LT3758 datasheet(11/28 Pages) AD

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LT8392

Rev. 0

For more information www.analog.com

OPERATION

The LT8392 is a current mode DC/DC controller that can

regulate output voltage, input or output current from input

voltage above, below, or equal to the output voltage. The

ADI proprietary peak-buck peak-boost current mode con-

trol scheme uses a single inductor current sense resistor

and provides smooth transition between buck region,

buck-boost region, and boost region. Its operation is best

understood by referring to the Block Diagram.

Power Switch Control

Figure 1 shows a simplified diagram of how the four

power switches A, B, C, and D are connected to the induc-

tor L, the current sense resistor RSENSE, power input VIN,

power output VOUT, and ground. The current sense resis-

tor RSENSE connected to the LSP and LSN pins provides

inductor current information for both peak current mode

control and reverse current detection in buck region,

buck-boost region, and boost region. Figure 2 shows the

current mode control as a function of VIN/VOUT ratio and

Figure 3 shows the operation region as a function of VIN/

VOUT ratio. The power switches are properly controlled

to smoothly transition between modes and regions.

Hysteresis is added to prevent chattering between modes

and regions.

There are a total of four states: (1) peak-buck current

mode control in buck region, (2) peak-buck current mode

control in buck-boost region, (3) peak-boost current

mode control in buck-boost region, and (4) peak-boost

current mode control in boost region. The following sec-

tions give detailed description for each state with wave-

forms, in which the shoot-through protection dead time

between switches A and B, between switches C and D are

ignored for simplification.

Figure 1. Simplified Diagram of the Power Switches

Figure 2. Current Mode vs VIN/VOUT Ratio

Figure 3. Operation Region vs VIN/VOUT Ratio

VOUT

SW1

SW2

TG2

BG2

8392 F01

TG1

BG1

VIN

RSENSE

PEAK-BUCK

PEAK-BOOST

VIN/VOUT

0.98 1.00 1.02

8392 F02

BUCK

(1)

(2)

(3)

BOOST

BUCK-BOOST

VIN/VOUT

0.85

0.75

1.00

1.18

1.33

8392 F03

(4)

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