TMP821 datasheet(6/13 Pages) TI1

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Lock Detection

Hall Input

Motor Output

Motor

locked

Off

Clamp voltage

Comparator voltage

Motor lock

cleared

Motor lock

detected

OFF

Return to

normal operation

Power

A few hundred milliseconds

TMP821

SLDS152 – JANUARY 2008

When a motor lock is detected, the TMP821 automatically shuts down its output current. When the motor lock is

removed, the TMP821 automatically restarts. Motor lock is detected when the Hall signal stops switching, as

shown in Figure 2.

Figure 2.

tON and tOFF are determined by the capacitor connected to LD:

tON = (CLD × (VLD_CLAMP – VLD_COMP) / ILD_CHARGE (seconds)

tOFF = (CLD × (VLD_CLAMP – VLD_COMP) / ILD_DISCHARGE (seconds)

Where:

CLD = capacitance of the external capacitor on LD

VLD_CLAMP = LD clamp voltage

VLD_COMP = LD comparator voltage

ILD_CHARGE = LD charge current

ILD_DISCHARGE = LD discharge current

NOTE:

After power is supplied to the device, the the lock detection pin (AL) may remain high

for a few hundred milliseconds (see Figure 3).

Figure 3. Power-On to AL Delay

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TMP821 Datasheet(PDF) 6 Page - Texas Instruments