参数资料
型号: MAX1838EEE+
厂商: Maxim Integrated Products
文件页数: 11/13页
文件大小: 0K
描述: IC SW USB DUAL W/FB 16-QSOP
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 100
应用: USB,外设
电源电压: 4 V ~ 5.5 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 16-SSOP(0.154",3.90mm 宽)
供应商设备封装: 16-QSOP
包装: 管件
Dual USB Switch with Fault Blanking
and Autoreset
during a load step. The MAX1838 is capable of driving
inductive loads, but avoid exceeding the device ’s
absolute maximum ratings. Usually the load inductance
is relatively small, and the MAX1838’s input includes a
substantial 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 MAX1838’s output below 6V and above -0.3V.
Turn-On and Turn-Off Behavior
In absence of faults, the MAX1838’s internal switches
turn on and off slowly under the control of the ON input.
The slow charge-pump switch-drive minimizes load tran-
sients on the upstream power source. Under thermal
fault and undervoltage lockout, the power device turns
off rapidly to protect the switch and the power source.
Layout and Thermal Dissipation
To optimize the switch response to output short-circuit
conditions, keep all traces as short as possible to reduce
the effect of undesirable parasitic inductance. Place
input and output capacitors no more than 5mm from
device leads. IN, AUX, and OUT pins must be connect-
ed with short traces to the power bus. Wide power bus
planes provide superior switch heat dissipation. While
the switches are on, power dissipation is small and the
package temperature rise is minimal. Calculate the
power dissipation for this condition as follows:
P = (I OUT ) 2 R ON
For the normal operating current (I OUT = 0.5A), the max-
imum on-resistance of the switch is 170m ? , and the
power dissipation is:
P = (0.5A) 2 x 0.170 ? = 43mW per switch
The worst-case power dissipation occurs when the
switch is in current limit and the output is greater than
1V. In this case, the power dissipated in each switch is
the voltage drop across the switch multiplied by the cur-
rent limit:
P = (I LIM ) (V IN - V OUT )
For a 5V input and 1V output, the maximum power dissi-
pation per switch is:
P = (1.2A) (5.5V - 1V) = 5.4W
Since the package power dissipation is only 667mW, the
MAX1838 die temperature will exceed the thermal shut-
down threshold and the switch output shuts down until
the junction temperature cools by 10 ° C. The duty cycle
and period are strong functions of the ambient tempera-
ture and the PC board layout.
A short circuit at the output causes the power dissipated
across the switch and the junction temperature to
increase. If the fault condition persists, the thermal-over-
load-protection circuitry activates, and the output shuts
down until the junction temperature decreases by 10 ° C
(see Thermal Shutdown).
100k ?
100k ?
AUX
0.1 μ F
AUXA
AUXB
FAULTB
FAULTA
IN
0.1 μ F
INA
INB
SEL
ON
MAX1838
OUTB2
OUTB1
OUTA2
OUTA1
ADJB
10 μ F
10 μ F
OUTB
OUTA
GND
ADJA
Figure 2. Typical Application Circuit
67k ?
67k ?
______________________________________________________________________________________
11
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MAX1838EEE-T 功能描述:电源开关 IC - USB Dual USB Switch w/Fault Blank RoHS:否 制造商:Micrel 电源电压-最小:2.7 V 电源电压-最大:5.5 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:SOIC-8 封装:Tube
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