L6227D View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

L6227D

DMOS DUAL FULL BRIDGE DRIVER WITH PWM CURRENT CONTROLLER

STMicroelectronics 

L6227

Figure 8. Output Current Regulation Waveforms

IOUT

VREF

RSENSE

tOFF

tON

VSENSE

VREF

0

1µs tBLANK

Slow Decay

tOFF

1µs tBLANK

Slow Decay

VRC

5V

tRCRISE

tRCRISE

2.5V

ON

tRCFALL

1µs tDT

tRCFALL

1µs tDT

SYNCHRONOUS RECTIFICATION

OFF

D02IN1351

B

C

DAB

C

D

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:

20KΩ ≤ 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

10/22

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