MAX703 Fast Delivery |IC PHOENIX CO.,LIMITED

MAX703 ,µP Reset IC with Battery-BackupApplicationsMAX704C/D 0°C to +70°C Dice*● Computers MAX704CPA 0°C to +70°C 8 PDIP● ControllersMAX70 ..
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MAX703
µP Reset IC with Battery-Backup
General Description
The MAX703/MAX704 microprocessor (μP) supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery control functions in μP systems. These devices significantly improve system reliability and accuracy compared to that obtained with separate ICs or discrete components.
The MAX703/MAX704 are available in 8-pin DIP and SO packages and provide four functions:
1) An active-low reset during power-up, power-down, and brownout conditions.
2) Battery-backup switching for CMOS RAM, CMOS μPs, or other low-power logic circuitry.
3) A 1.25V threshold detector for power-fail warning, low-battery detection, or for monitoring a power supply other than +5V.
4) An active-low manual reset input.
The MAX703 and MAX704 differ only in their supplyvolt-age monitor levels. The MAX703 generates a reset when the supply drops below 4.65V, while the MAX704 gener-ates a reset below 4.40V.
Applications●Computers●Controllers●Intelligent Instruments●Critical μP Power Monitoring
Features●Battery-Backup Power Switching●Precision Supply-Voltage Monitor • 4.65V (MAX703) • 4.40V (MAX704)●200ms Reset Pulse Width●Debounced TTL/CMOS-Compatible Manual Reset Input●200μA Quiescent Current●50nA Quiescent Current in Battery-Backup Mode●Voltage Monitor for Power-Fail or Low-Battery Warning●8-Pin DIP and SO Packages●Guaranteed RESET Assertion to VCC = 1V
*Dice are tested at TA = +25°C only.
**Contact factory for availability and processing to MIL-STD-883.
Devices in PDIP and SO packages are available in both leaded
and lead(Pb)-free packaging. Specify lead(Pb)-free by adding
the “+” symbol at the end of the part number when ordering.
Lead(Pb)-free not available for CERDIP package.
PARTTEMP RANGEPIN-PACKAGE
MAX703C/D0°C to +70°CDice*
MAX703CPA0°C to +70°C8 PDIP
MAX703CSA0°C to +70°C8 SO
MAX703EPA-40°C to +85°C8 PDIP
MAX703ESA-40°C to +85°C8 SO
MAX703MJA-55°C to +125°C8 CERDIP**
MAX704C/D0°C to +70°CDice*
MAX704CPA0°C to +70°C8 PDIP
MAX704CSA0°C to +70°C8 SO
MAX704EPA-40°C to +85°C8 PDIP
MAX704ESA-40°C to +85°C8 SO
MAX704MJA-55°C to +125°C8 CERDIP**
UNREGULATED DCREGULATED +5V
CMOS RAM
MICROPROCESSOR
3.6V
LITHIUM
BATTERY
PFI
PUSHBUTTON
SWITCH
0.1µF
VOUT
VBATT
VCC
NMI
VCC
GND
GND
GND
BUS
RESETRESET
PFO
VCC
MAX703
MAX704
PFOPFI
MAX703
MAX704
VBATT
RESETVCC
GND
VOUT
DIP/SO
TOP VIEW
MAX703/MAX704Low-Cost Microprocessor Supervisory
Circuits with Battery Backup
Typical Operating Circuit
Pin Coniguration
Ordering Information
Terminal Voltage (with respect to GND) VCC...................................................................-0.3V to +6.0V VBATT................................................................-0.3V to +6.0V All Other Inputs (Note 1).......................-0.3V to (VCB + 0.3V)Input Current VCC ..............................................................................200mA VBATT ............................................................................50mA GND................................................................................20mAOutput Current VOUT..............................Short-Circuit Protected for Up to 10s All Other Outputs ............................................................20mA
Rate-of-Rise VBATT, VCC................................................100V/μsOperating Temperature Range C Suffix................................................................0°C to +70°C E Suffix.............................................................-40°C to +85°C M Suffix..........................................................-55°C to +125°CContinuous Power Dissipation (TA = +70°C) 8-Pin PDIP (derated 9.09mW/°C above +70°C)..........727mW 8-Pin SO (derated 5.88mW/°C above +70°C).............471mW 8-Pin CERDIP (derated 8.00mW/°C above +85°C).....640mWStorage Temperature Range ............................-65°C to +160°CLead Temperature (soldering, 10s) .................................+300°C
(VCC = +4.75V to +5.5V for MAX703, VCC = +4.5V to +5.5V for MAX704, VBATT = 2.8V, TA = TMIN to TMAX, unless otherwise noted.)
