參數(shù)資料
型號(hào)： MAX1939EEI
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 穩(wěn)壓器
英文描述： Two-Phase Desktop CPU Core Supply Controllers with Controlled VID Change
中文描述： SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO28
封裝： 0.150 INCH, 0.025 INCH PITCH, MO-137, QSOP-28
文件頁(yè)數(shù)： 19/24頁(yè)
文件大?。?/td> 586K
代理商： MAX1939EEI
M
Two-Phase Desktop CPU Core Supply Controllers
with Controlled VID Change
______________________________________________________________________________________
19
(V
SAG
) is no longer a problem. The amount of overshoot
from stored inductor energy can be calculated as:
where I
PEAK
is the peak inductor current.
The undershoot at the rising load edge of a load tran-
sient is calculated from:
where
I
LOAD
is the change in load current, and K is
4μs.
To ensure stability, make sure that the zero frequency
created by the output capacitance, and the ESR of the
output capacitor do not exceed 50kHz. The zero fre-
quency is found from:
Currently, aluminum electrolytic, Sanyo POSCAP, and
Panasonic SP capacitors have ESR zero frequencies
well below 50kHz. When using ceramic capacitors, it
might be necessary to use a series resistance to
ensure that the ESR zero is below 50kHz.
Input Capacitor Selection
The input capacitor reduces peak currents drawn from
the power source and reduces noise and voltage ripple
on the input caused by the circuit
’
s switching. The input
capacitor must meet the ripple current requirement
(I
RMS
) imposed by the switching currents as defined by
the following equation:
I
RMS
has a maximum value when the input voltage
equals twice the output voltage (V
IN
= 2V
OUT
), so
I
RMS(MAX)
= I
LOAD
/ 2. For most applications, nontanta-
lum capacitors (ceramic, aluminum electrolytic, poly-
mer, or OS-CON) are preferred at the input because of
their robustness with high inrush currents typical of sys-
tems that may be powered from very low impedance
sources.
Multiple smaller value capacitors can be used in paral-
lel to satisfy the ESR and capacitance requirements.
Selecting a BST Capacitor
The BST capacitors must be large enough to handle
the gate-charging requirements of the high-side
MOSFETs. For most applications, 0.22μF ceramic
capacitors are recommended.
BST capacitors are needed to keep the voltage on the
BST_ pins from dropping too much when the high-side
MOSFET gates are charged. A capacitor value that
prevents V
BST
_ from dropping more than 100mV to
200mV is adequate. The capacitance needed for the
BST_ capacitor is calculated from:
where Q
GH
is the total gate charge of the high-side
MOSFET and
V
BST_
is the amount that the voltage on
the BST_ pin drops when the gate is charged. If using
multiple MOSFETs in parallel, use the sum of all the
gate charges for Q
GH
.
Setting the Current Limit
Current limit sets the maximum value of the inductor
“
valley
”
current. I
VALLEY
is calculated from the following
equation:
The current-limit threshold (I
LIMIT
) must be set higher
than the valley current:
The current-limit threshold is set by the voltage at ILIM
and the value of the current-sense resistors:
where V
ILIM
is the voltage on the ILIM pin (0.1V to 2V)
and R
CS
is the value of the current-sense resistor. If the
on-resistance of the low-side MOSFET is used for cur-
rent sensing, then the maximum value of the on-resis-
tance (overtemperature and part-to-part variation) must
be used for R
CS
.
I
V
R
LIMIT
ILIM
×
CS
=
10
I
I
LIMIT
VALLEY
>
I
I
LIR
2
VALLEY
LOAD MAX
2
=
×
(
)
1
C
Q
V
BST
GH
BST
_
_
=
I
I
V
V
V
V
RMS
LOAD
2
OUT
IN
OUT
IN
=
×
(
)
f
ESR
C
zESR
COUT
OUT
=
×
×
1
2
π
V
L
I
V
K
V
t
C
V
V
V
V
K
t
SAG
LOAD
OUT
IN
OFF MIN
(
OUT
OUT
IN
OUT
IN
OFF MIN
(
=
×
×
×
+
(
×
×
×
×
2
2
)
)
)
V
I
C
L
V
SOAR
PEAK
OUT
OUT
=
×
×
×
2
2
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參數(shù)描述
MAX1939EEI-T 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(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
MAX1940EEE 功能描述:電源開關(guān) IC - USB Triple USB Switch w/Autoreset RoHS:否 制造商:Micrel 電源電壓-最小:2.7 V 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-8 封裝:Tube
MAX1940EEE+ 功能描述:電源開關(guān) IC - USB Triple USB Switch w/Autoreset RoHS:否 制造商:Micrel 電源電壓-最小:2.7 V 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-8 封裝:Tube
MAX1940EEE+T 功能描述:電源開關(guān) IC - USB Triple USB Switch w/Autoreset RoHS:否 制造商:Micrel 電源電壓-最小:2.7 V 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-8 封裝:Tube
MAX1940EEE-T 功能描述:電源開關(guān) IC - USB Triple USB Switch w/Autoreset RoHS:否 制造商:Micrel 電源電壓-最小:2.7 V 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-8 封裝:Tube
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