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參數(shù)資料
| 型號(hào)： | MAX779LESA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Low-Voltage Input, 3V/3.3V/5V/ Adjustable Output, Step-Up DC-DC Converters |
| 中文描述： | 1 A SWITCHING REGULATOR, 150 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | 0.150 INCH, SOIC-8 |
| 文件頁(yè)數(shù)： | 7/12頁(yè) |
| 文件大?。?/td> | 117K |
| 代理商： | MAX779LESA |
_______________Detailed Desc ription
Operating Princ iple
The MAX777L/MAX778L/MAX779L combine a switch-
mode regulator with an NPN bipolar switch, current
limit, precision voltage reference, and active rectifier—
all in a single monolithic device. In shutdown mode,
the internal rectifier is completely turned off and dis-
connects the load from the source. Only two external
components are required in addition to the input
bypass capacitor: a 22μH inductor and a 100μF filter
capacitor.
A minimum off-time, current-limited, pulse-frequency-
modulation (PFM) control scheme combines the advan-
tages of pulse width modulation (PWM) (high output
power and efficiency) with those of a traditional PFM
pulse skipper (low quiescent currents).
External conditions (inductor value, load, and input volt-
age) determine the way the converter operates, as follows:
At light loads,
the current through the inductor starts at
zero, rises to a peak value, and drops down to zero in
each cycle (discontinuous-conduction mode). In this
case, the switching frequency is governed by a pair of
one-shots that set a maximum on-time inversely propor-
tional to VIN[t
ON
= 8.8/(V
IN
- 0.25)] and a minimum off-
time (1.3μs for MAX777L/MAX779L and 2.3μs for
MAX778L). With a 22μH inductor, LX’s peak current is
about 400mA and is independent of input voltage.
Efficiency at light loads is improved because of lower
peak currents.
At very light loads
, more energy is stored in the coil
than is required by the load in each cycle. The converter
regulates by skipping entire cycles. Efficiency is typically
65% to 75% in the pulse-skipping mode. Pulse-skipping
waveforms can be irregular, and the output waveform
contains a low-frequency component. Larger, low equiv-
alent series resistance (ESR) filter capacitors can help
reduce the ripple voltage if needed.
M
Low-Voltage Input, 3V /3.3V /5V /
Adjustable Output, S tep-Up DC-DC Converters
_______________________________________________________________________________________
7
MAX778L
DELAY
TIMER
t
OFF
DELAY
TIMER
t
ON
VREF
0.2025V
SHUTDOWN
CONTROL
SHDN
7
ACTIVE RECTIFIER
RECTIFIER
CONTROL
OUT
PGND
AGND
3
SEL 8
4
6
100
μ
F
V
OUT
100
μ
F
V
IN
22
μ
H
R
LIM
SWITCH
DRIVER
LX
ILIM
IN
2
1
1 : N
Figure 1. MAX778L Block Diagram
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| MAX780ACAG | 功能描述:電源開(kāi)關(guān) IC - 配電 RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
| MAX780ACAG+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX780ACAG-T | 功能描述:電源開(kāi)關(guān) IC - 配電 RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
| MAX780ACNG | 功能描述:電源開(kāi)關(guān) IC - 配電 RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
| MAX780AEAG | 功能描述:電源開(kāi)關(guān) IC - 配電 RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
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