S-8423 Series. Rev.2.0 BATTERY BACKUP IC

Transcription

1 Rev.2. BATTERY BACKUP IC The is a CMOS IC designed for use in the switching circuits of main and backup power supplies of 3- or 5- operation microcomputers. It consists of two voltage regulators, three voltage detectors, a switchover circuit, and a control circuit. In addition to being able to switch from primary to backup power supplies, the S Series has three types of voltage detection output signal corresponding to the power supply voltage. The special sequence for switch control prevents unnecessary exhaustion of the backup power supply; this feature is suitable for structuring backup systems. Features Applications Low power consumption ideo camera recorder Normal operation: 43 µa max. ( IN =6 ) Backup: 2.1 µa max. Still video camera Memory card oltage requlator SRAM backup equipment Small input/output voltage differences :.35 max. (I OUT =5mA) Output voltage tolerance : ±2% Three built-in voltage detectors (CS, PREEND, RESET) Detection voltage tolerance: ±2% Special sequence Backup voltage is not output, if the primary power supply voltage does not reach the RESET voltage that activates a CPU. Selection Guide Model No.** Output voltage* CS detection voltage CS release voltage RESET detection voltage (Ta=25 C) Min. Typ. Max. Min. Typ. Max. Min. Typ. Max. Min. Typ. Max. S-8423AFX S-8423NFX S-8423LFX * RO = ** The last digit X of the model No. changes depending upon the package form. ( X=S : 8-pin SSOP, X=T : 8-pin TSSOP ) Seiko Instruments Inc. 1

2 Block Diagram OUT IN REG2 M1 BAT CS voltage detector SW1 detection circuit RESET voltage detector PREEND voltage detector PREEND RESET CS Switch control circuit REG1 SW2 detection circuit RO SS Figure 1 Pin Assignment SS PREEND BAT CS 8-pin SSOP/TSSOP Top view RO IN 4 5 RESET Pin name CS RESET Functions Output pin of CS voltage detector Output pin of RESET voltage detector PREEND Output pin of PREEND voltage detector IN * Primary power supply input pin BAT * Backup power supply input pin * Output pin of voltage regulator 2 RO * Output pin of voltage regulator 1 SS Ground * Mount capacitors between SS (GND) and the IN, BAT,, and RO pins. (See Standard Circuit ) Figure 2 Absolute Maximum Ratings Table 1 Ta=25 C Parameter Symbol Ratings Unit -.3 to 17 Primary power supply input voltage IN SS -.3 to 17 Backup power supply input voltage BAT SS -.3 to 17 Output voltage of voltage regulator RO, SS -.3 to IN +.3 CS CS Output voltage of RESET RESET PREEND PRE SS Power dissipation P D 3 mw Operating temperature T opr -4 to +85 C Storage temperature T stg -4 to +125 C 2 Seiko Instruments Inc.

3 Electrical Characteristics 1. S-8423AFS/AFT o l t a g e r e g u l a t o r o l t a g e d e t e c t o r S w i t c h Table 2 (Unless otherwise specified : Ta=25 C) Parameter Symbol Conditions Min. Typ. Max. Unit Output voltage1 RO IN =6, I RO =3 ma I/O voltage difference 1 dif1 I RO =3 ma.2.35 m Load regulation 1 RO1 IN =6 I RO =1 µa to 4 ma 4 1 m Line regulation 1 RO2 IN =6 to 16 I RO =3 ma 38 1 m Temperature coefficient of Ta=-4 C to 85 C ±.47 m/ C 1 RO T a Output voltage 2 IN =6, I OUT =5 ma I/O voltage difference 2 dif2 I OUT =5 ma.2.35 m Load regulation 2 1 IN =6 I OUT =1 µa to 6 ma 5 11 m Line regulation 2 2 IN =6 to 16 I OUT =5 ma 5 11 m Temperature coefficient of T a Ta=-4 C to 85 C ±.47 m/ C Input voltage of primary power supply IN 16 CS detection voltage - DET1 Detects IN CS release voltage + DET RESET detection voltage - DET2 Detects RESET release voltage + DET DET2 - DET2 PREEND detection voltage - DET3 Detects - DET2 BAT PREEND release voltage + DET3 - DET3 - DET3 - DET Operating voltage opr IN or BAT DET1 T a Ta=-4 C to 85 C ±.57 m/ C Temperature coefficient of detection voltage RO DET2 T a DET3 T a Ta=-4 C to 85 C ±.33 m/ C Ta=-4 C to 85 C ±.36 m/ C DS =.5, RESET ma Sink current I SINK IN = BAT = PREEND ma 3 2. CS ma Leakage current I LEAK DS =16, IN =16.1 µa Switchover voltage SW1 BAT =2.8 + DET1 + DET1 + DET1 4 Detects IN CS output inhibit voltage SW2 BAT =3 Detects M1 switch leakage current I LEK IN =6 BAT = 1 µa 6 M1 switch resistance value R SW IN =open, BAT =3 I OUT =1 to 5 µa 1 Ω 7 Temperature coefficient of SW1 SW1 T a Ta=-4 C to 85 C ±.45 m/ C 4 Temperature coefficient of SW2 Ta=-4 C to 85 C ±.45 m/ C SW2 T a I SS1 IN =6, Unloaded µa I BAT1 BAT = µa Current consumption IN =open 8 I BAT2 BAT =3, Ta=25 C µa Unloaded Ta=85 C 3.5 µa Input voltage of backup power supply BAT Test cir. 5 Seiko Instruments Inc. 3

