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參數(shù)資料
| 型號： | MAX1552ETE |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 電源管理 |
| 英文描述： | Complete Power IC for Low-Cost PDAs |
| 中文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC16 |
| 封裝： | 4 X 4 MM, 0.80 MM HEIGHT, MO-220, TQFN-16 |
| 文件頁數(shù)： | 10/12頁 |
| 文件大小： | 324K |
| 代理商： | MAX1552ETE |
M
The circuit consists of the PWM source, capacitor C10,
and resistors R
D
and R
W
. To analyze the transfer func-
tion of the PWM circuit, it is easiest to first simplify it to
its Thevenin equivalent. The Thevenin voltage can be
calculated using the following formula:
V
THEV
= (D x V
OH
) + (1 - D) x V
OL
where D is the duty cycle of the PWM signal, V
OH
is the
PWM output high level (often 3.3V), and V
OL
is the
PWM output low level (usually 0V). For CMOS logic this
equation simplifies to:
V
THEV
= D x V
DD
where V
DD
is the I/O voltage of the PWM output. The
Thevenin impedance is the sum of resistors R
W
and R
D
:
R
THEV
= R
D
+ R
W
The output voltage (V
OUT
) as a function of the PWM
average voltage (V
THEV
) is:
When using the PWM adjustment method, R
D
isolates
the capacitor from the feedback loop of the MAX1552.
The cutoff frequency of the lowpass filter is defined as:
The cutoff frequency should be at least two decades
below the PWM frequency to minimize the induced AC
ripple at the output.
An important consideration is the turn-on transient cre-
ated by the initial charge on filter capacitor C10. This
capacitor forms a time constant with R
THEV
, which
causes the output to initialize at a higher-than-intended
voltage. This overshoot can be minimized by scaling
R
D
as high as possible compared to R1 and R2.
Alternatively, the μP can briefly keep the LCD disabled
until the PWM voltage has had time to stabilize.
PC Board Layout and Grounding
Careful PC board layout is important for minimizing
ground bounce and noise. Keep the MAX1552
’
s ground
pin and the ground leads of the input and output capaci-
tors less than 0.2in (5mm) apart. In addition, keep all
connections to FB and LX as short as possible. In partic-
ular, external feedback resistors should be as close to
FB as possible. To minimize output voltage ripple, and to
maximize output power and efficiency, use a ground
plane and solder GND directly to the ground plane.
Refer to the MAX1552 evaluation kit for a layout example.
Thermal Considerations
In most applications, the circuit is located on a multilay-
er board and full use of the four or more layers is rec-
ommended. For heat dissipation, connect the exposed
backside pad of the QFN package to a large analog
ground plane, preferably on a surface of the board that
receives good airflow. Typical applications use multiple
ground planes to minimize thermal resistance. Avoid
large AC currents through the analog ground plane.
f
R
C
C
THEV
×
π
×
=
×
1
2
10
V
R
R
V
R
R
OUT
THEV
THEV
1 25
×
.
)
×
=
+
+
(
1
1
2
1 25
1
Complete Power IC for
Low-Cost PDAs
10
______________________________________________________________________________________
CONTROL
V
REF
1.25V
DAC
AV
DD
V
DOUT
V
IN
MAX1552
SIMPLIFIED DC-TO-DC CONVERTER
V
OUT
(LCD BIAS)
i
1
i
2
i
D
R
D
R1
R2
ERROR AMP
FEEDBACK
RESISTORS
Figure 3. Adjusting the Output Voltage with a DAC
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PDF描述 |
|---|---|
| MAX1553ETA | High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs |
| MAX1553EVKIT | MAX1553 Evaluation Kit |
| MAX1554ETA | High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs |
| MAX1555EZK | PLASTIC ENCAPSULATED DEVICES |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1552ETE-T | 功能描述:PMIC 解決方案 Complete PMIC for PDAs RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| MAX1552EVKIT | 制造商:Maxim Integrated Products 功能描述:COMPLETE PMIC FOR LOW COST PDA'S - Rail/Tube |
| MAX1553ETA | 制造商:Maxim Integrated Products 功能描述:SMALLEST, HIGHEST-EFFICIENCY, 40V STEP-UP CON - Rail/Tube 制造商:Rochester Electronics LLC 功能描述: |
| MAX1553ETA+ | 制造商:Maxim Integrated Products 功能描述:LED DRVR 10SEGMENT 2.7V TO 5.5V 8TDFN EP - Rail/Tube |
| MAX1553ETA+T | 功能描述:LED照明驅(qū)動器 40V StepUp Converter for 2-10 White LEDs RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:SO-16N |
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