Datasheet

L9942 Device description
Doc ID 11778 Rev 7 13/40
2.13 Decay modes
Figure 4. Decay modes
A
SLOW
DECAY
Internal PWM_CLK
ON
B
Load
Current
Detail A: SWITCH ON AND SLOW DECAY
Step
Limit
HS
Detail B:
MIXED DECAY
T
When limit is reached so fast decay duration time is set by DM1 DM2 register0
T
FT
Filter time for the purpose of switch off delay in on mode is set by FT register6
T
CC
T
FT
DM2 DM1 DM0 MODE
0 0 0
register0
Time
Time
slow
DM2 DM1 DM0 MODE CURVE
X 0 1
register0
X 1 0
X 1 1
MD1
T
MD2
T
mc
T
Cross current protection time is set by SR1 SR0 register0
MD1
Filter time for purpose of delay when decay mode has to change after limit under-run
CC
T
T
CC
T
VS
on
on
VS
on
on
VS
on
on
MDx
=
mc
T
CC
+ 2T= T
FT
T
MD
T
FT
VS
on
on
VS
on
SLOW DECAY
MD2
or T
Fast decay is caused by
current through internal
diodes during cross current
protection time.
VS
OFF
ON
OFF
OFF
OFF
FAST
DECAY
MIXED
DECAY
T
MDx
Time
CC
T
SLOW DECAY
with delay
Load
Current
Load
Current
Step
Limit
LS
Time
T
FT
CC
T
SLOW DECAY
after current
undershoot
mc
T
Load
Current
FAST
DECAY
CC
T
CC
T
>
T
B
T
B
Blank time of load current comparator
FAST
DECAY
T
BCC
=T
fast decay
fast decay