DIODES AP63205 EVB User Guide

1. General Description

The AP63205 is a 2A, synchronous buck converter with up to 32V wide input voltage range, which fully integrates a 140mΩ high-side MOSFET and a 70mΩ low-side MOSFET to provide high efficiency step-down DC/DC conversion. The AP63205 adopts peak current mode control with the integrated compensation network, which makes AP63205 easily to be used by minimizing the off-chip component count. The AP63205 supports the Pulse Skipping Modulation (PSM) with typical 22µA Ultra-low Quiescent and achieved high efficient performance at light load conditions.

The AP63205 is fixed output buck converters with optimized design for Electromagnetic Interference (EMI) reduction. The AP63205 features Frequency Spread Spectrum (FSS) with ±6% jittering span of the 1.1MHz switching frequency and modulation rate 1/512 of switching frequency to reduce the conducted EMI. The converter has proprietary designed gate driver scheme to resist switching node ringing without sacrificing MOSFET turn on and turn off time, which further erases high frequency radiation EMI noise caused by the MOSFETs hard switching.

The AP63205 offers output overvoltage protection, cycle-by-cycle peak current limit, and thermal shutdown protection. The device is available in a low-profile TSOT23-6 package.

2. Key Features

• EMI Reduction with Switching Node Ringing-free
• 3.8V-32V Wide Input Voltage Range
• Up to 2A Continuous Output Load Current
• Shutdown Current: <1 µA
• 1.1MHz Switching Frequency with 6% Frequency Spread Spectrum (FSS)
• Precision Enable Threshold for Programmable UVLO Threshold and Hysteresis
• Low Dropout Mode Operation
• No External Compensation Required
• Current Limit Protection
• Short Circuit Protection
• Over Output Voltage Protection
• Thermal Shutdown

3. Function Block

The function block diagram illustrates the internal architecture of the AP63205. Key functional blocks include an internal reference voltage (0.4V, 0.8V, 1.1V), an error amplifier with compensation (Internal SS, COMP), an oscillator operating at 1MHz, a PWM comparator, and logic circuitry. These blocks manage the switching operation based on feedback (FB) and enable (EN) signals, controlling high-side (HS) and low-side (LS) MOSFETs. Voltage regulation (VCC Regulator), overvoltage protection (OVP), and undervoltage protection (UVP) are also depicted.

4. AP63205 EV Board Schematic

The AP63205 EV Board Schematic shows the external components connected to the AP63205 integrated circuit. The IC's pins (VIN, EN, FB, LX, BST, SW, GND) are connected to passive components. Input voltage (VIN) is filtered by input capacitors (C1-C3). The EN pin is controlled via a switch (J1) and resistor (R1). The FB pin is connected to the output voltage through a voltage divider (R2, R4) and also to the feedback capacitor (C4). The LX pin is connected to the switching node, which is also the connection point for the bootstrap capacitor (C5) and the output inductor (L1). The SW pin is the connection for the low-side MOSFET. Output capacitors (C6-C8) filter the output voltage (VOUT).

5. AP63205 EV Board Description

The EV board is a suitable evaluation board for the AP63205, a DC/DC converter. The board is targeted to be used in providing a simple and convenient evaluation environment for the AP63205. It requires parts and power supply connectors etc. on the board, which makes it easy to be evaluated.

6. AP63205 EV Board View

The image displays the AP63205 Evaluation Board. Key components are visible and labeled: the AP63205 IC, input capacitors (C1, C2, C3), output capacitors (C6, C7, C8), inductor (L1), resistors (R1, R2, R3, R4), and bootstrap capacitor (C5). Terminal points for VIN, GND, and VOUT are clearly marked, along with the EN pin connection.

7. Setting the Output Voltage of AP63205

The AP63205 is a fixed output buck converter; the output voltage is 5V. Connect the VFB pin to the output directly as shown in the schematic.

8. External Components Selection

1) Input & output Capacitors (Cin, Cout)

• For lower output ripple, low ESR is required.
• Low leakage current needed; X5R/X7R ceramic is recommended, using multiple capacitor parallel connection.
• The Cin and Cout capacitances should be greater than 10µF and 44µF respectively. 66µF output capacitance is recommended.

2) Bootstrap Voltage Regulator

• An external 0.1µF ceramic capacitor is required as a bootstrap capacitor between the BST and SW pins to work as a high-side power MOSFET gate driver.

3) Inductor (L)

• Low DCR for good efficiency.
• Inductance saturation current must be higher than the output current.
• The recommended inductance is 4.7µH.

9. EV Board BOM List for AP63205

10. Test Waveforms and Efficiency

Test Waveforms

The test waveform image captures the operational characteristics of the AP63205 EVB under specific test conditions (Vin=12V, Vo=5.0V, Io=2.0A). The oscilloscope display shows three traces:

• Blue Trace: Represents the AC-coupled output voltage (Vout-AC), showing minimal ripple.
• Yellow Trace: Represents the switching node voltage (Vsw), illustrating the switching transitions.
• Green Trace: Represents the inductor current (IL), showing its current waveform.

Efficiency Graph

The efficiency graph plots the conversion efficiency of the AP63205 as a function of output current. The test condition is Vin=12V and Vo=5V. The graph shows that the efficiency is high across a wide range of output currents, starting from approximately 70% at 10mA and increasing to around 95% at 100mA, and maintaining this high efficiency up to 1A and beyond.