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| 型号： | MAX1684EEE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 10/14页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 3.3V/ADJ 16QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 两者兼有 |
| 输出数： | 1 |
| 输出电压： | 3.3V，1.25 V ~ 14 V |
| 输入电压： | 2.7 V ~ 14 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 300kHz |
| 电流 - 输出： | 1A |
| 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： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-QSOP |
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
inductor peak current during the first half of each cycle,
based on the output error voltage. The MAX1684/
MAX1685s’ loop gain is relatively low to enable the use
of a small, low-value output filter capacitor. The 1.4%
transient load regulation from 0 to 1A is compensated
by an integrator circuit that lowers DC load regulation
to 0.01% typical. Slope compensation accounts for the
inductor-current waveform ’s down slope during the
second half of each cycle, and eliminates the inductor-
current staircasing characteristic of current-mode con-
trollers at high duty cycles.
PFM Control
In low-power mode, the MAX1684/MAX1685 switch
only as needed to service the load. This reduces the
switching frequency and associated losses in the
P-channel switch, the synchronous rectifier, and the
external inductor. During this PFM operation, a switch-
ing cycle initiates when the PFM comparator senses
that the output voltage has dropped too low. The
P-channel MOSFET switch turns on and conducts cur-
rent to the output-filter capacitor and load. The
MAX1684/MAX1685 then wait until the PFM comparator
senses a low-output voltage again.
In normal mode at light load (<150mA), the device also
operates in PFM. The PFM current comparator controls
both entry into PWM mode and the peak switch current
during PFM operation. Consequently, some jitter is nor-
mal during transition from PFM to PWM with loads
around 150mA, and it has no adverse impact on regu-
lation.
100% Duty-Cycle Operation
As the input voltage drops, the duty cycle increases
until the P-channel MOSFET turns on continuously,
achieving 100% duty cycle. Dropout voltage in 100%
duty cycle is the output current multiplied by the on-
resistance of the internal switch and inductor, approxi-
mately 0.35V (I OUT = 1A).
Very Low Duty-Cycle Operation
Because of the P-channel minimum on-time and dead-
time (duration when both switches are off), the
MAX1684/MAX1685s ’ switching frequency must
decrease in PWM or normal mode to maintain regula-
tion at a very low duty cycle. The total P-channel on-
time and dead-time is 290ns typical. As a result, the
MAX1684/MAX1685 maintain fixed-frequency regula-
tion at no load for V IN up to 10V OUT and 5V OUT ,
respectively (see PWM Fixed-Frequency Operation
Area graph in the Typical Operating Characteristics ).
For higher V IN at no load, the frequency decreases
based on the following equation:
f = V OUT / (V IN × 290ns)
At medium- to full-load current (>100mA), V IN can
increase slightly higher before the frequency decreas-
es.
Synchronous Rectification
Although the primary rectifier is an external Schottky
diode, a small internal N-channel synchronous rectifier
allows PWM operation at light loads. During the second
half of each cycle, when the inductor current ramps
below the zero-crossing threshold or when the oscilla-
tor period ends, the synchronous rectifier turns off. This
keeps excess current from flowing backward through
the inductor. Choose an appropriate inductor to limit
the PWM ripple current through the N-channel FET to
400mA P-P .
Current Limit and Soft-Start
The voltage at ILIM/SS sets the PWM current limit
(I LIM = 1.75A) and the low-power current limit (I LIMLP =
380mA). The PWM current limit applies when the
device is in PWM mode, in synchronized PWM mode,
or delivering a heavy load in normal mode (Table 1).
The I LIMLP limit applies when the device is in low-power
mode. An internal 4μA current source pulls ILIM/SS up
to CVL. To use the maximum current-limit thresholds,
leave ILIM/SS unconnected or connect it to a soft-start
capacitor. Connect an external resistor from ILIM/SS to
AGND to adjust the current-limit thresholds.
The PWM current-limit threshold is (I LIM ? R ILIM/SS ?
4μA) / V REF and is adjustable from 0.5A to 1.75A.
The low-power current-limit threshold is equal to (I LIMLP
? R ILIM/SS ? 4μA) / V REF and is adjustable from 110mA
to 380mA.
For example, when R ILIM/SS is 156k ? , the PWM current
limit threshold is 0.88A and the low-power current limit
threshold is 0.19A.
Connect a low-value capacitor from ILIM/SS to AGND
to achieve soft-start, limiting inrush current. ILIM/SS
internally shorts to AGND in shutdown to discharge the
soft-start capacitor. Do not connect ILIM/SS to REF or
CVL. Determine the soft-start duration by:
t SOFT-START = C ILIM/SS (1.25V / 4μA)
where t SOFT-START is the time from SHDN going high to
the regulator being able to supply full load current. For
example, a 0.1μF capacitor yields 31ms of soft-start.
10
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1685EEE | 功能描述:直流/直流开关转换器 14V 1A PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1685EEE+ | 功能描述:直流/直流开关转换器 14V 1A PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1685EEE+T | 功能描述:直流/直流开关转换器 14V 1A PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1685EEE-T | 功能描述:直流/直流开关转换器 14V 1A PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1685EVKIT | 功能描述:电源管理IC开发工具 Evaluation Kit for the MAX1684 MAX1685 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 |
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