Datasheet

OFF
ON
ON
OFF
+
-
+
-
PWM
NMOS
PMOS
V
OUT
GND
V
SW1
+
-
C
OUT
R
LOAD
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
During operation, EAMP output voltage (V
COMP
) increases for larger loads and decreases for smaller loads.
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.
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