MAX77816 datasheet(10/26 Pages) MAXIM

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H-Bridge Controller

H-Bridge architecture operates at 2.5MHz fixed frequency

with a pulse width modulated (PWM), current-mode con-

trol scheme. This topology is in a cascade of a boost

regulator and a buck regulator using a single inductor

and output capacitor. Buck, buck-boost, and boost stages

are 100% synchronous for highest efficiency in portable

applications.

There are three phases implemented with the H-bridge

switch topology, as shown in Figure 3:

● Φ1 Switch period (Phase-1: HS1 = ON, LS2 =

ON) stores energy in the inductor, ramping up the

inductor current at a rate proportional to the input volt-

age divided by inductance; VINBB/L.

● Φ2 Switch period (Phase-2: HS1 = ON, HS2 = ON)

ramps the inductor current up or down, depending on

the differential voltage across the inductor, divided by

inductance; ±(VINBB – VOUTBB)/L.

● Φ3 Switch period (Phase-3: LS1 = ON, HS2 = ON)

ramps down the inductor current at a rate proportional to

the output voltage divided by inductance; -VOUTBB /L.

2-Phase buck topology is utilized when VINBB > VOUTBB.

A switching cycle is completed in one clock period. Switch

period Φ2 is followed by switch period Φ3, resulting in an

inductor current waveform similar to Figure 4.

2-Phase boost topology is utilized when VINBB < VOUTBB.

A switching cycle is completed in one clock period. Switch

period Φ1 is followed by switch period Φ2, resulting in an

inductor current waveform similar to Figure 5.

Figure 4. 2-Phase Buck Mode Switching Current Waveforms

Figure 5. 2-Phase Boost Mode Switching Current Waveforms

Figure 3. Buck-Boost Switching Intervals

CLK

TSW

Ф2

Ф3

TSW

Ф2

Ф3

CLK

TSW

Ф2

Ф1

TSW

Ф2

Ф1

CLK

Ф 1

Ф 2

Ф 3

INBB

HS1

LS1

LXBB1

CHARGE L

DISCHARGE L

CHARGE/DISCHARGE L

OUTBB

HS2

LS2

LXBB2

MAX77816

High-Efficiency Buck-Boost Regulator

with 5A Switches

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