34704 datasheet(16/54 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34704

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

The 34704 is an multi-channel power management IC

(PMIC) meant to address power management needs for

various multimedia applications microprocessors in various

configurations with a target overall efficiency of > 80% at

typical loads.

The 34704 accepts an input voltage from various sources:

•1 cell Li-Ion/Polymer (2.7 to 4.2 V)

•5.0 V USB supply or AC wall adapter

The different channels are:

REGULATOR

REGULATOR TYPE

VOUT TYP (V)

IOUT TYP (MA)

IOUT MAX (MA)

TARGET APPLICATION

REG1(25)

Synchronous Boost

5.0

100

500

+5.0 V REF

REG2

Synchronous Buck-Boost

2.8 / 3.3

200

500

µP I/O

REG3

Synchronous Buck

1.2 / 1.5 / 1.8

150

550

µP Core

REG4

Synchronous Buck-Boost

1.8 / 2.5

100

300

DDR

REG5

Synchronous Buck-Boost

3.3

150

500

µP I/O

REG6(25)

Synchronous Boost

15.0

REF+

REG7(25)

Inverter Boost

-7.0

REF -

REG8

Synchronous Boost

15.0

Backlight Display

Notes

24.

Synchronous Buck-Boost: These regulators can work as pure BUCK regulator when the output voltage is lower than the input voltage;

and work as pure BOOST regulator when the input voltage is lower than the output voltage. Compensation should be done for the worst

case scenario, which is in most of the cases when the device is working as a boost converter, after compensating for this scenario it is

recommended to verify the buck operation to assure stability in the whole operating range.

25.

Available only on the 34704A

REG1, REG3, REG6, and REG8 use internal

compensation, while REG2, REG4, REG5, and REG7 use

external compensation.

The switching frequency of all regulators except REG6, 7,

& 8 can be selected through the FREQ pin between 750 kHz

and 2.0 MHz in 250 kHz steps. The high frequency operation

is meant to minimize the size of external components while

lower operating frequencies will allow for higher efficiency.

REG7 is limited to operate at a lower frequency to minimize

switching noise induced by driving the external switching

MOSFET, but also can operate at the 1.0 MHz value with

proper board layout. REG 6, 7, and 8 switching frequency can

be selected between 250 kHz and 1.0 MHz in 250 kHz steps

through I2C.

For all regulators and at lower loads, a pulse skipping

mode is implemented to maintain high efficiency.

Note that pulse skipping occurs when the regulator enters

into discontinuous conduction mode (DCM) at very light

loads, however transitions between DCM and CCM may

result in noisy switching nodes, therefore it is recommended

to design the regulators to work in CCM all the time. Pulse

skipping function is not guaranteed by circuit implementation.

The 34704 uses 4 different phases of switching for all

regulators except REG6, 7, and 8, to spread out the current

draw by the individual converters from the input supply over

time, to reduce the peak input current demand. This allows

for better EMI performance and reduction in the input filter

requirements.

Each regulator except REG1 uses an external feedback

resistor divider to set the output voltage. All output voltages

can be adjusted dynamically (Dynamic Voltage Scaling) on

the fly through an I²C serial interface. All converters, except

REG1, utilize automatic soft-start by ramping the reference

voltage to the error amplifier to prevent sudden change in

duty cycle and output current/voltage at power up. REG1

(VG) will limit the inrush current by implementing a peak

current detect and a constant off time.

The 34704 is equipped with a dual function Power On/Off

pin (ONOFF). This pin can be controlled by a mechanical

switch to turn the device on or off. Pressing and releasing the

mechanical switch turns the 34704 on while pressing and

holding the switch for a time period (programmable through

I2C) turns the 34704 off. Enable/disable control is also

granted through I2C for groups of regulators and the whole

IC.

34704 Datasheet(PDF) 16 Page - Freescale Semiconductor, Inc

34704 Datasheet(HTML) 16 Page - Freescale Semiconductor, Inc

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