4 2. S-8423NFS/NFT o l t a g e r e g u l a t o r o l t a g e d e t e c t o r S w i t c h Table 3 (Unless otherwise specified : Ta=25 C) Parameter Symbol Conditions Min. Typ. Max. Unit Test cir. Output voltage1 RO IN =3.6, I RO =15 ma I/O voltage difference 1 dif1 I RO =15 ma 6 18 m Load regulation 1 IN =3.6 RO1 I RO =1 µa to 2 ma 4 1 m Line regulation 1 IN =3.6 to 16 RO2 I RO =15 ma 38 1 m Temperature coefficient of RO RO Ta Ta=-4 C to 85 C ±.46 m/ C Output voltage 2 IN =3.6, I OUT =15 ma I/O voltage difference 2 dif2 I OUT =15 ma 2 6 m 1 Load regulation 2 IN =3.6 OUT1 I OUT =1 µa to 2 ma 5 11 m Line regulation 2 IN =3.6 to 16 OUT2 I OUT =15 ma 5 11 m Temperature coefficient of Ta Ta=-4 C to 85 C ±.46 m/ C Input voltage of primary power supply IN 16 CS detection voltage - DET1 Detects IN CS release voltage + DET m RESET detection voltage - DET2 Detects RESET release voltage + DET PREEND detection - DET3 Detects - DET2 - DET2 - DET2 BAT voltage PREEND release voltage + - DET3 - DET3 - DET3 DET Operating voltage opr IN or BAT Temperature coefficient of - DET1 detection voltage Ta Ta=-4 C to 85 C ±.47 m/ C - DET2 Ta Ta=-4 C to 85 C ±.34 m/ C - DET3 Ta Ta=-4 C to 85 C ±.37 m/ C I SINK DS =.5, RESET ma Sink current IN = BAT = PREEND ma 3 2. CS ma Leakage current I LEAK DS =16, IN =16.1 µa Switchover voltage BAT =2.8 SW1 Detects IN CS output inhibit voltage BAT =3 SW2 Detects M1 switch leakage I IN =3.6 LEK current BAT = M1 switch resistance R IN =open, SW value BAT =3 Temperature coefficient of SW1 Ta Temperature coefficient of SW2 Ta + DET DET DET µa 6 1 Ω 7 SW1 Ta=-4 C to 85 C ±.41 m/ C 4 SW2 Ta=-4 C to 85 C ±.43 m/ C 5 I SS1 IN =3.6, Unloaded µa I BAT1 BAT = µa Current consumption I IN =open BAT2 BAT =3, Ta=25 C µa 8 Unloaded Ta=85 C 3.5 µa Input voltage of backup power supply BAT Seiko Instruments Inc.

5 3. S-8423LFS/LFT o l t a g e r e g u l a t o r o l t a g e d e t e c t o r S w i t c h Table 4 (Unless otherwise specified : Ta=25 C) Parameter Symbol Conditions Min. Typ. Max. Unit Test cir. Output voltage1 RO IN =6, I RO =3 ma I/O voltage difference 1 dif1 I RO =3 ma.2.35 Load regulation 1 IN =6 RO1 I RO =1 µa to 4 ma 5 11 m Line regulation 1 IN =6 to 16 RO2 I RO =3 ma 5 11 m Temperature coefficient of RO RO Ta Ta=-4 C to 85 C ±.71 m/ C Output voltage 2 IN =6, I OUT =5 ma I/O voltage difference 2 dif2 I OUT =5 ma.2.35 Load regulation 2 IN =6 OUT1 I OUT =1 µa to 6 ma 5 11 m Line regulation 2 IN =6 to 16 OUT2 I OUT =5 ma 5 11 m Temperature coefficient of Ta Ta=-4 C to 85 C ±.71 m/ C Input voltage of primary power supply IN 16 CS detection voltage - DET1 Detects IN CS release voltage + DET RESET detection voltage - DET2 Detects RESET release voltage + DET PREEND detection - DET3 Detects - DET2 - DET2 - DET2 BAT voltage DET3 - DET3 PREEND release voltage + - DET3 DET Operating voltage opr IN or BAT DET1 Ta Ta=-4 C to 85 C ±.66 m/ C Temperature coefficient of - DET2 detection voltage Ta Ta=-4 C to 85 C ±.33 m/ C - DET3 Ta Ta=-4 C to 85 C ±.36 m/ C DS =.5, RESET ma Sink current I SINK IN = BAT = PREEND ma 2. CS ma 3 Leakage current I LEAK DS =16, IN =16.1 µa Switchover voltage BAT =2.8 SW1 Detects IN CS output inhibit voltage BAT =3 SW2 Detects M1 switch leakage current I IN =6 LEK BAT = M1 switch resistance value R IN =open, BAT =3 SW I OUT =1 to 5 µa Temperature coefficient of SW1 Ta Temperature coefficient of SW2 Ta + DET DET DET µa 6 1 Ω 7 SW1 Ta=-4 C to 85 C ±.51 m/ C 4 SW2 Ta=-4 C to 85 C ±.68 m/ C 5 I SS1 IN =6, Unloaded µa I BAT1 BAT = µa Current consumption IN =open Ta=25 C µa 8 I BAT2 BAT =3, Unloaded Ta=85 C 3.5 µa Input voltage of backup power supply BAT Seiko Instruments Inc. 5

