 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LT1618EMS Datasheet(PDF) 7 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LT1618EMS Datasheet(HTML) 7 Page - Linear Technology |
|
|
7 / 16 page  LT1618 7 sn1618 1618fas APPLICATIONS INFORMATION Setting Output Voltage To set the output voltage, select the values of R1 and R2 (see Figure 1) according to the following equation. RR VOUT 12 1 263 1 = ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ . – For current source applications, use the FB pin for over- voltage protection. Pick R1 and R2 so that the output voltage will not go too high if the load is disconnected or if the load current drops below the preset value. Typically choose R1 and R2 so that the overvoltage value will be about 20% to 30% higher than the normal output voltage (when in constant-current mode). This prevents the volt- age loop from interfering with the current loop in current source applications. For battery charger applications, pick the values of R1 and R2 to give the desired end of charge voltage. Selecting RSENSE/Current Sense Adjustment Use the following formula to choose the correct current sense resistor value (for constant current operation). RSENSE = 50mV/IMAX For designs needing an adjustable current level, the IADJ pin is provided. With the IADJ pin tied to ground, the nominal current sense voltage is 50mV (appearing be- tween the ISP and ISN pins). Applying a positive DC voltage to the IADJ pin will decrease the current sense voltage according to the following formula: V VV ISENSE IADJ = 1 263 0 8 25 .– ( . ) For example, if 1V is applied to the IADJ pin, the current sense voltage will be reduced to about 18mV. This adjustability allows the regulated current to be reduced without changing the current sense resistor (e.g. to adjust brightness in an LED driver or to reduce the charge current in a battery charger). If the IADJ pin is taken above 1.6V, the output of the error amplifier (the VC pin) will be pulled down and the LT1618 will stop switching. A pulse width modulated (PWM) signal can also be used to adjust the current sense voltage; simply add an RC filterto convert the PWM signal into a DC voltage for the IADJ pin. If the IADJ pin is not used, it should be tied to ground. Do not leave the pin floating. For applications needing only a simple one-step current sense adjustment, the circuit in Figure 2 works well. If a large value resistor (≥2MΩ) is placed between the IADJ pin and ground, the current sense voltage will reduce to about 25mV, providing a 50% reduction in current. Do not leave the IADJ pin open. This method gives a well-regulated current value in both states, and is controlled by a logic signal without the need for a variable PWM or DC control signal. When the NMOS transistor is on, the current sense voltage will be 50mV, when it is off, the current sense voltage will be reduced to 25mV. Figure 2 LT1618 IADJ 2M FULL CURRENT 1618 F02 Considerations When Sensing Input Current In addition to regulating the DC output current for current- source applications, the constant-current loop of the LT1618 can also be used to provide an accurate input current limit. Boost converters cannot provide output short-circuit protection, but the surge turn-on current can be drastically reduced using the LT1618’s current sense at the input. SEPICs, however, have an output that is DC- isolated from the input, so an input current limit not only helps soft-start the output but also provides excellent short-circuit protection. |
Similar Part No. - LT1618EMS |
|
Similar Description - LT1618EMS |
|
|
|
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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
