34716 datasheet(14/25 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34716

FUNCTIONAL DESCRIPTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

TRACKING AND SEQUENCING

This block allows the output of channel 2 of the 34716 to

track 1/2 the voltage applied at the VREFIN pin. This allows

the VREF and VTT voltages to track 1/2 VDDQ and assures that

none of them will be higher than VDDQ at any point during

normal operating conditions. For power down during a

shutdown (S5) mode, the 34716 uses internal discharge

MOSFETs (M8, M9, and M10 on Figure 2, page 2) to

discharge VDDQ, VTT, and VREF respectively. These

discharge MOSFETs are only active during shutdown mode.

Using this block along with controlling the SD and STBY pins

can offer the user the device for power sequencing by

controlling when to turn the 34716 outputs on or off.

BUCK CONVERTER

This block provides the main function of the 34716: DC to

DC conversion from an un-regulated input voltage to a

regulated output voltage used by the loads for reliable

operation. The buck converter is a high performance, fixed

frequency (externally adjustable),

Syncronous buck PWM

voltage-mode control with a minimum on time of 100ns.

It drives integrated 50 m

Ω N-channel power MOSFETs

saving board space and enhancing efficiency. The switching

regulator output voltage is adjustable with an accuracy of less

than ±2 % to meet DDR requirements. The regulator's

voltage control loop is compensated using a type III

compensation network, with external components to allow for

optimizing the loop compensation, for a wide range of

operating conditions. A typical Bootstrap circuit with an

internal PMOS switch is used to provide the voltage

necessary to properly enhance the high-side MOSFET gate.

The 34716 is designed to address DDR memory power

supplies. The integrated converter has the ability to supply up

to 5.0 A out of channel 1 and sink and source up to 3.0 A of

continuous current from channel 2, providing a full power

supply solution for DDR applications.

34716 데이터시트(PDF) 14 Page - Freescale Semiconductor, Inc

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