ISL6528CB datasheet(7/13 Pages) INTERSIL

Part #	ISL6528CB

Description	Dual Regulator - Standard Buck PWM and Linear Power Controller

Download	13 Pages

Scroll/Zoom	100%

Manufacturer	INTERSIL [Intersil Corporation]

Direct Link	http://www.intersil.com/cda/home

Logo

7 / 13 page

7

FN9038.4

March 9, 2006

The linear regulator output voltage is also set by means of

an external resistor divider as shown in Figure 4. The two

resistors used to set the output voltage should not exceed a

parallel equivalent value, referred to as RFB, of 5kΩ. This

restriction is due to the manner of implementation of the soft-

start function. The following relationship must be met:

To ensure the parallel combination of the feedback resistors

meets this criteria, choose a target value for RFB of less than

5k

Ω and then apply the following equations:

where VOUT2 is the desired linear regulator output voltage

and VREF is the internal reference voltage, 0.8V. For an

output voltage of 0.8V, simply populate R5 with a value less

than 5k

Ω and do not populate R6.

Converter Shutdown

Pulling and holding the FB2 pin above a typical threshold of

1.28V will shutdown both regulators. Upon release of the

FB2 pin, the regulators enter into a soft-start cycle which

brings both outputs back into regulation.

PWM Controller Feedback Compensation

A simplified representation of the voltage-mode control loop

used for output regulation by the standard buck converter is

shown in Figure 5. The output voltage, VOUT, is fed back to

the negative input of the error amplifier which is regulated to

the reference voltage level, VREF. The error amplifier output,

VE/A, is compared with the triangle wave produced by the

oscillator, VOSC, to provide a pulse-width modulated (PWM)

signal from the PWM comparator. This signal is then used to

switch the MOSFET and produce a PWM waveform with an

amplitude of VIN at the PHASE node. The square-wave

PHASE voltage is then smoothed by the output filter, LOUT

and COUT, to produce a DC voltage level.

The modulator transfer function is defined as VOUT/VE/A.

The internal PWM comparator and driver circuits equate to a

DC gain block dominated by the supply voltage, VIN, divided

by the peak-to-peak magnitude of the triangle wave, ∆VOSC.

The output filter components, LOUT and COUT, shape the

overall modulator small-signal transfer function by

contributing a double pole break frequency at FLC and a

zero at FESR.

Modulator Break Frequency Equations

The compensation network consists of the error amplifier

and the impedance networks ZIN and ZFB. They provide the

link between the modulator transfer function and a

controllable closed loop transfer function of VOUT/VREF. The

goal of component selection for the compensation network is

to provide a loop gain with high 0dB crossing frequency

(f0dB) and adequate phase margin. Phase margin is the

difference between the closed loop phase at f0dB and 180

degrees.

DRIVE2

FB2

COUT2

Q2

ISL6528

VOUT2

+3.3VIN

R5

R6

FIGURE 4. OUTPUT VOLTAGE SELECTION OF THE LINEAR

+

VOUT2

0.8

1 R5

R6

--------

+





×

=

RFB

R5 R6

×

R5 R6

+

---------------------- 5k

Ω

<

=

(EQ. 2)

R5

VOUT2

VREF

------------------- RFB

×

=

(EQ. 3)

R6

R5 VREF

×

VOUT2 VREF

–

----------------------------------------

=

(EQ. 4)

FLC

1

2

π

LO CO

×

----------------------------------------

=

FESR

1

2

π ESR C

O

×

-----------------------------------------

=

(EQ. 5)

(EQ. 6)

FIGURE 5. VOLTAGE-MODE BUCK CONVERTER

COMPENSATION DESIGN

VOUT

VREF

LOUT

CO

ESR

VIN

∆VOSC

ERROR

AMP

PWM

DRIVER

(PARASITIC)

+

-

0.8V

R1

R3

R2

C3

C2

C1

COMP

VOUT

FB

ZFB

ISL6528

ZIN

COMP

DETAILED COMPENSATION COMPONENTS

PHASE

VE/A

+

-

+

ZFB

ZIN

OSC

ISL6528

Similar Part No. - ISL6528CB

Manufacturer	Part #	Datasheet	Description
Intersil Corporation	ISL6528CB	390Kb / 13P	Dual Regulator - Standard Buck PWM and Linear Power Controller
Renesas Technology Corp	ISL6528CB	742Kb / 13P	Dual Regulator - Standard Buck PWM and Linear Power Controller
Intersil Corporation	ISL6528CB-T	390Kb / 13P	Dual Regulator - Standard Buck PWM and Linear Power Controller
Renesas Technology Corp	ISL6528CB-T	742Kb / 13P	Dual Regulator - Standard Buck PWM and Linear Power Controller
Intersil Corporation	ISL6528CBZ	390Kb / 13P	Dual Regulator - Standard Buck PWM and Linear Power Controller

More results

Similar Description - ISL6528CB

Manufacturer	Part #	Datasheet	Description
Intersil Corporation	ISL6528	390Kb / 13P	Dual Regulator - Standard Buck PWM and Linear Power Controller
Renesas Technology Corp	ISL6528	742Kb / 13P	Dual Regulator - Standard Buck PWM and Linear Power Controller
Richtek Technology Corp...	RT9204	282Kb / 14P	Dual Regulator - Standard Buck PWM DC-DC and Linear Power Controller
Richtek Technology Corp...	RT9204	186Kb / 14P	Dual Regulators - Standard Buck PWM DC-DC and Linear Controller
Intersil Corporation	ISL6529A	376Kb / 15P	Dual Regulator.Synchronous Rectified Buck PWM and Linear Power Controller
ON Semiconductor	NCP5220A	172Kb / 18P	3?뭝n?? PWM Dual Buck and Linear Power Controller December, 2005 ??Rev. 4
Intersil Corporation	ISL6529	623Kb / 19P	Dual Regulator.Synchronous Rectified Buck PWM and Linear Power Controller
ON Semiconductor	NCP5220	174Kb / 18P	3?뭝n?? PWM Dual Buck and Linear Power Controller November, 2004 ??Rev. 4
Silicon Standard Corp.	SS7529	587Kb / 8P	Synchronous Buck PWM and Linear Power Controller
uPI Group Inc.	UP6161	500Kb / 15P	Single 12V Input Supply Dual Regulator - Synchronous-Buck-PWM and Linear-Regulator Controller

More results

ISL6528CB Datasheet(PDF) 7 Page - Intersil Corporation

ISL6528CB Datasheet(HTML) 7 Page - Intersil Corporation

Similar Part No. - ISL6528CB

Similar Description - ISL6528CB

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13

Datasheet Download

Link URL