LTC3589_12 Datasheet, PDF (30/50 Pages) Linear Technology – 8-Output Regulator with Sequencing and I2C

LTC3589/LTC3589-1/
LTC3589-2
OPERATION
power-up state (PUP) until ON is held LOW for at least
400ms (PB400ms) or until PWR_ON is activated by the
PWR_ON pin. When the controller enters the PUP state
the open-drain WAKE pin releases HIGH. The WAKE pin
is typically used to enable the first regulator in a start-up
sequence. The pushbutton state will stay in PUP for five
seconds before transitioning to the power-on (PON) state.
Before leaving PUP, the PWR_ON pin must be brought
HIGH by the application to indicate that the system rails
are correct. If PWR_ON is not active at the end of five
seconds the pushbutton controller will continue directly
through PON to the power-down (PDN) state and pull the
WAKE pin down. Three events will cause the pushbutton
to leave the PON state: 1) lowering the PWR_ON pin, 2)
forcing a hard reset by holding the ON pin LOW for five
seconds, and 3) a fault condition is detected. Fault condi-
tions are low V_IN, device over temperature, or extended
undervoltage of one of the regulator outputs. All regulator
enables, the ON input, and PWR_ON signals are inhibited
for one second while in the PDN state. After one second
in PDN the pushbutton controller returns to POFF.
PBSTAT Operation
PBSTAT goes LOW 50ms after the initial pushbutton ap-
plication (ON LOW) and will stay LOW for a minimum of
50ms. PBSTAT will go HIGH coincident with ON going HIGH
unless ON goes HIGH before the 50ms minimum on-time.
Power-Up Using the Pushbutton
When in the POFF standby state, the LTC3589 is in com-
plete shutdown except the always active LDO1 and any
regulators enabled with the keep-alive control bits. Pull the
ON pin to ground with a pushbutton for 400ms to begin a
power-up sequence with the WAKE pin tied to an enable
pin. Drive PWR_ON high within five seconds to signal the
LTC3589 to remain in the power-on state.
Power-Down Using the Pushbutton
The pushbutton power-down operation is performed by
the system microprocessor by monitoring the PBSTAT pin.
Once in the PON state, the system controller is responsible
for deciding what action to take with a pushbutton event.
When the ON pin is held LOW for a 50ms debounce period,
the PBSTAT pin is pulled LOW. The system controller should
monitor the PBSTAT pin to determine the pushbutton has
been pushed. If the controller decides that a power-down
is desired, then it should drive the PWR_ON pin LOW.
Power-Up and Down Using PWR_ON Pin
An alternate power-up method is to drive the PWR_ON pin
to a HIGH state. After a delay of 50ms from the PWR_ON
signal, the WAKE pin will pull HIGH to drive regulator en-
able pins. When PWR_ON is HIGH for five seconds, the
sequence controller will enter the PON state. To power
down, drive the PWR_ON pin LOW. 50ms later WAKE will
pull low, all enabled regulators are disabled and the OVEN
command register is reset to 0x00.
Hard Reset Using the Pushbutton
When the ON pin is pulled LOW for five seconds, a hard
reset is initiated. At the end of five seconds, WAKE is
pulled LOW, the I²C command registers are reset to POR
states, enable pin states are ignored, and the one second
power-down timer is started. During the power-down time,
the enables continue to be ignored to allow the regulator
outputs to discharge. The RSTO pin is pulled LOW for
the power-down time to indicate a pushbutton hard reset
occurred. If the PWR_ON pin is LOW at the end of the
one second power-down time, the LTC3589 will remain
in standby mode. If PWR_ON is HIGH at the end of one
second and there are no fault conditions, the LTC3589 will
power-up in the same way shown in Figure 8.
Hard Reset Due to a Fault Condition
A hard reset due to V_IN undervoltage, extended undervolt-
age of an output rail, or an overtemperature condition
initiates a hard shutdown of the LTC3589. When the fault
occurs, wake is pulled LOW, the I²C command registers
are reset to POR states, enable pin inputs are ignored,
and the one second power-down timer is started. Dur-
ing the power-down time, the enables continue to be
ignored to allow the regulator outputs to discharge. If the
PWR_ON pin is LOW at the end of the power-down time,
the LTC3589 will remain in standby mode with just the
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