* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download How to Set Control Voltage In an Application Circuit
Ground loop (electricity) wikipedia , lookup
Ground (electricity) wikipedia , lookup
Power engineering wikipedia , lookup
Mercury-arc valve wikipedia , lookup
Stepper motor wikipedia , lookup
Pulse-width modulation wikipedia , lookup
Power inverter wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Three-phase electric power wikipedia , lookup
Variable-frequency drive wikipedia , lookup
History of electric power transmission wikipedia , lookup
Electrical substation wikipedia , lookup
Electrical ballast wikipedia , lookup
Power MOSFET wikipedia , lookup
Schmitt trigger wikipedia , lookup
Current source wikipedia , lookup
Power electronics wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Distribution management system wikipedia , lookup
Opto-isolator wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Current mirror wikipedia , lookup
Buck converter wikipedia , lookup
Voltage regulator wikipedia , lookup
Surge protector wikipedia , lookup
Stray voltage wikipedia , lookup
Alternating current wikipedia , lookup
RF Applications Engineering Technical Note µPG2250T5N How to Set Control Voltage In an Application Circuit uPG2250T5N Pin Connections As shown in the Pin Connections above, uPG2250T5N has three VDD pins for connection to external supply voltage. In most applications these pins are connected to the main power line/plane of the system. In addition, uPG2250T5N also has a control pin, Vcont, for the control of the PA. As indicated on the data sheet, Vcont should be set around 1.8V while VDD can be selected as high as 3.5V. Often the control voltage from a controller is the same or close to the main supply voltage, as a result when the system supply voltage is higher than 1.8V a question arises as to how control voltage can be lowered to the required level for Vcont of uPG2250T5N. This note provides a brief discussion on this issue. Generally there is a variety of methods to convert a DC voltage. In this particular case, one of the following two simple methods should be sufficient. The schematic for the two methods are shown at the end of this document. i. Serial Voltage-dropping Resistor This is the simplest way to lower the control voltage. In this method the voltage drop is simply proportional to the current drawn by the device, as a result the usual design consideration is whether it provides a stable enough bias point against current variation to ensure consistent PA performance. This is particularly important in a design for mass production. In general there are several factors that determine whether the voltage dropping resistor is an appropriate method for a real application. In the following a quantitative analysis is provided for the case of uPG2250T5N based on its performance characteristics As shown in the plots under the section of TYPICAL CHARACTERISTICS on the data sheet, the control current increases as a function of control voltage with a rate of 0.8mA/V in the range around Vcont=1.8V. This feature provides a negative feedback against the current variation. Also shown in the plot is that in the range of Vcont=1 to 2V, both Pout and IDD are relatively insensitive to Vcont. Both are favorable features for using voltage dropping resistor. Quantitatively, the plot shows the typical value of control current is about 1mA at Vcont=1.8V. For a system supply voltage of 3V, a 1.2kΩ resistor would drop the voltage from 3V to 1.8V. As 2 for the effect of current variation, the data sheet states the maximum control current at Vcont=1.8V is 3mA. Assuming in this case the Icont vs. Vcont curve has the same shape but with larger slope (Icont should reach 3mA instead of 1mA at Vcont=1.8V), a simple analysis shows the 1.2kΩ resistor would drop the voltage from 3V to about 1.4V in this case. The same plot shows that at Vcont=1.4V, Pout and IDD are only slightly lowered. In conclusion, a single serial resistor of 1.2 to 1.5kΩ can lower a supply voltage of 3 to 3.3V to the appropriate range for Vcont. The effect of the control current variation on the PA performance should be acceptable in most applications. ii. Voltage Divider For those applications where it is desirable to have minimum variation in bias condition, two resistors can be used to form a voltage divider. This method provides a more stable bias point against current variation. Its disadvantage is the extra component and power consumption. In this bias scheme the voltage drop is determined by the ratio of the two resistors’ values and the voltage stability is determined by their absolute values. A voltage divider with smaller resistor values provides a more stable voltage point, but consumes more power. uPG2250T5N R To microcontroller 3 Vcont Serial Resistor Method uPG2250T5N To microcontroller R1 3 Vcont R2 Voltage Divider Method 3