34716 datasheet(13/25 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34716

FUNCTIONAL DESCRIPTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

Figure 5. Block Illustration

INTERNAL BIAS CIRCUITS

This block contains all circuits that provide the necessary

supply voltages and bias currents for the internal circuitry. It

consists of:

• Internal Voltage Supply Regulator: This regulator

supplies the VDDI voltage that is used to drive the digital/

analog internal circuits. It is equipped with a Power-On-

Reset (POR) circuit that watches for the right regulation

levels. External filtering is needed on the VDDI pin. This

block will turn off during the shutdown mode.

• Internal Bandgap Reference Voltage: This supplies the

reference voltage to some of the internal circuitry.

• Bias Circuit: This block generates the bias currents

necessary to run all of the blocks in the IC.

SYSTEM CONTROL AND LOGIC

This block is the brain of the IC where the device

processes data and reacts to it. Based on the status of the

STBY and SD pins, the system control reacts accordingly and

orders the device into the right status. It also takes inputs

from all of the monitoring/protection circuits and initiates

power up or power down commands. It communicates with

the buck converter to manage the switching operation and

protects it against any faults.

OSCILLATOR

This block generates the clock cycles necessary to run the

IC digital blocks. It also generates the buck converters

switching frequency. The switching frequency can be

programmed by connecting a resistor divider to the FREQ

pin, between VDDI and GND pins (See Figure 1, page 1).

PROTECTION FUNCTIONS

This block contains the following circuits:

• Over Current Limit and Short Circuit Detection: This

block monitors the output of the buck converters for

over current conditions and short circuit events and

alerts the system control for further command.

• Thermal Limit Detection: This block monitors the

temperature of the device for overheating events. If the

temperature rises above the thermal shutdown

threshold, this block will alert the system control for

further commands.

• Output Overvoltage and Undervoltage Monitoring: This

block monitors the buck converters output voltages to

ensure they are within regulation boundaries. If not, this

block alerts the system control for further commands.

CONTROL AND SUPERVISORY FUNCTIONS

This block is used to interface with an outside host. It

contains the following circuits:

• Standby Control Input: An outside host can put the

34716 device into standby mode (S3 or Suspend-To-

RAM mode) by sending a logic “0” to the STBY pin.

• Shutdown Control Input: An outside host can put the

34716 device into shutdown mode (S5 or Suspend-To-

Disk mode) by sending a logic “0” to the SD pin.

• Power Good Output Signal: The 34716 can

communicate to an outside host that a fault has

occurred by pulling the voltage on the PG pin high

through a pull up resistor.

Internal Bias

System Control

Oscillator

Circuits

& Logic

Control &

Protection

Tracking &

Supervisory

Functions

Sequencing

2 x Buck Converter

34716 数据表(PDF) 13 Page - Freescale Semiconductor, Inc

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