参数资料
| 型号： | MAX1945REUI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/19页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 6A 28TSSOP |
| 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： | 1 |
| 输出电压： | 1.8V，2.5V，可调 |
| 输入电压： | 2.6 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 400kHz ~ 1.2MHz |
| 电流 - 输出： | 6A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SOIC（0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 28-TSSOP 裸露焊盘 |
1MHz, 1% Accurate, 6A Internal Switch
Step-Down Regulators
Soft-Start
The MAX1945R/MAX1945S employs digital soft-start to
reduce supply in-rush current during startup conditions.
When the device exits undervoltage lockout (UVLO),
shutdown mode, or restarts following a thermal-overload
event, the digital soft-start circuitry slowly ramps up the
voltages at REF and FB (see the Typical Operating
Characteristics ). An internal oscillator sets the soft-start
time to 3.7ms (typ). Use a of 0.22μF capacitor (min) to
reduce the susceptibility to switching noise.
Undervoltage Lockout (UVLO)
When V CC drops below 2.35V, the UVLO circuit inhibits
switching. Once V CC rises above 2.4V, UVLO clears
and the soft-start function activates.
Shutdown Mode
Drive CTL1 and CTL2 to ground to shut down the
MAX1945R/MAX1945S. In shutdown mode, the internal
MOSFETs stop switching and LX goes to high imped-
ance; REF and COMP go to ground.
Voltage Margining
The MAX1945R/MAX1945S provide selectable voltage
margining. The MAX1945R provides ±4% voltage mar-
gining, and the MAX1945S provides ±9% voltage margin-
ing. CTL1 and CTL2 set the voltage margins (Table 1).
Table 1. Setting Voltage Margin
Bootstrap (BST)
A capacitor connected between BST and LX and a
Schottky diode connected from IN to BST generate the
gate drive for the internal high-side N-channel MOSFET.
CTL1
0V
CTL2
0V
V OUT
MAX1945R MAX1945S
OFF OFF
When the low-side N-channel MOSFET is on, LX goes to
PGND. IN charges the bootstrap capacitor through the
Schottky diode. When the low-side N-channel MOSFET
turns off and the high side N-channel MOSFET turns on,
Voltage Margin
V CC
V CC
0V
V CC
0V
V CC
NOMINAL
-4%
+4%
NOMINAL
-9%
+9%
V LX goes to V IN . The Schottky diode prevents the capac-
R 1 = R 2 ? OUT
1 ?
V OUT × ( V IN ? V OUT )
f OSC × V IN × LIR × I OUT ( MAX )
itor from discharging into IN.
Frequency Select (SYNC)
The MAX1945R/MAX1945S operate in PWM mode with
a selectable fixed frequency or synchronized to an
external frequency. The devices switch at a frequency
of 500kHz when SYNC is connected to ground. The
devices switch at 1MHz with SYNC connected to V CC .
Apply an external frequency of 400kHz to 1.2MHz with
10% to 90% duty cycle at SYNC to synchronize the
switching frequency of MAX1945R/MAX1945S.
Output Voltage Select
The MAX1945R/MAX1945S feature selectable fixed and
adjustable output voltages. With FB connected to the
output, the output voltage is 1.8V when FBSEL is at
GND and 2.5V when FBSEL is at V CC (Figure 1). When
FBSEL is floating, connect FB to an external resistor
divider from V OUT to GND to set the output
voltage from 0.8V to 85% of V IN (Figure 2). Select R2 in
the 1k ? to 10k ? range. Calculate R1 using the follow-
ing equation:
? V ?
?
? V FB ?
where V FB = 0.8V.
Thermal Protection
Thermal-overload protection limits total power dissipa-
tion in the device. When the junction temperature (T J )
exceeds 165°C, a thermal sensor forces the device into
shutdown, allowing the die to cool. The thermal sensor
turns the device on again after the junction temperature
cools by 20°C, causing a pulsed output during continu-
ous overload conditions.The soft-start sequence begins
after a thermal-shutdown condition.
Design Procedure
V CC Decoupling
Because of the high switching frequency and tight out-
put tolerance, decouple V CC with 0.1μF capacitor from
V CC to GND with a 10 ? resistor from V CC to IN. Place
the capacitor as close to VCC as possible.
Inductor Design
Choose an inductor with the following equation:
L =
where LIR is the ratio of the inductor ripple current to
average continuous current at a minimum duty cycle.
Choose LIR between 20% to 40% of the maximum load
current for best performance and stability.
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1945SEUI | 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 |
| MAX1945SEUI+ | 功能描述:直流/直流开关调节器 1MHz 1% 6A Step-Down PWM 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 |
| MAX1945SEUI+T | 功能描述:直流/直流开关调节器 1MHz 1% 6A Step-Down PWM 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 |
| MAX1945SEUI-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 |
| MAX1946ETA | 制造商:Maxim Integrated Products 功能描述:SINGLE USB SWITCH WITH AUTORESET AND FAULT BL - Rail/Tube |
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