6 Test Circuit kω 1 kω IN SS RO or 1 µf IN SS BAT PREEND RESET CS 1 kω 3 4 When measuring DET3, apply 6 to IN IN SS IN BAT CS A BAT PREEND A 2.8 RESET A SS Measure the value after applying 5 or more to IN 5 6 F.G. IN SS CS 1 kω Oscilloscope Oscilloscope 6 A IN BAT SS 7 8 IN 1 3 IN BAT SS I S A A I BAT BAT SS Open and measure the value after applying 6 to 1 To measure I BAT2, first apply 3 to BAT and 6 or more to IN. Then open IN and measure the current when BAT is 3. Figure 3 6 Seiko Instruments Inc.

7 Operation Timing Chart (S-8423AFS/AFT) IN RO BAT CS PREEND RESET CS, and PREEND and RESET are pulled up to. Figure 4 Seiko Instruments Inc. 7

8 Operation The consists of two voltage regulators, and three voltage detectors. The voltage regulator 1 regulates input voltage IN and outputs to RO. The voltage regulator 2 outputs to. This section describes the functions and operations of each part. 1. oltage regulators 1 and 2 The built-in regulators have very small I/O voltage difference ( dif1 =.2 typ. at I RO =3 ma). The output voltage of RO and can be selected independently between 2.8 and 3.8 by.1 step. I/O voltage difference dif1 or dif2 Assume that the RO voltage when IN is 6 and I RO is 3 ma is initial. When the voltage of I/O voltage difference dif1 or dif2 and initial is applied to the IN pin, 95% of the initial voltage is output at the RO pin. 2. Switch The switch consists of the switch control circuit, SW1 and SW2 detection circuits, voltage regulator 2 and switch transistor M1. IN REG2 M1 BAT 2.1 SW1 detection circuit The SW1 detection circuit monitors the IN voltage and sends the results of detection to the switch control circuit. In the S- 8423AFS (CS detection voltage ranges from 4. to 5. ), detection voltage ( SW1 ) is set to 77±2% of CS release voltage + DET1 ; in the S-8423NFS (CS detection voltage ranges from 3. to 4. ) is set to 85±2% of CS release voltage + DET1 ). 2.2 SW2 detection circuit Switch control circuit SW1 detection circuit Figure 5 Switch SW2 detection circuit SW2 voltage detector monitors terminal voltage and keeps CS release voltage output low until terminal voltage rises to SW2. Then CS output changes from low to high if IN terminal voltage is more than + DET1 (CS release voltage), when terminal voltage rises to 95% of 2 (output voltage of voltage regulator 2). CS output changes from high to low regardless of SW2, if IN terminal voltage falls down to less than - DET1 (CS detection voltage). CS output holds high if IN temrinal voltage keeps higher than - DET1, when terminal voltage falls down to less than SW2 because of undershoot. 2.3 Switch control circuit The switch control circuit receives the signal from the SW1 detection circuit and controls M1 and voltage regulator 2. The switch control circuit operates in two statuses: the special and normal sequences. In the special sequence status, the circuit does not receive nor control signals according to the IN (or BAT ) voltage sequence. In the normal sequence status, the circuit receives and controls signals. Initially, the circuit is kept in the special sequence status. When IN increases until CS signal goes high, the circuit enters the normal sequence status. (1) Special sequence status When the IN (or BAT ) voltage rises, the switch control circuit is kept in the special sequence status until CS signal goes high. At that time, the switch control circuit turns voltage regulator 2 on and turns M1 off regardless of the status of the SW1 detection circuit. The voltage regulator 2 has a switchover function. 8 Seiko Instruments Inc.

