SMB119N View Datasheet(PDF) - Summit Microelectronics
Part Name
Description
MFG CO.
'SMB119N' PDF : 34 Pages View PDF
SMB119
APPLICATIONS INFORMATION (CONTINUED)
POWER ON/OFF DELAY
There is a programmable delay between when
channels in subsequent sequence positions are
enabled. The delay is programmable at 50, 25, 12.5
and 1.5ms intervals. This delay is programmable for
each of the seven sequence positions.
MANUAL MODE
The SMB119 provides 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.
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.
SEQUENCE TERMINATION TIMER
At the beginning of each sequence position, an internal
programmable timer will begin to time out. When this
timer has expired, the SMB119 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.
POWER OFF SEQUENCING
The SMB119 has 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.
When a power-off command is issued the SMB119 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.
INPUT AND OUTPUT MONITORING
The SMB119 monitors 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 SMB119 can be programmed to
respond in one of three ways, perform: a power-off
operation, a force-shutdown operation and-or it can
trigger the nRESET/HEALTHY pin.
SOFT START
The SMB119 provides 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.
Vout
R2
COMP1
+
R1 VREF –
Soft-Start Slew Rate=SRref* (1 + R2/R1)
Vout= Vref* (1 + R2/R1)
Figure 12 – 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
19
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