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参数资料
| 型号： | MAX1946ETA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/13页 |
| 文件大小： | 0K |
| 描述： | IC USB SW SGL AUTORESET 8TDFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1 |
| 应用： | USB，外设 |
| 电流 - 电源： | 40µA |
| 电源电压： | 2.7 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-WDFN 裸露焊盘 |
| 供应商设备封装： | 8-TDFN-EP（3x3） |
| 包装： | 标准包装 |
| 其它名称： | MAX1946ETA+TDKR |
Single USB Switch with Autoreset and
Fault Blanking in Tiny TDFN
Layout and Thermal Dissipation
INPUT
Keep all traces as short as possible to reduce the effect
2.7V TO 5.5V
IN
100k ?
of undesirable parasitic inductance, and to optimize the
switch response time to output short-circuit conditions.
0.1 μ F
OFF
IN
ON
MAX1946
FAULT
OUT
Place input and output capacitors no more than 5mm
from device leads. Connect IN and OUT to the power
bus with short traces. The exposed pad on the TDFN
ON
package underside must be soldered to the PC board in
SEL
GND
OUT
1 μ F
order to realize the rated package dissipation.
An active switch dissipates little power with minimal
change in package temperature. Calculate the power
*USB APPLICATIONS MAY REQUIRE
ADDITIONAL BULK CAPACITANCE
Figure 2. Typical Application Circuit
Output Capacitor
Bypass OUT to GND with a 1μF ceramic capacitor for
local decoupling. Additional bulk capacitance (up to
470μF) reduces output-voltage transients under dynamic
load conditions. Using output capacitors greater than
470μF can assert FAULT if the current limit cannot
charge the output capacitor within the 20ms fault-
blanking period. In addition to bulk capacitance, small-
value (0.1μF or greater) ceramic capacitors improve
the output’s resilience to electrostatic discharge (ESD).
Driving Inductive Loads
A wide variety of devices (mice, keyboards, cameras, and
printers) typically connect to the USB port with cables,
which can add an inductive component to the load. This
inductance causes the output voltage at the USB port to
oscillate during a load step. The MAX1946 drives induc-
tive loads, but avoid exceeding the device’s absolute
maximum ratings. The load inductance is usually relatively
small, and the MAX1946 input typically includes substan-
tial bulk capacitance from an upstream regulator as well
as local bypass capacitors, limiting overshoot. If severe
ringing occurs due to large load inductance, clamp the
MAX1946 output below +6V and above -0.3V.
Turn-On and Turn-Off Behavior
When turned on, the MAX1946 output ramps up over
1.2ms to eliminate load transients on the upstream
power source. When turned off, the output ramps down
for 3ms. Under fault conditions, the output of the
MAX1946 turns off rapidly to provide maximum safety
for the upstream power source and downstream
devices. Internal blocks shut down to minimize supply
current when the switch is off.
dissipation for this condition as follows:
P = (I OUT ) 2 R ON
At the normal operating current (I OUT = 0.5A) and the
maximum on-resistance of the switch (90m ? ), the
power dissipation is:
P = (0.5A) 2 0.09 ? = 22.5mW
The worst-case power dissipation occurs when the out-
put current is just below the current-limit threshold
(1.2A max) with an output voltage just greater than 1V.
In this case, the power dissipated is the voltage drop
across the switch multiplied by the current limit:
P = I LIM (V IN - V OUT )
For a 5V input and 1V output, the maximum power dis-
sipation per switch is:
P = 1.2A (5V - 1V) = 4.8W
Since the package power dissipation is 1951mW for the
8-pin TDFN, the MAX1946 die temperature exceeds the
+160 ° C thermal-shutdown threshold. The switch output
shuts down until the junction temperature cools by
15°C. The duty cycle and period are strong functions of
the ambient temperature and the PC board layout (see
the Thermal Shutdown section).
If the output current exceeds the current-limit threshold,
or the output voltage is pulled below the short-circuit
detect threshold, the MAX1946 enters a fault state after
20ms, at which point autoreset mode is enabled and
25mA is sourced by the output. For a 5V input, OUT
short-circuited to GND, and autoreset mode active, the
power dissipation is as follows:
P = 0.025A 5V = 0.125W
______________________________________________________________________________________
11
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相关代理商/技术参数 |
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| MAX1946EUA | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1947ETA18 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1947ETA18+ | 制造商:Maxim Integrated Products 功能描述:CONV DC-DC SGL-OUT STEP UP 8TDFN EP - Rail/Tube |
| MAX1947ETA18+T | 功能描述:直流/直流开关转换器 Step-Up w/RESET DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1947ETA18-T | 功能描述:直流/直流开关转换器 Step-Up w/RESET DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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