SMB214B datasheet(15/26 Pages) SUMMIT

15 / 26 page

SMB214A/B/C

Summit Microelectronics, Inc

2128 2.0 6/20/2008

APPLICATIONS INFORMATION

DEVICE OPERATION

POWER SUPPLY

There are four supply input pins on the SMB214A/B/C:

three HVSUP pins and the VBATT pin. Each supply

must be powered from an input voltage between 2.7-

6.0 volts.

The HVSUP0 though HVSUP2 are used to power the

HSDRV (PMOS driver) and LSDRV (NMOS driver)

outputs. The rail-to-rail swing on the HSDRV and

LSDRV pins is equal to the associated HVSUP supply

voltage.

The VBATT pin is internally regulated to 2.5V. This

2.5V supply is then filtered on the VDD_CAP pin and

used to power all internal circuitry. The VBATT pin 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.

OUTPUT VOLTAGE

All output voltages on the SMB214A/B/C can be set

via the non-volatile configuration registers.

Each of the three step-down output voltages on the

SMB214A/B/C can be adjusted for 100% duty cycle or

0% duty cycle operation.

When 100% duty cycle mode is selected, the output

voltage can be set up to the input voltage on the

device, while the minimum output voltage is limited to

the min duty cycle specification in the DC operating

characteristics section.

When the 0% duty cycle mode is selected, the

maximum duty cycle is limited to the max duty cycle

specification in the DC operating characteristics

section.

POWER-ON/OFF CONTROL

Sequencing can be initiated: automatically, by a

volatile I

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.

ENABLE

Each output can be enabled and disable by an enable

signal. The enable signal is can be provided from

either the PWREN pin 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). The default state is programmable.

CASCADE SEQUENCING

Each channel on the SMB214A/B/C may be placed in

any one of 3 unique sequence positions, as assigned

by the configurable non-volatile register contents. The

SMB214A/B/C navigate 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.

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 three sequence positions.

MANUAL MODE

The SMB214A/B/C 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.

FORCE-SHUTDOWN

When a battery fault occurs, a UV/OV is detected on

any output, or an I

2C 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 SMB214A/B/C 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.

SMB214B 数据表(PDF) 15 Page - Summit Microelectronics, Inc.

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