ADP1612/ADP1612 Step-Up Switching Regulator (Boost Converter)

 The ADP1612 is a step-up DC-to-DC switching regulator (also called a boost converter) manufactured by Analog Devices. It is designed to convert a lower input voltage to a higher output voltage efficiently. 

A typical step-up (boost) regulator configuration using the ADP1612 or ADP1613 is shown in figure below. 

Both ICs are nearly identical, with the primary difference being their switching frequency, which affects their pulse-width modulation (PWM) performance.

These regulators use PWM control and can achieve efficiencies of up to 94%, depending on the output voltage and load current, as illustrated in the figure below.

Generally, as the load current increases, the efficiency improves, while changes in output voltage have a smaller effect.

The operating frequency is selectable via pin 7 (FREQ):

• 650 kHz: For better efficiency and when larger external components are acceptable. Achieved by grounding pin 7 or leaving it floating.

• 1.3 MHz: For smaller external components, at the cost of slightly lower efficiency. Set by connecting pin 7 to VIN (pin 6).

The regulator accepts an input voltage range of 1.8 V to 5.5 V and can boost the output voltage up to 20 V.

To ensure reliable operation, the device includes:

• Thermal shutdown (TSD) protection, which disables the regulator above 150°C and re-enables it at 130°C.

• Under-voltage lockout (UVLO), which disables the output when the input voltage falls below the safe operating threshold.

Additional pins and components:

• Pin 8 (SS – Soft Start): Connect a capacitor to limit inrush current during power-up.

• Pin 3 (EN – Enable): Used to turn the regulator on or off.

• Pin 1 (COMP): Requires a series RC network for loop compensation.

• Pin 2 (FB – Feedback): Connects to a resistor voltage divider to regulate the output voltage.

• Pin 5 (SW – Switch Output): Connect an inductor between VIN and SW, and a Schottky diode from SW to VOUT for fast switching performance.

This design makes the ADP1612/1613 an efficient and flexible solution for applications that require converting a low supply voltage to a higher one.

Here's a detailed overview of its features and applications:

🔧 Key Features:

• Type: Step-Up (Boost) Switching Regulator

• Input Voltage Range: 1.8 V to 5.5 V

• Output Voltage Range: Up to 20 V

• Switching Frequency: 650 kHz (fixed)

• Maximum Output Current: Typically up to 1.3 A (depends on Vin, Vout)

• Internal Power Switch: Integrated 1.6 A, 0.13 Ω N-channel MOSFET

• Soft-Start Function: Limits inrush current at power-up

• Enable Pin: Allows on/off control

• Current-Mode PWM Control: For fast transient response and good stability

• Compact Package: Available in 8-lead MSOP and 3 mm × 3 mm LFCSP

⚙️ Typical Applications:

• TFT LCD Bias Supplies

• OLED Displays

• Industrial and Medical Instruments

• Portable and Battery-Powered Devices

• Low-Voltage Microcontroller or Sensor Systems needing a higher voltage

🧰 Basic Application Circuit:

In a basic configuration, you connect:

• Input: 1.8V to 5.5V (from batteries or low-voltage rails)

• Inductor: Between the input and switch pin

• Diode: Schottky diode for fast switching

• Output Capacitor: To filter output

• Feedback Divider: To set the output voltage using a resistor divider to the FB pin

🧮 Output Voltage Equation:

To set the output voltage, use:

$$V_{\text{OUT}}=V_{\text{REF}}(1+\frac{R1}{R2})$$

• Where $V_{\text{REF}}$ ≈ 1.23 V

• $R1$ and $R2$ are the resistors in the feedback voltage divider

🔋 Example Use Case:

If you have a 3.3 V supply (like from a Li-ion battery) and you need 12 V for an op-amp or LCD backlight, the ADP1612 can step up that voltage with good efficiency.

An alternative to this is the MT3608 boost converter.