Note 1: VCB is the greater of VCC and VBATT. The input voltage limits on PFI and MR may be exceeded if the current into these pins is limited to less than 10mA.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Operating Voltage Range VCC, VBATT(Note 2)05.5V
Supply Current (Excluding IOUT)ISUPPLYMAX70_C200350µAMAX70_E/M200500
ISUPPLY in Battery-Backup Mode (Excluding IOUT)VCC = 0V, VBATT = 2.8V
TA = +25°C0.051.0TA = TMIN to TMAX5.0
VBATT Standby Current(Note 3)5.5V > VCC > VBATT + 0.2V
TA = +25°C-0.10+0.02µA
TA = TMIN to TMAX-1.00+0.02
VOUT Output
IOUT = 5mAVCC - 0.05VCC - 0.025VIOUT = 50mAVCC - 0.5VCC - 0.25
VOUT in Battery-Backup ModeIOUT = 250µA, VCC < VBATT - 0.2VVBATT - 0.1VBATT - 0.02V
Battery Switch Threshold (VCC - VBATT)VCC < VRSTPower-up20mVPower-down-20
Battery Switchover Hysteresis40mV
RESET ThresholdVRST
MAX7034.504.654.75VMAX7044.254.404.50
RESET Threshold Hysteresis40mV
RESET Pulse WidthtRST140200280ms
RESET Output Voltage
VOHISOURCE = 800µAVCC - 1.5
VOL
ISINK = 3.2mA0.4
MAX70_C, VCC = 1V, VCC falling,VBATT = 0V, ISINK = 50µA0.3
MAX70_E/M, VCC = 1.2V, VCC falling, 0.3
MAX703/MAX704Low-Cost Microprocessor Supervisory
Circuits with Battery Backup
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Electrical Characteristics
(VCC = +4.75V to +5.5V for MAX703, VCC = +4.5V to +5.5V for MAX704, VBATT = 2.8V, TA = TMIN to TMAX, unless otherwise noted.)
Note 2: Either VCC or VBATT can go to 0V if the other is greater than 2.0V.
Note 3: “-” = battery-charging current, “+” = battery-discharging current.
(VCC = +5V, VBATT = 2.8V, TA = +25°C, unless otherwise noted.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
MR Input ThresholdVILLow0.8VVIHHigh2.0
MR Pulse WidthtMR150ns
MR to RESET DelaytMD250ns
MR Pullup CurrentMR = 0V100250600µA
PFI Input ThresholdVCC = 5V1.201.251.30V
PFI Input Current-25+0.01+25nA
PFO Output VoltageVOHISOURCE = 800µAVCC - 1.5V
VOLISINK = 3.2mA0.4
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX703 toc02
IOUT (mA)
OUT
(V)
VCC = 0V
VBATT = +2.8V
TA = +25°C
SLOPE = 80Ω
MAX703 toc03
500ms/div
MAX703 RESET OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
VCC
+5V
1V/div
+5V
1V/div
VBATT = 0V
TA = +25°C
RESET
330pF
2kΩ
RESETRESET
GND
VCCVCC
MAX703 toc04
MAX703 RESET RESPONSE TIME
+5V
+5V
VCC
1V/div
+4V
TA = +25ºC
RESET
30pF
10kΩ
RESETRESET
GND
VCCVCC
MAX703 toc05
POWER-FAIL COMPARATOR
RESPONSE TIME
+1.30V
+5V
VCC = +5V
TA = +25°CPFI
PFO
30pF
1kΩ
PFO
PFI
+5V
1.25V
MAX703 toc06
POWER-FAIL COMPARATOR
RESPONSE TIME
+1.30V
+3V
PFI
PFO30pF
PFO
1kΩ
PFI+5V
1.25V
VCC = +5V
TA = +25°C
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX703 toc01
IOUT (mA)
OUT
(V)302010
VCC = +5V
VBATT = +2.8V
TA = +25°C
SLOPE = 5Ω
MAX703/MAX704Low-Cost Microprocessor Supervisory
Circuits with Battery Backup
Electrical Characteristics (continued)
Typical Operating Characteristics
Figure 2. Timing DiagramFigure 1. Block Diagram
