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參數(shù)資料
| 型號： | ADP3025JRU-REEL |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | High Efficiency Dual Output Power Supply Controller |
| 中文描述： | DUAL SWITCHING CONTROLLER, 350 kHz SWITCHING FREQ-MAX, PDSO38 |
| 封裝： | MO-153BD-1, TSSOP-36 |
| 文件頁數(shù)： | 17/24頁 |
| 文件大小： | 609K |
| 代理商： | ADP3025JRU-REEL |
ADP3025
From the duty cycle, the required minimum
R
DS(ON)
for each
MOSFET can be derived by the following equations:
Rev. A | Page 17 of 24
Upper MOSFET:
)
1
)
(
2
)
(
T
I
V
P
V
UPPER
R
MAX
OUT
D
IN
ON
DS
α
+
×
×
×
=
(13)
Lower MOSFET:
)
1
×
)
(
)
(
2
)
(
T
I
V
V
P
V
×
LOWER
R
MAX
OUT
IN
D
IN
ON
DS
α
+
×
=
(14)
where
P
D
is the allowable power dissipation and α is the
temperature dependency of
R
DS(ON)
.
P
D
is determined by
efficiency and/or thermal requirements (see the Efficiency
Enhancement section). (1 + α
T
) is generally given for a
MOSFET in the form of a normalized
R
DS(ON)
versus
temperature curve, but α= 0.007/°C can be used as an
approximation for low voltage MOSFETs.
Maximum MOSFET power dissipation occurs at maximum
output current and can be calculated as follows:
Upper MOSFET:
(
)
T
R
I
V
V
UPPER
(
P
ON
DS
MAX
IN
OUT
D
α
+
×
×
×
=
1
)
)
(
2
(15)
Lower MOSFET:
(
)
T
R
I
V
V
V
LOWER
P
ON
DS
MAX
IN
OUT
IN
D
α
+
×
×
×
=
1
)
(
)
(
2
(16)
The Schottky diode, D1 in Figure 17, conducts only during the
dead time between conduction of the two power MOSFETs.
D1’s purpose is to prevent the body diode of the lower N-
channel MOSFET from turning on and storing charge during
the dead time, which could cost as much as 1% in efficiency. D1
should be selected for forward voltage of less than 0.5 V when
conducting I
MAX
. Recommended transistors for upper and lower
MOSFETs are given in Table 9.
Table 9. Recommended MOSFETs
Maximum Output
Vishay/Siliconix
International Rectifier
2 A
Si4412DY, 28 m
IRF7805, 11 m
4 A
Si4410DY, 13.5 m
IRF7811, 8.9 m
RF7805, 11 m
SOFT START
The soft start time of each of the switching regulators can be
programmed by connecting a soft start capacitor to the corres-
ponding soft start pin (SS3 or SS5). The time it takes each
regulator to ramp up to its full duty ratio depends proportion-
ally on the values of the soft start capacitors. The charging
current is 2.5 μA ±20%. The capacitor value to set a given soft
start time, t
SS
, is given by
( )
(
)
pF
V
8
μA
5
SS
SS
t
C
×
(17)
FIXED OR ADJUSTABLE OUTPUT VOLTAGE
Each of the ADP3025’s switching controllers can be pro-
grammed to operate with a fixed or adjustable output voltage.
As shown in Figure 17, putting the ADP3025 into fixed mode
gives a nominal output of 3.3 V and 5 V for the two switching
buck converters. By using two identical resistor dividers per
converter, any output voltage between 800 mV and 6.0 V can be
set. The center point of one divider is connected to the feedback
pin, FB, and the center point of the other identical divider is
connected to EAN. It is important to use 1% resistors. 10 k,
1% is a good value for the lower leg resistors. In this case, the
upper leg resistors for a given output voltage is determined by
(
)
kΩ
08
.
8
V
V
R
OUT
UPPER
=
(18)
Table 10 shows the resistor values for the most common output
voltages.
Table 10. Typical Feedback Resistor Values
V
OUT
1.5 V
R
UPPER
9.1 k
R
LOWER
10 k
EFFICIENCY ENHANCEMENT
The efficiency of each switching regulator is inversely
proportional to the losses during the switching conversion. The
main factors to consider when attempting to maximize
efficiency are
1.8 V
13 k
10 k
2.5 V
22 k
10 k
1.
Resistive losses, which include the R
DS(ON)
of upper and
lower MOSFETs, trace resistances, and output choke wire
resistance.
These losses contribute a major part of the overall power
loss in low voltage battery-powered applications. However,
trying to reduce these resistive losses by using multiple
MOSFETs and thick traces may lead to lower efficiency
and higher price. This is due to the trade-off between
reduced resistive loss and increased gate drive loss that
must be considered when optimizing efficiency.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ADP3025JRUZ-REEL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
| ADP3026 | 制造商:AD 制造商全稱:Analog Devices 功能描述:High-Efficiency Notebook Computer Power Supply Controller |
| ADP3026ARU | 制造商:AD 制造商全稱:Analog Devices 功能描述:High-Efficiency Notebook Computer Power Supply Controller |
| ADP3026JRUZ-REEL | 制造商:Rochester Electronics LLC 功能描述:DUAL OUTPUT SYNCHRNOUS BUCK CONTROLLER - Tape and Reel 制造商:Analog Devices 功能描述: |
| ADP3031 | 制造商:AD 制造商全稱:Analog Devices 功能描述:2 MHz PWM Boost Switching Regulator |
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