STMicroelectronics Demonstration board using a dual full-bridge L6227Q EVAL6227QR EVAL6227QR Fiche De Données

 13/27

 shows the typical operating waveforms of the output current, the voltage drop 

across the sensing resistor, the RC pin voltage and the status of the bridge. Immediately 
after the low-side power MOS turns on, a high peak current flows through the sensing 
resistor due to the reverse recovery of the freewheeling diodes. The L6227Q provides a 1 

µs 

blanking time t

BLANK

 that inhibits the comparator output so that this current spike cannot 

prematurely re-trigger the monostable.

 shows the magnitude of the off time t

OFF

 versus C

OFF

 and R

OFF

 values. It can be 

approximately calculated from the equations:

t

RCFALL

 = 0.6 · R

OFF

 · C

OFF

 

t

OFF

 = t

RCFALL

 + t

DT

 = 0.6 · R

OFF

 · C

OFF

 + t

DT

where R

OFF

 and C

OFF

 are the external component values and t

DT

 is the internally generated 

Dead Time with:

20 k

Ω ≤ R

OFF

 

≤ 100 kΩ

0.47 nF 

≤ C

OFF

 

≤ 100 nF

t

DT

 = 1 µs (typical value)

Therefore:

t

OFF(MIN)

 = 6.6 µs

t

OFF(MAX)

 = 6 ms

OFF

B

C

D

D

A

t

ON

t

OFF

t

OFF

B

C

ON

2.5V

0

Fast Deca

y

Fast Deca

y

Slow Decay

Slow Decay

1

µs  t

BLANK

t

RCRISE

1

µs  t

DT

1

µs  t

DT

t

RCRISE

t

RCFALL

t

RCFALL

SYNCHRONOUS OR QUASI
SYNCHRONOUS RECTIFICATION

1

µs  t

BLANK

5V

V

RC

V

SENSE

V

REF

I

OUT

V

REF

R

SENSE

D01IN1334