參數(shù)資料
型號： 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
文件頁數(shù)： 23/27頁
文件大?。?/td> 553K
代理商： RT8803A
RT8803A
23
DS8803A-05 August 2007
www.richtek.com
All brandname or trademark belong to their owner respectively
If
With other phase kept unchanged, this phase would share
(R
PX
+Rx)/R
PX
times current than other phases. Figure 6
and 7 show different current ratio setting for the power
stage when Phase 3 is programmed 2 times current than
other phases. Figure 8 and 9 compare the above current
ratio setting results.
Output Voltage Offset Function
To meet Intel
requirement of initial offset of load line,
RT8803A provides programmable initial offset function.
External resistor R
OFS
and voltage source at OFS pin
generate offset current
, where V
OFS
is 1V typical. One quarter of I
OFS
flows
through R
FB1
as shown in Figure 4. Error amplifier would
hold the inverting pin equal to V
DAC
- V
ADJ
. Thus output
voltage is subtracted from V
DAC
- V
ADJ
for a constant offset
voltage.
A positive output voltage offset is possible by connecting
R
OFS
to VDD instead of to GND. Please note that when
R
OFS
is connected to VDD, V
OFS
is V
DD
2V typically and
half of I
OFS
flows through R
FB1
. V
CORE
is rewritten as :
R
V
V
V
+
=
Current Ratio Setting
Current ratio adjustment is possible as described below.
It is important for achieving thermal balance in practical
application where thermal conditions between phases are
not identical. Figure 5 shows the application circuit of GM
for current ratio requirement. According to Basic Circuit
Theory
R
PX
+
+
Figure 7. GM1~2 Setting for current ratio function
Figure 6. GM3 Setting for current ratio function
Figure 4. Load Line and Offset Function
Figure 5
OFS
OFS
V
OFS
I
R
=
OFS
FB1
R
ADJ
V
DAC
CORE
V
4
R
×
V
=
OFS
FB1
ADJ
DAC
CORE
R
DCRx
I
1
R
Rx
Cx
R
SRx
R
Rx
×
VCx
LX
PX
PX
PX
+
×
×
×
=
DCRx
I
R
Rx
R
VCx
then
Cx
)
//R
(R
DCRx
L
LX
PX
PX
+
PX
X
X
×
×
=
×
=
T
L
X
DCRx
I
LX
V
OUT
Rx
Cx
VCx
+
-
R
PX
+
-
+
+
-
V
CORE
R
FB1
DAC
R
ADJ
X
4I
V
ADJ
4
I
OFS
EA
COMP
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參數(shù)描述
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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