SMB113A/B/SMB117/A
Preliminary Information
APPLICATIONS INFORMATION (CONTINUED)
MANUAL MODE
a power-off operation, a force-shutdown operation
and-or it can trigger the nRESET/HEALTHY pin.
The SMB113A/B and SMB117/A provide a manual
power-on mode in which each channel may be
enabled individually irrespective of the state of other
channels. In this mode, the enable signal has
complete control over the channel, and all sequencing
is ignored. In Manual mode, channels will not be
disabled in the event of a UV/OV fault on any output or
the VBATT pin.
SOFT START
The SMB113A/B and SMB117/A provide
a
programmable soft-start function for all PWM outputs.
The soft-start control limits the slew rate that each
output is allowed to ramp up without the need for an
external capacitor. The soft start slew rate is
proportional to the product of the output voltage and a
slew rate reference. This global reference is
programmable and may be set to 400, 200, 100, 67,
50, 33, 25, and 20 Volts per second. The slew rate
control can also be disabled on any channel not
requiring the feature.
FORCE-SHUTDOWN
When a battery fault occurs, a UV/OV is detected on
any output, or an I2C force-shutdown command is
issued, all channels will be immediately disabled,
ignoring sequence positions or power off delay times.
DYNAMIC VOLTAGE MANAGEMENT
SEQUENCE TERMINATION TIMER
The SMB113A/B/117/A have two additional voltage
settings, dynamic voltage control high and low
settings. Together with the nominal voltage setting,
three pre-determined voltage levels can be used. The
three voltage levels are ideal for situations where a
core voltage needs to be reduced for power
conservation.
At the beginning of each sequence position, an
internal programmable timer will begin to time out.
When this timer has expired, the SMB113A/B and
SMB117/A will automatically perform a force-shutdown
operation. This timer is user programmable with a
programmable sequence termination period (tPST) of
50, 100, 200 ms; this function can also be disabled.
The dynamic voltage control high and low settings
have the same voltage range as the controllers’
nominal output voltage. These settings are stored in
the non-volatile configuration registers and can be set
by a write to volatile configuration registers. The
dynamic voltage control command registers contain
two bits for each channel that adjust the output
voltages to the high, low or nominal set point after a
volatile I2C write command.
A seven level dynamic voltage control option is
available for channel 3. When enabled, seven level
dynamic voltage control allows channel 3 to be
dynamically modified to one of seven pre-determined
voltage levels. This transition is made by means of a
volatile I2C write command.
POWER OFF SEQUENCING
The SMB113A/B and SMB117/A have a power-off
sequencing operation. During a power off operation,
the supplies will be powered off in the reverse order
they where powered on in. During the power off
sequencing, all enables are ignored.
When a power-off command is issued the SMB113A/B
and SMB117/A will set the sequence position counter
to the last sequence position and disable that channel
without soft-start control; once off, the power off delay
for the channel(s) in the next to last sequence position
will begin to timeout, after which that channel(s) will be
disabled. This process will continue until all channels
have been disabled and are off. The programmable
If a channel fails to turn off within the sequence
termination period, the sequence termination timer will
initiate a force shutdown, if enabled.
When all channels are at their voltage setting, a bit is
set in the dynamic voltage control status registers.
INPUT AND OUTPUT MONITORING
Vout
R2
Both products monitor all outputs for under-voltage
(UV) and over-voltage (OV) faults. The monitored
levels are user programmable, and may be set at 5,
10, 15, and 20 percent of the nominal output voltage.
The VBATT pin is monitored for two user
programmable UV settings. The VBATT UV settings
are programmable from 2.55V to 3.45V in 150mV
increments. Once the UV/OV voltage set points have
been violated, the SMB113A/B and SMB117/A can be
programmed to respond in one of three ways, perform:
COMP1
+
–
VREF
R1
Soft-Start Slew Rate=SRref* (1 + R2/R1)
Vout= Vref* (1 + R2/R1)
Figure 6 – The output voltage is set by the voltage
divider. The VREF voltage is programmable from 0
to 1.0 volt in 4mV increments via the I2C interface
Summit Microelectronics, Inc
2111 2.4 6/24/2008
17
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
