RX5RZ Datasheet, PDF (14/25 Pages) RICOH electronics devices division – LOW DROPOUT AND LOW NOISE VOLTAGE REGULATOR

RN5VD
OPERATION
Current Source
Ra Comparator RD
–
+
Rb
Tr.2
Tr.1
Rc
Schmitt Trigger
CD
Output Capacitor
Fig. 1 Block Diagram
VDD
Pch
OUT
Nch
GND
12
3
45
Released Voltage +VDET
Detected Voltage –VDET
Supply Voltage
(VDD)
Minimum Operaing Voltage
GND
B
A Detector Threshold Hysteresis
Step
Step 1 Step 2 Step 3 Step 4 Step 5
Comparator (–) Pin
Input Voltage
I II
II
II I
Comparator Output L H Indefinite H L
Tr. 1, 2
OFF ON Indefinite ON OFF
Nch OFF ON Indefinite ON OFF
Output Tr.
Pch ON OFF Indefinite OFF ON
Output Voltage
(OUT)
GND
Fig. 2 Operation Diagram
Delay Time
Rb + Rc
I.
· VDD
Ra + Rb + Rc
Rb
II.
· VDD
Ra + Rb
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 an 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,
and the external capacitor is charged through CD pin, so that output voltage becomes equal to pulled-up voltage after a delay time tD (=0.69×10⁶×CD) .
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