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LT8390

8390fa

For more information www.linear.com/LT8390

OPERATION

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

When VIN is much higher than VOUT, the LT8390 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 cur-

rent 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

8390 F04

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

When VIN is slightly higher than VOUT, the LT8390 uses

peak-buck current mode control in buck-boost region

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

15%cycleandswitchDisalwaysturnedonfortheremain-

ing 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 comparator 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

8390 F05

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