LTC3882_15 Datasheet, PDF (63/104 Pages) Linear Technology – Dual Output PolyPhase Step-Down DC/DC Voltage Mode Controller with Digital Power System Management

LTC3882
APPLICATIONS INFORMATION
(bit 3 of STATUS_MFR_SPECIFIC). The existence of a
partial fault log can be detected by examining the header
of the log (MFR_FAULT_LOG). If the first two words of
the Fault Log Preface contain valid data as specified by
Table 2, and STATUS_MFR_SPECIFIC does not indicate the
presence of a complete fault log, then a partial log existed
in EEPROM at boot and has been retrieved to RAM. The
only way to then determine how much of the log is actually
valid is by subjective evaluation of the contents of each log
event record. MFR_CLEAR_FAULT_LOG will permanently
erase a partial fault log, allowing a subsequent log to be
written. It is a good practice to always check for a partial
fault log at power-up if fault logging is enabled (bit 7 of
MFR_CONFIG_ALL_LTC3882).
LTpowerPlay – An Interactive Digital Power GUI
LTpowerPlay is a powerful Windows-based development
environment that supports Linear Technology Power Sys-
tem Management ICs, including the LTC3882. LTpowerPlay
can be used to evaluate LTC products by connecting to a
Linear Technology demo circuit or user application. LTpow-
erPlay can also be used offline (no hardware present) to
build multiple IC configuration files that can be saved and
later reloaded. LTpowerPlay uses the DC1613 USB-to-I²C/
SMBus/PMBus controller to communicate with a system
for evaluation, development or debug. The software also
features automatic update to remain up-to-date with the
latest device drivers and documentation available from
Linear Technology. A great deal of context sensitive help
is available within LTpowerPlay, along with several tutori-
als. Complete information is available at http://www.linear.
com/ltpowerplay.
Interfacing to the DC1613
The LTC DC1613 USB-to-I²C/SMBus/PMBus controller
can be interfaced to the LTC3882 on any board for pro-
gramming, telemetry and system debug. This includes
the DC1936 from Linear Technology, or any customer
target system. The controller, when used in conjunction
with LTpowerPlay, provides a powerful way to debug an
entire power system. Faults are quickly diagnosed using
telemetry, fault status registers and the fault log. The final
configuration can be quickly developed and stored to the
LTC3882 EEPROM and/or LTpowerPlay configuration file.
The DC1613 can communicate with, program and even
power one or more LTC3882s, regardless of whether
system supplies are up. The DC2086 Powered Program-
ming Adapter can be used to extend the power sourcing
capability of the DC1613. Figure 47 illustrates an applica-
tion schematic for in-system programming of multiple
LTC3882s normally powered from a V_CC system supply
(5V to 12V). If V_CC is applied, the DC1613 will not supply
the LTC3882s on the board. If the DC2086 is used, PFETs
with lower R_DS(ON), such as the SiA907EDJT, should be
used in place of the TP0101K devices. Figure 48 shows an
example when the system normally provides 3.3V directly
to the LTC3882(s).
If system supplies are not up in either of these circuits, the
DC1613 will power the LTC3882 V_DD33 supply, allowing
in-circuit configuration or manufacturing customization.
These circuits also facilitate remote diagnostics, control
and reprogramming of the LTC3882 while the host system
is fully operational, permitting very flexible in-system
debugging.
If the system supply is restored while power is still applied
by the DC1613 or DC2086, the LTC3882 can often be ready
to initiate output soft-start before sufficient supply bias for
the power stage has been established. Create additional
LTC3882 delay with TON_DELAY or use a common sys-
tem RUN line to control both the LTC3882 and its related
power stages based on acceptable operating parameters,
as shown in Figure 55. The DC1613 I²C connections are
opto-isolated from the host PC USB. The DC1613 3.3V
current limit is only 100mA, so it should only be used to
power one or two LTC3882s in-system. Because of this
limited current sourcing capability, only the LTC3882s, their
associated pull-up resistors and the I²C pull-up resistors
should be powered from the isolated 3.3V supply provided
by the DC1613. Using the DC2086 will enable in-system
programming of several tens of LTC3882 devices without
normal system power applied. Any other device sharing
the I²C bus with the LTC3882 should not have body diodes
between their SDA/SCL pins and their respective logic
supply, because this will interfere with bus communica-
tion in the absence of system power. Hold the RUN pins
low externally to avoid providing power to the load until
the part is fully configured.
3882f
For more information www.linear.com/LTC3882
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