l9909 STMicroelectronics, l9909 Datasheet - Page 7

• Manufacturer Part Number: l9909
• Description: Dc Motor Driver With Position Control
• Manufacturer: STMicroelectronics

The following is the discriminating algorithm be-
tween fast and slow Vcc transients. The transient
voltage clamp is normally set at 70V. If Vcc rises
above the Vcc_ov=19V typ. over voltage shut-
down threshold, both Td_ov_1 and Td_ov_2 tim-
ers start. When the first timer stops (after 130 µ s
typ. delay) the clamp status is evaluated and
locked. If the transient has been fast enough and
the voltage clamp activated, then it remains 70V
active until the second timer stops (after 1ms de-
lay), then it deactivates by rising to 80V. If the
transient has been slow and the voltage clamp
unreached when the first timer stops, then it de-
activates by rising to 80V. A new 70V clamp cycle
may restart only by lowering Vcc below the 19V
over voltage shutdown threshold.
The VFB and VCOM input pins may connect to
the Vcc or lower voltage during the power supply
transients of Figs. 4 and 5.
L9909
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