Datasheet MP2307 (Monolithic Power Systems) - 6

MP2307 – 3A, 23V, 340KHz SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER OPERATION FUNCTIONAL DESCRIPTION
The converter uses internal N-Channel The MP2307 regulates input voltages from MOSFET switches to step-down the input 4.75V to 23V down to an output voltage as low voltage to the regulated output voltage. Since as 0.925V, and supplies up to 3A of load the high side MOSFET requires a gate voltage current. greater than the input voltage, a boost capacitor connected between SW and BS is needed to The MP2307 uses current-mode control to drive the high side gate. The boost capacitor is regulate the output voltage. The output voltage charged from the internal 5V rail when SW is low. is measured at FB through a resistive voltage divider and amplified through the internal When the FB pin voltage exceeds 20% of the transconductance error amplifier. The voltage at nominal regulation value of 0.925V, the over the COMP pin is compared to the switch current voltage comparator is tripped and the COMP (measured internally) to control the output pin and the SS pin are discharged to GND, voltage. forcing the high-side switch off. + CURRENT OVP 2 IN SENSE AMPLIFIER 1.1V -- + RAMP 5V OSCILLATOR FB 5 + -- CLK 110/340KHz 1 BS 0.3V -- -- S Q MP2393 -- R Q 3 SW SS 8 + + CURRENT ERROR COMPARATOR 0.925V + AMPLIFIER O COMP 6 4 GND EN 7 -- EN OK 1.2V OVP RECOMMENDED FOR LOCKOUT IN < 4.10V 2.5V + COMPARATOR NEW DESIGNSIN 7V + Zener INTERNAL REGULATORS 1.5V -- SHUTDOWN MP2307_BD01 COMPARATOR NOT
Figure 1—Functional Block Diagram
REFER T MP2307 Rev. 1.9 www.MonolithicPower.com
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5/28/2008 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2008 MPS. All Rights Reserved.