AP65455 4A, 18V, 650kHz ADAPTIVE COT STEP-DOWN CONVERTER Description Pin Assignments The AP65455 is an adaptive constant on-time mode synchronous buck converter providing high efficiency, excellent transient response and high DC output accuracy for low-voltage regulation in digital TV ( Top View ) and monitor. 1 10 The constant-on-time control scheme handles wide input/output EN VIN voltage ratios and provides low external component count. The FB 2 9 internal proprietary circuit enables the device to adopt both low VIN Exposed equivalent series resistance (ESR) output capacitors, such as 3 Pad 8 BST SP-CAP or POSCAP and ultra-low ESR ceramic capacitors. VREG5 4 7 SW SS The adaptive on-time control supports seamless transition between 11 continuous conduction mode (CCM) at higher load conditions and PGND 5 6 SW PG discontinuous conduction mode (DCM) at lighter load conditions. DCM allows AP65455 to maintain high efficiency at light load U-DFN3030-10 conditions. The AP65455 also features power good, programmable soft-start, UVLO, OTP, OVP and OCP to protect the circuit. This IC is available in U-DFN3030-10 package. Applications Features Gaming Consoles Fixed Frequency Emulated Constant On-Time Control Flat Screen TV Sets and Monitors Good Stability Independent of the Output Capacitor ESR Set-Top Boxes Fast Load Transient Response Home Audio Synchronous Rectification: 90m Internal High-side Switch and Consumer Electronics 57m Internal Low-Side Switch Network Systems Wide Input Voltage Range: 4.5V to 18V Green Electronics Output Voltage Range: 0.76V to 6V Power Good Indicator 4A Continuous Output Current 650kHz Switching Frequency Built-In Over-Current Limit Built-In Over-Voltage Protection 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 AP65455 Typical Applications Circuit INPUT V IN BST VIN C1 12V L1 OUTPUT 0.1F 1.5 H ON V SW OUT OFF EN AP65455 1.05V R1 PGOOD PG 8.25k R2 C3 FB C2 100k 44F R3 20 F VREG5 22.1k VREG5 SS C5 PGND C4 1F 8.2nF Figure 1 Typical Application Circuit Pin Descriptions Package Pin Function Name U-DFN3030-10 Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the EN 1 regulator, drive it low to turn off. EN 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 FB 2 divider connected to it from the output voltage. Internal power supply output pin to connect an additional capacitor. Connect a 1F (typical) VREG5 3 capacitor as close as possible to the VREG5 and PGND. 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 SS 4 PGND to set the soft-start period. Power Switching Output. SW is the switching node that supplies power to the output. Connect SW 6,7 the output LC filter from SW to the output load. Note that a capacitor is required from SW to BST to power the high-side switch. Bootstrap pin. A bootstrap capacitor is connected between the BST pin and SW pin. The voltage BST 8 across the bootstrap capacitor drives the internal high-side NMOS switch. A 0.1F (typical) capacitor is required for proper operation. Supply Input. A capacitor should be connected between the VIN pin and PGND pin to keep the VIN 9,10 DC input voltage constant. PG 5 Open drain power good output. Power ground and PGND. Exposed pad must be connected to PGND plane as large as possible PGND 11 (Exposed Pad) for maximum thermal performance. 2 of 15 AP65455 May 2017 Diodes Incorporated www.diodes.com Document number: DS37935 Rev. 2 - 2