34704_09 Datasheet, PDF (27/49 Pages) Freescale Semiconductor, Inc – Multiple Channel DC-DC Power Management IC

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
POWER-UP SEQUENCE
Following is the power up sequence from a battery
connection or a Power On signal through the ONOFF pin.
1. Battery initially connected to VIN.
2. LION pin is used to determine if a battery is being used
(High for Li-Ion battery).
3. At initial power up from a cold start like the above with
the battery first connected, the status of the ONOFF
pin is ignored and 34704A moves forward to step (5).
4. After the cold start or battery insertion power up,
activity on the ONOFF pin is used to determine if the
device is enabled or disabled. If the device is disabled,
then nothing happens. If the device is enabled then,
34704 moves forward to step (5).
5. The input battery UVLO signal de-asserts if the input
voltage is above the UVLO rising threshold.
6. REG1 VG starts up in peak detect PFM and REG1 VG
output starts rising.
7. V_DDI output voltage will start tracking REG1 VG output.
8. When REG1 VG output rises high enough such that
V_DDI voltage is in regulation a POR signal is released
and all internal circuitry can be enabled. I²C
communication will remain disabled for normal power
up sequence. The values of the FREQ and SS pins are
read at this point.
9. REG1 PWM control loop can take over control of
REG1 output once the VG voltage reaches a certain
threshold set internally.
10. When REG1 is in regulation, it will be used to supply
the Power MOSFET gate voltage for all of the other
regulators except REG7.
11. REG3 is enabled, then when REG3 is in regulation.
12. REG2 is enabled, then when REG2 is in regulation.
13. REG4 is enabled, then when REG4 is in regulation.
14. I²C communication is enabled now since the processor
supplies are up.
15. 34704A will de-assert the RST signal to indicate a
“Power Good” after 10ms of wait time. This output will
be connected to the reset pin of the microprocessor.
16. The microprocessor then takes over and can enable
REG1 VOUT1 and REG5 through REG8. The
processor needs to send a command for REG8 mode
of operation. The processor can also change REG5-8
soft start time before enabling them. The processor can
also power down the system with an ALLOFF
command.
For power sequencing needs, the different regulators are
grouped based on their function and how they relate to each
other and the entire system. This makes power sequencing
control a much easier task for the user where most of the
group internal sequencing in now handled by the PMIC. All
the processor has to do is to command the group and not
each regulator.
The regulators groups are as follows:
• GrpA: Includes REG1 (VOUT1)
• GrpB: Includes REG2, REG3, and REG4
• GrpC: Includes REG5, REG6, and REG7
• GrpD: Includes REG8
• GrpE: This is a special group. It includes REG5 when
GrpC/E power sequencing option#1 is chosen
SHUTDOWN SEQUENCES
• Processor can disable VOUT1 (GrpA) at any point it
desires
• Processor can disable REG8 (GrpD) at any point it desires
• Processor can disable REG5 (GrpE) at any point it desires
ONLY IF CCD sequencing option#1 is picked
• Processor can shutdown GrpC according to the CCD
power sequencing options 1, 2, 3, or 4 (see section “I²C
Programmability”)
• If any regulator in GrpC is shutting down due to a fault, the
other regulators in GrpC will also shutdown by following
the CCD power sequencing options 1, 2, 3, or 4 (see
section “I²C Programmability”)
• If any regulator in GrpB is shutting down due to a fault, the
other regulators in GrpB will also shutdown by following
the processor supplies shutdown sequence. Then, GrpA,
GrpC, GrpD, and GrpE (if applicable) will simultaneously
shutdown keeping any sequencing within each group as
necessary. VG will stay alive to perform a power up retry
for GrpB but only for one time. If the power up cycle is
successful, then normal operation is back. If the fault
returns, then the shutdown sequence is repeated and then
VG shuts down
• Processor can shutdown the 34704 by sending an
“ALLOFF” command, then GrpA, GrpC, GrpD, and GrpE
(if applicable) will simultaneously shutdown keeping any
sequencing within each group as necessary. Then, GrpB
will shutdown according to the processor supply shutdown
sequence. Then, VG will shut down.
• The previous shutdown event can also happen through the
ONOFF pin by pressing and holding the pin for a time
period (programmable through I²C with a default of 1sec)
• During battery depletion and when the input voltage
passes the UVLO falling threshold, all of the outputs will be
disabled without honouring the power down sequence
This is to guarantee that the outputs are off and battery is
not depleted further.
Analog Integrated Circuit Device Data
Freescale Semiconductor
34704
27