isl6551irec Intersil Corporation, isl6551irec Datasheet - Page 9

• Manufacturer Part Number: isl6551irec
• Description: Zvs Full Bridge Pwm Controller
• Manufacturer: Intersil Corporation

Shutdown Timing Diagrams
Shutdown Timing Descriptions
A (ON/OFF)
When the ON/OFF is pulled low, the soft-start capacitor is
discharged and all the drivers are disabled. When the
ON/OFF is released without a fault condition, a soft-start is
initiated.
B (OVERCURRENT)
If the output of the converter is over loaded, i.e., the PKILIM
is above the bandgap reference voltage (BGREF), the soft-
start capacitor is discharged very quickly and all the drivers
are turned off. Thereafter, the soft-start capacitor is charged
slowly, and discharged quickly if the output is overloaded
again. The soft-start will remain in hiccup mode as long as
the overload conditions persist. Once the overload is
removed, the soft-start capacitor is charged up and the
converter is then back to normal operation.
C (LATCHING SHUTDOWN)
The IC is latched off completely as the LATSD pin is pulled
high, and the soft-start capacitor is reset.
D (ON/OFF)
The latch cannot be reset by the ON/OFF.
LATSD
ON/OFF
ILIM_OUT
SOFT-START
DRIVER
ENABLE
SOFT-START
SHUTDOWN
VDD
FAULT
OFF
A
9
PKILIM < BGREF
PKILIM > BGREF
OVERCURRENT LATCHED
B
ISL6551IREC
C
E (LATCH RESET)
The latch is reset by removing the VDD. The soft-start
capacitor starts to be charged after VDD increases above
the turn-on threshold VDD
F (VDD UVLO)
The IC is turned off when the VDD is below the turn-off
threshold VDD
the undervoltage lockout (UVLO) circuit.
Block/Pin Functional Descriptions
Detailed descriptions of each individual block in the
functional block diagram on page 3 are included in this
section. Application information and design considerations
for each pin and/or each block are also included.
IC Bias Power (VDD, VDDP1, VDDP2)
• The IC is powered from a 12V
• VDD supplies power to both the digital and analog circuits
and should be bypassed directly to the VSS pin with an
0.1µF low ESR ceramic capacitor.
OFF/ON
D
LATCH CANNOT BE RESET BY ON/OFF
OFF
E
. Hysteresis VDD
LATCH RESET BY
REMOVING VDD
VDD
LATCH
RESET
FAULT
ON
ON
.
±
10% supply.
HYS
UNDERVOLTAGE
LOCKOUT
F
VDD
is incorporated in
OFF
September 2, 2008
FN6762.0