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| 型号： | MAX1971EEE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 13/21页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 0.75A DL 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： | 2 |
| 输出电压： | 1.5V，1.8V，2.5V，3.3V，可调 |
| 输入电压： | 2.6 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 700kHz |
| 电流 - 输出： | 750mA |
| 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 |
Dual, 180° Out-of-Phase, 1.4MHz, 750mA Step-
Down Regulator with POR and RSI/PFO
t SS = REF C REF = 4 . 8 × 10 4 × C REF
the PWM comparator’s inverting input. The PWM com-
parator turns off the internal high-side MOSFET when
this sum exceeds the integrated feedback voltage.
Current Limit
The internal MOSFET has a current limit of 1.2A (typ). If
the current flowing out of LX_ exceeds this maximum,
the high-side MOSFET turns off and the synchronous
rectifier MOSFET turns on. This lowers the duty cycle
and causes the output voltage to droop until the current
limit is no longer exceeded. There is also a synchro-
nous rectifier current limit of -0.85A. This is to protect
the device from current flowing into LX_. If the negative
current limit is exceeded, the synchronous rectifier is
turned off, and the inductor current continues to flow
through the high-side MOSFET body diode back to the
input until the beginning of the next cycle or until the
inductor current drops to zero.
V CC Decoupling
Due to the high-switching frequency and tight output
tolerance (±1%), decoupling between IN and V CC is
recommended. Connect a 10 ? resistor between IN and
V CC and a 0.1μF ceramic capacitor from V CC to GND.
Place the resistor and capacitor as close to V CC as
possible.
Startup
To reduce the supply inrush current, soft-start circuitry
ramps up the output voltage during startup. This is
done by charging the REF capacitor with a current
source of 25μA. Once REF reaches 1.2V, the output is
in full regulation. The soft-start time is determined from:
V
I REF
Soft-start occurs when power is first applied, and when
EN is pulled high with power already present. The part
also goes through soft-start when coming out of under-
voltage lockout (UVLO) or thermal shutdown. The range
of capacitor values for C REF is from 0.01μF to 1.0μF.
Undervoltage Lockout
If V CC drops below 2.35V, the MAX1970/MAX1971/
MAX1972 assume that the supply voltage is too low to
provide a valid output voltage, and the UVLO circuit
inhibits switching. Once V CC rises above 2.4V, the
UVLO is disabled and the soft-start sequence initiates.
Enable
A logic-enable input (EN) is provided. For normal oper-
ation, drive EN logic high. Driving EN low turns off both
outputs, and reduces the input supply current to
approximately 1μA.
Power-Fail Output
The input voltage is sensed for 5V (typical USB applica-
tions), and if V CC drops below 3.94V, the power-fail out-
put (PFO) goes high. The time from PFO going high to
the outputs going out of regulation depends on the oper-
ating output voltage and currents, and the upstream 5V
bus storage capacitor value, which is 120μF minimum
(per USB specification, version 2.0). The lower the oper-
ating voltages and currents, and the higher the storage
capacitor, the longer the elapsed time. PFO is an open-
drain output, and a 10k ? to 100k ? pullup resistor to
V CC , or either output, is recommended.
Power-On Reset
Power-on reset ( POR ) provides a system reset signal.
During power-up, POR is held low until both outputs
reach 92% of their regulated voltages, POR continues
to be held low for a delayed period, and then goes
high. This delay time (T D ) for MAX1970 is 16.6ms. The
MAX1971 and MAX1972 have a delay of 175ms. Figure
2 is an example of a timing diagram.
The POR comparator is designed to be relatively
immune to short-duration negative-going output glitch-
es.The Typical Operating Characteristics gives a plot of
maximum transient duration vs. POR comparator over-
drive. The graph was generated using a negative-going
pulse applied to an output, starting at 100mV above the
actual POR threshold, dropping below the POR thresh-
old by the percentage indicated as comparator over-
drive, and then returning to 100mV above the
threshold. The graph indicates the maximum pulse
width the output transient can have without causing
POR to trip low.
Reset Input
Reset input (RSI) is an input on the MAX1971 that,
when driven high, forces the POR to go low. When RSI
goes low, POR goes through a delay time identical to a
power-up event. See Figure 2 for timing diagram. RSI
allows software to command a system reset. RSI must
be high for a minimum period of 1μs in order to initiate
the POR .
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa-
tion. When the IC’s junction temperature exceeds T J =
+170°C, a thermal sensor shuts down the device,
allowing the IC to cool. The thermal sensor turns the
part on again after the junction temperature cools by
20°C. This results in a pulsed output during continuous
overload conditions.
During a thermal event, POR goes low, PFO goes high,
and soft-start is reset.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1972EEE | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX1972EEE+ | 功能描述:直流/直流开关调节器 Dual 180 Out 1.4MHz 750mA Step-Down RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX1972EEE+T | 功能描述:直流/直流开关调节器 Dual 180 Out 1.4MHz 750mA Step-Down RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX1972EEE-G05 | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1972EEE-T | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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