NOT RECOMMENDED FOR NEW DESIGN CONTACT US AP1538 18V 3A 300KHz BUCK CONVERTER Description Pin Assignments AP1538 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 AP1538 provides low-ripple power, high efficiency, and excellent 1 8 FB transient characteristics. The PWM control circuit is able to vary the duty ratio linearly from 0 up to 99%. This converter also contains an V ss 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 O C SET 3 6 O utput function and a short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced from 4 5 V CC 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, SOP-8L capacitors, and a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units ( To p V ie w ) for portable devices when coupled with the SOP-8L and SOP-8L-DEP mini-packages, providing such outstanding features as low current V ss 1 8 consumption. Since this converter can accommodate an input voltage FB up to 18V, it is also suitable for the operation via an AC adapter. 1 2 7 V ss EN Features 3 6 O utput O C SET 2 Input voltage : 3.6V to 18V 4 5 V CC (N ote 4 ) O utput Output voltage : 0.8V to V CC Output current : up to 3A Duty ratio: 0% to 99% PWM control SOP-8L-DEP (Dual Exposed Pads) Oscillation frequency: 300KHz typical Note: 4. Exposed pad 1 is connected to VSS and exposed pad 2 is connected to Output. The board layout for exposed pads needs to be considered Soft-start like, Current limit and Enable function to avoid short circuit. Thermal Shutdown function Built-in internal SW P-channel MOS Applications SOP-8L and SOP-8L-DEP: Available in Green Molding Compound (No Br, Sb) PC Motherboard Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) LCD Monitor Halogen and Antimony Free. Green Device (Note 3) Graphic Card For automotive applications requiring specific change control DVD-Video Player (i.e. parts qualified to AEC-Q100/101/200, PPAP capable, and Telecom Equipment manufactured in IATF 16949 certified facilities), please contact ADSL Modem us or your local Diodes representative. Printer and other Peripheral Equipment AP1538 Typical Application Circuit V = 5V/3A L1 OUT Vcc Output V IN 22uH R A Cc R C OCSET OCSET AP 1538 6.8K 3K Option Option* + + FB C OCSET C C IN OUT 0.1uF 470uF*** 470uF V EN SS - - R EN CVcc R B D1** 100K 1.3K 0.1uF C EN 0.1uF V V x ( R /R ) OUT FB 1+ A B = R = 0.7K~5K ohm B Notes: * Typical feedback compensation (Cc): 5600pF. ** SSuuggesggestteed d DDioIOdeDsE ISnc Porowpoerra tedSc Photowtkeyr P S/cNh: oBttk540 y P/sN: B540eries or PD series oS540r PDS5. 40 *** Suggested C for V < 1V 680uF. OUT OUT Pin Descriptions Pin Name Pin No. Description FB 1 Feedback pin Power-off pin H: Normal operation EN 2 (Step-down operation) L: Step-down operation stopped (All circuits deactivated) OCSET 3 Add an external resistor to set max output current V 4 IC power supply pin CC Switch Pin. Connect external inductor/diode here. Minimize trace area at this pin Output 5, 6 to reduce EMI 7, 8 GND Pin V SS 2 of 12 February 2020 AP1538 Diodes Incorporated www.diodes.com Document number: DS31451 Rev. 7 - 3