13892 datasheet(53/75 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.

skipping feature improves efficiency by reducing dynamic

switching losses simply by switching less often.

In its lowest power mode, the switcher can regulate using

hysteresis control known as a Pulse Frequency Modulation

(PFM) control scheme. The frequency spectrum will be a

function of input and output voltage, loading, and the external

components. Due to its spectral variance and lighter drive

capability, PFM mode is generally reserved for non-active

radio modes and Deep Sleep operation.

CURRENT LIMITER

A built in current limiter ensures that during normal

operation the maximum current through the coil is not

exceeded (refer to Electrical Characteristics). This current

limiter can be disabled by SPI bits.

SWITCHING FREQUENCY

A PLL generates the switcher system clocking from the

32.768 kHz crystal oscillator reference. To allow for spectral

optimization for reduction of spurious influence in a radion

environment, the PLL can be programmed via SPI from a

multiplication factor of 84 to 105, in steps of 3.

BOOST CONVERTERS

SWBST

SWBST is a boost switching regulator with a fixed 5.0 V

output. It runs at 2/3 of the switcher PLL frequency. SWBST

supplies the VUSB regulator for the USB system in OTG

mode, as well as the VBUS voltage at the UVBUS pin.

When SWBST is configured to supply the UVBUS pin in

OTG mode, the feedback will be switched to sense the

UVBUS pin instead of the SWBSTFB pin. Therefore, when

driving the VBUS for OTG mode, the output of the switcher

may rise to 5.75 V to compensate for the voltage drops in the

internal switches. Note that the parasitic leakage path for a

boost switcher will cause the output voltage SWBSTOUT and

SWBSTFB to sit at a Schottky drop below the battery voltage,

whenever SWBST is disabled. The switching NMOS

transistor is integrated on-chip. An external fly back Schottky

diode, inductor, and capacitor are required.

Figure 8. 13892 SWBST Block Diagram.

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