TS39105CP450RO 查看數據表（PDF） - TSC Corporation

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TS39105CP450RO

1A Ultra Low LDO with Enable

TSC Corporation 

TS39105

1A Ultra Low LDO with Enable

Application Information (Continue)

Enable Input

TS39105 versions feature an active-high enable (EN) input that allows ON/OFF control of the regulator. Current drain

reduces to “zero” when the device is shutdown, with only micro-amperes of leakage current. The EN input has

TTL/CMOS compatible thresholds for simple interfacing with logic interfacing. EN may be directly tied to ViN and pulled

up to the maximum supply voltage.

Transient Response and 3.3V to 2.5V or 2.5V to 1.8V Conversion

TS39105 has excellent transient response to variations in input voltage and load current. The device have been

designed to respond quickly to load current variations and input voltage variations. Large output capacitors are not

required to obtain this performance. A standard 10uF output capacitor, preferably tantalum, is all that is required.

Larger values help to improve performance even further. By virtue of its low dropout voltage, this device does not

saturate into dropout as readily as similar NPN base designs. When converting from 3.3V to 2.5V or 2.5V to 1.8V, the

NPN based regulators are already operating in dropout, with typical dropout requirements of 1.2V or greater,. To

convert down to 2.5V or 1.8V without operating in dropout, NPN based regulators require an input voltage of 3.7V at

the very least. The TS39105 will provide excellent performance with an input as low as 3.0V or 2.5V respectively. This

gives the PNP based regulators a distinct advantage over older, NPN based linear regulators.

Power Dissipation

From under curves, the minimum area of copper necessary for the par to operate safely can be determined. The

maximum allowable temperature rise must be calculated to determine operation along which curve.

Copper area lay out information

Determine the power dissipation requirements for the design along with the maximum ambient temperature at which

the device will be operated. Refer to power dissipation with copper area curve, which shows safe operating curves for

three different ambient temperatures with 25oC, 50oC, 85oC. From these curves, the minimum amount of copper can

be determined by knowing the maximum power dissipation required.

PD = (VIN- VOUT) * IOUT + VIN * IGND

If we used a 5.0V output device and a 6V input at an output current of 350mA, then the power dissipation is as follows:

PD = (6.0V- 5.0V) * 350mA + 5V * 4mA

PD = 350mW + 20mW

PD = 370mW

If the maximum ambient temperature is 85oC and the power dissipation is as above 375mW, the curve is shows that

the required area of copper is 80mm2.

4/7

Version: A08

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