L5988D View Datasheet(PDF) - STMicroelectronics

Part Name

Description

MFG CO.

L5988D

4 A continuous (more than 5 A pulsed) step-down switching regulator with synchronous rectification

STMicroelectronics 

Prev 11 12 13 14 15 16 17 18 19 20 Next

Functional description

L5988D

R1 (k)

43

47

56

62

82

110

150

220

Table 8. FSW resistor examples

fSW (kHz)

R2 (k)

198

360

215

180

245

120

261

91

295

56

322

43

343

33

361

27

fSW (kHz)

450

499

548

594

711

801

915

1022

To improve the line transient performance, the voltage feed forward is implemented by

changing the slope of the sawtooth according to the input voltage change (see Figure 6 a).

Figure 6. Sawtooth: voltage feed forward

The slope of the sawtooth does not change if the oscillator frequency is increased by an

external signal or adjusted by the external resistor (see Figure 7). As a consequence the

gain of the PWM stage is a function of the switching frequency and its contribution must be

taken in account when performing the calculations of the compensation network (see

Section 6.4.1 on page 29 and Section 6.4.2 on page 33).

Figure 7. Sawtooth: synchronization and frequency adjust

16/52

DocID15324 Rev 4

Share Link: