PIC16F616-ESLASHML datasheet(96/172 Pages) APEX

96 / 172 page

PIC16F616/16HV616

DS41288A-page 94

Preliminary

10.4.6

PROGRAMMABLE DEAD-BAND

DELAY MODE

In half-bridge applications where all power switches are

modulated at the PWM frequency, the power switches

normally require more time to turn off than to turn on. If

both the upper and lower power switches are switched

at the same time (one turned on, and the other turned

off), both switches may be on for a short period of time

until one switch completely turns off. During this brief

interval, a very high current (shoot-through current) will

flow through both power switches, shorting the bridge

supply. To avoid this potentially destructive shoot-

through current from flowing during switching, turning

on either of the power switches is normally delayed to

allow the other switch to completely turn off.

In Half-Bridge mode, a digitally programmable dead-

band delay is available to avoid shoot-through current

from destroying the bridge power switches. The delay

occurs at the signal transition from the non-active state

to the active state. See Figure 10-16 for illustration.

The lower seven bits of the associated PWM1CON

of microcontroller instruction cycles (TCY or 4 TOSC).

FIGURE 10-16:

EXAMPLE OF HALF-

BRIDGE PWM OUTPUT

FIGURE 10-17:

EXAMPLE OF HALF-BRIDGE APPLICATIONS

Period

Pulse Width

(1)

P1A(2)

P1B(2)

td = Dead-Band Delay

Period

(1)

Note 1:

At this time, the TMR2 register is equal to the

PR2 register.

Output signals are shown as active-high.

P1A

P1B

FET

Driver

FET

Driver

V+

V-

Load

Standard Half-Bridge Circuit (“Push-Pull”)

PIC16F616-E/ML Datasheet(PDF) 96 Page - Cirrus Logic

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