AP3503E 340kHZ 3A SYNCHRONOUS DC-DC BUCK CONVERTER Description Pin Assignments The AP3503E is a 340kHz fixed frequency, current mode, PWM (Top View) synchronous buck (step-down) DC-DC converter, capable of driving a 3A load with high efficiency, excellent line and load regulation. The AP3503E exhibits high efficiency at light load. The device integrates BS 8 SS 1 N-channel power MOSFET switches with low on-resistance. Current mode control provides fast transient response and cycle-by-cycle EN IN 2 7 current limit. EP COMP SW 3 6 The AP3503E employs complete protection to ensure system 5 FB GND 4 security. Including output Over Voltage Protection, input Under Voltage Lock Out, programmable Soft Start, Over Temperature Protection and hiccup mode Short Circuit Protection. PSOP-8 This IC is available in PSOP-8 package. Applications Features LCD TV Set Top Box Input Voltage Range: 4.5V to 18V Portable DVD Fixed 340kHz Frequency Digital Photo Frame High Efficiency at Light Load High Efficiency: up to 95% Output Current: 3A Current Mode Control Built-In Over Current Protection Built-In Thermal Shutdown Function Built-In UVLO Function Built-In Over Voltage Protection Programmable Soft-Start Hiccup Mode SCP 1 of 11 AP3503E November 2018 Diodes Incorporated www.diodes.com Document number: DS41539 Rev. 2 - 2 AP3503E Typical Applications Circuit Input Voltage=12V R4 C11 C12 100k 10F/25V 10F/25V 1 8 BS SS C5 0.1F 2 7 IN EN C4 C6 Output Voltage=3.3V L 10H 10nF Optional 3 6 SW COMP C3 R3 3.3nF 13k 4 5 GND FB R2 10k C22 C21 22F/25V 22F/25V D1 R1 Optional 26.1k Pin Descriptions Pin Number Pin Name Function Bootstrap pin. A bootstrap capacitor is connected between the BS pin and SW pin. The voltage across 1 BS the bootstrap capacitor drives the internal high-side power MOSFET Supply power input pin. A capacitor should be connected between the IN pin and GND pin to keep the 2 IN input voltage constant 3 SW Power switch output pin. This pin is connected to the inductor and bootstrap capacitor 4 GND Ground pin Feedback pin. This pin is connected to an external resistor divider to program the system output 5 FB voltage. When the FB pin voltage exceeds 1.1V, the over voltage protection is triggered. When the FB pin voltage is below 0.3V, the oscillator frequency is lowered to realize short circuit protection Compensation pin. This pin is the output of the transconductance error amplifier and the input to the 6 COMP current comparator. It is used to compensate the control loop. Connect a series RC network from this pin to GND. In some cases, an additional capacitor from this pin to GND pin is required Control input pin. EN is a digital input that turns the regulator on or off. Drive EN high/low to turn on/off 7 EN the regulator. Pull up with 100k resistor for automatic startup Soft-start control input pin. SS controls the soft-start period. Connect a capacitor from SS to GND to set 8 SS the soft-start period. A 0.1F capacitor sets the soft-start period to 15ms. To disable the soft-start feature, leave SS unconnected EP Exposed pad. It should be connected to GND in PCB layout 2 of 11 AP3503E November 2018 Diodes Incorporated www.diodes.com Document number: DS41539 Rev. 2 - 2 AP3503E