R3112x
OPERATION
V
DD
Ra
RD
Comparator
Pch
Nch
-
Schmitt Trigger
+
Current Source
O
UT
Tr.2
Rb
Rc
Tr.1
Vref
GND
Output Capacitor
CD
Fig. 1 Block Diagram with an external capacitor
1
2
3
4
5
Operation Status
1
2
II
H
3
II
4
II
H
5
I
Released Voltage +VDET
Detector Threshold -VDET
HYSTERESIS
RANGE
B
Compartor(-) Pin
Input Voltage
A
I
Compartor Output
Tr.1, 2
L
Indefinite
L
Supply Voltage(VDD
)
OFF ON Indefinite ON OFF
OFF ON Indefinite ON OFF
Minimum Operating
Voltge
VDDL
GND
Nch
Output Tr.
Pch ON OFF Indefinite OFF ON
Delay Time
Output Voltage(OUT)
Rb+Rc
Ra+Rb+Rc
I
V
DD
DD
Rb
Ra+Rb
II
V
GND
Fig. 2 Operation Diagram
1. Output voltage is equal to supply voltage. (As for Nch open drain type, equal to pull-up voltage.)
2. When the supply voltage is down to the detector threshold voltage level(Point A),
>
Vref VDD×(Rb+Rc)/(Ra+Rb+Rc) is true, then output of the comparator is reversed from “L” to “H”, therefore
=
output voltage becomes GND level.
3. When the supply voltage is lower than minimum operating voltage, the operation of output transistor is
indefinite. In the case of Nch open drain type, output voltage is equal to pull-up voltage.
4. Output Voltage becomes GND level.
5. When the supply voltage is higher than released voltage (Point B), Vref VDD×Rb/(Ra+Rb) is true, then
=
output of the comparator reaches the threshold level, and Output of Shmitt Trigger is reversed from “H” to
“L”, then output voltage is equal to supply voltage. (As for Nch open drain type, equal to pull-up voltage.)
∗) The difference between released voltage and detector threshold voltage means hysteresis range voltage.
10
RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
