AM4964 datasheet(17/21 Pages) DIODES

17 / 21 page

AM4964

Document number: DS37241 Rev. 2 - 2

17 of 21

www.diodes.com

June 2014

AM4964

A Product Line of

Diodes Incorporated

Applications Note (cont.)

If lock detection causes device to enter output shutdown, the CT pin will discharge the C4 capacitor with IDHG provide tOFF period. The tOFF is the

time the device waits before next auto-restart. During tOFF period, the C4 is discharged for the high threshold, VCTH to low threshold VCTL at the

discharge current IDHG which is typically 0.2μA.

OFF

CTH

CHG

The thresholds voltage and discharge current are fixed, therefore the tOFF time depends only on the value of C4.

OFF

For CT of 0.4

μs, t

OFF is 4.7s before the next auto restart.

Thermal Shutdown

AM4964 includes a thermal shutdown function. When the device junction temperature is higher than +176ºC typical, the thermal shutdown

function is triggered and the low side output transistors in H bridge driver will be turned off. When the IC junction temperature drops below +148ºC

typical, the device will recover.

Status Output - FG Output

The FG output pin is an open collector output which switches ON (pulled low) and OFF (pulled high with an external resistor) depending on the

magnetic phase of the motor. The external pull up resistor should be connected to the FG pin.

The FG pin has series resistors of

25Ω typical integrated in the FG output structure to increased robustness against reverse supply connection of

the FG to ground. The typical value for external pull-up on FG is 10k

.

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