ISL6334DIRZ datasheet(14/28 Pages) INTERSIL

14 / 28 page

FN6802.2

August 31, 2010

the error in the reference voltage (output of the DAC) and

offset errors in the OFS current source, remote-sense and

error amplifiers. Intersil specifies the guaranteed tolerance of

the ISL6334D to include the combined tolerances of each of

these elements.

The output of the error amplifier, VCOMP, is compared to

sawtooth waveforms to generate the PWM signals. The

PWM signals control the timing of the Intersil MOSFET

drivers and regulate the converter output to the specified

reference voltage. The internal and external circuitry, which

control voltage regulation, are illustrated in Figure 6.

The ISL6334D incorporates an internal differential remote

sense amplifier in the feedback path. The amplifier removes

the voltage error encountered when measuring the output

voltage relative to the local controller ground reference point,

resulting in a more accurate means of sensing output

voltage. Connect the microprocessor sense pins to the

non-inverting input, VSEN, and inverting input, RGND, of the

remote-sense amplifier. The remote-sense output, VDIFF, is

connected to the inverting input of the error amplifier through

an external resistor.

A digital-to-analog converter (DAC) generates a reference

voltage based on the state of logic signals at pins VID7

through VID0. The DAC decodes the eight 6-bit logic signal

(VID) into one of the discrete voltages shown in Table 2. All

VID pins have no internal pull-up current sources after tD3.

After tD3, each VID input offers a minimum 30µA pull-up to

an internal 2.5V source for use with open-drain outputs. The

pull-up current diminishes to zero above the logic threshold

to protect voltage-sensitive output devices. External pull-up

resistors can augment the pull-up current sources in case

leakage into the driving device is greater than 30µA.

FIGURE 6. OUTPUT VOLTAGE REGULATION LOOP

EXTERNAL CIRCUIT ISL6334D INTERNAL CIRCUIT

COMP

RFB

VDIFF

VSEN

RGND

ERROR AMPLIFIER

VOUT+

DIFFERENTIAL

REMOTE-SENSE

AMPLIFIER

VCOMP

REF

DAC

RREF

CREF

VOUT-

TABLE 2. VR11 VID 8-BIT

VID7 VID6 VID5 VID4 VID3 VID2 VID1 VID0 VOLTAGE

0000

000

OFF

0000

001

OFF

0000

010

1.60000

0000

011

1.59375

0000

100

1.58750

0000

101

1.58125

0000

110

1.57500

0000

111

1.56875

0001

000

1.56250

0001

001

1.55625

0001

010

1.55000

0001

011

1.54375

0001

100

1.53750

0001

101

1.53125

0001

110

1.52500

0001

111

1.51875

0010

000

1.51250

0010

001

1.50625

0010

010

1.50000

0010

011

1.49375

0010

100

1.48750

0010

101

1.48125

0010

110

1.47500

0010

111

1.46875

0011

000

1.46250

0011

001

1.45625

0011

010

1.45000

0011

011

1.44375

0011

100

1.43750

0011

101

1.43125

0011

110

1.42500

0011

111

1.41875

0100

000

1.41250

0100

001

1.40625

0100

010

1.40000

0100

011

1.39375

0100

100

1.38750

0100

101

1.38125

0100

110

1.37500

0100

111

1.36875

ISL6334D

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