Reset IC with battery backup function

Transcription

1 Reset IC with battery backup function BAAF / BA / BAF The BAAF, BA, and BAF are reset ICs with a battery backup function, designed for equipment using SRAMs and other similar components. These ICs are configured of a reset signal and CS signal output unit and a power supply switching unit. If the BAAF detects that the power supply has dropped to. or lower, it outputs the CS, CSB, and Reset signals to set the SRAM in backup mode. If the voltage drops to. or lower, the power supply switches to the battery. With the BA and BAF, in the same way, a power supply of. is detected, and if the voltage drops to. or lower, the power supply switches to the battery. These ICs allow SRAMs to be write protected and allow the system to be reset, in addition to switching between the power supply and the battery. Applications Equipment using SRAMs (cards, cassettes, facsimile machines, copiers, word processors, personal computers, etc.) Features ) Equipped with battery backup function. ) Equipped with both CS signals (CS and CSB) and Reset signals. ) Low current dissipation when powered from battery. ) Low voltage loss when powered from battery. ) Smooth switching between power supply and battery. Absolute maximum ratings (Ta = C) Parameter Symbol Limits Unit Power supply voltage CC.0 Output current IOUT 0 (BAAF) 0 (BA / BAF) ma Output current IOUT 00 µa Power dissipation Pd 00 (BA) 0 (BAAF) (BAF) mw Operating temperature Topr 0 ~ C Storage temperature Tstg 0 ~ C IOUT indicates the output current on the CC side, and IOUT the output current on the BAT side. Reduced by.0mw for each increase in Ta of C over C. Reduced by.mw for each increase in Ta of C over C.

2 Block diagram CC N.C. o CSB BAAF / BA / BAF REF CC Power supply voltage Input / output circuit Reset Pin descriptions Pin No. Pin name Function Substrate Reset Reset output CS CS output BAT Battery power supply CSB CSB output O Power supply output N.C. CS BAT Pin Reset output Pin Battery power supply Pin Power supply (CC) Pin Power supply output CC CC CC Pin CSB output Pin CS output Pin Power supply output

3 BAAF / BA / BAF Electrical characteristics BAAF (unless otherwise noted, Ta = C, RRES = CC =, ) Parameter Symbol Min. Typ. Max. Unit Conditions No-load current dissipation ICC.0 ma CC =, BAT = I / O voltage differential SAT CC =, BAT =, IO = ma o output voltage O.. CC =, BAT =, IO = ma o output voltage O.0.0 CC =, BAT =, IO = ma o output voltage O.0. CC =, BAT =, IO = 0mA Detection voltage S..0. CC = H L Detection hysteresis voltage SH 00 m CC = L H Reset output low level voltage RESL 0. CC = Reset leakage current IRESH 0. µa CC =, RRES = Reset operating limit voltage OPL 0.. CC = H L, RES 0. CS output low level voltage CSL 0. CC =, BAT =, ICS = µa CS output high level voltage CSH. CC =, BAT =, ICS = µa CSB output low level voltage CSBL 0. CC =, BAT =, ICSB = µa CSB output high level voltage CSBH o 0. CC =, BAT =, ICSB = µa Detection voltage temperature characteristic S % / C Switching voltage B..0. CC = H L, BAT =, RO = 00kΩ Switching hysteresis voltage BH 00 m CC = L H, BAT =, RO = 00kΩ Switching voltage temperature characteristic B % / C Backup current dissipation ICCB 0. µa CC =, BAT = I / O voltage differential SAT CC =, BAT =, IO = µa o output voltage O.0.0 CC =, BAT =, IO = µa o output voltage O.0. CC =, BAT =, IO = 00µA o output voltage O CC 0. IO = 0mA Reverse current IOR 0. µa CC =, BAT = (Note) IO, ICS, and ICSB are when flowing toward the pin and when flowing away from the pin. Not designed for radiation resistance.

4 BAAF / BA / BAF BA / F (unless otherwise noted, Ta = C, RRES = CC =, ) Parameter Symbol Min. Typ. Max. Unit Conditions No-load current dissipation ICC.0 ma CC =, BAT = I / O voltage differential SAT CC =, BAT =, IO = ma o output voltage O.. CC =, BAT =, IO = ma o output voltage O.0.0 CC =, BAT =, IO = ma o output voltage O.0. CC =, BAT =, IO = 0mA Detection voltage S CC = H L Detection hysteresis voltage SH 00 m CC = L H Reset output low level voltage RESL 0. CC =. Reset leakage current IRESH 0. µa CC =, RRES = Reset operating limit voltage OPL 0.. CC = H L, RES 0. CS output low level voltage CSL 0. CC =., BAT =, ICS = µa CS output high level voltage CSH. CC =, BAT =, ICS = µa CSB output low level voltage CSBL 0. CC =, BAT =, ICSB = µa CSB output high level voltage Detection voltage temperature characteristic Switching voltage Switching hysteresis voltage Switching voltage temperature characteristic Backup current dissipation I / O voltage differential o output voltage o output voltage o output voltage Reverse current CSBH KS B BH KB ICCB SAT O O O IOR (Note) IO, ICS, and ICSB are when flowing toward the pin and when flowing away from the pin. Not designed for radiation resistance. o % / C m % / C CC =., BAT =, ICSB = µa CC = H L, BAT =, RO = 00kΩ CC = L H, BAT =, RO = 00kΩ.0.0 CC µa CC =, BAT = CC =, BAT =, IO = µa CC =, BAT =, IO = µa CC =, BAT =, IO = 00µA IO = 0mA 0. µa CC =, BAT =

