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參數(shù)資料
| 型號： | MAX8500 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Hex Inverters With Open-Drain Outputs 14-CDIP -55 to 125 |
| 中文描述： | PWM buck轉(zhuǎn)換器，帶有旁路FET，適用于N-CDMA/W-CDMA手機 |
| 文件頁數(shù)： | 8/14頁 |
| 文件大小： | 296K |
| 代理商： | MAX8500 |
M
PWM Buc k Converters with Bypass FET
for N-CDMA/W-CDMA Handsets
8
_______________________________________________________________________________________
GND
BATT
INPUT 2.6V TO5.5V
OUTPUT 0.4V TOV
BATT
SKIP
SHDN
REF
R
8.2k
C
1000pF
LX
OUT
REFIN
PGND
COMP
10
μ
F
4.7
μ
F
4.7
μ
H
DAC
PWM
LDO
1MHz
OSC
MAX8500-
MAX8503
g
m
Figure 1. MAX8500
–
MAX8503 Functional Diagram and Typical Operating Circuit
PWM Control
The MAX8500
–
MAX8504 use a fixed-frequency, current-
mode, PWM controller capable of achieving 100% duty
cycle. Current-mode feedback provides cycle-by-cycle
current limiting, superior load and line response, as well
as overcurrent protection for the internal MOSFET and
rectifier. A comparator at the P-channel MOSFET switch
detects overcurrent at 1.5A.
During PWM operation, the MAX8500
–
MAX8504 regulate
output voltage by switching at a constant frequency and
then modulating the duty cycle with PWM control. The
error-amp output, the main switch current-sense signal,
and the slope compensation ramp are all summed using
a PWM comparator. The comparator modulates the out-
put power by adjusting the peak inductor current during
the first half of each cycle based on the output error volt-
age. The MAX8500
–
MAX8504 have relatively low AC
loop gain coupled with a high gain integrator to enable
the use of a small, low-valued output filter capacitor. The
resulting load regulation is 0.03% at 0 to 600mA.
Normal Mode Operation
Connecting
SKIP
to GND enables normal operation. This
allows automatic PWM control at medium and heavy
loads and skip mode at light loads to improve efficiency
and reduce quiescent current to 280μA. Operating in nor-
mal mode also allows the MAX8500
–
MAX8504 to pulse
skip when the peak inductor current drops below 148mA,
corresponding to a load current of approximately 75mA.
During skip operation, the MAX8500
–
MAX8504 switch
only as needed to service the load, reducing the switch-
ing frequency and associated losses in the internal switch
and synchronous rectifier.
There are three steady-state operating conditions for the
MAX8500
–
MAX8504 in normal mode. The device per-
forms in continuous conduction for heavy loads in a
manner identical to forced-PWM mode. The inductor cur-
rent becomes discontinuous at medium loads, requiring
the synchronous rectifier to be turned off before the end
of a cycle as the inductor current reaches zero. The
device enters into skip mode when the converter output
voltage exceeds its regulation limit before the inductor
current reaches its skip threshold level.
During skip mode, a switching cycle initiates when the
output voltage has dropped out of regulation. The
P-channel MOSFET switch turns on and conducts cur-
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8500ETC | 功能描述:直流/直流開關轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| MAX8501ETC | 功能描述:直流/直流開關轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| MAX8501SA | 制造商:Maxim Integrated Products 功能描述:- Rail/Tube |
| MAX8502ETC | 功能描述:直流/直流開關轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| MAX8503ETC | 功能描述:直流/直流開關轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
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