Read Harman Kardon AVR 135 (serv.man3) Service Manual online
14
OPERATION
FIG. 1 Block Diagram
Operation Diagram
Step 1. Output Voltage is equal to Power Source Voltage (V
DD
).
Step 2. When Input Voltage to Comparator reaches the state of Vref
≥
V
DD
·(Rb+Rc)/(Ra+Rb+Rc)at Point A (Detected Voltage –V
DET
), the output of Com-
parator is reserved, so that Output Voltage becomes GND.
Step 3. In the case of CMOS Output, Output Voltage becomes unstable when Supply Voltage (V
DD
) is smaller than Minimum Operating Voltage. In the
case of Nch Open Drain Output, a pulled-up voltage is output.
Step 4. Output Voltage becomes equal to GND.
Step 5. When Input Voltage to Comparator reaches the state of Vref
≤
V
DD
· (Rb)/(Ra+ Rb) at Point B (Released Voltage +V
DET
), the output of Comparator is reversed,
so that Output Voltage becomes equal to Supply Voltage (V
DD
).
FIG. 2 Operation Diagram
Step
Step 1
Step 2
Step 3
Step 4
Step 5
Comparator(+) Pin
Input Voltage
I
II
II
II
I
Comparator Output
H
L
Indefinite
L
H
Tr. 1
OFF
ON
Indefinite
ON
OFF
Output Tr.
Pch
ON
OFF
Indefinite
OFF
ON
Nch
OFF
ON
Indefinite
ON
OFF
I
.
Rb + Rc
Ra + Rb + Rc
·V
DD
II.
Rb
Ra + Rb
·V
DD
GND
OUT
V
DD
Ra
Rb
Rc
Tr.1
Vref
Pch
Nch
–
+
Detector Threshold Hysteresis
t
PLH
1
2
3
4
5
A
B
• In R
×
5VT
××
A, Nch Tr. drain is
connected to OUT pin.
• In R
×
5VT
××
C, Nch Tr. drain
and Pch Tr. drain are connected
to OUT pin.
Released Volage +V
DET
Supply Volage
Detected Volage –V
DET
(V
DD
)
Minimum Operating Volage
GND
Output Volage
(OUT)
GND
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