9 (2) Normal sequence status When IN voltage increases until CS signal, which monitors terminal, goes high, the switch control circuit enters the normal sequence. Once the circuit enters the normal sequence, it turns voltage regulator 2 and M1 on and off according to the IN voltage as shown in Table 5. It takes hundreds µs in the worst case until voltage regulator 2 goes ON from OFF. During this period, as both voltage regulator 2 and M1 are OFF, voltage may drop. To protect this drop, do not fail to add 1 µf or more of capacitor to terminal. The circuit returns to the special sequence status, when RESET signal goes low. Table 5 IN voltage oltage regulator 2 M1 IN > SW1 ON OFF 2 IN < SW1 OFF ON BAT - dif3 2.4 Switch transistor M1 OUT dif3 oltage regulator 2 is also used for switch from IN to. IN REG2 BAT Therefore, no reverse current flows from to IN, when voltage M1 regulator 2 is off. The output voltage of voltage regulator 2 can be selected between 2.8 and 3.8 by.1 step. The ON resistance of M1 is 1 Ω or less when I OUT is between 1 Figure 6 Definitions of diff3 and 5 µa. Therefore, when M1 is turned on to connect to BAT, the maximum voltage drop dif3 due to M1 is 1 I OUT (output current). The minimum output at the pin is BAT -dif3 (max.). When voltage regulator 2 is on and M1 is off, the leakage current of M1 is kept below 1 µa ( IN =6, Ta=25 C) with the BAT pin connected to the ground ( SS ). 3. oltage detector The has three voltage detectors and SW2 voltage detector. Three detectors feature high precision and low power consumption with hysteresis characteristics. And SW2 voltage detector inhibit CS release output. The power of CS voltage detector is supplied from the IN and BAT pins. Therefore, the output is stable as long as the primary or backup power supplies are within the operating voltage range (2 to 16 ). All outputs are Nch open-drains, and need about 1 kω of pull-up resistors. (1) CS voltage detector CS monitors IN terminal voltage. The detection voltage can be selected between 3. and 5. by.1 step. The result of detection is output at the CS pin: L for lower voltages than the detection level and H for higher voltages than the release level. (2) PREEND voltage detector PREEND monitors the BAT pin. The detection voltage can be selected between 2.2 and 2.7 by.1 step, and also higher than RESET voltage with any difference voltage, indicating that the backup power supply is running out. The result of detection is output at the PREEND pin: L for lower voltages than the detection level and H for higher voltages than the release level. The power of this detector is supplied from IN terminal. The output is valid only when voltage is supplied from IN terminal to terminal ( IN SW1 ) and the output when voltage is supplied from BAT terminal to terminal ( IN < SW1 ) is L. Seiko Instruments Inc. 9

10 (3) RESET voltage detector RESET monitors the pin. The detection voltage can be selected between 2. and 2.7 by.1 step. The result of detection is output at the RESET pin: L for lower voltages than the detection level and H for higher voltages than the release level. RESET outputs normal logic when terminal voltage is 1. or more terminal NOTE PREEND and RESET are detected at different pins. In practice, current is taken from the BAT side, so consider the I/O voltage difference ( dif3 ) of M1 when M1 is turned on. Input voltage Release voltage Detection voltage Output voltage Figure 7 Detection potentials of voltage detectors Transient Response 1. Line transient response against input voltage fluctuation Input voltage fluctuation differs with the types of the signal applied: type I (square wave between 6. and 1 ) and type II (square wave from to 1 ) (see Figure 8). This section describes the ringing waveforms and parameter dependency of each type. For reference, Figure 9 describes the measuring circuit. Type I: Square wave between 6. and 1 1 Input voltage 6. Output voltage deviation Type II: Square wave from to 1 Overshoot Undershoot Input voltage 1 Overshoot Output voltage deviation Undershoot Figure 8 Fast amplifier IN S-8423 SS C OUT R L Oscilloscope P.G Figure 9 Measuring circuit 1 Seiko Instruments Inc.

11 Type I pin C OUT =22 µf, I OUT =5 ma, Ta=25 C Input voltage (5 /div) 6 1 Output voltage (1 m/div) t (2µs/div) Figure 1 Type I ringing waveform ( pin) RO pin C RO =22 µf, I RO =3 ma, Ta=25 C Input voltage (5 /div) 6 1 Output voltage (1 m/div) t (2 µs/div) Figure 11 Type I ringing waveform ( RO pin) Table 6 Type I parameter dependency Parameter Conditions Method to decrease overshoot Method to decrease undershoot Output current I OUT 5 to 6 ma Decrease Decrease Load capacitance C RO 5 to 47 µf Increase Increase Input fluctuation IN 1 to 4 Decrease Decrease Temperature Ta -4 C to +85 C Low temperature Low temperature Seiko Instruments Inc. 11

12 Type II pin C OUT =22 µf, I OUT =5 ma, Ta=25 C Input voltage (5 /div) 1 Output voltage (1 m/div) t (2 µs/div) Figure 12 Type II ringing waveform ( pin) RO pin C RO =22 µf, I RO =3 ma, Ta=25 C Input voltage (5 /div) 1 Output voltage (1 m/div) t (2 µs/div) Figure 13 Type II ringing waveform ( RO pin) Table 7 Type II parameter dependency Parameter Conditions Method to decrease overshoot Method to decrease undershoot Output current I OUT 5 to 6 ma Load capacitance C OUT 5 to 22 µf Decrease Decrease Load capacitance C OUT 22 to 47 µf Increase Increase Temperature Ta -4 C to +85 C Low temperature Low temperature For reference, the following pages describe the results of measuring the ringing s at the and RO pins using the output current (I OUT ), load capacitance (C RO ), input fluctuation width ( IN ), and temperature as parameters. 12 Seiko Instruments Inc.

