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MITSUMI
System Reset (with battery back-up) PST620, 621
System Reset (with battery back-up)
Monolithic IC PST620, 621
Outline
These ICs are part of the regular series of back-up ICs, and use capacitors (super capacitor, large capacity chemical capacitor) as back-up power supply. They control 1-chip microcomputer high-speed, low-speed, and stand-by modes (MNI control). These ICs also are capable of controlling data save in EPROM and other nonvolatile memories during power outage.
Features
1. Low current consumption 2. Capacitors (super capacitor, large capacity chemical capacitor) are used for back-up power supply, lowering system cost 3. Stable 1-chip microcomputer crystal oscillator rise time maintained with the built-in pulse shaver. 4. In addition to power outage detection for main power supply (+5V), there are built-in pins to detect AC power supply and +5V power supply primary side 5. Reset signal output by back-up power supply (super capacitor, large capacity chemical capacitor) detection
Package
DIP-8B (PST620DDB, PST621DDB) SOP-8C (PST620DFT, PST621DFT)
Applications
1. 2. 3. 4. VCR Audio equipment Communications equipment Rice cookers, etc.
Pin Assignment
8 7 6 5
1
2
3
4
Pin Description
PST620
Pin No. 1 2 3 4 5 6 7 8 Pin name VAC VCC1 VCC2 TC RE PSCONT CE GND Function Has +2.0V detection voltage to detect AC power supply and stable power supply primary side, for quick power outage detection. +5V main power supply Back-up power supply (back-up capacitor connected) Pulse width setting pin for pulse shaver (capacitor and resistor connected) Reset output Pulse shaver ON/OFF switching High : OFF Low : ON Chip enable signal output GND
MITSUMI
System Reset (with battery back-up) PST620, 621
PST621
Pin No. 1 2 3 4 5 6 7 8 Pin name VAC VCC1 VCC2 TC
--------------------------------
Function
Has +2.0V detection voltage to detect AC power supply and stable power supply primary side, for quick power outage detection.
RE
MODE CE GND
+5V main power supply Back-up power supply (back-up capacitor connected) Pulse width setting pin for pulse shaver (capacitor and resistor connected) Reset output Switches 1-chip microcomputer mode with pulse shaver output signal Chip enable signal output (power outage detection signal) GND
Block Diagram
PST620 PST621
Absolute Maximum Ratings
Item Storage temperature Operating temperature Power supply voltage TC input input voltage Allowable loss
(Ta=25C) Symbol TSTG TOPR VCC max. VC max. Pd Rating -40~+125C -20~+70C -0.3~+10V VCC1+0.3V 450mW
MITSUMI
System Reset (with battery back-up) PST620, 621
Electrical Characteristics
Item Detection voltage 1 Detection PST620 voltage 2 PST621 Detection voltage 3 Hysteresis voltage 1 Hysteresis voltage 2 Hysteresis voltage 3 Detection voltage temperature coefficient 1 Detection voltage temperature coefficient 2 Detection voltage temperature coefficient 3 Low-level output voltage 1 Low-level output voltage 2 Low-level output voltage 3 Operation limit voltage 1 Operation limit voltage 2 Consumption current 1 Consumption current 2 Consumption current 3 Consumption current 4 Consumption current 5 Output current while on 1 Output current while on 2 Transport delay time 1 Transport delay time 2 Transport delay time 3 Transport delay time 4 AC pin input resistance One-shot pulse width One-shot output voltage TC pin threshold voltage TC input input current PS pin input H level voltage PS pin input L level voltage PS pin input H level current
(Ta=25C) Measurement conditions RL1=47k CE output, VCC1=L H 1 RL2=47k, RE output VCC2=H L 1 RL1=47k, CE output, VAC=H L 1 RL1=47k, CE output, VCC1=L H L RL2=47k, CE output, VCC2=L H L RL1=47kCE output, VAC=L H L Min. 4.00 2.00 2.90 1.85 75 25 45 Typ. 4.20 2.15 3.10 2.00 150 50 90 0.01 0.02 0.01 0.1 0.1 0.2 0.8 0.8 5.0 2.0 8.0 2.0 8.0 4.0 2.0 4.0 2 2 10 50 40 80 1.0 14 0.1 2.0 0.2 0.4 0.4 1.0 1.0 8.5 3.5 14.5 3.5 14.5 7.0 3.5 A 7.0 mA V %/C Max. Units 4.40 2.30 V 3.30 2.15 300 100 mV 180
Symbol VS1 VS2 VS3 VS1 VS2 VS3 VS/ T VS/ T VS/ T VOL1 VOL2 VOL3 VOP1 VOP2 ICC1 ICC2 ICC1 ICC2 ICC1 ICC2 ICC2 ICC2 IOL1 IOL2 TPLH1 TPLH2 TPLH3 TPLH4 RACIN Tpd VTOL VCTH ICIN VPSH VPSL IPSH
*
*
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RL1=47k, CE output RL2=47k, RE output RL1=47k, CE output VCC1=VS1 min.-0.05V, RL1=47k CE output VCC2=VS2 min.-0.05V, RL2=47kz RE output VCC1=0V, VCC2=VS2 typ./0.85 RL1=47k, CE output RL1=47k, VOL1 < 0.4V CE output = RL2=47k, VOL2 < 0.4V RE output = VCC1=VCC2=VS1/0.85 RL1=RL2= VCC1=VCC2=VS1 min.-0.05V RL1=RL2= VCC1=VCC2=VS2 min.-0.05V RL1=RL2= VCC1=0V RL1=RL2=, VCC2=VS1T typ./0.85 VCC1=0V RL1=RL2= VCC2=VS2 min.-0.05V VCC1=VS1 min.-0.05V, RL1=0 CE output VCC2=VS2 min.-0.05V, RL2=0 RE output VCC1=VS1 typ.0.4V, RL2=47k CE output VCC2=VS2 typ.0.4V, RL2=47k RE output VCC1=VS1 typ.0.4V, RL2=47k CE output VCC2=VS2 typ.0.4V, RL2=47k RE output Cd=0.47F Rd=100k, VCC1=VS1 typ.0.4V VCC1=VS1 typ./0.85, RL1=47k RE output, 1 RL1=47k, VC=L H VCC1=VS1 typ./0.85, VC=5.0V
V
A
S
0.5 6
*
21 0.4 1
2.0 VPSH=2.0V 0.6 10
M mS V V A V V A
Note 1 : 1 Connect TC pin to GND. Note 2 : Except where noted otherwise, VAC=5V, Vc=OPEN.
