3
dc1033bf
DEMO MANUAL DC1033B
OPERATING PRINCIPLES
The DC1033B operates from 2.7V to 28V applied to either
V1 or V2. Configuration of M1 and M2 of the LTC2952
determines the power path to the output voltage and the
example DC/DC converter (U4). P-Channel MOSFETs U2
and U3 are driven by the LTC2952 for the ideal diode
feature providing a low forward voltage drop. J1 and J2
provide a bypass option if one or both of the PFETs in U3
are not needed. A pushbutton turns on and off the Enable
that drives the DC/DC converter and in some configuration
also turns on and off the ideal diode power paths. The
pushbutton on and off times are set by jumper selectable
external capacitors. The status of G1STAT indicates the
status of G1. PFO gives an output signal (shown with an
LED) if voltage at the PFI input is below the threshold.
RST and INT provide maintenance to a microprocessor
on a power up or power down. Immediate shutdown can
be done by pulling low on KILL.
CONFIGURATION A
(M1 low, M2 low): Pushbutton Controller with Automatic
Load Switching Between WALL and Battery
Set both JP1 (M1CONFG) and JP2 (M2CONFG) to LO to
enable both ideal diodes always. V
S
will be the ideal diode
OR of V1 and V2 where V
S
equals the higher of the two
supplies minus the slight ideal diode drop. G1STAT LED
turns on when V2 > V1. The pushbutton turns on and off the
EN pin which drives the shutdown of the DC/DC converter.
CONFIGURATION B
(M1 low, M2 monitor): Pushbutton Controller with Pref
-
erential WALL Operation and Automatic Load Switching
to Battery
Set JP1 (M1CONFG) to LO and JP2 (M2CONFG) to V2MON
to configure M2 as a monitor on the Wall Adapter voltage
V2. When V2 is above the trip threshold, the ideal diode
for V2 is turned on always, while the ideal diode for V1
is shutdown, even if V1 is greater than V2. V
S
will then
equal V2 minus the ideal diode voltage drop.
When V2 falls below the trip threshold, both ideal diodes
are enabled. V
S
will be the ideal diode OR of V1 and V2
where V
S
equals the higher of the two supplies minus the
slight ideal diode drop. The pushbutton turns on and off the
EN pin which drives the shutdown of the DC/DC converter.
CONFIGURATION C
(M1 high, M2 high): Pushbutton Control of Ideal Diodes
Drivers
Set JP1 (M1CONFG) to HI and JP2 (M2CONFG) to TIEM1.
M1 has an internal pull-up current and pulls up M2 as
well when tied together. This sets up the pushbutton to
have full control on both ideal diodes and the EN pin. On
a pushbutton turn on, both ideal diode drivers are turned
on as well as the DC/DC converter. V
S
will be the ideal
diode OR of V1 and V2 where V
S
equals the higher of the
two supplies minus the ideal diode drop. On a pushbut
-
ton turn off, both ideal diode drivers are shutdown and
V
S
is turned off.
CONFIGURATION D
(M1 high, M2 monitor): Battery Backup with Pushbutton
Power Path Controller
Set JP1 (M1CONFG) to HI and JP2 (M2CONFG) to V2MON.
M1 is set high due to its internal pull-up current. M2 moni
-
tors V2. When V2 is below the trip threshold, both ideal
diodes are shutdown always and the input to the PB pin is
ignored. When V2 is above the trip threshold, the pushbut
-
ton has full control of the EN pin and ideal diode drivers.
Also while M1 is high, a transition on M2 will force a
pushbutton turn on or turn off. To test this, move the V2
input to be above and below the trip threshold.
