Characteristics and application of low dropout linear regulator

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MAX6469-MAX6484

The MAX6469 to MAX6484 series are low-dropout linear regulators that differ in function from model to model.

Main features: There is internal setting output voltage, the output voltage is 1.5~3.3V (there is a model corresponding to 0.1V every phase), and the output voltage is also set by the user; the input voltage is 2.5~5. .5v; output noise voltage is low, typically 7 5μ VRMs (MAx6477-MAx6484); within the operating temperature range, the output voltage accuracy is within ±2%; the output current is guaranteed to reach 300mA; the differential voltage is low, and the output current is At 300mA, the voltage difference Voo is 114mV (typ.); the operating current is 83μA, and the power consumption is 0.1μA in the off state; there is input reverse current protection, overheating and output short circuit protection; there is a reset signal output connected to the microprocessor. There are four different timeout periods; the RESET signal has push-pull output and open-drain output; there are manual reset function (with MR terminal) with remote control feedback; 6-pin SOT23-6 package, 8 tubes Foot TDFN package and 6-bump GBA package; operating temperature range -40- +85 °C.

Applications: Handheld instruments, PCMCA cards and USB devices, cellular and cordless phones, notebook computers, digital cameras, Bluetooth components and wireless LANs.

Application of electric foot: different models have different functions, the last two digits of the model are 69/70/7 l/72 and 77\78/79/80 with SET terminal, the output voltage can be set; the last two digits of the model is 75 /76/83/84 is a fixed voltage output, but has a current expansion function, which can be extended by an external NPN transistor; the last two digits of the model are 71/72/73/74 and 79/80/8 1/82. On the other hand, manual reset can be realized; all models have RESET; except for the last two digits of the model, 71/72/79/80, there are SHDN terminals, which can realize the shutdown control (active low). The user can follow the circuit. Ask to choose a model.

The adjustable output circuit is shown above. Vout=Vref(1+R1/R2), Vrel=1.23V. Generally, R2 is set to 51kΩ, and R1 can be obtained from the required Vout. The (MR) terminal in the above figure is the manual reset terminal. The expandable circuit is shown below.

It can output 1A current after expansion (this function is available in 75/76/83/84 models). To meet the μP requirement of 3.3V working voltage, the fixed output should be selected with a model suffix of 33 (output 3.3V). In the figure, RPUILL uP is the reset pull-up resistor.

The output current Iout(TOTAL)=Iout×(B+1)≈lout×β after the expansion is performed, where β is the amplification factor of the current-expanding transistor, and the maximum Iout=300 mA.