欢迎访问ic37.com |
会员登录 免费注册
发布采购

AMS1505CT 参数 Datasheet PDF下载

AMS1505CT图片预览
型号: AMS1505CT
PDF下载: 下载PDF文件 查看货源
内容描述: 5A低压差稳压器 [5A LOW DROPOUT VOLTAGE REGULATORS]
分类和应用: 稳压器调节器输出元件
文件页数/大小: 9 页 / 80 K
品牌: ADMOS [ ADVANCED MONOLITHIC SYSTEMS ]
 浏览型号AMS1505CT的Datasheet PDF文件第1页浏览型号AMS1505CT的Datasheet PDF文件第2页浏览型号AMS1505CT的Datasheet PDF文件第3页浏览型号AMS1505CT的Datasheet PDF文件第4页浏览型号AMS1505CT的Datasheet PDF文件第5页浏览型号AMS1505CT的Datasheet PDF文件第7页浏览型号AMS1505CT的Datasheet PDF文件第8页浏览型号AMS1505CT的Datasheet PDF文件第9页  
AMS1505  
APPLICATION HINTS  
Thermal resistance specification for both the Control Section and  
the Power Transistor are given in the electrical characteristics.  
The thermal resistance of the Control section is given as  
0.65°C/W and junction temperature of the Control section can  
run up to 125°C. The thermal resistance of the Power section is  
given as 2.7°C/W and junction temperature of the Power section  
can run up to 150°C. Due to the thermal gradients between the  
power transistor and the control circuitry there is a significant  
difference in thermal resistance between the Control and Power  
sections.  
Virtually all the power dissipated by the device is dissipated in  
the power transistor. The temperature rise in the power transistor  
will be greater than the temperature rise in the Control section  
making the thermal resistance lower in the Control section. At  
power levels below 12W the temperature gradient will be less  
than 25°C and the maximum ambient temperature will be  
determined by the junction temperature of the Control section.  
This is due to the lower maximum junction temperature in the  
Control section. At power levels above 12W the temperature  
gradient will be greater than 25°C and the maximum ambient  
temperature will be determined by the Power section. In both  
cases the junction temperature is determined by the total power  
dissipated in the device. For most low dropout applications the  
power dissipation will be less than 12W.  
Protection Diodes  
Unlike older regulators, the AMS1505 family does not need any  
protection diodes between the adjustment pin and the output and  
from the output to the input to prevent die over-stress. Internal  
resistors are limiting the internal current paths on the AMS1505  
adjustment pin, therefore even with bypass capacitors on the  
adjust pin no protection diode is needed to ensure device safety  
under short-circuit conditions. The Adjust pin can be driven on a  
transient basis ±7V with respect to the output without any device  
degradation.  
Diodes between the Output pin and VPOWER pin are not usually  
needed. Microsecond surge currents of 50A to 100A can be  
handled by the internal diode between the Output pin and VPOWER  
pin of the device. In normal operations it is difficult to get those  
values of surge currents even with the use of large output  
capacitances. If high value output capacitors are used, such as  
1000mF to 5000mF and the VPOWER pin is instantaneously shorted  
to ground, damage can occur. A diode from output to input is  
recommended, when a crowbar circuit at the input of the  
AMS1505 is used (Figure 6). Normal power supply cycling or  
even plugging and unplugging in the system will not generate  
current large enough to do any damage.  
The power in the device is made up of two components: the  
power in the output transistor and the power in the drive circuit.  
The power in the control circuit is negligible.  
VCONTROL  
+
D1*  
D2*  
The power in the drive circuit is equal to:  
CONTROL  
POWER OUTPUT  
VOUT  
VPOWER  
PDRIVE = (VCONTROL - VOUT)(ICONTROL  
)
+
+
AMS1505  
SENSE  
where ICONTROL is equal to between IOUT/100(typ) and  
IOUT/58(max).  
The power in the output transistor is equal to:  
ADJ  
R1  
R2  
POUTPUT = (VPOWER -VOUT)(IOUT  
)
The total power is equal to:  
PTOTAL = PDRIVE + POUTPUT  
Figure 6. Optional Clamp Diodes Protect Against  
Input Crowbar Circuits  
Junction-to-case thermal resistance is specified from the IC  
junction to the bottom of the case directly below the die. This is  
the lowest resistance path for the heat flow. In order to ensure the  
best possible thermal flow from this area of the package to the  
heat sink proper mounting is required. Thermal compound at the  
If the AMS1505 is connected as a single supply device with the  
control and power input pins shorted together the internal diode  
between the output and the power input pin will protect the  
control input pin. As with any IC regulator, none the protection  
circuitry will be functional and the internal transistors will break  
down if the maximum input to output voltage differential is  
exceeded.  
case-to-heat sink interface is recommended.  
A thermally  
conductive spacer can be used, if the case of the device must be  
electrically isolated, but its added contribution to thermal  
resistance has to be considered.  
Thermal Considerations  
The AMS1505 series have internal power and thermal limiting  
circuitry designed to protect the device under overload conditions.  
However maximum junction temperature ratings should not be  
exceeded under continuous normal load conditions. Careful  
consideration must be given to all sources of thermal resistance  
from junction to ambient, including junction-to-case, case-to-heat  
sink interface and heat sink resistance itself.  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140