Ricoh R3111x Series - Manual (Page 14)

R3111x
14
•
Operation of R3111xxxxC
Vref
Ra
Rb
Rc
V
DD
OUT
GND
Tr.1
Nch
Pch
Comparator
Block Diagram (R3111xxxxC)
t
PLH
GND
GND
V
DDL
-V
DET
+V
DET
Detector Threshold
Released Voltage
Minimum Operating Voltage
1 2 3 4 5
A
B Detector Threshold
Hysteresis
Supply Voltage
(V
DD
)
Output Voltage
(V
OUT
)
Step 1 2 3 4 5
Comparator (+)
Pin Input Voltage
I II II II I
Comparator Output H L Indefinite L H
Tr.1 OFF ON Indefinite ON OFF
Pch ON OFF Indefinite OFF ON
Output Tr.
Nch OFF ON Indefinite ON OFF
I ×V
DD
Rb +Rc
Ra +Rb+Rc
II ×V
DD
Rb
Ra +Rb
Operation Diagram
•
Explanation of operation
Step 1. The output voltage is equal to the supply voltage (V
DD
).
Step 2. At Point “A”, Vref >
=
V
DD
×(Rb+Rc)/(Ra+Rb+Rc) is true, as a result, the output of comparator is reversed
from "H" to "L", therefore the output voltage becomes the GND level. The voltage level of Point A
means a detector threshold voltage (
−V
DET
).
Step 3. When the supply voltage is lower than the minimum operating voltage, the operation of the output
transistor becomes indefinite.
Step 4. The output Voltage is equal to the GND level.
Step 5. At Point “B”, Vref
<
=
V
DD
×Rb/(Ra+Rb) is true, as a result, the output of comparator is reversed from "L" to
"H", then the output voltage is equal to the supply voltage (V
DD
). The voltage level of Point B means a
released voltage ( +V
DET
).
∗) The difference between a released voltage and a detector threshold voltage is a detector threshold hysteresis.
Output
Delay Time