IR3523

Page 16 of 37

June 20, 2008

Output 1 (Vtt) Adaptive Voltage Positioning

Adaptive Voltage Positioning is needed to reduce the output voltage deviations during load transients and the power

dissipation of the load at heavy load. IR3523 only provides AVP on output1. The circuitry related to the voltage

and the remote sense differential amplifier output. An internal current source whose value is programmed by the

same external resistor that programs the oscillator frequency sinks current from the FB1 pin. The error amplifier

desired amount of fixed offset voltage above the DAC voltage.

The VDRP1 pin voltage is a buffered reproduction of the IIN1 pin which is connected to the current share bus

ISHARE. The voltage on ISHARE represents the system average inductor current information. At each phase IC, an

RC network across the inductor provides current information which is gained up 32.5X and then added to the

to maintain FB1 to be equal to the VDAC1 reference voltage, an additional current will flow into the FB1 pin equal to

the desired converter output impedance. The offset and slope of the converter output impedance are referenced to

VDAC1 and therefore independent of the VDAC1 voltage.

VOSEN1-

CSIN-

CSIN+

IIN1

CSIN-

EAOUT1

ISHARE

VDRP1

Phase IC

Phase IC

ISHARE

VOUT1

RFB1

Current Sense

Amplifier

3k

3k

RDRP1

+

-

VDAC

VDAC

Remote

Sense

Amplifier

VDAC1

VDAC1

FB1

IFB

Current Sense

Amplifier

Error

Amplifier

VDRP

Amplifier

Control IC

VOSEN1+

CSIN+

Figure 9 - Adaptive voltage positioning