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参数资料
| 型号： | MAX1973 |
| 厂商： | Maxim Integrated Products, Inc. |
| 英文描述： | Smallest 1A, 1.4MHz Step-Down Regulators |
| 中文描述： | 尺寸最小的1A、1.4MHz降压型稳压器 |
| 文件页数： | 11/15页 |
| 文件大小： | 331K |
| 代理商： | MAX1973 |
Voltage Margining and Shutdown
A voltage-margining feature is provided on the
MAX1973 to shift the output voltage up or down by 4%.
Voltage margining is useful for the automatic testing of
systems at high and low supply conditions to find
potential failures. See Table 1 for the MAX1973 voltage
margining and shutdown truth table.
A shutdown feature is included on both the MAX1973
and the MAX1974. Shutdown turns off the IC and
reduces the supply current about 0.1μA. For the
MAX1974, drive ON high for normal operation, or low
for shutdown. For the MAX1973, drive both CTL1 and
CTL2 high for normal operation, or drive both low for
shutdown. For a simple enable/shutdown function with
no voltage margining on the MAX1973, connect CTL1
to CTL2 and drive as one input.
Power-OK Output (POK)
A power-OK output (POK) is provided on the MAX1974.
This is an open-drain output indicating when the output
voltage is in regulation. If the output voltage falls below
90% of its nominal value, POK goes low. POK remains
low until the output voltage rises to 92.5% of its nominal
value. At that point, POK goes high impedance. To use
POK as a logic output, connect a 10k
to 100k
pullup
resistor from POK to the power supply of the logic
receiving the POK signal. POK continues to function in
shutdown or UVLO. Note that a minimum voltage of 1V
at IN is required to ensure that POK provides a valid
output. When V
IN
drops to zero, POK is high imped-
ance. See the
Typical Operating Characteristics.
Applications Information
Output Voltage Selection
The output voltage can be set to one of two preset val-
ues, or can be set by an external resistor-divider. For
preset output voltages, connect FB to the output as
shown in Figures 2 and 3. Connect FBSEL to GND or IN
to select the desired preset output voltage (see Table 2).
To set the output voltage to a value other than the preset
values, FBSEL is not connected, and FB is connected to
a voltage-divider as shown in Figures 4 and 5. Select a
value for R2 in the 1k
to 22k
range, and then calcu-
late the value of R1 from the following equation:
For the MAX1973, V
FB
= 1.25V, allowing its output to be
set down to 1.25V. For the MAX1974, V
FB
= 0.75V,
allowing its output to be set down to 0.75V
The MAX1973/MAX1974 PWM circuitry is capable of a
stable minimum duty cycle of 17%. This limits the mini-
mum output voltage that can be generated to 0.17
V
IN
. Instability may result for V
IN
/V
OUT
ratios below 0.17.
Inductor Selection
A 2.2μH to 4.7μH inductor with a saturation current of at
least 1.25A is recommended for full-load (1mA) applica-
tions. For lower load currents, the inductor current rating
can be reduced. For most applications, use an inductor
with a current rating 1.25 times the maximum required
output current. For best efficiency, the inductor
’
s DC
resistance should be as small as possible. See Table 3
for recommended inductors and manufacturers.
For most designs, the inductor value (L
INIT
) can be
derived from the following equation:
L
V
V
I
OUT MAX
(
V
V
LIR
f
INIT
OUT
IN
OUT
IN
SW
=
(
)
×
×
×
)
R
R
V
V
OUT
FB
1
2
1
=
×
M
Smallest 1A, 1.4MHz Step-Down Regulators
______________________________________________________________________________________
11
CTL1
GND
CTL2
GND
FUNCTION
Shutdown
GND
IN
Positive voltage margining,
regulation voltage increased 4% from
normal operation
IN
GND
Negative voltage margining,
regulation voltage lowered 4% from
normal operation
IN
IN
Normal operation
Table 1. CTL_ Input Functions (MAX1973)
OUTPUT VOLTAGE
MAX1973
1.8V
2.5V
FBSEL
MAX1974
1V
1.5V
GND
IN
Not Connected
Adjustable down
to 1.25V
Adjustable down to
0.75V
Table 2. Preset Output Voltages
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1973EUB | Smallest 1A, 1.4MHz Step-Down Regulators |
| MAX1974EUB | Smallest 1A, 1.4MHz Step-Down Regulators |
| MAX1976ETT-T | Low-Input-Voltage, 300mA LDO Regulators with RESET in SOT and TDFN |
| MAX1976EZT-T | Low-Input-Voltage, 300mA LDO Regulators with RESET in SOT and TDFN |
| MAX1978 | Integrated Temperature Controllers for Peltier Modules |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1973EUB | 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 |
| MAX1973EUB+ | 功能描述:直流/直流开关调节器 1A 1.4MHz 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 |
| MAX1973EUB+T | 功能描述:直流/直流开关调节器 1A 1.4MHz 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 |
| MAX1973EUB-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 |
| MAX1973EVKIT | 功能描述:直流/直流开关调节器 Evaluation Kit for the MAX1973 MAX1974 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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