S-818A20AMC-BGA-T2 Ver la hoja de datos (PDF) - Seiko Instruments Inc
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S-818A20AMC-BGA-T2 Datasheet PDF : 23 Pages
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Rev.1.2
LOW DROPOUT CMOS VOLTAGE REGULATOR
S-818 Series
Operation
VIN
1. Basic operation
Figure 7 shows the block diagram of the S-818
Series.
The error amplifier compares a reference voltage
VREF with the part of the output voltage divided by the
feedback resistors Rs and Rf. It supplies the output
transistor with the gate voltage, necessary to ensure
certain output voltage free of any fluctuations of input
voltage and temperature.
Current
source
Vref
Error amplifier
Reference
voltage
circuit
*1
VOUT
Rf
Rs
VSS
*1 Parasitic diode
Figure 7 Typical Circuit Block Diagram
2. Output transistor
The S-818 Series uses a low on-resistance Pch MOS FET as the output transistor.
Be sure that VOUT does not exceed VIN+0.3 V to prevent the voltage regulator from being broken due to
inverse current flowing from VOUT pin to VIN pin through the parasitic diode.
3. Power Off Pin (ON/OFF Pin)
This pin activates and inactivates the regulator.
When the ON/OFF pin is switched to the power off level, the operation of all internal circuit stops, the built-in
Pch MOSFET output transistor between VIN and VOUT pin is switched off, suppressing current consumption.
The VOUT pin goes to the Vss level due to internal divided resistance of several MΩ between VOUT pin and
VSS pin.
The structure of the ON/OFF pin is shown in Figure 8. Since the ON/OFF pin is neither pulled down nor pulled
up internally, do not keep it in the floating state. Current consumption increases if a voltage of 0.3 V to VIN-0.3
V is applied to the ON/OFF pin. When the power off pin is not used, connect it to the VIN pin for product type
"A" and to the VSS pin for product type "B".
Table 6 Power off pin function by product type
Product
type
A
A
B
B
ON/OFF pin
“H” : Power on
“L” : Power off
“H” : Power off
“L” : Power on
Internal
circuit
Operating
Stop
Stop
Operating
VOUT pin
voltage
Set value
VSS level
VSS level
Set value
Current
consumption
Iss1
Iss2
Iss2
Iss1
VIN
ON/OFF
Figure 8 OVNS/OSFF Pin
Seiko Instruments Inc.
7
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