13 Reference data: Type I 1. I OUT dependency 1.1 pin 1.2 RO pin.5 C OUT =22 µf, Ta=25 C.5 C RO =22 µf, Ta=25 C I OUT (ma) I RO (ma) 2. C RO dependency 2.1 pin 2.2 RO pin.5 I OUT =5 ma, Ta=25 C.5 I RO =3 ma, Ta=25 C C OUT (µf) C RO (µf) Overshoot Undershoot Seiko Instruments Inc. 13

14 3. IN dependency IN shows the difference between the low voltage fixed to 6 and the high voltage. For example, IN =2 means the difference between 6 and pin 3.2 RO pin.4 I OUT =5 ma C OUT =22 µf, Ta=25 C.4 I RO =3 ma C RO =22 µf, Ta=25 C IN IN Temperature dependency 4.1 pin 4.2 RO pin.5.4 I OUT =5 ma C OUT =22 µf.5.4 I RO =3 ma C RO =22 µf Ta ( C) Ta ( C) 1 Overshoot Undershoot 14 Seiko Instruments Inc.

15 Reference data: Type II 1. I OUT dependency 1.1 pin 1.2 RO pin.5 C OUT =22 µf, Ta=25 C.5 C RO =22 µf, Ta=25 C I OUT (ma) I RO (ma) 2. C RO dependency 2.1 pin 2.2 RO pin.5.5 I OUT =5 ma I RO =3 ma Ta=25 C Ta=25 C C OUT (µf) C RO (µf) 3. Temperature dependency 3.1 pin 3.2 RO pin.4.5 IOUT =5 ma C OUT =22 µf.4.5 IRO =3 ma C RO =22 µf Ta ( C) Ta ( C) Overshoot Undershoot Seiko Instruments Inc. 15

16 2. Load transient response based on output current fluctuation The overshoot and undershoot are caused in the output voltage if the output current fluctuates between 1 µa and 5 ma (between 1 µa and 3 ma at the RO pin) while the input voltage is costant. Figure 14 shows the output voltage fluctuation due to change of output current. Figure 15 shows the measuring circuit for reference. The latter half of this section describes ringing waveform and parameter dependency. Output current 5 ma 1 µa Output voltage deviation Figure 14 Overshoot Undershoot IN Oscilloscope SS C OUT Figure 15 Measuring circuit Output current fluctuation causes ringing. Figure 18 shows the ringing waveform at the pin and Figure 19 shows that waveform at the RO pin. pin IN =6., C OUT =22 µf, Ta=25 C Output current 5 ma 1 µa Output voltage (5m/div) RO pin Output current t (5 ms/div) t (2 µs/div) Figure 16 waveform due to output current fluctuation ( pin) IN =6., C RO =22 µf, Ta=25 C 3 ma 1 µa Output voltage (1m/div) t (5 ms/div) t (2 µs/div) Figure 17 waveform due to output current fluctuation ( RO pin) 16 Seiko Instruments Inc.

17 Table 8 Parameter dependency due to output current fluctuation Parameter Method to decrease overshoot Method to decrease undershoot Input voltage IN Load capacitance C RO Increase Increase Output fluctuation I OUT Decrease Decrease Temperature Ta Low temperature Low temperature Reference data 1. IN dependency 1.1 pin 1.2 RO pin.2 C OUT =22 µf, Ta=25 C.2 C RO =22 µf, Ta=25 C IN IN C OUT dependency 2.1 pin 2.2 RO pin.2 IN =6., Ta=25 C.2 IN =6., Ta=25 C C OUT (µf) C RO (µf) 5 Overshoot Undershoot Seiko Instruments Inc. 17

18 3. IOUT Dependency I OUT or I RO shows the fluctuation between the low current stabilized at 1 µa and the high current. For example. I OUT = 1 ma means the fluctuation between 1 µa and 1 ma. 3.1 pin 3.2 RO pin IN =6, C OUT =22 µf, Ta=25 C IN =6, C RO =22 µf, Ta=25 C I OUT (ma) I RO (ma) 6 4. Temperature dependecy 4.1 pin.2 IN =6., C OUT =22 µf 4.2 RO pin.2 IN =6., C RO =22 µf Ta ( C) Ta ( C) 1 Overshoot Undershoot 18 Seiko Instruments Inc.

