LT8350RVPBF datasheet(12/24 Pages) AD

12 / 24 page

LT8350

Rev. 0

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OPERATION

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

When VIN is slightly higher than VOUT, the LT8350 uses

peak-buck current mode control in buck-boost region

(Figure 5). In each switching cycle, switch C is turned on

for the beginning 20% cycle and switch D is turned on

for the remaining 80% cycle. At the beginning of every

cycle, switches A and C are turned on and the inductor

current ramps up. After 20% 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 cur-

rent threshold commanded by VC voltage at buck current

comparator A1 during (A+D) phase, switch A is turned off

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

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

When VIN is slightly lower than VOUT, the LT8350 uses

peak-boost current mode control in buck-boost region

(Figure 6). In each switching cycle, switch A is turned on

for the beginning 80% cycle and switch B is turned on for

the remaining 20% cycle. At the beginning of every cycle,

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

When VIN is much higher than VOUT, the LT8350 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 volt-

age at buck current comparator A1 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.

100% OFF

100% ON

A + D

B + D

A + D

B + D

8350 F04

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

20%

80%

20%

B + D

A + D

A + C

B + D

8350 F05

20%

80%

20%

B + D

A + D

A + C

B + D

8350 F06

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

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

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