Electronic Components Datasheet Search |
|
LT1071 Datasheet(PDF) 7 Page - Linear Technology |
|
LT1071 Datasheet(HTML) 7 Page - Linear Technology |
7 / 12 page 7 LT1070/LT1071 OPERATION midfrequencies in the energy storage inductor. This greatly simplifies closed-loop frequency compensation under widely varying input voltage or output load condi- tions. Finally, it allows simple pulse-by-pulse current limiting to provide maximum switch protection under output overload or short-circuit conditions. A low drop- out internal regulator provides a 2.3V supply for all internal circuitry of the LT1070/LT1071. This low drop- out design allows input voltage to vary from 3V to 60V with virtually no change in device performance. A 40kHz oscillator is the basic clock for all internal timing. It turns “on” the output switch via the logic and driver circuitry. Special adaptive antisat circuitry detects onset of satura- tion in the power switch and adjusts driver current instantaneously to limit switch saturation. This mini- mizes driver dissipation and provides very rapid turn-off of the switch. A 1.2V bandgap reference biases the positive input of the error amplifier. The negative input is brought out for output voltage sensing. This feedback pin has a second function; when pulled low with an external resistor, it programs the LT1070/LT1071 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. The LT1070/ LT1071 will then regulate the value of the flyback pulse with respect to the supply voltage. This flyback pulse is directly proportional to output voltage in the traditional transformer coupled flyback topology regulator. By regu- lating the amplitude of the flyback pulse, the output voltage can be regulated with no direct connection be- tween input and output. The output is fully floating up to the breakdown voltage of the transformer windings. Multiple floating outputs are easily obtained with addi- tional windings. A special delay network inside the LT1070/ LT1071 ignores the leakage inductance spike at the leading edge of the flyback pulse to improve output regulation. The error signal developed at the comparator input is brought out externally. This pin (VC) has four different functions. It is used for frequency compensation, current limit adjustment, soft starting and total regulator shut- down. During normal regulator operation this pin sits at a voltage between 0.9V (low output current) and 2.0V (high output current). The error amplifiers are current output (gm) types, so this voltage can be externally clamped for adjusting current limit. Likewise, a capacitor coupled external clamp will provide soft start. Switch duty cycle goes to zero if the VC pin is pulled to ground through a diode, placing the LT1070/LT1071 in an idle mode. Pulling the VC pin below 0.15V causes total regulator shutdown, with only 50 µA supply current for shutdown circuitry biasing. See AN19 for full application details. TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for the LT1071) R1* R2** 1070/71 TA16 D1 SETS IB(ON) SETS IB(OFF) * ** D2 C1 VSW VIN LT1070/LT1071 GND Q1 Driving High Voltage NPN Driving High Voltage FET (for Off-Line Applications, See AN25) 1070/71 TA03 10V TO 20V D1 VSW G D S Q1 VIN LT1070/LT1071 GND + |
Similar Part No. - LT1071 |
|
Similar Description - LT1071 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |