參數(shù)資料
型號(hào)： PT4855
廠商： Texas Instruments, Inc.
英文描述： "3.3V/1.5V/1.2V 25A
中文描述： 3.3V/1.5V/1.2V 25A 輸出 48V 輸入的三路輸出 DC/DC 轉(zhuǎn)換器
文件頁(yè)數(shù)： 11/13頁(yè)
文件大?。?/td> 233K
代理商： PT4855
Application Notes
For technical support and more information, see inside back cover or visit www.ti.com
Adjusting the Output Voltages of the PT4850
Triple-Output DC/DC Converters
The output voltages of the PT4850 series of triple-output
DC/DC converters, Vo
1
, Vo
2
and Vo
3
, are independently
adjustable. The adjustment method uses a single external
resistor,
1
which may be used to adjust a selected output
by up to ±10% from the factory preset value. The value
of the resistor determines the magnitude of adjustment,
and the placement of the resistor determines the direction
of adjustment (up or down). The resistor values can be
calculated using the appropriate formula (see below),
using the constants provided in Table 3-2. Alternatively
the resistor value may be selected directly from Table 3-3
and Table 3-4, for Vo
1
and Vo
2
/Vo
3
respectively. The
placement of each resistor is as follows.
Adjust Up:
To increase a specific output, add a resistor R
1
between the appropriate
V
x
Adj
(V
1
Adj, V
2
Adj, or V
3
Adj)
and the output common (COM). See Figure 3-1(a)
and Table 3-1 for the resistor placement and pin connec-
tions.
Figure 3-1b
PT4850 Series
Calculation of Adjust Values
The adjust resistor value may also be calculated using an
equation. In each case, the equation for R
1
[Adjust Up] is
different to that for
(R
2
)
[Adjust Down]. For the PT4850
series, the following points should be noted.
Vo
1
uses different equations to Vo
2
and Vo
3
. The
equations are defined for the desired output voltage.
The equations for Vo
2
and Vo
3
are based on the
percentage of desired adjustment. Both Vo
2
and Vo
3
use the same constants, which are common for all
output voltages.
Vo
1
Adjust:
R
1
[Adjust Up]
3
=
2.5 R
o
V
a
– V
o
– R
s
k
(R
2
)
[Adjust Down]
3
=
R
o
(V
a
– 2.5
) – R
s
V
o
– V
a
k
Where: V
o
= Original output voltage
= Adjusted output voltage
R
o
= The resistance value in Table 3-2
R
s
= The series resistance from Table 3-2
V
a
Vo
2
/ Vo
3
Adjust:
R
1
[Adjust Up]
3
=
50 · R
o
n%
–R
s
k
(R
2
)
[Adjust Down]
3
=
R
o
· (50 – n%)–R
s
n%
k
Where: R
o
= The resistance value in Table 3-2
R
s
= The series resistance from Table 3-2
n% = The desired adjustment from the
nominal (in percent)
(R
2
)
+Vo
x
+V
x
Adj
COM
+Vo
x
(Adjusted Down)
Output
Common
PT4850
#
#
#
# - See Table 3-1 for pin connections,
where Vo
x
equals Vo
1
, Vo
2
, or Vo
3
Figure 3-1a
R
1
+Vo
x
+V
x
Adj
COM
+Vo
x
(Adjusted Up)
Output
Common
PT4850
#
#
#
# - See Table 3-1 for pin connections,
where Vo
x
equals Vo
1
, Vo
2
, or Vo
3
Adjust Down:
Add a resistor
(R
2
)
, between the appropriate
V
x
Adj
(V
1
Adj, V
2
Adj, or V
3
Adj) and the output being
adjusted,
+Vo
x
. See Figure 3-1(b) and Table 3-1 for the
resistor placement and pin connections.
Table 3-1; Adjust Resistor Pin Connections
To Adjust Up
Connect R
1
from
Vo
x
Adj
To Adjust Down
Connect
(R
2
)
from
Vo
x
Adj
to
to
Vo
x
COM
Vo
1
Vo
2
Vo
3
8
17
21
12
18
18
8
17
21
9
16
22
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PT4855C 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Triple-Output Iso DC-DC Cnvtr RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
PT4855N 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Triple-Output Iso DC-DC Cnvtr RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
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