參數(shù)資料
型號： MAX1778EUG
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 穩(wěn)壓器
英文描述： Quad-Output TFT LCD DC-DC Converters with Buffer
中文描述： 2.05 A SWITCHING REGULATOR, 1250 kHz SWITCHING FREQ-MAX, PDSO24
封裝： 4.40 MM, 1.10 MM HEIGHT, MO-153AD, TSSOP-24
文件頁數(shù)： 26/38頁
文件大小： 1051K
代理商： MAX1778EUG
M
Quad-Output TFT LCD DC-DC
Converters with Buffer
26
______________________________________________________________________________________
where
η
is the efficiency, f
OSC
is the oscillator frequen-
cy (see
Electrical Characteristics
), and I
MAIN
includes
the primary load current and the input supply currents
for the charge pumps (see
Charge-Pump Input Power
and Efficiency Considerations
), linear regulator, and
VCOM buffer. Considering the typical application cir-
cuit, the maximum average DC load current
(I
MAIN(MAX)
) is 300mA with an 8V output. Based on the
above equations and assuming 85% efficiency, the
inductance value is then chosen to be 4.7μH.
The inductor
’
s saturation current rating should exceed
the peak inductor current throughout the normal operat-
ing range. The peak inductor current is then given by:
Under fault conditions, the inductor current may reach
up to 1.85A (I
LIM(MAX)
), see Electrical Characteristics).
However, the controller
’
s fast current-limit circuitry
allows the use of soft-saturation inductors while still pro-
tecting the IC.
The inductor
’
s DC resistance may significantly affect
efficiency due to the power loss in the inductor. The
power loss due to the inductor
’
s series resistance (P
LR
)
may be approximated by the following equation:
where R
L
is the inductor
’
s series resistance. For best per-
formance, select inductors with resistance less than the
internal N-channel MOSFET on-resistance (0.35
typ).
Use inductors with a ferrite core or equivalent. To mini-
mize radiated noise in sensitive applications, use a
shielded inductor.
Output Capacitor
Output capacitor selection depends on circuit stability
and output voltage ripple. A 10μF ceramic capacitor
works well in most applications (Tables 1 and 2).
Additional feedback compensation is required (see
Feedback Compensation
) to increase the margin for
stability by reducing the bandwidth further. In cases
where the output capacitance is sufficiently large, addi-
tional feedback compensation will not be necessary.
Output voltage ripple has two components: variations in
the charge stored in the output capacitor with each LX
pulse, and the voltage drop across the capacitor
’
s
equivalent series resistance (ESR) caused by the cur-
rent into and out of the capacitor:
where I
PEAK
is the peak inductor current (see Inductor
Selection). For ceramic capacitors, the output voltage
ripple is typically dominated by V
RIPPLE(C)
. The voltage
rating and temperature characteristics of the output
capacitor must also be considered.
Feedback Compensation
For stability, add a pole-zero pair from FB to GND in the
form of a compensation resistor (R
COMP
) in series with
a compensation capacitor (C
COMP
) as shown in Figure
2. Select R
COMP
to be half the value of R2, the low-side
feedback resistor.
Integrator Capacitor
The MAX1778/MAX1880
–
MAX1885 contain an internal
current integrator that improves the DC load regulation
but increases the peak-to-peak transient voltage (see
the load-transient waveforms in the
Typical Operating
Characteristics
). For highly accurate DC load regula-
tion, enable the current integrator by connecting a
470pF (
OSC
= 1MHz)/1000pF (
OSC
= 500kHz)
capacitor to INTG. To minimize the peak-to-peak tran-
sient voltage at the expense of DC regulation, disable
the integrator by connecting INTG to REF. When using
the MAX1883/MAX1884/MAX1885, connect a 100k
resistor to GND when disabling the integrator.
Input Capacitor
The input capacitor (C
IN
) in step-up designs reduces
the current peaks drawn from the input supply and
reduces noise injection. The value of C
IN
is largely
determined by the source impedance of the input sup-
ply. High source impedance requires high input capac-
itance, particularly as the input voltage falls. Since
step-up DC-DC converters act as
“
constant-power
”
loads to their input supply, input current rises as input
voltage falls. A good starting point is to use the same
capacitance value for C
IN
as for C
OUT
.
V
V
V
V
I
AND
V
V
V
V
I
C
RIPPLE
RIPPL( )
≈
RIPPLE ESR
RIPPLE ESR
PEAK ESR COUT
RIPPLE( )
MAIN
IN
MAIN
MAIN
OUT OSC
+
,
(
)
(
)
(
)
=
≈
P
R
I
X V
V
IN
LR
L
MAIN
MAIN
2
I
I
V
V
LIR
2
PEAK
MAIN MAX
MAIN
IN MIN
(
+
(
)
)
=
1
1
η
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1778EUG+ 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Quad-Output TFT LCD w/Buffer RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1778EUG+T 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Quad-Output TFT LCD w/Buffer RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1778EUG-T 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1778EVKIT 功能描述:電源管理IC開發(fā)工具 MAX1778/80/81/82 Eval Kit RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
MAX1779EUE 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
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