ir3092 International Rectifier Corp., ir3092 Datasheet - Page 19

• Manufacturer Part Number: ir3092
• Description: 2 Phase Opteron, Athlon, Or Vr10.x Control Ic
• Manufacturer: International Rectifier Corp.

VCC and 5VUVL Under Voltage Lock Outs, a VID=11111x fault, or low Enable pin immediately set the fault latch causing
SS/DEL to begin discharging. The hiccup duration is controlled by a 5.5uA discharge current until the Discharge
Comparator Threshold of 0.26V is reached. If the fault has cleared, the fault latch will reset allowing a normal soft-start to
occur.
A delay is included if an over-current condition occurs after a successful soft start sequence. This is required since over-
current conditions can occur as part of normal operation due to load transients or VID transitions. If an over-current fault
occurs during normal operation, the Over Current Comparator will initiate the discharge of the capacitor at SS/DEL but
will not set the fault latch immediately. If the over-current 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. An additional discharge current is introduced during an over
current condition. The 5.5uA discharge current results in a long delay duration where SS/DEL discharges from its 4V
peak to the 3.75V fault delay threshold. This potentially long over-current protection activation delay could result in
potential power stage damage therefore an additional 45uA discharge current source assists the 5.5uA discharge current
if an over current condition is occurring and the SS/DEL capacitor is above 3.75V. 30mV of hysteresis is included in the
Delay Comparator to prevent PWRGD chatter when SS/DEL is at the delay threshold.
The SS/DEL capacitor will continue to discharge until it reaches 0.26V where the fault latch is reset allowing a normal soft
start to occur. If an over-current 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%
hiccup mode duty cycle regardless of at what point the over-current condition occurs.
The converter can be disabled if the SS/DEL pin is pulled below 0.9V.
VCC
(12V)
5VUVL
SS/DEL
VOUT
PWRGD
IOUT
Page 19 of 37
4.3V
(5VUVL GATES
3.75V
FAULT MODE)
1.3V
START-UP
(VOUT CHANGES DUE TO
LOAD AND VID CHANGES)
NORMAL OPERATION
OCP THRESHOLD
Figure 8 – Operating Waveforms
OCP
DELAY
HICCUP OVER-CURRENT
PROTECTION
RE-START
AFTER OCP
CLEARS
06/25/04
POWER-DOWN
(VCC GATES
FAULT MODE)
7.6V
UVLO
IR3092