19 3. Selecting Load Capacitance The results in 1 and 2 show that the parameter dependency due to the input voltage fluctuation of type II is the opposite of type I, and the output current fluctuation (the of ringing is small). Comparing types I and II with respect to the input voltage fluctuation allows the proper load capacitance to be determined. For example, Figure 18 shows the C OUT dependency of types I and II at pin, respectively. This shows that the proper load capacitance C OUT is 22 µf or more Type I Type II Overshoot C OUT (µf) Figure 18 When IC chips or capacitors connected to the RO and pins have sufficient room for overshoot and little room for undershoot ( output voltage is close to the detection voltage of the RESET voltage detector), use of a capacitor of 22 µf or more is recommended. In both cases, check the temperature characteristics. Standard Circuit + 1 µf - RO RO 1 kω IN BAT µf µf*.1 µf 3 SS CS RESET PREEND 1kΩ 1kΩ 1kΩ * Always add 1 µf or more of capacitor to and RO temrinal. Figure 19 Seiko Instruments Inc. 19

20 Application Circuits 1. Merits in designing (1) A switching circuit for primary and backup power supplies is usually configured with discrete components. The S-8423 Series enables you to configure the circuit with a single chip. Some microcomputers can enter standby mode (or low clock mode) from normal mode (or high clock mode) only, and need about 3 each time they are used. If a low voltage (such as the backup voltage) is applied to these microcomputers initially, they may run away and vast current consumption may flow. The is designed to have a special sequence that stops the backup voltage until the primary power supply voltage reaches the initial voltage that trips the switch. (2) Systems can be structured easily. Three types of built-in voltage detectors (CS, PREEND, and RESET) send three types of voltage detection signal to microcomputers. (3) Battery service life are prolonged. - The I/O voltage difference of the voltage regulator 2 switch is very small, and allows the primary power supply to be used until just before they are completely discharged. - The current consumption during backup operation is very small (2.1 µa max.), and allows the backup power supply to have a long service life. 2. Design considerations In applications with small I RO or I OUT, output voltages ( RO and ) may rise to cause the load stability to violate standards. Set I RO and I OUT to 1 µa or more. Attach the proper capacitor to the pin to prevent the RESET voltage detector (which monitors the pin) from being active due to undershoot. Watch for overshoot and ensure it does not exceed the ratings of the IC chips and/or capacitors attached to the RO and pins. Power dissipation of SSOP8 package is shown as Figure 2. To prevent improper oscillation of the IC, attach a capacitor of.1µf or more to the RO pin. When the IN starts to rise from voltage that is more than SW1, a low pulse of less than 4 ms flows through the PREEND pin even when BAT is more than the PREEND release voltage. Thus when monitoring the PREEND pin, always make sure it is more than 4 ms after the rising of IN. When IN falls to, design peripheral circuits so that IN falls at the falling edge of 1 ms or more (C OUT = 1µF, C RO = 1µF). In the case of a falling edge of 1 ms or less, the RESET pin goes L. 4 Not mounted Power dissipation P D (mw) Ambient temperature Ta ( C) Figure 2 Power dissipation 2 Seiko Instruments Inc.

21 3. Application examples (1) When using a timer microcomputer for backup and displaying PREEND on the main CPU + 1 µf - 1 kω RD 6 1 µf 1 kω.1 µf + - IN CS BAT PREEND CS CC Timer microcomputer 3 + RO RESET RESET 1 µf - SS C D 1 kω LCD CC + - Main CPU RESET INT SEGφ Address and data * RESET can be delayed by R D and C D. (2) When using rechargeable battery as a backup battery Figure µf µf - RO 6 + 1µF -.1 µf IN BAT CS 1 kω 1 kω CC Microcompute INT 3 RESET RESET SS Backup battery can be floating-recharged by using voltage regulator1 Figure 22 Seiko Instruments Inc. 21

22 (3) Memory card Card unit IN + IN + BDT2 - PREEND CS - SRAM CS BDT1 RESET BAT SS.1 µf 3 CS Figure Seiko Instruments Inc.

23 Characteristics 1. oltage regulator (S-8423AFS) 1.1 Input voltage ( IN )-Output voltage ( RO ) (REG1) (1) Ta=85 C 4.3 I RO =1 ma, 3 ma, 5 ma, 7 ma (2) Ta=25 C 4.3 I RO =1 ma, 3 ma, 5 ma, 7 ma RO 3.3 RO I RO=1 ma 2.8 I RO=1 ma I RO=7 ma I RO=7 ma IN IN (3) Ta=-4 C 4.3 I RO =1 ma, 3 ma, 5 ma, 7 ma RO I RO=1 ma I RO=7 ma IN 1.2 Input voltage ( IN )-Output voltage ( ) (REG2) (1) Ta=85 C I OUT =1 ma, 3 ma, 5 ma, 7 ma, 9 ma (2) Ta=25 C I OUT =1 ma, 3 ma, 5 ma, 7 ma, 9 ma I OUT=1 ma I OUT=1 ma I OUT=9 ma I OUT=9 ma IN IN (3) Ta=-4 C 4.3 I OUT =1 ma, 3 ma, 5 ma, 7 ma, 9 ma I OUT=1 ma I OUT=9 ma IN Seiko Instruments Inc. 23

