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参数资料
| 型号： | MAX1775EEE-T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 16-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 控制器 |
| 输出数： | 2 |
| 频率 - 最大： | 1.25MHz |
| 占空比： | 100% |
| 电源电压： | 2.7 V ~ 28 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
Dual-Output Step-Down
DC-DC Converter for PDA/Palmtop Computers
TOFFMIN
V MIN
CS+
TONMIN
CS-
V VALLEY
FB
S
Q
PON
PON
V IN
PSW
V REF
R
V O
V CLM
S
Q
NON
NSW
R
V ZERO
NONOVERLAP
PROTECTION
Figure 2. Simplified Control System Block Diagram
Regulation Control Scheme
The MAX1775 has a unique operating scheme that
allows PWM operation at medium and high current, with
automatic switching to pulse-skipping mode at lower
currents to improve light-load efficiency. Figure 2
shows a simplified block diagram.
Under medium- and heavy-load operation, the inductor
current is continuous and the part operates in PWM
mode. In this mode, the switching frequency is set by
either the minimum on-time or the minimum off-time,
depending on the duty cycle. The duty cycle is approx-
imately the output voltage divided by the input voltage.
If the duty cycle is less than 50%, the minimum on-time
controls the frequency; and the frequency is approxi-
mately f ≈ 2.5MHz D, where D is the duty cycle. If the
duty cycle is greater than 50%, the minimum off-time
sets the frequency; and the frequency is approximately
f ≈ 2.5MHz (1 - D).
In both cases, the voltage is regulated by the error
comparator. For low duty cycles (<50%), the P-channel
MOSFET turns on for the minimum on-time, causing
fixed-on-time operation. During the P-channel MOSFET
on-time, the output voltage rises. Once the P-channel
MOSFET turns off, the voltage drops to the regulation
threshold, at which time another cycle is initiated. For
high duty cycles (>50%), the P-channel MOSFET
remains off for the minimum off-time, causing fixed off-
time operation. In this case, the P-channel MOSFET
remains on until the output voltage rises to the regula-
tion threshold. Then the P-channel MOSFET turns off for
the minimum off-time, initiating another cycle.
By switching between fixed on-time and fixed off-time
operation, the MAX1775 can operate at high input-out-
put ratios, yet still operate up to 100% duty cycle for
low dropout. Note that when operating in fixed on-time,
the minimum output voltage is regulated; but in fixed
off-time operation, the maximum output voltage is regu-
lated. Thus, as the input voltage drops below approxi-
mately twice the output voltage, a decrease in line
regulation can be expected. The drop in voltage is
approximately V DROP ≈ V RIPPLE . At light output loads,
the inductor current is discontinuous, causing the
MAX1775 to operate at lower frequencies, reducing the
MOSFET gate drive and switching losses. In discontin-
uous mode, under most circumstances, the on-time will
be a fixed minimum of 400ns.
The MAX1775 features four separate current-limit
threshold detectors and a watchdog timer for each of
its step-down converters. In addition to the more com-
mon peak current detector and zero crossing detector,
each converter also provides a valley current detector
(I VALLEY ) and a minimum current detector (I MIN ). I VALLEY
is used to force the inductor current to drop to a lower
level after hitting peak current before allowing the P-
channel MOSFET to turn on. This is a safeguard against
inductor current significantly overshooting above the
peak current when the inductor discharges too slowly
when V OUT /L is small. I MIN is useful in ensuring that a
minimum current is built up in the inductor before turn-
ing off the P-channel MOSFET. This helps the inductor
to charge the output near dropout when dI/dt is small
(because (V IN - V OUT ) / L is small) to avoid multiple
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1775EEE-TG069 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1775EVKIT | 功能描述:直流/直流开关转换器 Evaluation Kit for the MAX1775 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 |
| MAX1776EUA | 功能描述:直流/直流开关转换器 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 |
| MAX1776EUA+ | 功能描述:直流/直流开关转换器 24V 600mA 100% Duty Cycle Step-Down 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 |
| MAX1776EUA+ | 制造商:Maxim Integrated Products 功能描述:SEMICONDUCTOR ((NW)) |
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