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R3113D441X

LOW VOLTAGE DETECTOR

RICOH Co.,Ltd. 

R3113D

OPERATION

Ra

Rb

Vref

Rc

Comparator

Figure 1. Block Diagram

VDD

Pch

OUT

Nch

GND

Released Voltage(+VDET)

Supply Voltage Detector Threshold(-VDET)

(VDD)

Minimum Operating Voltage

GND

Output Voltage

(VOUT)

GND

12

3

45

B

Detector Threshold

Hysteresis

A

tPLH

Step

12

3

45

Comparator

Pin Input Voltage

I

Comparator

Output

H

II

III

IV V

L Inde-finite L H

Tr.1

OFF ON Inde-finite ON OFF

Output

Tr.

Pch ON OFF Inde-finite OFF ON

Nch OFF ON Inde-finite ON OFF

I.

Rb + Rc

Ra + Rb + Rc

× VDD

II.

Rb

Ra + Rb

× VDD

Figure 2. Operation Diagram

Step 1. The output voltage is equal to the supply voltage (VDD).

Step 2. At Point “A”, Vref >= VDD×(Rb+Rc)/(Ra+Rb+Rc) is true, as a result, the output of comparator is reverse,

and output voltage becomes to GND level. The voltage level of Point A means detector threshold voltage,

or (−VDET).

Step 3. When the supply voltage is less than minimum operating voltage, the operation of output transistor

becomes indefinite, and in the case that output is pulled up to VDD, the output voltage equals to VDD

voltage.

Step 4. The output voltage equals to GND level.

Step 5. At Point “B”, Vref >= VDD×Rb/(Ra+Rb) is true, Output of the comparator is reverse, and output voltage is

equal to the supply voltage, or (VDD). The voltage level of Point B means released voltage, or (+VDET).

∗ The difference between released voltage and detector threshold voltage is the detector threshold hysteresis.

10

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