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参数资料
| 型号： | MAX1858EEG |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | Dual 180∑ Out-of-Phase PWM Step-Down Controller with Power Sequencing and POR |
| 中文描述： | DUAL SWITCHING CONTROLLER, 600 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封装： | 0.150 INCH, QSOP-24 |
| 文件页数： | 16/22页 |
| 文件大小： | 553K |
| 代理商： | MAX1858EEG |
M
Dual 180° Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
16
______________________________________________________________________________________
inductor
’
s saturation rating must exceed the peak-
inductor current at the maximum defined load current
(I
LOAD(MAX)
):
Setting the Valley Current Limit
The minimum current-limit threshold must be high
enough to support the maximum expected load current
with the worst-case low-side MOSFET on-resistance
value since the low-side MOSFET
’
s on-resistance is
used as the current-sense element. The inductor
’
s valley
current occurs at I
LOAD(MAX)
minus half of the ripple
current. The current-sense threshold voltage (V
ITH
)
should be greater than voltage on the low-side MOSFET
during the ripple-current valley:
where R
DS(ON)
is the on-resistance of the low-side
MOSFET (N
L
). Use the maximum value for R
DS(ON)
from the low-side MOSFET
’
s data sheet, and additional
margin to account for R
DS(ON)
rise with temperature is
also recommended. A good general rule is to allow
0.5% additional resistance for each
°
C of the MOSFET
junction temperature rise.
Connect ILIM_ to VL for the default 100mV (typ) cur-
rent-limit threshold. For an adjustable threshold, con-
nect a resistor (R
ILIM
_) from ILIM_ to GND. The
relationship between the current-limit threshold (V
ITH
_)
and R
ILIM
_ is:
where R
ILIM
_ is in
and V
ITH
_ is in V.
An R
ILIM
resistance range of 100k
to 600k
corre-
sponds to a current-limit threshold of 50mV to 300mV.
When adjusting the current limit, 1% tolerance resistors
minimize error in the current-limit threshold.
For foldback current limit, a resistor (R
FBI
) is added
from ILIM pin to output. The value of R
ILIM
and R
FBI
can then be calculated as follows:
First select the percentage of foldback, P
FB
, from 15%
to 30%, then:
If R
ILIM_
results in a negative number, select a low-side
MOSFET with lower R
DS(ON)
or increase P
FB_
or a com-
bination of both for the best compromise of cost, effi-
ciency, and lower power dissipation during short circuit.
Input Capacitor
The input filter 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, nontantalum capacitors
(ceramic, aluminum, polymer, or OS-CON) are preferred
at the input due to their robustness with high inrush cur-
rents typical of systems that can be powered from very
low impedance sources. Additionally, two (or more)
smaller-value low-ESR capacitors can be connected in
parallel for lower cost. Choose an input capacitor that
exhibits less than +10
°
C temperature rise at the RMS
input current for optimal long-term reliability.
Output Capacitor
The key selection parameters for the output capacitor
are capacitance value, ESR, and voltage rating. These
parameters affect the overall stability, output ripple volt-
age, and transient response. The output ripple has two
components: variations in the charge stored in the out-
put capacitor, and the voltage drop across the capaci-
tor
’
s ESR caused by the current flowing into and out of
the capacitor:
V
V
V
RIPPLE
RIPPLE ESR
RIPPL( )
+
(
)
I
I
V
V
V
V
RMS
LOAD
OUT
IN
OUT
IN
=
(
)
-
R
P
V
(
P
and
R
V
P
V
R
P
-
V
FBI
FB
OUT
1
-
FB
ILIM
ITH
10
-
FB
ITH
FBI
FB
OUT
=
×
6
=
×
×
1
(
×
[
]
5 10
10
1
(
-
)
)
)
R
V
0.
A
ILIM
ITH
_
_
=
μ
V
R
I
LIR
2
ITH
DS ONMAX
(
LOAD MAX
>
×
×
,
)
(
)
1
-
I
I
LIR
2
I
PEAK
LOA(
LOAD(
=
+
)
)
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| MAX1858EEG+ | 功能描述:电压模式 PWM 控制器 Dual 180 Out Buck Controllers RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1858EEG+T | 功能描述:电压模式 PWM 控制器 Dual 180 Out Buck Controllers RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1858EEG-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1858EVKIT | 功能描述:DC/DC 开关控制器 Evaluation Kit for the MAX1858 MAX1875 MAX1876 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX185ACNG | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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