ISL6520CBZ-T datasheet(6/11 Pages) INTERSIL

Part #	ISL6520CBZ-T

Description	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller

Download	11 Pages

Scroll/Zoom	100%

Manufacturer	INTERSIL [Intersil Corporation]

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

Logo

6 / 11 page

6

FN9009.4

October 4, 2005

Please note that the capacitors CIN and CO may each

represent numerous physical capacitors. Locate the ISL6520

within 3 inches of the MOSFETs, Q1 and Q2. The circuit traces

for the MOSFETs’ gate and source connections from the

ISL6520 must be sized to handle up to 1A peak current.

Figure 4 shows the circuit traces that require additional layout

consideration. Use single point and ground plane construction

for the circuits shown. Minimize any leakage current paths on

the COMP/OCSET pin and locate the resistor, ROSCET close

to the COMP/OCSET pin because the internal current source is

only 20

µA. Provide local VCC decoupling between VCC and

GND pins. Locate the capacitor, CBOOT as close as practical to

the BOOT and PHASE pins. All components used for feedback

compensation should be located as close to the IC a practical.

Feedback Compensation

Figure 5 highlights the voltage-mode control loop for a

synchronous-rectified buck converter. The output voltage

(VOUT) is regulated to the Reference voltage level. The

error amplifier (Error Amp) output (VE/A) is compared with

the oscillator (OSC) triangular wave to provide a pulse-

width modulated (PWM) wave with an amplitude of VIN at

the PHASE node. The PWM wave is smoothed by the output

filter (LO and CO).

Modulator Break Frequency Equations

The compensation network consists of the error amplifier

(internal to the ISL6520) and the impedance networks ZIN

and ZFB. The goal of the compensation network is to provide

a closed loop transfer function with the highest 0dB crossing

frequency (f0dB) and adequate phase margin. Phase margin

is the difference between the closed loop phase at f0dB and

180 degrees. The equations below relate the compensation

network’s poles, zeros and gain to the components (R1, R2,

R3, C1, C2, and C3) in Figure 7. Use these guidelines for

locating the poles and zeros of the compensation network:

1. Pick Gain (R2/R1) for desired converter bandwidth.

2. Place 1ST Zero Below Filter’s Double Pole (~75% FLC).

3. Place 2ND Zero at Filter’s Double Pole.

4. Place 1ST Pole at the ESR Zero.

5. Place 2ND Pole at Half the Switching Frequency.

6. Check Gain against Error Amplifier’s Open-Loop Gain.

7. Estimate Phase Margin - Repeat if Necessary.

The modulator transfer function is the small-signal transfer

function of VOUT/VE/A. This function is dominated by a DC

Gain and the output filter (LO and CO), with a double pole

break frequency at FLC and a zero at FESR. The DC Gain of

the modulator is simply the input voltage (VIN) divided by the

peak-to-peak oscillator voltage

∆VOSC.

Compensation Break Frequency Equations

Figure 6 shows an asymptotic plot of the DC/DC converter’s

gain vs frequency. The actual Modulator Gain has a high gain

peak due to the high Q factor of the output filter and is not

shown in Figure 6. Using the above guidelines should give a

Compensation Gain similar to the curve plotted. The open

loop error amplifier gain bounds the compensation gain.

FIGURE 4. PRINTED CIRCUIT BOARD SMALL SIGNAL

LAYOUT GUIDELINES

+5V

ISL6520

COMP/OCSET

GND

VCC

BOOT

D1

LO

CO

VOUT

Q1

Q2

PHASE

+VIN

CBOOT

CVCC

+5V

FLC

1

2

π x LO x CO

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

=

FESR

1

2

π x ESR x CO

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

=

FIGURE 5. VOLTAGE-MODE BUCK CONVERTER

COMPENSATION DESIGN

VOUT

REFERENCE

LO

CO

ESR

VIN

∆VOSC

ERROR

AMP

PWM

DRIVER

(PARASITIC)

ZFB

+

-

REFERENCE

R1

R3

R2

C3

C2

C1

COMP

VOUT

FB

ZFB

ISL6520

ZIN

COMPARATOR

DRIVER

DETAILED COMPENSATION COMPONENTS

PHASE

VE/A

+

-

+

-

ZIN

OSC

FZ1

1

2

π x R

2 x C1

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

=

FZ2

1

2

π x R

1

R3

+

() x C

3

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

=

FP1

1

2

π x R

2 x

C1 x C2

C1 C2

+

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







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

=

FP2

1

2

π x R

3 x C3

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

=

ISL6520

Similar Part No. - ISL6520CBZ-T

Manufacturer	Part #	Datasheet	Description
Intersil Corporation	ISL6520CBZ	323Kb / 11P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller
Renesas Technology Corp	ISL6520CBZ	718Kb / 11P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller

More results

Similar Description - ISL6520CBZ-T

Manufacturer	Part #	Datasheet	Description
Intersil Corporation	ISL6520A	296Kb / 12P	Single Synchronous Buck Pulse-Width Modulation PWM Controller
Intersil Corporation	ISL6520	323Kb / 11P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller
Renesas Technology Corp	ISL6406	986Kb / 18P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller Oct 21, 2015
Intersil Corporation	ISL6406	357Kb / 17P	Single Synchronous Buck Pulse-Width Modulation PWM Controller
	ISL6520ACB-T	296Kb / 12P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller
	ISL6527	329Kb / 16P	Single Synchronous Buck Pulse-Width Modulation PWM Controller
	ISL6526	330Kb / 15P	Single Synchronous Buck Pulse-Width Modulation PWM Controller
Renesas Technology Corp	ISL6520A	674Kb / 12P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller
	ISL6520B	632Kb / 11P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller
	ISL6527	841Kb / 17P	Single Synchronous Buck Pulse-Width Modulation (PWM) Controller

More results

ISL6520CBZ-T Datasheet(PDF) 6 Page - Intersil Corporation

ISL6520CBZ-T Datasheet(HTML) 6 Page - Intersil Corporation

Similar Part No. - ISL6520CBZ-T

Similar Description - ISL6520CBZ-T

Html Pages

1 2 3 4 5 6 7 8 9 10 11

Datasheet Download

Link URL