LT3758 datasheet(12/28 Pages) AD

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LT8392

Rev. 0

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OPERATION

(1) Peak-Buck in Buck Region (VIN >> VOUT)

When VIN is much higher than VOUT, the LT8392 uses

peak-buck current mode control in buck region (Figure 4).

Switch C is always off and switch D is always on. At the

beginning of every cycle, switch A is turned on and the

inductor current ramps up. When the inductor current

hits the peak buck current threshold commanded by VC

voltage at buck current comparator A3 during (A+D)

phase, switch A is turned off and switch B is turned on

for the rest of the cycle. Switches A and B will alternate,

behaving like a typical synchronous buck regulator.

Figure 4. Peak-Buck in Buck Region (VIN >> VOUT)

Figure 5. Peak-Buck in Buck-Boost Region (VIN ~> VOUT)

100% OFF

100% ON

A+D

B+D

8392 F04

(2) Peak-Buck in Buck-Boost Region (VIN ~> VOUT)

When VIN is slightly higher than VOUT, the LT8392 uses

peak-buck current mode control in buck-boost region

(Figure 5). Switch C is always turned on for the begin-

ning 15% cycle and switch D is always turned on for the

remaining 85% cycle. At the beginning of every cycle,

switches A and C are turned on and the inductor current

ramps up. After 15% cycle, switch C is turned off and

switch D is turned on, and the inductor keeps ramping

up. When the inductor current hits the peak buck current

threshold commanded by VC voltage at buck current com-

parator A3 during (A+D) phase, switch A is turned off and

switch B is turned on for the rest of the cycle.

15%

85%

15%

A+D

A+C

B+D

A+D

A+C

B+D

8392 F05

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