Functional description
5
Functional description
L5988D
The L5988D is based on a voltage mode control loop. Therefore the duty ratio of the internal
switch is obtained through a comparison between a saw-tooth waveform (generated by an
oscillator) and the output voltage of the error amplifier as shown in Figure 3. The advantage
of this technique is the very short conduction time of the power elements thanks to the
proper operation of the control loop without a precise current sense, which instead is
required in current mode regulators. Thanks to this architecture the L5988D supports
extremely low conversion ratio (D = VOUT/VIN) even at very high switching frequency
(up to 1 MHz).
Figure 3. Voltage mode control loop
VOUT
VREF
OSCILLATOR RAMP
PWM
E/A
The main internal blocks are represented in Figure 4.
Figure 4. Internal block diagram
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DocID15324 Rev 4