SMB119 datasheet(18/34 Pages) SUMMIT

18 / 34 page

SMB119

Summit Microelectronics, Inc

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 0.1

µA when asserted. In this mode all channels are

shut off. When asserted the SMB119 will not respond to

2C 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

2C 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

When enabling a channel from the enable register, 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

contents.

The

SMB119 navigates between each sequence position

using a feedback-based cascade-sequencing circuit.

Cascade sequencing is the process in which each

channel

continually

compared

against

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)

SMB119 Datasheet(PDF) 18 Page - Summit Microelectronics, Inc.

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