ISL6556ACB-T Intersil, ISL6556ACB-T Datasheet - Page 17
![no-image](/images/manufacturer_photos/0/3/341/intersil_sml.jpg)
ISL6556ACB-T
Manufacturer Part Number
ISL6556ACB-T
Description
IC CTRLR MULTIPHASE VRM10 28SOIC
Manufacturer
Intersil
Datasheet
1.ISL6556ACBZ.pdf
(25 pages)
Specifications of ISL6556ACB-T
Applications
Controller, Intel VR10X
Voltage - Input
3 ~ 12 V
Number Of Outputs
4
Voltage - Output
0.84 ~ 1.6 V
Operating Temperature
0°C ~ 70°C
Mounting Type
Surface Mount
Package / Case
28-SOIC (7.5mm Width)
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
ISL6556ACB-T
Manufacturer:
INTERSIL
Quantity:
20 000
ISL6556A to protect the microprocessor load when an
overvoltage condition occurs.
At the inception of an overvoltage event, all PWM outputs
are commanded low until the voltage at VSEN falls below
0.6V with valid VCC or 1.5V otherwise. This causes the
Intersil drivers to turn on the lower MOSFETs and pull the
output voltage below a level that might cause damage to the
load. The PWM outputs remain low until VDIFF falls to the
programmed DAC level when they enter a high-impedance
state. The Intersil drivers respond to the high-impedance
input by turning off both upper and lower MOSFETs. If the
overvoltage condition reoccurs, the ISL6556A will again
command the lower MOSFETs to turn on. The ISL6556A will
continue to protect the load in this fashion as long as the
overvoltage condition recurs.
Simultaneous to the protective action of the PWM outputs, the
OVP pin pulls to VCC delivering up to 100mA to the gate of a
crowbar MOSFET or SCR placed either on the input rail or the
output rail. Turning on the MOSFET or SCR collapses the
power rail and causes a fuse placed further up stream to blow.
The fuse must be sized such that the MOSFET or SCR will
not overheat before the fuse blows. The OVP pin is tolerant to
12V (see Absolute Maximum Ratings), so an external resistor
pull up can be used to augment the driving capability. If using
a pull up resistor in conjunction with the internal overvoltage
protection function, care must be taken to avoid nuisance trips
that could occur when VCC is below 2V. In that case, the
controller is incapable of holding OVP low.
Once an overvoltage condition is detected, normal PWM
operation ceases until the ISL6556A is reset. Cycling the
voltage on EN or ENLL or VCC below the POR-falling
threshold will reset the controller. Cycling the VID codes will
not reset the controller.
Overcurrent Protection
ISL6556A has two levels of overcurrent protection. Each
phase is protected from a sustained overcurrent condition on
a delayed basis, while the combined phase currents are
protected on an instantaneous basis.
In instantaneous protection mode, the ISL6556A takes
advantage of the proportionality between the load current
and the average current, I
condition. See the Channel-Current Balance section for
more detail on how the average current is measured. The
average current is continually compared with a constant
100μA reference current as shown in Figure 10. Once the
average current exceeds the reference current, a
comparator triggers the converter to shutdown.
In individual overcurrent protection mode, the ISL6556A
continuously compares the current of each channel with the
same 100μA reference current. If any channel current
exceeds the reference current continuously for eight
consecutive cycles, the comparator triggers the converter to
shutdown.
AVG
17
to detect an overcurrent
ISL6556A
At the beginning of overcurrent shutdown, the controller
places all PWM signals in a high-impedance state
commanding the Intersil MOSFET driver ICs to turn off both
upper and lower MOSFETs. The system remains in this state
a period of 4096 switching cycles. If the controller is still
enabled at the end of this wait period, it will attempt a soft
start. If the fault remains, trip-retry cycles continue
indefinitely as shown in Figure 11 until either controller is
disabled or the fault is cleared. Note that the energy
delivered during trip-retry cycling is much less than during
full-load operation, so there is no thermal hazard during this
kind of operation.
General Design Guide
This design guide is intended to provide a high-level
explanation of the steps necessary to create a multi-phase
power converter. It is assumed that the reader is familiar with
many of the basic skills and techniques referenced below. In
addition to this guide, Intersil provides complete reference
designs that include schematics, bills of materials, and example
board layouts for all common microprocessor applications.
Power Stages
The first step in designing a multi-phase converter is to
determine the number of phases. This determination
depends heavily on the cost analysis which in turn depends
on system constraints that differ from one design to the next.
Principally, the designer will be concerned with whether
components can be mounted on both sides of the circuit
board; whether through-hole components are permitted; and
the total board space available for power-supply circuitry.
Generally speaking, the most economical solutions are
those in which each phase handles between 15 and 20A. All
surface-mount designs will tend toward the lower end of this
current range. If through-hole MOSFETs and inductors can
be used, higher per-phase currents are possible. In cases
where board space is the limiting constraint, current may be
pushed as high above 30A per phase, but these designs
FIGURE 11. OVERCURRENT BEHAVIOR IN HICCUP MODE.
0A
0V
OUTPUT CURRENT, 50A/DIV
OUTPUT VOLTAGE,
500mV/DIV
F
SW
= 500kHz
2ms/DIV