34704 datasheet(21/54 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34704

FUNCTIONAL DESCRIPTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

operation, or shuts down after a failure to regain normal

operation.

• A hard over-current limit (short-circuit limit) that is higher

than the cycle by cycle limit at which the device reacts by

shutting down the output immediately. This is necessary to

prevent damage in case of a short-circuit. After that, only

GrpB will attempt a one time retry after a time-out period of

10 ms and will go through a new soft start cycle

Output Over-voltage/Under-voltage Monitoring

In the case of an output over-voltage/under-voltage, the

user has two options that can be programmed through the

I2C interface:

Response A: The output will switch off automatically and

the 34704 would alert the processor through I2C that such an

event happened.

Response B: The output will not switch off. Rather the

34704 communicates to the processor that an over-voltage/

under-voltage condition has occurred and waits for the

processor decision to either shutoff or not; in the mean time

the control loop will try to fix itself.

NOTE: If Response A is set on any of the regulators from

GrpB, and a OV/UV event occurs in the correspondig

regulator, the complete device will shutdown and try to restart

as long as the OV/UV is no longer present. This will also set

the RST signal low until REG2, 3 and 4 are on regulation.

LOGIC AND CONTROL

Startup Sequencing

At power up, the VG regulator starts ramping up in peak

detect mode. Meanwhile, VDDI is tracking VG until it reaches

regulation and releases a POR signal that enables the

internal circuitry and reads the FREQ and SS configuration to

ramp up REG2, REG3 and REG4, that serve as the MPU

main power supplies. Once the MPU is up, I2C

communication is available to enable or disable GrpA, GrpC,

GrpD and GrpE. An extra sequence can be configured for

REG5, REG6 and REG7, changing the order in which they

ramp up when enabled. See Power-Up Sequence on page

28.

Soft Start Control

During power up the 34704 reads the SS terminal to

configure a default soft start timing for all regulators when

these are enabled. Soft start for REG5 to REG8 can be

changed via I2C at any time after power up has successfully

completed.

Phase Control

REG1 to REG5 use the main Switching frequency FSW1,

which is configured through the FREQ terminal at power up.

FSW1 uses 4 different phases of switching (clock is 80

degrees out of phase) to spread out the current draw by the

individual converters from the input supply over time to

reduce the peak input current demand. The remaining

regulators use FSW2 which can be programmed at any time

via I2C after a successful power up sequence.

Fault Register

The 34704 has a dedicate fault register accessible via I2C

which indicate which regulator is detecting a fault situation. In

addition to this, each channel has its own fault register which

indicates the type of fault detected in that regulator.

I2C communication and Registers

The 34704 can communicate using a standard I2C,

communication protocol or an accurate I2C protocol. During

the first one, the device processes the given command as

soon as it has received it. During the accurate data

communication, the device requires that each read/write

command be sent twice to validate the data. The 34704

provides a user accessible register map that allows various

general IC configurations as well as independent control of

each regulator, including fault flag registers and all

configurable features for each regulator.

OUTPUT GROUPS - REGULATORS

The 34704 is divided in 5 different groups which are

arranged as follows:

• GrpA: Includes REG1(26) (VOUT1)

• GrpB: Includes REG2, REG3, and REG4

• GrpC: Includes REG5, REG6(26), and REG7(26)

• GrpD: Includes REG8

• GrpE: This is a special group. It includes REG5 when

GrpC/E power sequencing option#1 is chosen

Turning on/off each group would cause all contained

regulators to turn on/off.

Notes

26.

Only on 34704A

34704 Datasheet(PDF) 21 Page - Freescale Semiconductor, Inc

34704 Datasheet(HTML) 21 Page - Freescale Semiconductor, Inc

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