*
MITSUMI
System Reset (with battery back-up) PST620, 621
Characteristics
ICC1 (A) 15.00
(PST620, 621 series. However, VS2 in PST620 series only.)
Current consumption
ICC1 (A) 15.00
VS1
(V) 4.400 (V) 4.400
1.500/div
1.500/div
.4400/div
.4400/div
.0000 .0000
1.000/div
.0000 10.00 VCC1(V)
.0000 .0000
.0900/div
.0000 10.00 VCC1 (V)
VS2
(V) 2.300 (V) 2.300
VOL
CS (V) 10.00 REST (V) 10.00
.2300/div
.2300/div
1.000/div
1.000/div
.0000 2.100
.0200/div
.0000 2.300 VCC1 (V)
.0000 .0000
1.000/div
.0000 10.00 VCC1 (V)
1 shot pulse width-Temperature
Pulse width (mS)
10
Vs1 detection voltage-Temperature
Vs1 detection voltage (V)
4.30
5
4.20
0
-25
0
25
50
75
4.10
-25
0
25
50
75
Temperature (C)
Temperature (C)
Vs2 detection voltage-Temperature
2.20
Vs3 detection voltage-Temperature
2.10
Vs2 detection voltage (V)
Vs3 detection voltage (V)
2.10
2.00
2.00
1.90 -25 0 25 50 75
-25
0
25
50
75
Temperature (C)
Temperature (C)
MITSUMI
System Reset (with battery back-up) PST620, 621
Timing Chart
PST620
VCC1 VCC2 CE TC
Delay Delay 4.2V 2.15V
RE
Note : Connect VAC pin to VCC when not using.
AC power supply AC rectifier or regulator primary side CE
VTX
Note 1: VTH is set at 2.0V and hysteresis voltage at 90mV. 1. Use a resistor to divide the detected voltage so that it equals VTH when monitoring regulator primary side power supply. 2. When monitoring AC voltage rectified as in the application circuit, set so that it equals VTH by lowering the constant and dividing with a resistor. Refer to application circuit diagram. Note 2: VAC input and VS1 are OR, so either signal makes CE low when power outage is detected.
PST621
AC VCC1 CE MODE VCC2 RESET
3.1V 4.2V
Application Circuits
VAC input : Power supply transformer secondary voltage detection
MITSUMI
System Reset (with battery back-up) PST620, 621
1. Connection 1. +5V power supply to VCC1 (Pin 2). 2. Connect back-up capacitor to VCC2 (Pin 3). 3. Connect a diode between VCC1 (Pin 2) and VCC2 (Pin 3). 4. Connect pulse width setting resistor and capacitor to PC (Pin 4) when using pulse shaver. 5. RE output (Pin 5) is reset signal output and is output when VCC is less than 2.15V. 6. When using pulse shaver, PSCONT (Pin 6) is high level. 7. CE output (Pin 7) is for chip enable signal and goes low when power outage is detected. 2. Theory of Operation 1. When +5V power is supplied normally, it is charged to the back-up capacitor via a diode. 2. The back-up capacitor starts back-up if +5V power supply voltage drops for some reason and VCC1 goes below 4.2V, and at the same time the CE signal switches the 1-chip microcomputer to standby mode, so that it operates on low current consumption. 3. When +5V power supply recovers and goes over 4.2V, an RE output signal of a certain width is output, and this signal resets the 1-chip microcomputer. At the same time normal mode starts and the time until crystal oscillator output stabilizes is reset. 4. If +5V power supply does not recover, and back-up capacitor voltage goes below 2.15V, reset is carried out by the RE output signal to prevent the microcomputer from running wild. 3. Setting AC power supply power outage detection 1. Theory of operation for detecting AC voltage AC voltage is rectified and smoothed by the capacitor. This voltage is divided and set at VAC input detection voltage, +2V. At this time the smoothing capacitor and dividing resistor time constants are used to set AC voltage missing waveform. 2. VAC voltage setting (R1, R2) Set resistor ratio at the midpoint between R1 and R2 so that the voltage to be detected is +2V. Impressed AC voltage There is are no limitations on AC voltage as it is divided by R1 and R2 and applied to PST620. 3. Setting time constants to detect AC voltage (C4, R1+R2) For impressed AC voltage of 5Vrms, and C4 and R1+R2 time constant of 60mS, set so that AC voltage detects power outage when approximately 2 waveforms are missed. The time constants can be set to detect missing AC waveforms.
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Application Circuits
VAC input : Stable power supply primary voltage detection

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