ADP1055ACPZ-R7 datasheet(21/140 Pages) AD

21 / 140 page

Data Sheet

ADP1055

Rev. A | Page 21 of 140

PWM AND SYNCHRONOUS RECTIFIER OUTPUTS

(OUTA, OUTB, OUTC, OUTD, SR1, SR2)

The PWM and SR outputs are used for control of the primary

side drivers and the synchronous rectifier drivers. These outputs

can be used for several control topologies, such as full-bridge,

phase-shifted ZVS configurations and interleaved, two switch

forward converter configurations. Delays between the rising and

falling edges can be individually programmed (see Figure 24).

Figure 24. PWM Timing Diagram

Take special care to avoid shoot-through and cross-conduction.

It is recommended that the software GUI be used to program

these outputs. Figure 25 shows an example configuration to

drive a full-bridge topology with synchronous rectification.

Figure 25. PWM Pin Assignment for Full-Bridge, Phase-Shifted Topology

with Synchronous Rectification

Go and Auto Go Command

The PWM outputs (OUTA to OUTD) and the SR outputs (SR1

and SR2) are all synchronized with each other. Therefore, when

reprogramming more than one of these outputs, it is important

to first update all the registers and then latch the information

into the ADP1055 at the same time. This simultaneous updating

of the PWM outputs is facilitated by the GO command

(Register 0xFE00). The GO command acts as a gate to apply all

functions related to the commands at the same time.

The GO command gates the following functions:



Frequency synchronization



Line voltage feedforward



Double update rate, volt-second balance



Digital filter settings



Frequency and PWM settings



Voltage reference change

During reprogramming, the outputs are temporarily disabled.

It is recommended that the PWM outputs be disabled when

not in use.

The PMBus allows the user to change the voltage setting and

the switching frequency on-the-fly. The auto go command

(Register 0xFE5B) is an added level of protection that restricts the

user from making a change to certain commands (see Table 203).

For more information about the various programmable

switching frequencies and PWM timings, see the Switching

Frequency Programming section.

SYNCHRONOUS RECTIFICATION

SR1 and SR2 are recommended for use as the PWM control

signals when using synchronous rectification. These PWM

signals can be configured much like the other PWM outputs.

t11

t10

tPERIOD

t12

PWM1 (OUTA)

PWM2 (OUTB)

PWM3 (OUTC)

PWM4 (OUTD)

SYNC RECT 1 (SR1)

SYNC RECT 2 (SR2)

ISOLATOR

DRIVER

OUTA

OUTB

OUTC

OUTD

SR1 SR2

VIN

OUTA

OUTD

OUTC

OUTB

SR1

SR2

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