SMB117 datasheet(17/32 Pages) SUMMIT

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SMB113A/B/SMB117/A

Preliminary Information

Summit Microelectronics, Inc

2111 2.4 6/24/2008

APPLICATIONS INFORMATION (CONTINUED)

MANUAL MODE

The SMB113A/B and SMB117/A 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 SMB113A/B and

SMB117/A 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.

POWER OFF SEQUENCING

The SMB113A/B and SMB117/A have a power-off

sequencing operation. During a power off operation,

the supplies will be powered off in the reverse order

they where powered on in. During the power off

sequencing, all enables are ignored.

When a power-off command is issued the SMB113A/B

and SMB117/A will set the sequence position counter

to the last sequence position and disable that channel

without soft-start control; once off, the power off delay

for the channel(s) in the next to last sequence position

will begin to timeout, after which that channel(s) will be

disabled. This process will continue until all channels

have been disabled and are off. The programmable

If a channel fails to turn off within the sequence

termination period, the sequence termination timer will

initiate a force shutdown, if enabled.

INPUT AND OUTPUT MONITORING

Both products monitor all outputs for under-voltage

(UV) and over-voltage (OV) faults. The monitored

levels are user programmable, and may be set at 5,

10, 15, and 20 percent of the nominal output voltage.

The

VBATT

monitored

for

two

user

programmable UV settings. The VBATT UV settings

are programmable from 2.55V to 3.45V in 150mV

increments. Once the UV/OV voltage set points have

been violated, the SMB113A/B and SMB117/A can be

programmed to respond in one of three ways, perform:

a power-off operation, a force-shutdown operation

and-or it can trigger the nRESET/HEALTHY pin.

SOFT START

The

SMB113A/B

and

SMB117/A

provide

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. 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.

DYNAMIC VOLTAGE MANAGEMENT

The SMB113A/B/117/A have two additional voltage

settings, dynamic voltage control high and low

settings. Together with the nominal voltage setting,

three pre-determined voltage levels can be used. The

three voltage levels are ideal for situations where a

core voltage needs to be reduced for power

conservation.

The dynamic voltage control high and low settings

have the same voltage range as the controllers’

nominal output voltage. These settings are stored in

the non-volatile configuration registers and can be set

by a write to volatile configuration registers.

The

dynamic voltage control command registers contain

two bits for each channel that adjust the output

voltages to the high, low or nominal set point after a

volatile I2C write command.

A seven level dynamic voltage control option is

available for channel 3. When enabled, seven level

dynamic voltage control allows channel 3 to be

dynamically modified to one of seven pre-determined

voltage levels. This transition is made by means of a

volatile I

2C write command.

When all channels are at their voltage setting, a bit is

set in the dynamic voltage control status registers.

–

VREF

COMP1

Vout

Vout= Vref* (1 + R2/R1)

Soft-Start Slew Rate=SRref* (1 + R2/R1)

Figure 6 – The output voltage is set by the voltage

divider. The VREF voltage is programmable from 0

to 1.0 volt in 4mV increments via the I

2C interface

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