參數(shù)資料
型號： MAX1875EEG
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 穩(wěn)壓器
英文描述： Fixed-Point Digital Signal Processor 288-BGA MICROSTAR
中文描述： DUAL SWITCHING CONTROLLER, 600 kHz SWITCHING FREQ-MAX, PDSO24
封裝： 0.150 INCH, QSOP-24
文件頁數(shù)： 15/21頁
文件大?。?/td> 493K
代理商： MAX1875EEG
As a general rule, a smaller inductor ripple current results
in less output ripple voltage. Since inductor ripple current
depends on the inductor value and input voltage, the out-
put ripple voltage decreases with larger inductance and
increases with higher input voltages. However, the induc-
tor ripple current also impacts transient-response perfor-
mance, especially at low V
IN
- V
OUT
differentials. Low
inductor values allow the inductor current to slew faster,
replenishing charge removed from the output filter capac-
itors by a sudden load step. The amount of output-volt-
age sag is also a function of the maximum duty factor,
which can be calculated from the minimum off-time and
switching frequency:
where t
OFF(MIN)
is the minimum off-time (see the
Electrical Characteristics
), and f
SW
is set by R
OSC
(see
the
Setting the Switching Frequency
section).
Compensation
Each voltage-mode controller section employs a
transconductance error amplifier whose output is the
compensation point of the control loop. The control loop
is shown in Figure 7. For frequencies much lower than
Nyquist, the PWM block can be simplified to a voltage
amplifier. Connect R
COMP_
and C
COMP_A
from COMP
to GND to compensate the loop (see Figure 7). The
inductor, output capacitor, compensation resistor, and
compensation capacitors determine the loop stability.
Since the inductor and output capacitor are chosen
based on performance, size, and cost, select the com-
pensation resistor and capacitors to optimize control-
loop stability.
To determine the loop gain (A
L
), consider the gain from
FB to COMP (A
COMP/FB
), from COMP to LX (A
LX/COMP
),
and from LX to FB (A
FB/LX
). The total loop gain is:
where:
assuming an ideal integrator, and assuming that
C
COMP_B
is much less than C
COMP_A
.
for frequencies lower than Nyquist.
Therefore:
For an ideal integrator this loop gain approaches infinity
at DC. In reality the g
M
amplifier has a finite output
impedance which imposes a finite, but large, loop gain.
It is this large loop gain that provides DC load accura-
cy. The dominant pole occurs due to the integrator, and
for this analysis, it can be approximated to occur at DC.
R
COMP
creates a zero at:
The inductor and capacitor form a double pole at:
At some higher frequency the output capacitor
’
s
impedance becomes insignificant compared to its ESR,
and the LC system becomes more like an LR system,
turning a double pole into a single pole. This zero
occurs at:
f
R
ESR
ESR OUT
=
×
1
2
π
f
LC
LC
OUT
=
×
1
2
π
f
R
C
Z COMP A
_
COMP
COMP A
_
_
_
=
×
1
2
π
A
g
SC
V
V
OUT
SR
SR
V
V
SR
S LC
L
M COMP
_
COMP A
COMP COMP A
COMP COMP B
IN
RAMP
SET
ESR OUT
OUT
×
+
+
×
×
×
+
+
_
_
_
1
1
1
1
A
V
V
V
V
sR
S LC
SR
S LC
OUT
SR
V
V
V
FB LX
/
FB
LX
SET
OUT
+
1
ESR OUT
+
OUT
ESR OUT
SET
OUT
ESR OUT
OUT
=
=
+
+
+
1
1
1
A
V
V
V
V
LX COMP
/
LX
COMP
IN
RAMP
=
=
A
V
V
+
+
g
SC
sR
sR
COMP FB
COMP
FB
M COMP
_
COMP
COMP COMP A
COMP COMP B
/
_
_
=
×
1
1
A
A
A
A
L
COMP FB
LX COMP
/
FB LX
/
=
×
×
/
V
L I
I
V
V f
t
C
V
V
V f
t
SAG
LOAD
LOAD
OUT
OFF MIN
(
OUT OUT
IN
OUT
OFF MIN
(
=
+
(
)
)
)
1
2
2
2
-
-
-
M
Dual 180° Out-of-Phase PWM Step-
Down Controllers with POR
______________________________________________________________________________________
15
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MAX1875EEG+ 功能描述:電壓模式 PWM 控制器 Dual 180 Out PWM Step-Down RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX1875EEG+T 功能描述:電壓模式 PWM 控制器 Dual 180 Out PWM Step-Down RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX1875EEG-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 安裝風格: 封裝 / 箱體:CPAK
MAX1875EVKIT 功能描述:DC/DC 開關(guān)控制器 Evaluation Kit for the MAX1875 MAX1876 MAX1858 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 安裝風格: 封裝 / 箱體:CPAK
MAX1876AEEG 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 安裝風格: 封裝 / 箱體:CPAK
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