SMB119N View Datasheet(PDF) - Summit Microelectronics
Part Name
Description
MFG CO.
'SMB119N' PDF : 34 Pages View PDF
SMB119
APPLICATIONS INFORMATION (CONTINUED)
BATTERY MONITORING
The battery voltage is monitored for two user-
programmable UV settings via the VBATT pin.
Monitoring is accomplished by a comparator-based
approach, in which a programmable voltage reference
is compared against the monitored signal. Each
channel possesses a dedicated reference voltage
generated by a programmable level shifting digital to
analog converter.
The SMB119 contains two user programmable voltage-
monitoring levels (POWER_FAIL, nBATT_FAULT), one
of which triggers a corresponding status pin when
exceeded. Battery voltage, like all monitored voltages,
is compared against a user programmable voltage set
internally by a digital to analog converter.
When asserted, the POWER_FAIL pin is latched and
will not be released as long as the voltage on the
battery is below the POWER_FAIL level. Once the
voltage on the battery has risen above the
POWER_FAIL level the following condition will clear the
latch and allow the POWER_FAIL pin to be released:
an I2C POWER FAIL CLEAR command is issued. Once
this condition has been met, the POWER_FAIL pin will
be released after a power-fail timeout period (tPFTO) of
3.0-4.5ms. The POWER_FAIL level is user
programmable from 2.55-3.6.0V at 150 mV increments.
When the voltage at the VBATT pin falls below the
second user programmable level, the active low
nBATT_FAULT pin will be asserted. This pin is not
latched and is used to indicate the impending loss of
power to the SMB119. After the nBATT_FAULT pin has
been asserted, a battery fault timeout period (tBFTO) of
3.0-4.5ms must pass in which the battery voltage
exceeds the nBATT_FAULT threshold before it will be
released. The nBATT_FAULT threshold is user
programmable from 2.55-3.6.0V at 150 mV increments.
Upon assertion of either the nBATT_FAULT or
POWER_FAIL pin the SMB119 can be programmed to
respond in one of three ways, it may perform: a power-
off operation, a force-shutdown operation, or take no
action. When programmed to perform a power-off or
force-shutdown operation the SMB119 can optionally
be programmed to latch the outputs off until the power
on pin is toggled or an I2C power-on command is
issued.
LDO STANDBY VOLTAGE
The LDO has a programmable output voltage from 1.5V
to 3.75V. It is capable of supplying up to 80mA and has
UV and OV monitoring levels with corresponding fault
responses. The channel 3 LDO can be sequenced on
Summit Microelectronics, Inc
21
in any of the eight sequence positions, and can be
enabled and disabled at any time.
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; see Figure 6.
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.
OUTPUT VOLTAGE
The PWM output voltages are set by a resistive voltage
divider from the output to the COMP1 node. For the
buck channels (Ch[7:5]), the voltage divider is internal
to the part and programmable. The resistive divider
may be set by adjusting a 100kΩ resistor string with 8
taps from R1 = 20-90kΩ. For the boost outputs
(Ch[2:1]), the resistive divider is external and any
appropriate value of R1 an R2 can be chosen. The
reference voltage that sets the output is user
programmable, and may be set anywhere from 0-1.000
volt at 4mV increments.
PROGRAMMABLE SWITCHING FREQUENCY
The SMB119 has a 1000kHz switching frequency. If a
different frequency is desirable, please contact the
Summit factory.
DYNAMIC VOLTAGE MANAGEMENT
The SMB119 has three voltage settings, nominal,
margin high, and margin low. The nominal setting is the
voltage that the converter regulates at by default, while
the margin high and margin low voltages are
transitioned to by means of a volatile I2C write
command. A status register is provided to indicate the
current margin state of each channel.
A seven level margining option is also available for
channels 4 and 5 of the SMB119 device. When
enabled, seven level margining allows channels 4 and
5 to be dynamically modified to one of seven pre-
determined voltage levels. When seven level
margining is enabled channels 3, 6 and 7 loose the
margin high and margin low settings.
While a channel is dynamically changing its voltage the
UV/OV flags can be disabled temporarily, allowing the
channels time to reached the new voltage settings.
Note: Configuration writes or reads of registers
should not be performed while dynamic voltage
management.
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