L6986H datasheet(46/68 Pages) STMICROELECTRONICS

46 / 68 page

In the SLAVE mode the L6986H sets the internal oscillator at 250 kHz typ. (see Table 2) and drives the line

accordingly.

Figure 49. L6986H synchronization driving capability

In order to safely guarantee that each regulator recognizes itself in SLAVE mode when synchronized, the external

master must drive the SYNCH pin with a clock signal frequency higher than the maximum oscillator spread of the

selected line in Table 2 for at least 10 internal clock cycles.

Once recognized as SLAVE the synchronization range is:

•

275 - 1.4 MHz if fSW < 500 kHz

•

475 kHz - 2.2 MHz if fSW >=500 kHz

example 1: selecting RFSW = 0 Ω to VCC

Table 13. Example of oscillator frequency selection

Symbol

RVCC (E24 series) RGND (E24 series)

fSW min.

fSW typ.

fSW max.

fSW

0 Ω

225

250

275

the device enters in slave mode after 10 pulses at frequency higher than 275 kHz and so it is able to synchronize

to a clock signal in the range 275 kHz - 1.4 MHz (see Figure 48. Synchronization pulse definition).

Example 2: selecting RFSW = 0 Ω to GND

Table 14. Example of oscillator frequency selection (2)

Symbol

RVCC (E24 series) RGND (E24 series)

fSW min.

fSW typ.

fSW max.

fSW

0 Ω

450

500

550

The device enters in slave mode after 10 pulses at frequency higher than 550 kHz and so it is able to synchronize

to a clock signal in the range 475 kHz - 2.2 MHz (see Figure 48. Synchronization pulse definition).

L6986H

Synchronization (LNM)

DS12905 - Rev 2

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