欢迎访问ic37.com |
会员登录 免费注册
发布采购

AAT4250IJS-T1 参数 Datasheet PDF下载

AAT4250IJS-T1图片预览
型号: AAT4250IJS-T1
PDF下载: 下载PDF文件 查看货源
内容描述: 压摆率受控负载开关 [Slew Rate Controlled Load Switch]
分类和应用: 电源电路开关电源管理电路光电二极管
文件页数/大小: 12 页 / 194 K
品牌: ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
 浏览型号AAT4250IJS-T1的Datasheet PDF文件第4页浏览型号AAT4250IJS-T1的Datasheet PDF文件第5页浏览型号AAT4250IJS-T1的Datasheet PDF文件第6页浏览型号AAT4250IJS-T1的Datasheet PDF文件第7页浏览型号AAT4250IJS-T1的Datasheet PDF文件第8页浏览型号AAT4250IJS-T1的Datasheet PDF文件第10页浏览型号AAT4250IJS-T1的Datasheet PDF文件第11页浏览型号AAT4250IJS-T1的Datasheet PDF文件第12页  
AAT4250  
Slew Rate Controlled Load Switch  
For maximum current, refer to the following equation:  
by consulting the chart of RDSON vs. VIN. The Rds  
reported for 5 volt RDS can be scaled by the ratio  
seen in the chart to derive the Rds for 4 volt VIN:  
175mx 120m/115m= 183m. Derated for  
temperature: 183mx (1 + .002800 x (125°C -  
25°C)) = 235m. The power dissipation for a  
100mA load is calculated as follows:  
1/2  
IOUT(MAX) < ( PD(MAX) / RDS  
)
For example, if VIN = 5V, RDS(MAX)=224mand TA  
= 25°C, IOUT(MAX) = 1.7A. If the output load current  
were to exceed 1.7A or if the ambient temperature  
were to increase, the internal die temperature will  
increase, and the device will be damaged.  
PD(MAX) = I2OUT x RDS  
PD(100mA) = (100mA)2 x 235mΩ  
PD(100mA) = 2.35mW  
Higher peak currents can be obtained with the  
AAT4250. To accomplish this, the device thermal  
resistance must be reduced by increasing the heat  
sink area or by operating the load switch in a duty  
cycle manner. Duty cycles with peaks less than  
2ms in duration can be considered using the  
method below.  
PD(87.5%D/C) = %DC x PD(100mA)  
PD(87.5%D/C) = 0.875 x 2.35mW  
PD(87.5%D/C) = 2.1mW  
The power dissipation for 100mA load at 87.5%  
duty cycle is 2.1mW. Now the power dissipation for  
the remaining 12.5% of the duty cycle at 2A is cal-  
culated:  
High Peak Output Current Applications  
Some applications require the load switch to oper-  
ate at a continuous nominal current level with short  
duration high current peaks. Refer to the IDM spec-  
ification in the Absolute Maximum table to ensure  
the AAT 4250’s maximum pulsed current rating is  
not exceeded. The duty cycle for both output cur-  
rent levels must be taken into account. To do so,  
first calculate the power dissipation at the nominal  
continuous current level, and then add in the addi-  
tional power dissipation due to the short duration  
high current peak scaled by the duty factor.  
PD(MAX) = I2OUT x RDS  
PD(2A) = (2A)2 x 235mΩ  
PD(2A) = 940mW  
PD(12.5%D/C) = %DC x PD(2A)  
PD(12.5%D/C) = 0.125 x 940mW  
PD(12.5%D/C) = 117.5mW  
The power dissipation for 2A load at 12.5% duty  
cycle is 117mW. Finally, the two power figures are  
summed to determine the total true power dissipa-  
tion under the varied load.  
For example, a 4V system using an AAT4250 oper-  
ates at a continuous 100mA load current level and  
has short 2A current peaks, as in a GSM applica-  
tion. The current peak occurs for 576µs out of a  
4.61ms period.  
PD(total) = PD(100mA) + PD(2A)  
PD(total) = 2.1mW + 117.5mW  
PD(total) = 120mW  
The maximum power dissipation for the AAT4250  
operating at an ambient temperature of 85°C is  
267mW. The device in this example will have a  
total power dissipation of 120mW. This is well with  
in the thermal limits for safe operation of the  
device, in fact, at 85°C, the AAT4250 will handle a  
2A pulse for up to 28% duty cycle. At lower ambi-  
ent temperatures the duty cycle can be further  
increased.  
First, the current duty cycle is calculated:  
% Peak Duty Cycle: X/100 = 576µs/4.61ms  
% Peak Duty Cycle = 12.5%  
The load current is 100mA for 87.5% of the 4.61ms  
period and 2A for 12.5% of the period. Since the  
Electrical Characteristics do not report RDS MAX for 4  
volts operation, it must be calculated approximated  
4250.2001.12.0.94  
9