ꢀ OPERATION
VDD
OUT
Comparator
Ra
Current Source
Schmitt Trigger
-
RD
Pch
Nch
+
Rb
Rc
Tr.2
Tr.1
Vref
GND
Output Capacitor
CD
Fig. 1 Block Diagram with an external capacitor
Operation Status
1
Ι
2
ΙΙ
H
3
ΙΙ
4
ΙΙ
H
5
Ι
1
2
3
4
5
Released Voltage
+VDET
B
Comparator(-) Pin
Input Voltage
HYSTERESIS RANGE
Detector Threshold
-VDET
A
Comparator Output
Tr.1, 2
L
Indefinite
L
Supply Voltage
(VDD)
VDDL
OFF ON
OFF ON
OFF
OFF
Indefinite ON
Indefinite ON
Minimum Operating
Voltage
GND
Nch
Output Tr.
Pch
ON
OFF Indefinite OFF ON
Output Voltage
(OUT)
Delay Time
Ι
Rb+Rc ×VDD
GND
Ra+Rb+Rc
Rb
ΙΙ
×VDD
Ra+Rb
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.
Rev. 1.10
- 2 -
RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
