Electronic Components Datasheet Search |
|
LT1584CT-3.45 Datasheet(PDF) 9 Page - Linear Technology |
|
LT1584CT-3.45 Datasheet(HTML) 9 Page - Linear Technology |
9 / 12 page 9 LT1584/LT1585/LT1587 APPLICATIONS INFORMATION handle microsecond surge currents of 50A to 100A. Even with large value output capacitors it is difficult to obtain those values of surge currents in normal operation. Only with large values of output capacitance, such as 1000 µF to 5000 µF, and with the input pin instantaneously shorted to ground can damage occur. A crowbar circuit at the input of the LT1584/LT1585/LT1587 can generate those levels of current, and a diode from output to input is then recom- mended. This is shown in Figure 2. Usually, normal power supply cycling or system “hot plugging and unplugging” will not generate current large enough to do any damage. The adjust pin can be driven on a transient basis ±7V with respect to the output, without any device degradation. As with any IC regulator, exceeding the maximum input-to- output voltage differential causes the internal transistors to break down and none of the protection circuitry is then functional. maximum supply voltage. When power is first applied, the input voltage rises and the output voltage follows the input. The input-to-output voltage remains small and the regula- tor can supply large output currents. This action permits the regulator to start-up into very heavy loads. With higher input voltages, a problem can occur where the removal of an output short does not permit the output voltage to recover. This problem is not unique to the LT1584 devices and is present on the LT1083/LT1084/ LT1085 family and older generation linear regulators. The problem occurs with a heavy output load, a high input voltage, and a low output voltage. An example is immedi- ately after the removal of a short circuit. The load line of such a load may intersect the output current curve at two points. If this happens, two stable output operating points exist for the regulator. With this double intersection, the power supply may require cycling down to zero and back up again to make the output recover. This situation does not occur with the LT1585/LT1587 because no foldback circuitry is required to provide safe-area protection. Ripple Rejection The typical curve for ripple rejection reflects values for the LT1584/LT1585/LT1587 fixed output voltage parts be- tween 3.3V and 3.6V. In applications that require improved ripple rejection, use the adjustable devices. A bypass capacitor from the adjust pin to ground reduces the output ripple by the ratio of VOUT/1.25V. The impedance of the adjust pin capacitor at the ripple frequency should be less than the value of R1 (typically in the range of 100 Ω to 120 Ω) in the feedback divider network in Figure 2. There- fore, the value of the required adjust pin capacitor is a function of the input ripple frequency. For example, if R1 equals 100 Ω and the ripple frequency equals 120Hz, the adjust pin capacitor should be 22 µF. At 10kHz, only 0.22µF is needed. Output Voltage The LT1584/LT1585/LT1587 adjustable regulators develop a 1.25V reference voltage between the output pin and the adjust pin (see Figure 3). Placing a resistor R1 between these two terminals causes a constant current to flow through R1 and down through R2 to set the overall output voltage. Normally, this current is the specified minimum Overload Recovery The LT1584 devices have safe-area protection similar to the LT1083/LT1084/LT1085. The safe-area protection de- creases current limit as input-to-output voltage increases. This behavior keeps the power transistor inside a safe operating region for all values of input-to-output voltage. The LT1584 protection circuitry provides some output current at all values of input-to-output voltage up to the 7V Figure 2 LT1584-3.3 D1 1N4002 (OPTIONAL) GND VIN VOUT IN OUT C1 10 µF + C2 22 µF + LT1584 D1 1N4002 (OPTIONAL) ADJ VIN VOUT IN OUT LT1584 • F02 C1 10 µF + C2 22 µF R1 R2 + CADJ + |
Similar Part No. - LT1584CT-3.45 |
|
Similar Description - LT1584CT-3.45 |
|
|
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 |