2AS01 datasheet(11/24 Pages) INFINEON

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Datasheet

30 Jun 2006

Preliminary Data

ICE2AS01/S01G

ICE2BS01/S01G

Functional Description

recovery time. To avoid a premature termination of the

switching pulse this spike is blanked out with a time

constant of tLEB = 220ns. During that time the output of

the Current-Limit Comparator cannot switch off the

gate drive.

3.5.2

Propagation Delay Compensation

In case of overcurrent detection the shut down of the

external Power Switch is delayed due to the

propagation delay of the circuit. This delay causes an

overshoot of the peak current Ipeak which depends on

the ratio of dI/dt of the peak current (see Figure 14).

Figure 14 Current Limiting

The overshoot of Signal2 is bigger than of Signal1 due

to the steeper rising waveform.

A propagation delay compensation is integrated to

bound the overshoot dependent on dI/dt of the rising

primary current. That means the propagation delay

time between exceeding the current sense threshold

Vcsth and the switch off of the external Power Switch is

compensated over temperature within a range of at

least

So current limiting is now capable in a very accurate

way (see Figure 16).

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 15).

The propagation delay compensation is done by

means of a dynamic threshold voltage Vcsth (see Figure

15). In case of a steeper slope the switch off of the

driver is earlier to compensate the delay.

Figure 15 Dynamic Voltage Threshold Vcsth

Figure 16 Overcurrent Shutdown

3.6

PWM-Latch

The oscillator clock output applies a set pulse to the

PWM-Latch when initiating the external Power Switch

conduction. After setting the PWM-Latch can be reset

by the PWM-OP, the Soft-Start-Comparator, the

Current-Limit-Comparator, Comparator C3 or the

Error-Latch of the Protection Unit. In case of reseting

the driver is shut down immediately.

3.7

Driver

The driver is a fast totem pole gate drive, which is

designed to avoid cross conduction currents and which

is equipped with a Zener diode Z1 (see Figure 17) in

order to improve the control of the gate attached power

Sense

Limit

Propagation Delay

Overshoot1

peak1

Signal1

Signal2

Overshoot2

peak2

Sense

peak

Sense

≤

csth

OSC

Signal1

Signal2

Sense

Propagation Delay

max. Duty Cycle

off time

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

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