24 1.3 I/O voltage difference (dif1)-output voltage (REG1) (1) Ta=85 C 1.5 I RO =1 ma, 3 ma, 5 ma, 7 ma (2) Ta=25 C 1.5 I RO =1 ma, 3 ma, 5 ma, 7 ma RO initial 1. I RO=1 ma RO initial 1. I RO=1 ma (%).95 (%).95 I RO=7 ma I RO=7 ma IN -initial IN -initial (3) Ta=-4 C 1.5 I RO =1 ma, 3 ma, 5 ma, 7 ma I RO=1 ma RO initial 1. (%).95 I RO=7 ma IN -initial initial : RO value when input voltage is I/O voltage difference ( dif2 )-Output voltage (REG2) (1) Ta=85 C 1.5 I OUT = 1 ma, 3 ma, 5 ma, 7 ma, 9 ma (2) Ta=25 C 1.5 I OUT = 1 ma, 3 ma, 5 ma, 7 ma, 9 ma initial (%) IOUT=1 ma I OUT=9 ma initial (%) IOUT=1 ma I OUT=9 ma IN -initial IN -initial (3) Ta=-4 C 1.5 I OUT = 1 ma, 3 ma, 5 ma, 7 ma, 9 ma initial (%) IOUT=1 ma I OUT=9 ma IN -initial initial : value when input voltage is Seiko Instruments Inc.

25 1.5 Output current (I RO )-Output voltage ( RO ) 1.6 Output current (I OUT )-Output voltage ( ) RO Ta= -4 C 25 C 85 C IN = IN =6. Ta= -4 C 25 C 85 C Output voltage ( RO )-Temperature RO (m) I RO (ma) IN =6, I RO =3 ma Based on RO voltage when Ta is 25 C 1.8 Output voltage ( )-Temperature (m) I OUT (ma) IN =6, I OUT =5 ma Based on RO voltage when Ta is 25 C I/O voltage difference ( dif1 )-Temperature.4 I RO =3 ma I/O voltage difference ( dif2 )-Temperature.4 I OUT =5 ma.3 dif1.2 dif Input stability ( RO )-Temperature 1.12 Input stability ( )-Temperature.1.8 I RO =3 ma.1.8 I OUT =5 ma RO IN RO (%/).6.4 IN (%/) Seiko Instruments Inc. 25

26 1.13 Load stability ( RO )-Temperature 1.14 Load stability ( )-Temperature RO (m) IN =6 (m) IN =6 26 Seiko Instruments Inc.

27 2. oltage regulator (S-8423LFS) 2.1 Input voltage ( IN )-Output voltage ( RO ) (REG1) (1) Ta=85 C (2) Ta=25 C 6. I RO =1 ma, 3 ma, 5 ma, 7 ma 6. I RO =1 ma, 3 ma, 5 ma, 7 ma RO 5. RO I RO=1 ma I RO=7 ma I RO=1 ma I RO=7 ma IN IN (3) Ta=-4 C 6. I RO =1 ma, 3 ma, 5 ma, 7 ma RO I RO=1 ma I RO=7 ma IN 2.2 Input voltage ( IN )-Output voltage ( ) (REG2) (1) Ta=85 C I OUT =1 ma, 3 ma, 5 ma, 7 ma, 9 ma (2) Ta=25 C I OUT =1 ma, 3 ma, 5 ma, 7 ma, 9 ma I OUT=1 ma I OUT=9 ma I OUT=1 ma I OUT=9 ma IN IN (3) Ta=-4 C 6. I OUT =1 ma, 3 ma, 5 ma, 7 ma, 9 ma I OUT=1 ma I OUT=9 ma IN Seiko Instruments Inc. 27

28 2.3 I/O voltage difference (dif1)-output voltage (REG1) (1) Ta=85 C 1.5 I RO =1 ma, 3 ma, 5 ma, 7 ma (2) Ta=25 C 1.5 I RO =1 ma, 3 ma, 5 ma, 7 ma RO initial 1. I RO=1 ma RO initial 1. I RO=1 ma (%).95 (%).95 I RO=7 ma IN -initial 1. I RO=7 ma IN -initial (3) Ta=-4 C 1.5 I RO =1 ma, 3 ma, 5 ma, 7 ma RO initial (%) I RO=1 ma I RO=7 ma IN -initial initial : RO value when input voltage is I/O voltage difference ( dif2 )-Output voltage (REG2) (1) Ta=85 C 1.5 I OUT = 1 ma, 3 ma, 5 ma, 7 ma, 9 ma (2) Ta=25 C 1.5 I OUT = 1 ma, 3 ma, 5 ma, 7 ma, 9 ma initial (%) I OUT=1 ma initial (%) I OUT=1 ma I OUT=9 ma I OUT=9 ma IN -initial IN -initial (3) Ta=-4 C 1.5 I OUT = 1 ma, 3 ma, 5 ma, 7 ma, 9 ma initial 1. IOUT=1 ma (%).95 I OUT=9 ma initial : value when input voltage is IN -initial 28 Seiko Instruments Inc.

