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参数资料
| 型号： | MAX1742EEE |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | Replaced by TMS320C6410 : |
| 中文描述： | 4.7 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | QSOP-16 |
| 文件页数： | 12/16页 |
| 文件大小： | 597K |
| 代理商： | MAX1742EEE |
M
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
12
______________________________________________________________________________________
2) Select the constant off-time as a function of input
voltage, output voltage, and switching frequency.
3) Select R
TOFF
as a function of off-time.
4) Select the inductor as a function of output voltage,
off-time, and peak-to-peak inductor current.
Setting the Output Voltage
The output of the MAX1742/MAX1842 is selectable
between one of three preset output voltages: 2.5V,
1.8V, and 1.5V. For a preset output voltage, connect FB
to the output voltage and connect FBSEL as indicated
in Table 3. For an adjustable output voltage, connect
FBSEL to GND and connect FB to a resistive divider
between the output voltage and ground (Figure 4).
Regulation is maintained for adjustable output voltages
when V
FB
= V
REF
. Use 50k
for R1. R2 is given by the
equation:
where V
REF
is typically 1.1V.
Programming the Switching Frequency
and Off-Time
The MAX1742/MAX1842 features a programmable
PWM mode switching frequency, which is set by the
input and output voltage and the value of R
TOFF
, con-
nected from TOFF to GND. R
TOFF
sets the PMOS
power switch off-time in PWM mode. Use the following
equation to select the off-time according to your
desired switching frequency in PWM mode:
where:
t
OFF
= the programmed off-time
V
IN
= the input voltage
V
OUT
= the output voltage
V
PMOS
= the voltage drop across the internal
PMOS power switch
V
NMOS
= the voltage drop across the internal
NMOS synchronous-rectifier switch
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.
Inductor Selection
The key inductor parameters must be specified: inductor
value (L) and peak current (I
PEAK
). The following equa-
tion 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 losses 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 cur-
rent 1.125 times the DC load current:
where: I
OUT
= maximum DC load current
LIR = ratio of peak-to-peak AC inductor current
to DC load current, typically 0.25
L
V
t
I
LIR
OUT
OFF
OUT
×
=
×
t
V
V
V
+
f
V
V
V
OFF
IN
(
OUT
PMOS
PWM
IN
PMOS
NMOS
–
=
(
)
)
R2
R1
V
V
1
OUT
REF
=
Figure 4. Adjustable Output Voltage
PIN
2.5
V
CC
Output voltage
1.5
1.8
REF
Output voltage
Adjustable
GND
Resistive
divider
FB
OUTPUT
VOLTAGE
(V)
FBSEL
Unconnected
Output voltage
Table 3. Output Voltage Programming
LX
R2
R1
R1 = 50k
R2 = R1(V
OUT
/ V
REF
- 1)
V
REF
= 1.1V
FB
V
OUT
MAX1742
MAX1842
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1843 | 2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in QFN Package |
| MAX1843EGI | 2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in QFN Package |
| MAX1845 | Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit |
| MAX1845EEI | Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit |
| MAX1845ETX | Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1742EEE+ | 功能描述:直流/直流开关调节器 1A/2.7A 1MHz Step Down Regulator 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 |
| MAX1742EEE+T | 功能描述:直流/直流开关调节器 1A/2.7A 1MHz Step Down Regulator 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 |
| MAX1742EEE-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 |
| MAX1742EVKIT | 功能描述:直流/直流开关调节器 Evaluation Kit for the MAX1742 MAX1842 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 |
| MAX17434GTL+ | 制造商:Maxim from Components Direct 功能描述:THE MAXIM MAX17434GTL+ IS A PWM REGULATOR. - Rail/Tube 制造商:Maxim 功能描述:The Maxim MAX17434GTL+ is a PWM Regulator. |
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