IR3094M International Rectifier Corp., IR3094M Datasheet - Page 16

• Manufacturer Part Number: IR3094M
• Description: 3 Phase Pwm Controller For Point Of Load
• Manufacturer: International Rectifier Corp.

A delay is included if any of the four fault conditions occurs after a successful soft start sequence. This is required
since momentary faults can occur as part of normal operation due to load transients such as exciting an over-
current condition. If any fault occurs during normal operation, the SS/DEL capacitor will discharge through a 55uA
current sink but will not set the fault latch immediately. If the fault condition persists long enough for the SS/DEL
capacitor to discharge below the 3.75V threshold of the delay comparator, the Fault latch will be set pulling the Error
Amplifier’s output low, inhibiting switching and de-asserting the PWRGD signal. The SS/DEL capacitor is then
discharged through a 6uA discharge current resulting in a long hiccup duration.
The SS/DEL capacitor will continue to discharge until it reaches 0.265V where the fault latch is reset allowing a
normal soft start to occur. If a fault condition is again encountered during the soft start cycle, the fault latch will be
set without any delay and hiccup mode will begin. During hiccup mode the 10 to 1 charge to discharge ratio results
in a 9.1% hiccup mode duty cycle regardless of at what point a fault condition occurs.
OVP fault immediately sets the fault latch causing SS/DEL to begin to discharge and this fault can only be cleared
by cycling power to the IR3094 on and off.
If SS/DEL pin is pulled below 0.8V, the converter can be disabled.
Soft-start delay time
to allow the soft start. The soft start time
zero to V
1. VCC Under Voltage Lock Out
2. 5VUVL Under Voltage Lock Out
3. Low Enable pin
4. Over Current condition.
VCC
(12V)
5VUVL
SS/DEL
VOUT
PWRGD
IOUT
Page 16 of 29
O.
t
SS
4.36V
(5VUVL GATES
3.75V
can be programmed by C
FAULT MODE)
1.1V
START-UP
t
SSDEL
(VOUT CHANGES DUE TO
is the time SS/DEL charged up to 1.1V. After that the error amplifier output is released
LOAD AND VID CHANGES)
NORMAL OPERATION
C
SS
OCP THRESHOLD
Figure 7 – Operating Waveforms
I
SS
CHG
t
V
SS
using equation (3).
O
*
represents the time during which converter output voltage rises from
t
SS
OCP
DELAY
60
*
10
V
O
6
HICCUP OVER-CURRENT
PROTECTION
*
t
SS
(3)
RE-START
AFTER OCP
CLEARS
IR3094PBF
09/26/05
POWER-DOWN
(VCC GATES
FAULT MODE)
7.0V
UVLO