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| 型号： | MAX1843ETI+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 10/13页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 2.7A 28TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 类型： | 降压（降压） |
| 输出类型： | 两者兼有 |
| 输出数： | 1 |
| 输出电压： | 1.5V，1.8V，2.5V，可调 |
| 输入电压： | 3 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 2.7A |
| 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： | 28-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Synchronous Rectification in TQFN Package
Programming the Switching Frequency
and Off-Time
The MAX1843 features a programmable PWM mode
The peak inductor current at full load is 1.125 x I OUT if
the above equation is used; otherwise, the peak current
is calculated by:
switching frequency, which is set by the input and out-
put voltage and the value of R TOFF , connected from
TOFF to GND. R TOFF sets the pMOS power switch off-
time in PWM mode. Use the following equation to select
I PEAK = I OUT +
V OUT × t OFF
2 × L
the off-time according to the desired switching frequen-
cy in PWM mode:
Choose an inductor with a saturation current at least as
high as the peak inductor current. The inductor you
select should exhibit low losses at your chosen operating
( V IN OUT PMOS )
t OFF =
? V ? V
f PWM ( V IN ? V PMOS + V NMOS )
frequency.
Capacitor Selection
The input filter capacitor reduces peak currents and
where: t OFF = the programmed off-time
V IN = the input voltage
V OUT = the output voltage
noise at the voltage source. Use a low-ESR and low-
ESL capacitor located no further than 5mm from IN.
Select the input capacitor according to the RMS input
ripple-current requirements and voltage rating:
V PMOS = the voltage drop across the internal
pMOS power switch
V NMOS = the voltage drop across the internal
nMOS synchronous-rectifier switch
I RIPPLE = I LOAD
V OUT ( V IN
V IN
?
V OUT )
f PWM = switching frequency in PWM mode
Select R TOFF according to the formula:
R TOFF = (t OFF - 0.07μs) (110k ? / 1.00μs)
Recommended values for R TOFF range from 36k ? to
430k ? for off-times of 0.4μs to 4μs.
where I RIPPLE = input RMS current ripple.
The output filter capacitor affects the output voltage rip-
ple, output load-transient response, and feedback-loop
stability. For stable operation, the MAX1843 requires a
minimum output ripple voltage of V RIPPLE ≥ 1% x V OUT .
The minimum ESR of the output capacitor should be:
Inductor Selection
The key inductor parameters must be specified: induc-
tor value (L) and peak current (I PEAK ). The following
ESR > 1 % ×
L
t OFF
C OUT ≥ OFF 79 μ FV / μ s
equation includes a constant, denoted as LIR, which is
the ratio of peak-to-peak inductor AC current (ripple
current) to maximum DC load current. A higher value of
LIR allows smaller inductance but results in higher loss-
es and ripple. A good compromise between size and
losses is found at approximately a 25% ripple-current
to load-current ratio (LIR = 0.25), which corresponds to
a peak inductor current 1.125 times the DC load cur-
rent:
Stable operation requires the correct output filter capac-
itor. When choosing the output capacitor, ensure that:
t
V OUT
Integrator Amplifier
An internal transconductance amplifier fine tunes the
output DC accuracy. A capacitor, C COMP , from COMP
L =
V OUT × t OFF
I OUT × LIR
to V CC compensates the transconductance amplifier.
For stability, choose C COMP = 470pF.
A large capacitor value maintains a constant average
output voltage but slows the loop response to changes
where: I OUT = maximum DC load current
LIR = ratio of peak-to-peak AC inductor current
to DC load current, typically 0.25
in output voltage. A small capacitor value speeds up
the loop response to changes in output voltage but
decreases stability. Choose the capacitor values that
result in optimal performance.
10
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1843ETI+ | 功能描述:直流/直流开关调节器 2.7A 1MHz 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 |
| MAX1843ETI+T | 功能描述:直流/直流开关调节器 2.7A 1MHz 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 |
| MAX1844EEP | 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 |
| MAX1844EEP+ | 功能描述:电流型 PWM 控制器 Step-Down Controller 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 |
| MAX1844EEP+T | 功能描述:电流型 PWM 控制器 Step-Down Controller 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 |
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