Global Focus SILENCER S12V Series, Service Manual, Page: 18 / 30

Functional Description
S12V Service Manual Page 6-3
M
OTOR
C
URRENT
S
ENSE
C
IRCUIT
The voltage drop across R18, R19, R20 and R21 is proportional to the current through the drive
motor. This voltage is applied to U4 pin14. This is a negative feedback that counteracts the
PWM pulse to limit current draw of the motor. This voltage is also applied to ADC pin 22 of
U1 to supply current draw feedback. This feedback is used to control the PWM ramp during
acceleration.
M
OTOR
D
RIVE
T
EMPERATURE
C
IRCUIT
The voltage drop across temperature sensor TH1 is applied to ADC pin 19 of U1 to supply
temperature feedback for the motor drive MOSFETs. If the temperature exceeds safe limits for
the MOSFETs the PWM drive is shutdown.