ISL6554CB Intersil, ISL6554CB Datasheet - Page 10

• Manufacturer Part Number: ISL6554CB
• Description: IC PWM CORE VOLTAGE REG 20-SOIC
• Manufacturer: Intersil

Specifications of ISL6554CB

• Applications: Controller, Intel Itanium®
• Voltage - Input: 4.75 ~ 5.25 V
• Number Of Outputs: 4
• Voltage - Output: 0.95 ~ 1.7 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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 32 to 2048 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 10.24ms, then a ramp
of 10.08ms.
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.
CORE Voltage Programming
The voltage identification pins (VID0, VID1,VID2,VID3 and
VID4) set the CORE output voltage. Each VID pin is pulled to
VCC by an internal 20µA current source and accepts open-
collector/open-drain/open-switch-to-ground or standard low-
voltage TTL or CMOS signals.
Table 1 shows the nominal DAC voltage as a function of the
VID codes. The power supply system is ±1% accurate over
the operating temperature and voltage range.
FIGURE 6. SHORT APPLIED TO SUPPLY AFTER POWER-UP
VID4
1
1
1
1
1
1
1
1
1
SHORT APPLIED HERE
VOLTAGE IDENTIFICATION CODE AT
HICCUP MODE. SUPPLY POWERED BY ATX SUPPLY
TABLE 1. VOLTAGE IDENTIFICATION CODES
ATX SUPPLY ACTIVATED BY ATX “PS-ON PIN”
CORE LOAD CURRENT = 31A, 5V LOAD = 5A
VID3
PROCESSOR PINS
1
1
1
1
1
1
1
1
0
SUPPLY FREQUENCY = 200kHz, V
VID2
1
1
1
1
0
0
0
0
1
10
VID1
1
1
0
0
1
1
0
0
1
VID0
1
0
1
0
1
0
1
0
1
IN
= 12V
VCC
Output Off
PGOOD
SHORT
CURRENT
50A/DIV.
(V
0.975
1.000
1.025
1.050
1.075
1.100
1.125
0.95
DC
CORE
)
ISL6554
Current Sensing and Balancing
Overview
The ISL6554 samples the on-state voltage drop across each
synchronous rectifier MOSFET, Q2, as an indication of the
inductor current in that phase (see Figure 7). Neglecting AC
effects (to be discussed later), the voltage drop across Q2 is
simply r
inductor current, is either 1/2, 1/3, or 1/4 of the total current
(I
The voltage at Q2’s drain, the PHASE node, is applied to the
R
ISEN pin. This pin is held at virtual ground, so the current
through R
The I
following functions:
Overcurrent, Selecting RISEN
The current detected through the R
averaged with the current(s) detected in the other 1, 2, or 3
channels. The averaged current is compared with a
trimmed, internally generated current, and used to detect
an overcurrent condition.
1. Detection of an overcurrent condition
2. Balance the I
LT
ISEN
TABLE 1. VOLTAGE IDENTIFICATION CODES (Continued)
VID4
), depending on how many phases are in use.
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ISEN
VOLTAGE IDENTIFICATION CODE AT
resistor to develop the I
DS(ON)
ISEN
current provides information to perform the
VID3
(Q2) x inductor current (I
is I
PROCESSOR PINS
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
L
L
currents in multiple channels
x r
DS(ON)
VID2
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
(Q2) / R
ISEN
VID1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
current to the ISL6554
ISEN
ISEN
L
). Note that I
resistor is
VID0
.
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
February 11, 2005
VCC
(V
1.150
1.175
1.200
1.225
1.250
1.275
1.300
1.325
1.350
1.375
1.400
1.425
1.450
1.475
1.500
1.525
1.550
1.575
1.600
1.625
1.650
1.675
1.700
L
FN9003.3
DC
CORE
, the
)