RN5VD
OPERATION
VDD
Current Source
RD
Ra Comparator
–
Pch
Nch
Schmitt Trigger
+
OUT
GND
Rb
Tr.2
Tr.1
Rc
CD
Output Capacitor
FIG. 1 Block Diagram
1
2
3
4
5
Step
Step 1 Step 2
Step 3
Step 4 Step 5
Comparator (–) Pin
Input Voltage
I
II
H
II
II
H
I
B
Released Voltage +VDET
Detector Threshold Hysteresis
A
Detected Voltage –VDET
Supply Voltage
(VDD)
Comparator Output
L
Indefinite
Indefinite
Indefinite
L
Tr. 1, 2
OFF ON
OFF ON
ON OFF
ON OFF
Minimum Operaing Voltage
GND
Nch
Output Tr.
Pch
ON OFF Indefinite OFF ON
Output Voltage
(OUT)
Delay Time
Rb + Rc
· VDD
I.
Ra + Rb + Rc
Rb
GND
· VDD
II.
Ra + Rb
FIG. 2 Operation Diagram
Step 1. Output Voltage is equal to Pull-up Voltage.
Step 2. When Input Voltage(VDD) reaches the state of Vref≥VDD · (Rb+Rc) /(Ra+Rb+Rc) at Point A (Detected Voltage –VDET) , the output of Comparator is
reversed, so that Output Voltage becomes GND. Discharging is performed from CD pin connected to External Capacitor. No delay time is generated.
Step 3. Output Voltage becomes indefinite when Power Source Voltage(VDD) is smaller than Minimum Operating Voltage. When the output is pulled up, VDD is
output.
Step 4. Output Voltage becomes equal to GND.
Step 5. When Input Voltage(VDD) reaches the state of Vref≤VDD · Rb/(Ra+Rb) at Point B (Released Voltage +VDET) , the output of Comparator is reversed,
6
and the External Capacitor is charged through CD pin, so that Output Voltage becomes equal to Pulled-up Voltage after a delay time tD (=0.69×10 ×CD) .
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RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
