OFF

ON

ON

OFF

+

- +-

PWM

NMOS

PMOS

GND

+

-

LM4510

SNVS533C – SEPTEMBER 2007 – REVISED MAY 2013

www.ti.com

OPERATION IN SYNCHRONOUS CONTINUOUS CONDUCTION MODE (CYCLE 1, CYCLE 2)

Figure 24. Schematic of Synchronous Boost Converter

Synchronous boost converter is shown in Figure 24. At the start of each cycle, the oscillator sets the driver logic

and turns on the NMOS power device and turns off the PMOS power device.

Cycle 1 Description

Refer to Figure 25. NMOS switch turn-on

→ Inductor current increases and flows to GND.

PMOS switch turn-off

→ Isolate VOUT from SW → Output capacitor supplies load current.

Figure 25. Equivalent Circuit During Cycle 1

When the sum of the ramp compensation and the sensed NMOS current reaches a level determined by the

EAMP output voltage, the PWM COMP resets the logic, turning off the NMOS power device and turning on the

PMOS power device.

Cycle 2 Description

Refer to Figure 26. NMOS Switch turn-off

→ PMOS Switch turn-on→ Inductor current decreases and flows

through PMOS

→ Inductor current recharges output capacitor and supplies load current.

Figure 26. Equivalent Circuit During Cycle 2

After the switching period the oscillator then sets the driver logic again repeating the process.

10

Submit Documentation Feedback

Copyright © 2007–2013, Texas Instruments Incorporated

Product Folder Links: LM4510