5 BAAF / BA / BAF Measurement circuit SAT = CC O IO RO 00kΩ O (B) A ICC CC RRES (S.B.OPL) RRES 0kΩ BAAF (BA / F) ICSB CSB A ICCB.IOR IRES A RES CS ICS BAT (OPL) (S) Fig.

6 BAAF / BA / BAF Circuit operation These ICs have two distinct functions, a logic output function and a power supply switching function. The logic output circuit consists of the following: () Reset output (NPN Tr open collector) () CS output (PNP Tr open collector pull-down resistor) () CSB output (NPN Tr open collector pull-up resistor) The power supply switching circuit consists of a PNP power transistor and an SBD (Schottky barrier diode). The normal power supply CC and the battery backup power supply (BAT) are both connected to the switching circuit. When the PNP power transistor is turned on and off, the IC power is switched from the normal power supply to the battery backup power supply, and vice versa. The detection circuit consists of a standard voltage source REF and a hysteresis comparator. The power supply CC is detected using a split resistance. When the drops below the detection voltage (BAAF: S =.typ. when CC drops and S 0.typ. when CC rises; BA / F: S =.typ. when CC drops, and S 0.typ. when CC rises), the Reset signal (Low) and the CS signal (CS-Low, CSB-High) are output by the logic output function, and the SRAM (or other memory device) is switched to backup mode. If the power supply CC drops further and goes below the switching voltage (BAAF and BA / F: B =.typ. when CC drops, B 0.typ. when CC rises), the SBD develops a forward bias because the PNP power transistor is off. The power supply output O switches from the power supply CC to the battery power supply (BAT). When the normal power supply CC rises, the above process is reversed. (BAAF) (BA / F) CC S [.Typ.] [.Typ.] B [.Typ.] O O (cc) [SAT] O O (BAT) [SAT] RESET O RESH [ CC] CS RESL [ ] CSH [ CC] CSL [ ] CSB CSBH [ O] CSBL [ ] Fig. Timing chart

7 Application example cc BAAF / BA / BAF SRAM DD C 0µF C 0.0µF R 0kΩ ref SRAM CEB SRAM CE BATTERY CPU Reset Fig. Operation notes () Power supply CC These ICs are designed to operate with at CC =, but can also operate at CC values of other than. However, the following conditions must be met: (equation) { S SH < CC < CCMax. CC BAT < () Battery voltage BAT These ICs are designed to operate with at BAT =, but can also operate at BAT values of other than. However, the following conditions must be met: (equation) { BAT < B CC BAT < where) S: detection voltage SH: detection hysteresis voltage B: switching voltage

8 BAAF / BA / BAF Electrical characteristic curves (BAAF) CHIP SELECT OLTAGE: CS () 0 BAT = CHIP SELECT BAR OLTAGE: CSB () 0 BAT = RESET OLTAGE: CSB () Fig. CS output voltage vs. 0 0 Fig. CSB output voltage vs. 0 0 Fig. Reset output voltage vs. OUTPUT OLTAGE: O () 0 BAT = RO = 00kΩ OUTPUT OLTAGE: O ().0... CC = BAT = OUTPUT OLTAGE: O ()... CC = BAT = OUTPUT CURRENT: IO (ma) OUTPUT CURRENT: IO (µa) CHIP SELECT OLTAGE: CS () 0 Fig. Output voltage vs. power supply voltage Electrical characteristic curves (BA / F) BAT = 0 0 Fig. 0 CS output voltage vs. CHIP SERECT BAR OLTAGE: CSB () Fig. Output voltage vs. output current (!) (when power supply is detected) BAT = 0 0 Fig. CSB output voltage vs. RESET OLTAGE: RES () 0 Fig. Output voltage vs. output current (@) (when using battery backup) 0 0 Fig. Reset output voltage vs.

9 BAAF / BA / BAF OUTPUT OLTAGE: O () 0 BAT = RO = 00kΩ OUTPUT OLTAGE: O ().0.. CC = BAT = OUTPUT OLTAGE: O ()... CC = BAT = OUTPUT CURRENT: IO (ma) OUTPUT CURRENT: IO (µa) Fig. Output voltage vs. power supply voltage Fig. Output voltage vs. output current (!) (when power supply is detected) Fig. Output voltage vs. output current (@) (when using battery backup) External dimensions (Units: mm) BAAF, BAF BA.0 ± 0.. ± 0.. ± 0.. ± ± ± 0. 0.Min. 0. ± 0.. ± 0.. ± 0. 0.Min.. ± ± 0. 0 ~ 0. ± SOP DIP