SMB119 datasheet(21/34 Pages) SUMMIT

21 / 34 page

SMB119

Summit Microelectronics, Inc

APPLICATIONS INFORMATION (CONTINUED)

BATTERY MONITORING

The battery voltage is monitored for two user-

programmable UV settings via the VBATT pin.

Monitoring is accomplished by a comparator-based

approach, in which a programmable voltage reference

is compared against the monitored signal. Each

channel possesses a dedicated reference voltage

generated by a programmable level shifting digital to

analog converter.

The SMB119 contains two user programmable voltage-

monitoring levels (POWER_FAIL, nBATT_FAULT), one

of which triggers a corresponding status pin when

exceeded. Battery voltage, like all monitored voltages,

is compared against a user programmable voltage set

internally by a digital to analog converter.

When asserted, the POWER_FAIL pin is latched and

will not be released as long as the voltage on the

battery is below the POWER_FAIL level. Once the

voltage

the

battery

has

risen

above

the

POWER_FAIL level the following condition will clear the

latch and allow the POWER_FAIL pin to be released:

an I

2C POWER FAIL CLEAR command is issued. Once

this condition has been met, the POWER_FAIL pin will

be released after a power-fail timeout period (tPFTO) of

3.0-4.5ms.

The

POWER_FAIL

level

user

programmable from 2.55-3.6.0V at 150 mV increments.

When the voltage at the VBATT pin falls below the

second user programmable level, the active low

nBATT_FAULT pin will be asserted. This pin is not

latched and is used to indicate the impending loss of

power to the SMB119. After the nBATT_FAULT pin has

been asserted, a battery fault timeout period (tBFTO) of

3.0-4.5ms must pass in which the battery voltage

exceeds the nBATT_FAULT threshold before it will be

released. The nBATT_FAULT threshold is user

programmable from 2.55-3.6.0V at 150 mV increments.

Upon assertion of either the nBATT_FAULT or

POWER_FAIL pin the SMB119 can be programmed to

respond in one of three ways, it may perform: a power-

off operation, a force-shutdown operation, or take no

action. When programmed to perform a power-off or

force-shutdown operation the SMB119 can optionally

be programmed to latch the outputs off until the power

on pin is toggled or an I

2C power-on command is

issued.

LDO STANDBY VOLTAGE

The LDO has a programmable output voltage from 1.5V

to 3.75V. It is capable of supplying up to 80mA and has

UV and OV monitoring levels with corresponding fault

responses. The channel 3 LDO can be sequenced on

in any of the eight sequence positions, and can be

enabled and disabled at any time.

SOFT START

The SMB119 provides a 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; see Figure 6.

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.

OUTPUT VOLTAGE

The PWM output voltages are set by a resistive voltage

divider from the output to the COMP1 node. For the

buck channels (Ch[7:5]), the voltage divider is internal

to the part and programmable. The resistive divider

may be set by adjusting a 100kΩ resistor string with 8

taps from R1 = 20-90kΩ. For the boost outputs

(Ch[2:1]), the resistive divider is external and any

appropriate value of R1 an R2 can be chosen. The

reference voltage that sets the output is user

programmable, and may be set anywhere from 0-1.000

volt at 4mV increments.

PROGRAMMABLE SWITCHING FREQUENCY

The SMB119 has a 1000kHz switching frequency. If a

different frequency is desirable, please contact the

Summit factory.

DYNAMIC VOLTAGE MANAGEMENT

The SMB119 has three voltage settings, nominal,

margin high, and margin low. The nominal setting is the

voltage that the converter regulates at by default, while

the margin high and margin low voltages are

transitioned to by means of a volatile I

2C write

command. A status register is provided to indicate the

current margin state of each channel.

A seven level margining option is also available for

channels 4 and 5 of the SMB119 device. When

enabled, seven level margining allows channels 4 and

5 to be dynamically modified to one of seven pre-

determined voltage levels.

When seven level

margining is enabled channels 3, 6 and 7 loose the

margin high and margin low settings.

While a channel is dynamically changing its voltage the

UV/OV flags can be disabled temporarily, allowing the

channels time to reached the new voltage settings.

Note: Configuration writes or reads of registers

should not be performed while dynamic voltage

management.

SMB119 датащи(PDF) 21 Page - Summit Microelectronics, Inc.

SMB119 датащи(HTML) 21 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