Am4964 – Diodes AM4964 User Manual
Page 17
AM4964
Document number: DS37241 Rev. 2 - 2
17 of 21
June 2014
© Diodes Incorporated
AM4964
A Product Line of
Diodes Incorporated
N
E
W
P
R
O
D
U
C
T
Applications Note
(cont.)
If lock detection causes device to enter output shutdown, the CT pin will discharge the C4 capacitor with I
DHG
provide t
OFF
period. The t
OFF
is the
time the device waits before next auto-restart. During
t
OFF
period, the C4 is discharged for the high threshold, V
CTH
to low threshold V
CTL
at the
discharge current I
DHG
which is typically 0.2
μA.
OFF
CTH
CT
CHG
The thresholds voltage and discharge current are fixed, therefore the t
OFF
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 h
as series resistors of
25Ω typical integrated in the
FG output structure t
o increased robustness against reverse supply connection of
the
FG t
o ground.
The typical value for external pull-up on FG is 10k
.