L6207PD datasheet(10/23 Pages) STMICROELECTRONICS

10 / 23 page

L6207

10/23

Figure 8. Output Current Regulation Waveforms

Figure 9 shows the magnitude of the Off Time tOFF versus COFF and ROFF values. It can be approximately cal-

culated from the equations:

tRCFALL = 0.6 · ROFF · COFF

tOFF = tRCFALL + tDT = 0.6 · ROFF · COFF + tDT

where ROFF and COFF are the external component values and tDT is the internally generated Dead Time with:

20K

Ω ≤ ROFF ≤ 100KΩ

0.47nF

≤ COFF ≤ 100nF

tDT = 1µs (typical value)

Therefore:

tOFF(MIN) = 6.6µs

tOFF(MAX) = 6ms

These values allow a sufficient range of tOFF to implement the drive circuit for most motors.

The capacitor value chosen for COFF also affects the Rise Time tRCRISE of the voltage at the pin RCOFF. The

Rise Time tRCRISE will only be an issue if the capacitor is not completely charged before the next time the

monostable is triggered. Therefore, the on time tON, which depends by motors and supply parameters, has to

OFF

tON

tOFF

2.5V

Slow Decay

µs tBLANK

tRCRISE

SYNCHRONOUS RECTIFICATION

µs tBLANK

VRC

VSENSE

VREF

IOUT

VREF

RSENSE

D02IN1351

tOFF

µs tDT

tRCFALL

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