R3111x
• Operation of R3111xxxxB
VDD
Comparator
Ra
OUT pin should be pulled-up to
DD or an external voltage level.
OUT
V
Rb
Rc
Vref
Nch
Tr.1
GND
Block Diagram (R3111xxxxB)
1
2
3
Step
1
I
2
II
3
I
Released Voltage +VDET
Detector Threshold
Hysteresis
B
A
Comparator (−)
Pin Input Voltage
Detector Threshold
Supply Voltage
(VDD
-
V
DET
)
Comparator Output
Tr.1
L
H
L
Minimum Operating Voltage VDDL
GND
OFF ON OFF
ON OFF ON
Output Tr.
Nch
Rb+Rc
Ra+Rb+Rc
Pull-up Voltage
I
×VDD
Output Voltage
Output
Delay Time
(VOUT
)
Rb
Ra+Rb
II
×VDD
t
PLH
GND
Operation Diagram
• Explanation of operation
Step 1. The output voltage is equal to the GND level.
>
Step 2. At Point “A”, Vref VDD×(Rb+Rc)/(Ra+Rb+Rc) is true, as a result, the output of comparator is reversed
=
from "L" to "H", therefore the output voltage becomes the pull-up voltage. The voltage level of Point A
means a detector threshold voltage (−VDET).
<
Step 3. At Point “B”, Vref VDD×Rb/(Ra+Rb) is true, as a result, the output of comparator is reversed from "H" to
=
"L", then the output voltage is equal to the GND level. The voltage level of Point B means a released
voltage (+VDET).
∗) The difference between a released voltage and a detector threshold voltage is a detector threshold hysteresis.
13
RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
