SMB110 datasheet(20/34 Pages) SUMMIT

20 / 34 page

SMB110

Preliminary Information

Summit Microelectronics, Inc

2099 2.3 3/1/2005

APPLICATIONS INFORMATION

DEVICE OPERATION

POWER SUPPLY

The SMB110 can be powered from an input voltage

between 2.7-6.0 volts applied between the VBATT pin

and ground. The input voltage applied to the VBATT pin

is internally regulated and used as an internal VBATT

supply.

The

VBATT

monitored

UnderVoltage Lockout (UVLO) circuit, which prevents

the device from turning on when the voltage at this

node is less than the UVLO threshold.

POWER-ON/OFF CONTROL

The outputs on the SMB110 can be turned on in one of

three ways: first a general purpose enable input pin

PWREN0, second an I

2C Power on command can be

issued, or third if a programmable bit is set to initiate

the power on process when the UVLO threshold is

exceeded. a restart will only occur if the power-on pin is

toggled or an I

2C Power on command is issued.

ENABLE

Once a power on command has been issued, the

power on process can be controlled by means of an

enable signal. Each channel can be controlled by one

of four enable signals and the assignment type can be

mixed and matched for each of the four channels. The

enable signal can stall the power-on process until the

enable is valid, or disable a controller once all supplies

have been enabled. There are two ways to generate

the enable signal; the first approach allows the enable

signal to be assigned the PWREN0 pin, and the second

approach allows the enable to be controlled by the

contents of a volatile register that can be written to at

any time. This volatile register will be automatically

initialized once the UVLO threshold has been exceeded

to a known programmed state.

POWER-ON SEQUENCING

Each channel on the SMB110 may be placed in any

one of four unique sequence positions. To provide

programmable order, the SMB110 navigates between

these sequence positions 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.

Once power-on sequencing has been initiated,

automated sequencing may commence in one of three

ways (Figure 7): normal sequencing, sequencing with

enable, and sequencing with channel bypass. In

addition, each channel may be powered on in a manual

mode, independent of the sequence position. The

power-on sequencing mode selection is programmable

over the I

2C bus and stored in the non-volatile memory.

NORMAL CASCADE SEQUENCING

During Normal Sequencing, the sequence position

counter is initialized to the first sequence position

(position 1), each channel occupying this position then

waits an individual programmable timeout period (tPPTO)

of 1.5, 12.5, 25, or 50 ms. Once enabled, all channels

occupying the first sequence position will begin a soft-

start. As the output voltage of the channel is ramped

up, it is monitored by a comparator based, user

programmable, under-voltage threshold sensor. After

this threshold is exceeded, indicating that the selected

channel(s) have reached their nominal operating range

the sequence position counter is incremented, and fault

monitoring begins for that channel. Once all channels

occupying the first sequence position have surpassed

their under-voltage thresholds, the power-on delay for

the next sequence position will begin. This process

continues until all channels have been sequenced on

and are above their under-voltage threshold.

SEQUENCING WITH ENABLE

During the Sequencing With Enable mode, sequencing

commences as with the Normal Sequencing, except

that prior to a channel beginning to soft-start, the

enable corresponding to that channel must be asserted.

In the event that the enable is not asserted, sequencing

will halt indefinitely until a valid enable is provided.

Once a valid enable is provided, a soft-start function will

begin for that channel. This process will continue until

all channels occupying the first sequence position are

above their under-voltage settings, at which point the

sequence position counter will be incremented.

SEQUENCING WITH CHANNEL BYPASS

When the Sequencing With Channel Bypass mode is

selected, sequencing will commence as with the

Sequencing With Enable, except that if the enable

signal is not asserted by the end of the power-on delay

period, that channel will be bypassed. If no other

channels occupy the current sequence position, the

sequence position counter will

incremented

beginning the power-on delay for all channels in the

next sequence position. Once a channel has been

bypassed, it may still be enabled any time prior to a

power off operation.

SMB110 датащи(PDF) 20 Page - Summit Microelectronics, Inc.

SMB110 датащи(HTML) 20 Page - Summit Microelectronics, Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

датащи скачать

ссылки URL