SMB119N View Datasheet(PDF) - Summit Microelectronics
Part Name
Description
MFG CO.
'SMB119N' PDF : 34 Pages View PDF
SMB119
APPLICATIONS INFORMATION
DEVICE OPERATION
POWER SUPPLY
The SMB119 can be powered from an input voltage
between +2.7 and +6.0 volts applied between the
VBATT pin and ground. The SMB119 is optimized for
use with a rechargeable single cell Lithium ion battery,
but may also be powered from a rectified AC adaptor or
three AA batteries. The input voltage applied to the
VBATT pin is filtered by an external filter capacitor
attached between the VDD_CAP pin and ground; this
filtered voltage is then used as an internal VDD supply.
The VDD_CAP node is monitored by an Under-voltage
Lockout (UVLO) circuit, which prevents the device from
turning on when the voltage at this node is less than the
UVLO threshold.
SHUTDOWN
A shutdown pin is provided, that disconnects power
from the SMB119 and reduces the current consumption
to 0.1µA when asserted. In this mode all channels are
shut off. When asserted the SMB119 will not respond to
I2C commands.
Once the voltage on the VBATT input supply pin
exceeds the UVLO threshold a 10 to 20ms delay must
pass before supplies can be enabled. During this period
the non-volatile registers are initialized with the default
values from the nonvolatile memory.
POWER-ON/OFF CONTROL
Sequencing can be initiated: automatically, by a volatile
I2C Power on command, or by asserting the PWREN
pin. When the PWREN pin is programmed to initiate
sequencing, it can be level or edge triggered. The
PWREN input has a programmable de-bounce time of
100, 50, or 25ms. The de-bounce time can also be
disabled.
When configured as a push-button enable, PWREN
must be asserted longer than the de-bounce time
before sequencing can commence, and pulled low for
the same period to disable the channels.
INDEPENDENT CHANNEL ENABLE CONTROL
Each output can be enabled and disable by an enable
signal. The enable signal is can be provided from either
the Enable pins or by the contents of the enable
register.
When enabling a channel from the enable register, the
register contents default state must be set so that the
output will be enabled or disabled following a POR
(power on reset).
When Default On is selected, the channel will turn on
after its sequence position is reached or power is
applied—depending on the sequencing type. When
Default Off is selected, the channel will not turn on until
SEQUENCING
Each channel on the SMB119 may be placed in any
one of 7 unique sequence positions, as assigned by the
configurable non-volatile register contents. The
SMB119 navigates between each sequence position
using a feedback-based cascade-sequencing circuit.
Cascade sequencing is the process in which each
channel is continually compared against a
programmable reference voltage until the voltage on
the monitored channel exceeds the reference voltage,
at which point an internal sequence position counter is
incremented and the next sequence position is entered.
In the event that a channels enable input is not
asserted when the channel is to be sequenced on, that
sequence position will be skipped and the channel in
the next sequence position will be enabled.
Figure 11 – Power on sequencing waveforms.
Time = 4ms/devision, Scale = 1V/devision
Ch 1 = 3.3V output (Yellow trace)
Ch 2 = 2.5V output (Blue trace)
Ch 3 = 1.8V output (Purple trace)
Ch 4 = 1.2V output (Green trace)
Summit Microelectronics, Inc
18
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