR x R
ADJ
/ R
CSN
) x I
OUT
= LL x I
OUT
V
OUT
= V
DAC
V
ADJ
= V
DAC
LL x I
OUT
LL = DCR(PTC) x R
ADJ
(NTC) / R
CSN
DCR is the inductor DCR which is a PTC resistance.
Ω
Ω
×
≥
330
1m
5A
R
1.3V
CSN2
Q1
Q2
Q3
-
-
CMP
CMP
CMP
0.39 x V
CC
0.33 x V
CC
0.28 x V
CC
TSEN
R1
R
NTC
V
CC
5V
V
TSEN
R1
R2
R
NTC
ADJ
R
ADJ
Figure 14. R
ADJ
Connection for Thernal Compensation
Temperature
V
TSEN
VR_FAN
VR_HOT
0.28 x V
CC
0.33 x V
CC
0.39 x V
CC
V
TSEN
is inversely proportional
to Temperature.
Figure 13. VR_HOT and VR_FAN Signal vs TSEN Voltage
If R
ADJ
is connected as in Figure 14, R
ADJ
= R1 + (R2//
R
NTC
), which is a negative temperature correlated
resistance. By properly selecting R1 and R2, the positive
temperature coefficient of DCR can be canceled by the
negative temperature coefficient of R
ADJ
. Thus the load
line will be thermally compensated.
Over Current Protection
Phase current OCP
RT8803A uses an external resistor R
IMAX
connected to
IMAX pin to generate a reference current I
IMAX
for over
current protection :
IMAX
IMAX
R
where V
IMAX
is typical 1.0V . OCP comparator compares
each sensed phase current I
X
with this reference current
as shown in Figure 15. Equivalently, the maximum phase
current I
LX(MAX)
is calculated as below:
IMAX
V
I
=
LX
CSNX
R
IMAX
IMAX
R
X
CSNX
DCR
X
LX(MAX)
I
IMAX
3
×
IMAX
R
IMAX
I
X(MAX)
IMAX
I
X(MAX)
R
V
2
R
I
V
2
3
2
3
I
2
1
I
3
1
×
=
×
=
×
=
=
=
Figure 15. Over Current Comparator
+
-
1/3 I
X
1/2 I
IMAX
OCP Comparator
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相關(guān)代理商/技術(shù)參數(shù) |
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| RT8803A_11 | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:2/3-Phase PWM Controller for High-Density Power Supply |
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