ISL68137_16 Datasheet, PDF (13/53 Pages) Intersil Corporation – Digital Dual Output, 7-Phase Configurable PWM

ISL68137
Functional Description
Overview
The ISL68137 is a digital dual output 7-phase PWM controller
that can be programmed for single output 7+0, dual output 6+1,
5+2, or 4+3 phase operation. Operation using less than 7 phases
between 2 outputs is also supported. Existing digital multiphase
solutions utilize analog comparator based schemes (nonlinear)
to bolster the inadequate transient response common to many
digital multiphase solutions. The ISL68137 uses a linear voltage
regulation scheme to address transient loads. As a result, it is
much easier for users to configure and validate their designs
when compared with nonlinear schemes. By combining a
proprietary low noise and zero latency digital current sense
scheme with cutting edge digital design techniques, Intersil is
able to meet transient demands without resorting to nonlinear
schemes. In addition, the ISL68137 can store up to 8 user
configurations in NVM and allows the user to select the desired
configuration via pin-strap (CONFIG). The result is a system that is
easy to configure and deploy.
A number of performance enhancing features are supported in
the ISL68137. These include AVSBus control, diode braking,
automatic phase dropping, DCR/resistor/smart power stage
current sense support, load line regulation and multiple
temperature sensing options.
To facilitate configuration development, the PowerNavigator™
GUI provides a step-by-step arrangement for setup and
parametric adjustment. Once a configuration has been set, the
user may employ PowerNavigator™ to monitor telemetry or use a
direct PMBus interface based on the supported command set.
PWM Modulation Scheme
The ISL68137 uses Intersil's proprietary linear synthetic current
modulation scheme to improve transient performance. This is a
unique constant frequency, dual edge PWM modulation scheme
with both PWM leading and trailing edges being independently
moved to give the best response to transient loads. Current
balance is an inherent part of the regulation scheme. The
modulation scheme is capable of overlapping pulses should the
load profile demand such operation. In addition, the modulator is
capable of adding or removing pulses from a given cycle in
response to regulation demands while still managing maximum
average frequency to safe levels. For DC load conditions the
operating frequency is constant.
PMBus Address Selection
When communicating with multiple PMBus devices on a single
bus, each device must have its own unique address so the host
can distinguish between the devices. The device address can be
set using a 1% resistor on the SA pin according to the pin-strap
options listed in Table 2.
TABLE 2. RESISTOR VALUES TO ADDRESS MAPPING
R SA
(Ω)
PMBus
ADDRESS
R SA
(Ω)
PMBus
ADDRESS
0
60h
1500
50h
180
61h
1800
51h
330
64h
2200
54h
470
65h
2700
55h
680
40h
3300
58h
820
41h
3900
59h
1000
44h
4700
5Ch
1200
45h
5600
5Dh
Phase Configuration
The ISL68137 supports up to two regulated outputs through
seven configurable phases. Either output is capable of controlling
up to seven phases in any arbitrary mix. Phase assignments are
accomplished via the PowerNavigator™ GUI.
While the device supports arbitrary phase assignment, it is good
practice to assign phases to Output 1 in descending sequential
numerical order starting from Phase 6. For example, a 4-phase
rail could consist of phases 6, 5, 4 and 3. For Output 0, phases
would be assigned starting from Phase 0 in ascending sequential
numerical order.
Automatic Phase Add and Drop
In order to produce the most optimal efficiency across a wide
range of output loading, the modulator supports automatic
dropping or adding of phases. Use of automatic phase dropping
is optional. If automatic phase dropping is enabled, the number
of active phases at any time is determined solely by load current.
During operation, phases of Output 1 will drop beginning with the
lowest phase number assigned. Phase dropping begins with the
highest assigned phase number. Figure 8 illustrates the typical
characteristic of efficiency vs load current vs phase count.
I2 ^{I3 I4}
I5
I1
0 20 40 60 80 100 120 140 160 180
LOAD (A)
FIGURE 8. EFFICIENCY vs PHASE NUMBER
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September 27, 2016