IR3523

Page 17 of 37

June 20, 2008

Output1 Inductor DCR Temperature Compensation

A negative temperature coefficient (NTC) thermistor can be used for Output1 inductor DCR temperature

compensation. The thermistor should be placed close to the Output1 inductors and connected in parallel with the

feedback resistor, as shown in Figure 10. The resistor in series with the thermistor is used to reduce the nonlinearity

of the thermistor.

EAOUT1

+

-

IIN1

VDAC1

IFB

VDAC1

Control IC

Error

Amplifier

RDRP1

VDRP

Amplifier

VDRP1

Rt

RFB12

RFB11

FB1

VOSEN1+

VOUT1

VOSEN1-

Remote

Sense

Amplifier

Figure 10 - Temperature compensation of Output1 inductor DCR

Remote Voltage Sensing

VOSENX+ and VOSENX- are used for remote sensing and connected directly to the load. The remote sense

differential amplifiers with high speed, low input offset, and low input bias current ensure accurate voltage sensing

and fast transient response.

Start-up Sequence

The IR3523 has a programmable soft-start function to limit the surge current during the converter start-up. A

capacitor connected between the SS/DELx and LGND pins controls soft start timing, over-current protection delay

and hiccup mode timing. A charge current of 50uA and discharge currents of 47uA and 4.5uA control the up slope

and down slope of the voltage at the SS/DEL pin respectively.