VIPER37

Operation description

Doc ID 022218 Rev 1

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Figure 27.

Timing diagram: behavior after short-circuit

8.6

Oscillator

The switching frequency is internally fixed to 60 kHz or 115 kHz. In both cases the switching

frequency is modulated by approximately ±4 kHz (60 kHz version) or ±8 kHz

(115 kHz version) at a 250 Hz (typ.) rate, so that the resulting spread-spectrum action

distributes the energy of each harmonic of the switching frequency over a number of side-

band harmonics having the same energy on the whole but smaller amplitudes.

8.7

Current mode conversion with adjustable current limit set

point

This device is a current mode converter: the drain current is sensed and converted into

voltage that is applied to the non-inverting pin of the PWM comparator. This voltage is

compared with the one on the feedback pin through a voltage divider on a cycle-by-cycle

basis.

Figure 16).

Table 8).