NOT RECOMMENDED FOR NEW DESIGN CONTACT US AP1539 18V 4A 300KHz BUCK CONVERTER Description Pin Assignments AP1539 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, ( To p V ie w ) error amplifier, internal PMOS. V ss 1 8 AP1539 provides low-ripple power, high efficiency, and excellent FB transient characteristics. The PWM control circuit is able to vary the 1 V ss duty ratio linearly from 0 up to 99%. This converter also contains an 2 7 EN error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. An enable function, an over current protect 3 6 O utput O C SET function and a short circuit protect function are built inside, and when 2 OCP or SCP happens, the operation frequency will be reduced from V CC 4 5 (N ote 4 ) O utput 300KHz to 50KHz. Also, an internal compensation block is built in to minimum external component count. With the addition of an internal P- channel Power MOS, a coil, capacitors, and a diode connected SOP-8L-DEP (Dual Exposed Pads) externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units for portable devices when Note: 4. Exposed pad 1 is connected to V and exposed pad 2 is connected to SS coupled with the SOP-8L-DEP mini-package, providing such Output. The board layout for exposed pads needs to be considered to outstanding features as low current consumption. Since this converter avoid short circuit. can accommodate an input voltage up to 18V, it is also suitable for the operation via an AC adapter. Applications PC Motherboard Features LCD Monitor Input voltage: 3.6V to 18V Graphic Card Output voltage: 0.8V to V CC DVD-Video Player Output current: up to 4A Telecom Equipment Duty ratio: 0% to 99% PWM control ADSL Modem Oscillation frequency: 300KHz typ. Printer and other Peripheral Equipment Soft-start like, Current limit and Enable function Microprocessor core supply Thermal Shutdown function Built-in internal SW P-channel MOS SOP-8L-DEP: Available in Green Molding Compound (No Br, Sb) Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. Green Device (Note 3) For automotive applications requiring specific change control (i.e. parts qualified to AEC-Q100/101/200, PPAP capable, and manufactured in IATF 16949 certified facilities), please contact us or your local Diodes representative. AP1539 Typical Application Circuit V = 5V/4A L1 OUT V Vcc Output IN 22uH R Cc A R C OCSET OCSET AP 1539 6.8K 3.9K Option Option* + + FB C OCSET C C IN OUT 0.1uF 470uF V 470uF*** EN SS - - R EN R CVcc B D1** 100K 1.3K 0.1uF C EN 0.1uF V V x ( R /R ) OUT FB 1+ A B = = 0.7K~5K ohm R B Notes: * Typical feedback compensation (Cc): 5600pF. ** Suggested DIODES Power Schottky P/N: B540 series or PDS540. Suggested Diodes Incorporated Power Schottky P/N: B540 series or PDS540. *** Suggested C for V < 1V 680uF. OUT OUT Pin Descriptions Pin Name Pin No. Description FB 1 Feedback pin Power-off pin EN 2 H: Normal operation (Step-down operation) L: Step-down operation stopped (All circuits deactivated) OCSET 3 Add an external resistor to set max output current 4 IC power supply pin V CC Switch Pin. Connect external inductor/diode here. Minimize trace area at this pin to Output 5, 6 reduce EMI V 7, 8 GND Pin SS 2 of 12 February 2020 AP1539 Diodes Incorporated www.diodes.com Document number: DS31477 Rev. 6 - 3