- 您现在的位置：买卖IC网 > PDF目录1838 > MAX1678EUA+T (Maxim Integrated Products)IC REG BOOST SYNC 3.3V/ADJ 8UMAX PDF资料下载
参数资料
| 型号： | MAX1678EUA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 8/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BOOST SYNC 3.3V/ADJ 8UMAX |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | 升压（升压） |
| 输出类型： | 两者兼有 |
| 输出数： | 1 |
| 输出电压： | 3.3V，2 V ~ 5.5 V |
| 输入电压： | 0.7 V ~ 5.5 V |
| 电流 - 输出： | 90mA |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-uMAX |
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
Operating Principle
The MAX1678 employs a proprietary constant-peak-
current control scheme that combines the ultra-low qui-
V LX
escent current of traditional pulse-skipping PFM
converters with high-load efficiency.
When the error comparator detects that the output volt-
age is too low, it turns on the internal N-channel
V OUT
V BATT
V BATT
(DEAD TIME)
(ON TIME)
MOSFET switch for an internally calculated on-time
(Figure 2). During the on-time, current ramps up in the
inductor, storing energy in the magnetic field. When the
I L
K
K
V OUT - V BATT
t
I PEAK = K
MOSFET turns off during the second half of each cycle,
the magnetic field collapses, causing the inductor volt-
age to force current through the synchronous rectifier,
transferring the stored energy to the output filter
capacitor and the load. The output filter capacitor
stores charge while the current from the inductor is
I PEAK
V BATT
L
(ON TIME)
(DEAD TIME)
high, then holds up the output voltage until the second
half of the next switching cycle, smoothing power flow
to the load. The ideal on-time of the N-channel MOSFET
t ON
t OFF
t ON
OR DEAD TIME
t
changes as a function of input voltage. The on-time is
determined as follows:
Figure 2. Switching Waveforms
t ON =
K
V BATT
V OUT
C OUT
where K is typically 8V-μs.
The peak inductor current (assuming a lossless circuit)
can be calculated from the following equation:
MAX1678
PDRV
OUT
P
V IN
L1
I PEAK =
K
L
TIMING
CIRCUIT
NDRV
N
LX
The P-channel MOSFET (synchronous rectifier) turns on
when the N-channel MOSFET turns off. The circuit oper-
ates at the edge of discontinuous conduction; therefore,
the P-channel synchronous rectifier turns off immediately
after the inductor current ramps to zero. During the dead
time after the P-switch has been turned off, the damping
switch connects LX and BATT. This suppresses EMI noise
due to LC ringing of the inductor and parasitic capaci-
tance at the LX node (see Damping Switch section). The
error comparator starts another cycle when V OUT falls
below the regulation threshold. With this control scheme,
the MAX1678 maintains high efficiency over a wide range
of loads and input/output voltages while minimizing
switching noise.
Start-Up Operation
The MAX1678 contains a low-voltage start-up oscillator
(Figure 1). This oscillator pumps up the output voltage
to approximately 1.7V, the level at which the main DC-
DC converter can operate. The 150kHz fixed-frequency
oscillator is powered from the BATT input and drives an
NPN switch. During start-up, the P-channel synchronous
START-UP
OSCILLATOR
GND
Figure 3. External Schottky Diode to Improve Start-Up with
Heavy Load
rectifier remains off and its body diode (or an external
diode, if desired) is used as an output rectifier. The mini-
mum start-up voltage is a function of load current (see
Typical Operating Characteristics). In normal operation,
when the voltage at the OUT pin exceeds 1.7V, the DC-
DC converter is powered from the OUT pin (boot-
strapped) and the main control circuitry is enabled.
Once started, the output can maintain the load as the
battery voltage decreases below the start-up voltage.
To improve start-up capability with heavy loads, add a
Schottky diode in parallel with the P-channel synchro-
nous rectifier (from LX to OUT) as shown in Figure 3
(see Typical Operating Characteristics).
8
_______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1679EUA+ | IC BATT CHRGR 1CELL LITH 8-UMAX |
| MAX1681ESA | IC REG MULTI CONFIG ADJ 8SOIC |
| MAX1683EUK-T | IC REG SWITCHED CAP DBL SOT23-5 |
| MAX1685EEE-T | IC REG BUCK SYNC 3.3V/ADJ 16QSOP |
| MAX1686HEUA | IC CHRG PUMP FOR SIM CARD 8-UMAX |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1678EVKIT | 功能描述:电源管理IC开发工具 Evaluation Kit for the MAX1678 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX1679EUA | 功能描述:电池管理 Battery Charger Current-Limited Sply RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1679EUA+ | 功能描述:电池管理 Battery Charger Current-Limited Sply RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1679EUA+T | 功能描述:电池管理 Battery Charger Current-Limited Sply RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1679EUA-T | 功能描述:电池管理 Battery Charger Current-Limited Sply RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
发布紧急采购，3分钟左右您将得到回复。