DS1227 Datasheet, PDF (6/20 Pages) Dallas Semiconductor – KickStarter Chip

DS1227
sistor (if present) will then cause the voltage on MODE4
to further decay until it reaches ground or until the next
ON4 negative transition, whichever comes first.
When MODE4 is initially grounded as described above,
V_CCO4 power is switched from the V_DCO pin, regardless
of whether or not V_CCO1, V_CCO2, or V_CCO3, are powered
on. This means that V_CCO4 will be switched with the volt-
age present on V_DCO, which could be from +3V to +5V
depending on the configuration, input battery voltage
used, and whether or not V_CCO1, V_CCO2, or V_CCO3 are
switched on.
The above described sampling operation of V_CCO4 and
SENSE in response to ON4 also takes place when a
kickstart has already occurred and V_CCO1 is on. If
SENSE is found to be active in this condition, an inter-
rupt will be signalled on the INT/ACK pin.
MICRO ENERGY MANAGEMENT
In addition to the kickstarting features described above,
the DS1227 allows sections of system circuitry to be in-
dividually powered up or down under command of the
microcontroller. This capability is referred to as the Mi-
cro Energy Management feature of the DS1227.
V_CCO2 and V_CCO3 are auxiliary power supply outputs
which may be switched on or off via the ON2/OFF2 and
ON3/OFF3 pins, respectively. The ON2/OFF2 and
ON3/OFF3 control pins are intended for connection to
two microcontroller’s port pins configured as outputs.
The corresponding V_CCO output pins can then be turned
on or off as desired under control of the system applica-
tion software.
The ON2/OFF2 and ON3/OFF3 inputs are level acti-
vated. The corresponding V_CCO output therefore turns
on when the on/off pin is high and off when it is low.
These inputs are active only if the V_CCO1 output is on
and the INT/ACK output has been set to a high state sig-
nalling a power on reset condition.
When V_CCO2 or V_CCO3 are turned on, they will remain
on until the corresponding control input is taken low by
the software. This is true even if the OFF1 input is taken
to its active low state at the time that either ON2/OFF2,
ON3/OFF3, or both, are high.
Once OFF1 is activated, the current states of
ON2/OFF2 and ON3/OFF3 are internally latched and
further activity on these pins is ignored. If both of the cor-
responding outputs (V_CCO2 and V_CCO3) are turned off at
this time and boost operation has been selected, then
the internal oscillator is killed and the DC-to-DC conver-
ter will be shut down. If either V_CCO2 and/or V_CCO3 are
left switched on when OFF1 is activated, they will re-
main switched on even after V_CCO1 has been turned off.
If the DS1227 has been configured for boost operation,
the DC-to-DC converter will remain operational during
the entire time that V_CCO1 is turned off so that +5 volts
will continue to be supplied on either or both of these
output pins. These pins can be shut off only when kick-
starting occurs once again and V_CCO1 is switched on
and INT/ACK has been set high.
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