13892 datasheet(52/75 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

13892

FUNCTIONAL DEVICE OPERATION

Because of an order from the United States International Trade Commission, BGA-packaged product lines and part numbers indicated here currently are not

available from Freescale for import or sale in the United States prior to September 2010: MC13892VK and MC13892VL in 139, 186 MAPBGA packages.

Figure 7. Buck Switch Diagram

The Buck switcher topology includes an integrated

synchronous rectifier, meaning that the rectifying diode is

implemented on chip as a low ohmic FET. The placement of

an external diode is therefore not required, but overall

switcher efficiency may benefit from this. The buck

converters permit a 100% duty cycle operation.

During normal operation several power modes are

possible, depending on the loading. For medium and full

loading, synchronous PWM control is the most efficient while

maintaining a constant switching frequency.

The output voltages of the buck switchers are SPI

configurable and two output ranges are available, individually

programmed with SWxHI for SW2, SW3, and SW4 bucks,

SW1 is limited to only one output range. Presets are available

for both the Normal and Standby operation.

The first voltage range that applies for all the Buck

switchers goes from 0.6 to 1.375 V in 25 mV steps. The

second one does not apply for SW1 and goes from 1.1 to

1.85 V also in 25 mV steps.

SW1 and SW2 include pin controlled Dynamic Voltage

Scaling (DVS) operation. When transitioning from one

voltage to another, the output voltage slope is controlled in

steps of 25 mV per time step (time step as defined for DVS

stepping for SW1 and SW2, fixed at 4.0

μs for SW3, and

SW4). This allows for support of dynamic voltage scaling

(DVS) by using SPI driven voltage steps, state machine

defined modes, and direct DVSx pin control. SW1 and SW2

also include the Switcher Increment/Decrement (SID)

feature, with which, an increment command will increase the

set point voltage by a single 25 mV step, and a decrement

command will decrease it in the same amount of voltage. The

transition time for the step will be the same as programmed

for the DVS feature. Maximum and minimum voltages are

programmable to ensure the switcher voltage does not go out

a specific range. Panic mode is also included to quickly return

the switcher voltage to its normal programmed set point.

When initially activated, switcher outputs will apply

controlled stepping to the programmed value. The soft start

feature limits the inrush current at startup.

Point of Load feedback is intended for minimizing errors

due to board level IR drops.

MODES OF OPERATION

Two PWM modes are available:

PWM-NPS: sacrifices low load efficiency for a continuous

switching operation.

PWM-PS: offers better low load efficiency by allowing the

absence of switching cycles at low output loading. This pulse

13892 Datasheet(PDF) 52 Page - Freescale Semiconductor, Inc

13892 Datasheet(HTML) 52 Page - Freescale Semiconductor, Inc

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