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LT8390

8390fa

For more information www.linear.com/LT8390

(3) Peak-Boost in Buck-Boost Region (VIN <~ VOUT)

WhenVINisslightlylowerthanVOUT,theLT8390usespeak-

boost current mode control in buck-boost region (Figure

6). Switch A is always turned on for the beginning 85%

cycle and switch B is always turned on for the remaining

15% cycle. At the beginning of every cycle, switches A and

C are turned on and the inductor current ramps up. When

the inductor current hits the peak boost current threshold

commanded by VC voltage at boost current comparator

A4 during (A+C) phase, switch C is turned off and switch

D is turned on for the rest of the cycle. After 85% cycle,

switch A is turned off and switch B is turned on for the

rest of the cycle.

OPERATION

Figure 6. Peak-Boost in Buck-Boost Region (VIN <~ VOUT)

Figure 7. Peak-Boost in Boost Region (VIN << VOUT)

15%

85%

15%

A+D

A+C

B+D

A+D

A+C

B+D

8390 F06

(4) Peak-Boost in Boost Region (VIN << VOUT)

When VIN is much lower than VOUT, the LT8390 uses

peak-boost current mode control in boost region (Figure

7). Switch A is always on and switch B is always off. At

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

the inductor current ramps up. When the inductor cur-

rent hits the peak boost current threshold commanded by

VC voltage at boost current comparator A4 during (A+C)

phase, switch C is turned off and switch D is turned on

for the rest of the cycle. Switches C and D will alternate,

behaving like a typical synchronous boost regulator.

100% ON

100% OFF

A+D

A+C

A+D

A+C

8390 F07

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