ICE3AS02G datasheet(12/22 Pages) INFINEON

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ICE3AS02 / ICE3AS02G / ICE3BS02 / ICE3BS02G

Functional Description

Version 1.2

02 Sep 2005

Current Limiting is now possible in a very accurate way.

E.g. Ipeak = 0.5A with RSense = 2. Without Propagation Delay

Compensation the current sense threshold is set to a static

voltage level Vcsth=1V. A current ramp of

dI/dt = 0.4A/µs, that means dVSense/dt = 0.8V/µs, and a

propagation delay time of i.e. tPropagation Delay =180ns leads

then to an Ipeak overshoot of 14.4%. By means of propagation

delay compensation the overshoot is only about 2% (see

Figure 13).

Figure 13

Overcurrent Shutdown

The Propagation Delay Compensation is realized by means

of a dynamic threshold voltage Vcsth (see Figure 14). In case

of a steeper slope the switch off of the driver is earlier to

compensate the delay.

Figure 14

Dynamic Voltage Threshold Vcsth

3.6

Control Unit

The Control Unit contains the functions for Active Burst

Mode and Auto Restart Mode. The Active Burst Mode and

the Auto Restart Mode are combined with an Adjustable

Blanking Window which is depending on the external Soft

Start capacitor. By means of this Adjustable Blanking

Window, the IC avoids entering into these two modes

accidentally. Furthermore it also provides a certain time

whereby the overload detection is delayed. This delay is

useful for applications which normally works with a low

current and occasionally require a short duration of high

current.

3.6.1

Adjustable Blanking Window

Figure 15

Adjustable Blanking Window

VSoftS is clamped at 4.4V by the closed switch S1 after the

SMPS is settled. If overload occurs VFB is exceeding 4.8V.

Auto Restart Mode can’t be entered as the gate G5 is still

blocked by the comparator C3. But after VFB has exceeded

4.8V the switch S1 is opened via the gate G2. The external

Soft Start capacitor can now be charged further by the

0,9

0,95

1,05

1,1

1,15

1,2

1,25

1,3

0,2

0,4

0,6

0,8

1,2

1,4

1,6

1,8

with compensation

without compensation

Sense

csth

OSC

Signal1

Signal2

Sense

Propagation Delay

max. Duty Cycle

off time

5.4V

4.8V

1.32V

4.4V

Control Unit

Ω

Active

Burst

Mode

Auto

Restart

Mode

SoftS

6.5V

SoftS

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