Electronic Components Datasheet Search |
|
US1150CP Datasheet(PDF) 5 Page - UNISEM |
|
US1150CP Datasheet(HTML) 5 Page - UNISEM |
5 / 5 page US1150 2-5 Rev. 1.2 10/28/99 The US1150 keeps a constant 1.25V between the Vsense pin and the Vadj pin. By placing a resistor R1 across these two pins and connecting the Vsense and Vout pin together , a constant current flows through R1, adding to the Iadj current and into the R2 resistor producing a voltage equal to the (1.25/R1)*R2 + Iadj*R2 .This voltage is then added to the 1.25V to set the output voltage. This is summarized in the above equation. Since the minimum load current requirement of the US1150 is 10 mA , R1 is typically selected to be a 121 Ω resistor so that it automatically satisfies this condition. Notice that since the Iadj is typically in the range of 50uA it only adds a small error to the output voltage and should be considered when very precise output voltage setting is required. Load Regulation Since the US1150 has separate pins for the output (Vout) and the sense (Vsense), it is ideal for providing true re- mote sensing of the output voltage at the load.This means that the voltage drops due to parasitic resistance such as PCB traces between the regulator and the load are compensated for using remote sensing. Figure 3 shows a typical application of the US1150 with remote sensing. Figure 3 - Schematic showing connection for best load regulation Stability The US1150 requires the use of an output capacitor as part of the frequency compensation in order to make the regulator stable. Typical designs for the microproces- sor applications use standard electrolytic capacitors with typical ESR in the range of 50 to 100 m Ω and an output capacitance of 500 to 1000uF. Fortunately as the ca- pacitance increases, the ESR decreases resulting in a fixed RC time constant. The US1150 takes advantage of this phenomena in making the overall regulator loop stable. For most applications a minimum of 100uF aluminum electrolytic capacitor such as Sanyo, MVGX series ,Panasonic FA series as well as the Nichicon PL series insures both stability and good transient response. Thermal Design The US1150 incorporates an internal thermal shutdown that protects the device when the junction temperature exceeds the allowable maximum junction temperature. Although this device can operate with junction tempera- tures in the range of 150 °C ,it is recommended that the selected heat sink be chosen such that during maxi- mum continuos load operation the junction temperature is kept below this number. The example below shows the steps in selecting the proper surface mount pack- age. Assuming, the following conditions: Vout=2.7V Vin=3.3V Vctrl=5V Iout=2A DC Avg Calculate the maximum power dissipation using the fol- lowing equation: Pd=Iout*(Vin-Vout) + (Iout/60)*(Vctrl - Vout) Pd=2*(3.3-2.7) + (2/60)*(5-2.7)=1.28 W Using table below select the proper package and the amount of copper board needed. Pkg Copper θJA(°C/W) Max Pd Max Pd Area (Ta=25 °C) (Ta=45 °C) TO263 1.4"X1.4" 25 4.4W 3.6W TO263 1.0"X1.0" 30 3.7W 3.0W TO263 0.7"X0.7" 35 3.1W 2.6W TO263 Pad Size 45 2.4W 2.0W SO8 1.0"X1.0" 55 2.0W 1.63W Note: Above table is based on the maximum junction temperature of 135 °C. As shown in the above table, any of the two packages will do the job. For low cost applications the SO8 pack- age is recommended. 1150app3-1.0 R1 R2 Vin Vctrl RL US1150 Vsense Adj Vout Vctrl Vin |
Similar Part No. - US1150CP |
|
Similar Description - US1150CP |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |