STMicroelectronics Demonstration board using a dual full-bridge L6227Q EVAL6227QR EVAL6227QR Datenbogen
Produktcode
EVAL6227QR
L6227Q
Circuit description
13/27
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
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.
Figure 10.
Output current regulation waveforms
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
SYNCHRONOUS RECTIFICATION
1
µs t
BLANK
5V
V
RC
V
SENSE
V
REF
I
OUT
V
REF
R
SENSE
D01IN1334