ISL6223 Datasheet, PDF (9/15 Pages) Intersil Corporation – Mobile Microprocessor CORE Voltage Regulator Multi-Phase Buck PWM Controller

ISL6223
Overcurrent
In the event of an overcurrent condition, the overcurrent
protection circuit reduces the average current delivered to
less than 25% of the current limit. When an overcurrent
condition is detected, the controller forces all PWM outputs
into a three state mode. This condition results in the gate
driver removing drive to the output stages. The ISL6223
goes into a wait delay timing cycle that is equal to the Soft-
Start ramp time. PGOOD also goes “low” during this time
due to VSEN going below its threshold voltage. To lower the
average output dissipation, the Soft-Start initial wait time is
increased from 64 to 4096 cycles, then the Soft-Start ramp is
initiated. At a PWM frequency of 200kHz, for instance, an
overcurrent detection would cause a dead time of 20.48ms,
then a ramp of 20.16ms.
At the end of the delay, PWM outputs are restarted and the
Soft-Start ramp is initiated. If a short is present at that time,
the cycle is repeated. This is the hiccup mode.
Figure 6 shows the supply shorted under operation and the
hiccup operating mode described above. Note that due to
the high short circuit current, overcurrent is detected before
completion of the start-up sequence so the delay is not quite
as long as the normal Soft-Start cycle.
SHORT APPLIED HERE
PGOOD
SHORT
CURRENT
50A/DIV.
FIGURE 6. SHORT APPLIED TO SUPPLY AFTER POWER-UP
VCORE
DACOUT
INDUCTOR
CURRENTS
FIGURE 7. VID CHANGES FROM 1.3V TO 1.6V. THE LOAD
CURRENT IS SET TO 10A.
DACOUT Pin
The internal DAC output is brought out to pin 11, DACOUT,
in ISL6223. The typical output impedance of the DAC is
1.7kΩ. The DACOUT pin allows the user to connect a
capacitor between this pin and the ground to form an RC
filter to slow down the voltage transition at the non-inverting
input of the error amplifier, when the VID code is being
changed. Slower voltage transition reduces the inrush
current to avoid tripping the overcurrent protection during the
transition. Typical systems require the transition to be
finished within 100µs, therefore, a time constant of 30µs to
40µs is a good tradeoff between the inrush current and the
transition time. Connecting a 22nF capacitor to the DACOUT
results in a time constant of 37µs for the RC filter. Figure 7
shows the waveforms for the VID changes from 1.3V to 1.6V.
From top to bottom, the waveforms are the core voltage, the
DACOUT, and the two inductor currents.
TABLE 1. VOLTAGE IDENTIFICATION CODES
VOLTAGE IDENTIFICATION CODE AT
PROCESSOR PINS
VID4
VID3 VID2 VID1 VID0
1
1
1
1
1
1
1
1
1
0
VCC_CORE
(V_DC)
Shutdown
0.925
1
1
1
0
1
0.950
1
1
1
0
0
0.975
1
1
0
1
1
1.000
1
1
0
1
0
1.025
1
1
0
0
1
1.050
1
1
0
0
0
1.075
1
0
1
1
1
1.100
1
0
1
1
0
1.125
1
0
1
0
1
1.150
1
0
1
0
0
1.175
1
0
0
1
1
1.200
1
0
0
1
0
1.225
1
0
0
0
1
1.250
1
0
0
0
0
1.275
0
1
1
1
1
Shutdown
0
1
1
1
0
1.300
0
1
1
0
1
1.350
0
1
1
0
0
1.400
0
1
0
1
1
1.450
0
1
0
1
0
1.500
0
1
0
0
1
1.550
0
1
0
0
0
1.600
0
0
1
1
1
1.650
0
0
1
1
0
1.700
0
0
1
0
1
1.750
0
0
1
0
0
1.800
0
0
0
1
1
1.850
0
0
0
1
0
1.900
0
0
0
0
1
1.950
0
0
0
0
0
2.000
9