SIP2802 datasheet(8/10 Pages) VISHAY

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Document Number: 72660

S11-0598-Rev. E, 25-Apr-11

Vishay Siliconix

SiP2800, SiP2801, SiP2802, SiP2803, SiP2804, SiP2805

This datasheet is subject to change without notice.

THE PRODUCT DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000

Item (a) in the above list is a static dc value, and can

generally be calculated with good accuracy. Item (b) will

increase with operating frequency, but will be fixed for a

given value of FOSC. Item (c) is usually the dominant term in

the calculation of ICC, as the power required to drive the

external power switch will typically increase as FOUT is

increased. The most common example of this is seen in

driving the gate of a power MOSFET. In such applications,

the gate capacitances must be charged once each switching

cycle. This calculation is simplified by using the gate charge

term given by most MOSFET manufacturers, allowing the

use of the formula:

IDRIVE = FOUT x Qg of the chosen MOSFET.

A first approximation of the necessary dropping resistor

value is then given by:

R = [(Nominal VSUPPLY) - 12 V]/(Nominal ICC)

Here R is in ohms and ICC is in amperes.

The resistor limiting the current into the VCC pin should be

selected such that ICC(min) equals the worst-case maximum

sum of the above currents, while holding ICC(max) to as low a

value above that number as practicable (for best overall

efficiency), and nevermore than 25 mA above that number

(to avoid exceeding the IC’s internal clamp diode ratings).

VCC must be bypassed to GND with a good quality 0.1 µF

ceramic capacitor, as close to the part as possible. This will

help avoid problems created by high-frequency noise on the

power supply of the part. An electrolytic or tantalum capacitor

may be placed in parallel with the ceramic capacitor if more

capacitance is needed or desired.

FUNCTIONAL BLOCK DIAGRAM

Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon Tech-

nology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and reliability

data, see www.vishay.com/ppg?72660.

OUT

COMP

VCC

GND

OSC

Leading Edge

Blanking

Reference

Voltage

UVLO

Soft-Start

REF

SiP2801/4/5 Only

1.5 V

REF/2

Overcurrent

Comparator

Voltage Error

Amplifier

PWM

Comparator

13.5 V

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