ISL68134_16 Datasheet, PDF (12/50 Pages) Intersil Corporation – Digital Dual Output, 7-Phase Configurable PWM

ISL68134
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
52h
180
63h
1800
53h
330
66h
2200
56h
470
67h
2700
57h
680
42h
3300
5Ah
820
43h
3900
5Bh
1000
46h
4700
5Eh
1200
47h
5600
5Fh
Phase Configuration
The ISL68134 supports up to two regulated outputs through four
configurable phases. Either output is capable of controlling up to
four 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 3. For example, a 3-phase
rail could consist of Phases 3, 2 and 1. 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 7 illustrates the typical
characteristic of efficiency vs load current vs phase count.
I3
I2
I1
0 10 20 30 40 50 60 70 80 90
LOAD (A)
FIGURE 7. EFFICIENCY vs PHASE NUMBER
Phases are dropped one at a time with a user programmed drop
delay between drop events. As an example, suppose the delay is
set to 1ms and 3 phases are active. Should the load suddenly
drop to a level needing only 1 phase, the ISL68134 will begin by
dropping a phase after 1ms. An additional phase will be dropped
each 1ms thereafter until only 1 phase remains.
In addition to the described load current add/drop thresholds,
the fast phase add function provides a very rapid response to
transient load conditions. This feature continuously monitors the
system regulation error and should it exceed the user set
threshold, all dropped phases will be readied for use. In this way,
there is no delay should all phases be needed to support a load
transient. The fast phase add threshold is set in the
PowerNavigator™ GUI. Output current threshold for adding and
dropping phases can also be configured.
To ensure dropped phases have sufficient boot capacitor charge
to turn on the high-side MOSFET after a long period of disable, a
boot refresh circuit turns on the low-side MOSFET of each
dropped phase to refresh the boot capacitor. Frequency of the
boot refresh is programmable via PowerNavigator™.
Output Voltage Configuration
Output voltage set points and thresholds for each output can be
configured with PowerNavigator™ GUI. Parameters such as
output voltage, V_OUT margin high/low and V_OUT OV/UV faults
thresholds can be configured with GUI. Additionally, output
voltage and margin high/low can be adjusted during regulation
via PMBus command VOUT_COMMAND, VOUT_MARGIN_HIGH
and VOUT_MARGIN_LOW for further tuning. The following V_OUT
relationships must be maintained for correct operation:
VOUT_OV_FAULT_LIMIT > VOUT_COMMAND
(VOUT_MARGIN_HIGH and VOUT_MARGIN_LOW, if used) >
VOUT_UV_FAULT_LIMIT. Additionally, the V_OUT commands are
bounded by VOUT_MAX and VOUT_MIN to provide protection
against incorrect set points being sent to the device. The
ISL68134 also incorporates AVSBus functionality for high speed
changes to the V_OUT target.
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FN8817.0
September 28, 2016