AP65454 4A, 18V, 650kHz ADAPTIVE COT STEP-DOWN CONVERTER Description Pin Assignments The AP65454 is an adaptive constant on-time mode synchronous ( Top View ) buck converter providing high efficiency, excellent transient response and high DC output accuracy for low-voltage regulation in digital TVs EN 1 8 VIN and monitors. BS 2 7 FB The constant-on-time control scheme handles wide input/output voltage ratios and provides low external component count. The VREG5 3 6 SW internal proprietary circuit enables the device to adopt both low equivalent series resistance (ESR) output capacitors, such as SS 4 5 GND SP-CAP or POSCAP as well as ultra-low ESR ceramic capacitors. SO-8EP The AP65454 also features programmable soft-start, UVLO, OTP and OCP to protect the circuit. This IC is available in SO-8EP package. AP65454 operates in continuous conduction mode (CCM) in light-load conditions for better EMI performance. AP65453 and AP65455 are the options for light-load efficiency enhancement. Features Applications Fixed Frequency Emulated Constant On-Time Control Gaming Consoles Flat Screen TV Sets and Monitors Good Stability Independent of the Output Capacitor ESR Set-Top Boxes Fast Load Transient Response Distributed Power Systems Synchronous Rectification: 90m Internal High-Side Switch and Home Audio 57m Internal Low-Side Switch Consumer Electronics Wide Input Voltage Range: 4.5V to 18V Network Systems FPGA, DSP and ASIC Supplies Output Voltage Range: 0.76V to 6V Green Electronics 4A Continuous Output Current 650kHz Switching Frequency Built-in Overcurrent Limit Built-in Thermal Shutdown Protection Programmable Soft-Start Pre-Biased Start-Up Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. Green Device (Note 3) Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. 2. See AP65454 Typical Applications Circuit INPUT 7 V 8 IN BST L1 IN C5 12V OUTPUT 1.5 H 6 0.1F V OUT ON SW 1 AP65454 1.05V EN OFF R1 2 8.25k C2 C1 FB R2 44F 20 F 3 4 22.1k VREG5 C4 SS 5 C3 GND 8.2nF 1F Figure 1. Typical Application Circuit Pin Descriptions Pin Number Function Pin Name SO-8EP Enable input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low EN 1 to turn off. It can be safely connected to VIN directly for automatic startup. Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage divider connected FB 2 to it from the output voltage. Internal power supply output pin to connect an additional capacitor. Connect a 1F (typical) capacitor as close as VREG5 3 possible to the VREG5 and GND. This pin is not active when EN is low. Soft-start control input pin. SS controls the soft start period. Connect a capacitor from SS to GND to set the soft-start SS 4 period. GND 5 Ground pin is the main power ground for the switching circuit. Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter SW 6 from SW to the output load. Note that a capacitor is required from SW to BS to power the high-side switch. Bootstrap pin. A bootstrap capacitor is connected between the BS pin and SW pin. The voltage across the bootstrap BS 7 capacitor drives the internal high-side NMOS switch. A 0.1F (typical) capacitor is required for proper operation Supply input pin. A capacitor should be connected between the VIN pin and GND pin to keep the DC input voltage VIN 8 constant. EP 9 Connect the exposed thermal pad to GND on the PCB. 2 of 13 AP65454 December 2015 Diodes Incorporated www.diodes.com Document number: DS38483 Rev. 1 - 2