29 2.5 Output current (I RO )-Output voltage ( RO ) 2.6 Output current (I OUT )-Output voltage ( ) RO 5.15 IN = Ta= -4 C 25 C C Ta= -4 C 25 C C 5. IN = I RO (ma) I OUT (ma) 2.7 Output voltage ( RO )-Temperature RO (m) IN =6, I RO =3 ma Based on RO voltage when Ta is 25 C 2.8 Output voltage ( )-Temperature (m) IN =6, I OUT =5 ma Based on voltage when Ta is 25 C I/O voltage difference ( dif1 )-Temperature 2.1 I/O voltage difference ( dif2 )-Temperature.3 I RO =3 ma.3 I OUT =5 ma.2.2 dif1.1 dif Input stability ( RO )-Temperature 2.12 Input stability ( )-Temperature.1.8 I RO =3 ma.1.8 I OUT =5 ma RO IN RO (%/).6.4 IN (%/) Seiko Instruments Inc. 29

30 2.13 Load stability ( RO )-Temperature 2.14 Load stability ( )-Temperature RO (m) IN =6 (m) IN =6 3 Seiko Instruments Inc.

31 3. Switch 3.1 Switch voltage ( SW1 )-Temperature 3.2 CS output prohibition voltage ( SW2 )-Temperature SW1 (m) 5 4 Based on SW1 voltage when Ta is 25 C SW2 (m) Based on SW2 voltage when Ta is 25 C Input voltage ( BAT )- BAT Switch resistance 3.4 BAT Switch resistance-temperature 1 8 I OUT =5 µa 1 8 BAT =3, I OUT =5 µa R SW (Ω) 6 4 R SW (Ω) BAT BAT Switch leak current (I LEK )-Temperature 5 4 IN =6., BAT = I LEK (na) Seiko Instruments Inc. 31

32 4. oltage detectors 4.1 CS voltage detector (1) Detection voltage (- DET1 )-Temperature (2) Output current (I SINK ) 5 25 Based on CS (- DET1 ) voltage when Ta is 25 C 25 2 IN =3.6 Ta=25 C - DET1 (m) I SINK (ma) IN = DS (3) Output current (I SINK )-Temperature 3. IN = BAT =2., DS =.5 I 2. SINK (ma) RESET voltage detector (1) Detection voltage (- DET2 )-Temperature (2) Output current (I SINK ) (- DET2 ) (m) 5 25 Based on RESET (- DET2 ) voltage when Ta is 25 C I SINK (ma) IN =2. Ta=25 C -25 IN = DS (3) Output current (I SINK ) -Temperature 4. IN = BAT =2., DS =.5 I SINK (ma) Seiko Instruments Inc.

33 4.3 PREEND voltage detector (1) Detection voltage (- DET3 )-Temperature (2) Output current (I SINK ) - DET3 (m) 5 25 Based on PREEND (- DET3 ) voltage when Ta is 25 C I SINK (ma) IN =2. Ta=25 C IN = DS (3) Output current (I SINK )-Temperature I SINK (ma) IN = BAT =2., DS = Seiko Instruments Inc. 33

34 5. Current consumption 5.1 IN - IN current consumption (I SS1 ) 5.2 BAT - BAT2 current consumption (I BAT2 ) 4 1 IN =open 3 2 I SS1 (µa) 1 Ta= 85 C 25 C -4 C I BAT2 (µa) Ta=8 C Ta=25 C Temperature IN BAT =open BAT =3 18 Ta=-4 C BAT (1) I SS1 (2) I BAT1 6 4 IN =6., BAT =3. IN =6., BAT =3. I SS1 (µa) 4 I BAT1 (na) (3) I BAT2 2. IN =open, BAT =3 1.5 I BAT2 (µa) Seiko Instruments Inc.

35

36

37

38 The information herein is subject to change without notice. Seiko Instruments Inc. is not responsible for any problems caused by circuits or other diagrams described herein whose industrial properties, patents or other rights belong to third parties. The application circuit examples explain typical applications of the products, and do not guarantee any mass-production design. When the products described herein include Strategic Products (or Service) subject to regulations, they should not be exported without authorization from the appropriate governmental authorities. The products described herein cannot be used as part of any device or equipment which influences the human body, such as physical exercise equipment, medical equipment, security system, gas equipment, vehicle or airplane, without prior written permission of Seiko Instruments Inc.