Part Number: AP3445LW6-7

Manufacturer: Diodes Incorporated

Description: Switching Voltage Regulators DCDC Conv LV Buck

Shipped from: Shenzhen/HK Warehouse

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AP3445LW6-7 Description

Both the AP3445 and the AP3445L are step-down DC-DC converters with a capacity of 2 A. The constant-frequency PWM control maintains great stability and transient response even when subjected to a heavy load. There is no necessity for any external compensating components. A single Li+/Li-polymer cell, numerous Alkaline/NiMH cells, and other standard power sources can all be used with the AP3445/L because it supports a range of input voltages from 2.7V to 5.5V. This makes it possible to use several conventional power sources. The output voltage can be adjusted from 0.6V up to the input voltage. The AP3445/L has an internal power switch and synchronous rectifier, which helps to reduce the number of external parts while simultaneously achieving a high-efficiency level.

During the shutdown process, the input is cut off from the output, and the current draw is less than 1 microampere. Other important characteristics include protection against overheating and short circuits and a lockout for low voltage that stops the battery from discharging. The AP3445/L has a maximum output current of 2 A while drawing just 55 A of quiescent current when it is not connected to a load. The AP3445/L is an excellent option for high output voltage. These high current applications call for a low dropout threshold because of their integrated MOSFETs with ultra-low RDS(ON) and their ability to operate at 100% duty cycle. The pulse skip mode helps keep the system’s efficiency high even under light loads. Package options for the AP3445/L include the SOT26 (SC74R) option.

AP3445LW6-7 Features

  • Voltage Range: 2.7 to 5.5 volts.
  • Voltage: 0.6V to VIN 0.6V as the output Precision of 1.5% for Reference Voltage.
  • 55µA (Typ) (Typ) Quiescent Current Without Load
  • 1 A is the shutdown current.
  • Duty cycle operation at 100%.
  • The switching frequency of 1 MHz.
  • No External Payment Is Necessary.
  • Thermostatic shutdown
  • Package SOT26 (SC74R).
  • Completely Lead-Free & Compliant with RoHS (Notes 1 & 2).
  • Free of halogens and antimony. “Green” Appliance (Note 3).

Applications information

The current mode-regulated synchronous buck regulator with built-in power MOSFETs is the AP3445/L. Current mode control and a large loop bandwidth that makes it possible to respond to load transients quickly ensure excellent line regulation and load regulation. Please refer to the functional block diagram and application schematic of the AP3445/typical L for further details.

The high-side P-FETs inside the buck controller are powered by it. Even if the DC power source is not regulated, the buck regulator can still function, like a battery, if the voltage is between 2.7 and 5.5 volts. Any voltage between 0.6V and VIN can be used to regulate the converter’s output voltage. To account for the feedback loop, internal changes are made.

● Under Voltage Lockout (UVLO) Circuit

When the VIN falls to a level lower than the threshold of the UVLO detector, the UVLO circuit begins to operate, VREF is stopped, and both the high-side switch and the low-side switch built-in switch transistors become “OFF.” As a direct consequence of this, VOUT decreases in proportion to the load as well as the capacitance value of COUT. When the VIN increases at a higher rate than the voltage that the UVLO has released, the IC will restart the procedure.

● Short Circuit Protection and Recovery

When the VIN falls below the UVLO detection threshold, the UVLO circuit starts to run, VREF stops, and the built-in switch transistors for the high-side switch and the low-side switch flip “OFF.” Consequently, the value of VOUT will drop in inverse proportion to the capacitance value of COUT. The IC will restart the process when the VIN voltage rises higher than the UVLO released voltage.

● Over Voltage Protection (AP3445L only)

The AP3445L incorporates internal output OVP circuits. If VOUT stays at or above 120% of the permitted threshold for more than 40 ms, the power will be cut off. The AP3445L will remain in the latch-off condition until the VIN or Enable voltage is regenerated, at which point it will restart normally.

● Over Temperature Protection

If the maximum junction temperature is exceeded, the thermal temperature safety circuitry built into the integrated circuit will keep it safe and prevent it from malfunctioning. If the junction temperature rises above +150 degrees Celsius, the MOSFET switching power supply and the internal control circuit will become inoperable. When the junction temperature drops to +130 degrees Celsius, the AP3445/L will automatically restart itself thanks to the soft start circuit, which will keep an eye on the situation.

● Setting the Output Voltage

Selecting R1 and R2 will allow you to program the appropriate output voltage. The choice of resistor R1 is made based on a design tradeoff between the circuit’s efficiency and the output voltage’s precision. When R1 is set to high values, the current consumed in the feedback network is reduced. The precision of the output voltage, however, suffers as a result of the bias current that is present in the error amplifier. The following table provides a selection of resistors for common output voltages. An optional capacitor with a value ranging from 10pF to 470pF improves stability and boosts the phase margin.

● Input Capacitor

The input capacitor dampens the switching noise produced by the unit and the surge current induced by the input supply. When the higher MOSFET is turned on, it is essential that the input capacitor can handle the ripple current produced by the device. As a consequence of this, it must have a low ESR to reduce the number of losses. The input capacitor’s root means square (RMS) current rating is an important characteristic that needs to be greater than the RMS input current.

Choose an input capacitor with an RMS rating greater than half the maximum load current as a good rule of thumb. When doing this, you may put the maximum strain on the capacitor without causing any damage to it. Because of the significant di/dt swings they will be subjected to, electrolytic or ceramic input capacitors are the better choice. If tantalum is going to be used, surge protection is an absolute must. In that case, there is a risk that the capacitor will explode. A ceramic capacitor rated at 22 Farads will serve the purpose of most applications.


The output capacitor limits voltage ripple, keeping the feedback loop stable, and lessens overshoot at the output. When it comes to the power supply’s responsiveness, the output capacitor is a fundamental component. In reality, it provides the load current during the initial microseconds of the load transient. The converter is intelligent enough to detect the load transient and ramp up the duty cycle, but the inductor value caps the current slope.

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