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| 型號(hào)： | MAX1901EAI |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | 500kHz Multi-Output, Low-Noise Power-Supply Controllers for Notebook Computers |
| 中文描述： | 0.2 A DUAL SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | 5.30 MM, MO-150, SSOP-28 |
| 文件頁(yè)數(shù)： | 25/33頁(yè) |
| 文件大?。?/td> | 649K |
| 代理商： | MAX1901EAI |
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M
500kHz Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
______________________________________________________________________________________
25
where C
RSS
is the reverse transfer capacitance of the
high-side MOSFET (a data sheet parameter), I
GATE
is
the DH gate-driver peak output current (1.5A typical),
and 20ns is the rise/fall time of the DH driver (20ns typ).
P(gate) = Q
G
f
V
L
where V
L
is the internal-logic-supply voltage (5V), and
Q
G
is the sum of the gate-charge values for low-side
and high-side switches. For matched MOSFETs, Q
G
is
twice the data sheet value of an individual MOSFET. If
V
OUT
is set to less than 4.5V, replace V
L
in this equa-
tion with V
BATT
. In this case, efficiency can be
improved by connecting V
L
to an efficient 5V source,
such as the system 5V supply:
P(diode) = I
LOAD
V
FWD
t
D
f
where t
D
is the diode-conduction time (120ns typ) and
V
FWD
is the forward voltage of the diode.
This power is dissipated in the MOSFET body diode if
no external Schottky diode is used:
P(cap) = (I
RMS
)
2
x R
ESR
where I
RMS
is the input ripple current as calculated in the
Design Procedure
and
Input-Capacitor Value
sections.
Light-Load Efficiency Considerations
Under light loads, the PWM operates in discontinuous
mode, where the inductor current discharges to zero at
some point during the switching cycle. This makes the
inductor current
’
s AC component high compared to the
load current, which increases core losses and I
2
R loss-
es in the output filter capacitors. For best light-load effi-
ciency, use MOSFETs with moderate gate-charge
levels, and use ferrite, MPP, or other low-loss core
material.
P tran
(
V
(
I
f
V
C
I
ns
IN
LOAD
IN
RSS
GATE
)
/
=
×
×
×
×
×
)
[
]
3
2
20
-
SYMPTOM
CONDITION
ROOT CAUSE
SOLUTION
Sag or droop in V
OUT
under step-load change
Low V
IN
- V
OUT
differential, <1.5V
Limited inductor-current slew rate
per cycle.
Increase bulk output capacitance per
formula (see the
Low-Voltage Operation
section). Reduce inductor value.
Dropout voltage is too
high (V
OUT
follows V
IN
as
V
IN
decreases)
Low V
IN
- V
OUT
differential, <1V
Maximum duty-cycle limits
exceeded.
Reduce operation to 333kHz. Reduce
MOSFET on-resistance and coil DCR.
Unstable
—
jitters between
different duty factors and
frequencies
Low V
IN
- V
OUT
differential, <0.5V
Normal function of internal low-
dropout circuitry.
Increase the minimum input voltage or
ignore.
Secondary output won
’
t
support a load
Low V
IN
- V
OUT
differential,
V
IN
< 1.3
V
OUT(MAIN)
Not enough duty cycle left to
initiate forward-mode operation.
Small AC current in primary can
’
t
store energy for flyback
operation.
Reduce operation to 333kHz. Reduce
secondary impedances; use a Schottky
diode, if possible. Stack secondary
winding on the main output.
Poor efficiency
Low input voltage,
<5V
V
L
linear regulator is going into
dropout and isn
’
t providing good
gate-drive levels.
Use a small 20mA Schottky diode for
boost diode. Supply V
L
from an external
source.
Won
’
t start under load or
quits before battery is
completely dead
Low input voltage,
<4.5V
V
L
output is so low that it hits the
V
L
UVLO threshold.
Supply V
L
from an external source other
than V
IN
, such as the system 5V supply.
Table 5. Low-Voltage Troubleshooting Chart
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| MAX1901EAI+ | 功能描述:DC/DC 開(kāi)關(guān)控制器 500kHz Multi-Output Power-Supply Ctlr RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1901EAI+T | 功能描述:DC/DC 開(kāi)關(guān)控制器 500kHz Multi-Output Power-Supply Ctlr RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1901EAI-T | 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1901ETJ | 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1901ETJ+ | 功能描述:DC/DC 開(kāi)關(guān)控制器 500kHz Multi-Output Power-Supply Ctlr RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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