Datasheet MP8765 (Monolithic Power Systems) - 9

MP8765 ─ 24V, HIGH CURRENT SYNCHRONOUS STEP-DOWN CONVERTER PIN FUNCTIONS PIN # Name Description
Supply Voltage. The IN pin supplies power for internal MOSFET and regulator. The MP8765 operate from a +5V to +22V input rail. An input capacitor is needed to 1 VIN decouple the input rail. Use wide PCB traces and multiple vias to make the connection. 2 PGND Power Ground. Use wide PCB traces and multiple vias to make the connection Power good output, the output of this pin is an open drain signal and is high if the output voltage is higher than 95% of the nominal voltage. There is a delay from FB ≥ 95% to PGOOD goes high. 4 PG Note: If PG is pulled up to an external voltage, PG will not de-assert (Logic low) if EN is low or if input power is off. It is recommended that PG is pulled up to VCC pin and in this case PG will de-assert (Logic low) when EN is Low or if input power is off. Refer to Applications section for additional details. 3, 5 NC PFM/PWM mode selection pin. Float MODE pin or pull it higher than 2V, MP8765 6 MODE always works in force PWM mode; Connecting MODE pin to ground enables PFM mode at light load condition. VOUT pin is used to sense the output voltage of the Buck regulator, connect this pin 7 VOUT to the output capacitor of the regulator directly. Switch Output. Connect this pin to the inductor and bootstrap capacitor. This pin is driven up to the VIN voltage by the high-side switch during the on-time of the PWM 8,9 duty cycle. The inductor current drives the SW pin negative during the off-time. The Exposed SW on-resistance of the low-side switch and the internal diode fixes the negative Pad 15, 16 voltage. Use wide and short PCB traces to make the connection. Try to minimize the area of the SW pattern. Bootstrap. A capacitor connected between SW and BS pins is required to form a 10 BST floating supply across the high-side switch driver. Internal 5V LDO output. The driver and control circuits are powered from this voltage. Decouple with a minimum 1µF ceramic capacitor as close to the pin as 11 VCC possible. X7R or X5R grade dielectric ceramic capacitors are recommended for their stable temperature characteristics. Feedback. An external resistor divider from the output to GND, tapped to the FB pin, 12 FB sets the output voltage. It is recommended to place the resistor divider as close to FB pin as possible. Vias should be avoided on the FB traces. Enable pin. EN is a digital input that turns the regulator on or off. Drive EN high to 13 EN turn on the regulator, drive it low to turn it off. Connect EN with VIN through a pull-up resistor or a resistive voltage divider for automatic startup. Do not float this pin. Analog ground. The internal reference is referred to AGND. Connect the GND of the 14 AGND FB divider resistor to AGND for better load regulation. MP8765 Rev. 1.1 www.MonolithicPower.com
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