PINNAMEFUNCTIONVOUTSupply Output for CMOS RAM. When VCC is above the reset threshold, VOUT connects to VCC through a p-channel MOSFET switch. When VCC is below the reset threshold, the higher of VCC or VBATT is connected to VOUT.VCC+5V Supply InputGNDGroundPFIPower-Fail Comparator Input. When PFI is less than 1.25V, PFO goes low; otherwise PFO remains high. Connect PFI to GND or VCC when not used.PFOPower-Fail Comparator Output. It goes low and sinks current when PFI is less than 1.25V; otherwise PFO remains high. MRManual Reset Input. Generates a reset pulse when pulled below 0.8V. This active-low input is TTL/CMOS compatible and can be shorted to ground with a switch. It has an internal 250µA pullup current. Leave loating when not used.RESETReset Output. Remains low while VCC is below the reset threshold (4.65V for the MAX703, 4.40V for the MAX704). It remains low for 200ms after VCC rises above the reset threshold (Figure 2) or MR goes from low to high. VBATTBackup-Battery Input. When VCC falls below the reset threshold, VBATT is switched to VOUT if VBATT is 20mV greater than VCC. When VCC rises 20mV above VBATT, VCC is switched to VOUT. The 40mV hysteresis prevents repeated switching if VCC falls slowly.
BATTERY-SWITCHOVER
CIRCUITRY
GND
1.25V
RESET
GENERATORRESET
PFO
VOUTVBATT
VCC
PFI
1.25V
MAX703
MAX704
RESET
PFO*
VBATT = 3.0V
*PFO DEPENDS ON PFI EXCEPT IN BATTERY-BACKUP MODE, WHERE PFO IS LOW.
+5V
VCC
VOUT
+5V
+5V
+5V
VRST
3.0V
tRST
MAX703/MAX704Low-Cost Microprocessor Supervisory
Circuits with Battery Backup
Pin Description
Detailed Description
RESET OutputμP’s reset input starts the μP in a known state. Whenever the μP is in an unknown state, it should be held in reset. The MAX703/MAX704 assert reset when VCC is low, preventing code-execution errors during power-up, power-down, or brownout conditions.
When VBATT is 2V or more, RESET is always valid, irrespective of VCC. On power-up, as VCC rises, RESET remains low. When VCC exceeds the reset threshold, an internal timer holds RESET low for a time equal to the reset pulse width (typically 200ms); after this interval,
RESET goes high (Figure 2). If a power-fail or brown-out condition occurs (i.e., VCC drops below the reset threshold), RESET is asserted. As long as VCC remains below the reset threshold, the internal timer is continually restarted, causing the RESET output to remain low. Thus, a brownout condition that interrupts a previously initiated reset pulse causes an additional 200ms delay from the end of the last interruption.
Power-Fail Comparator
The PFI input is compared to an internal reference. If PFI is less than 1.25V, PFO goes low. The power-fail com-parator can be used as an undervoltage detector to signal a failing power supply. In the Typical Operating Circuit, an external voltage-divider at PFI is used to monitor the unregulated DC voltage from which the regulated +5V supply is derived.
The voltage-divider can be chosen so the voltage at PFI falls below 1.25V just before the +5V regulator drops out. PFO is then used as an interrupt to prepare the μP for power-down.
To conserve power, the power-fail comparator is turned off and PFO is forced low when the MAX703/MAX704 enter battery-backup mode.
Backup-Battery Switchover
In the event of a brownout or power failure, it may be nec-essary to preserve the contents of RAM. With a backup battery installed at VBATT, the MAX703/MAX704 auto-matically switch RAM to backup power when VCC fails.
As long as VCC exceeds the reset threshold, VCC con-nects to VOUT through a 5Ω p-channel MOSFET power switch. Once VCC falls below the reset threshold, RESET goes low and VCC or VBATT (whichever is higher) switch-es to VOUT. Note that VBATT switches to VOUT through an 80Ω switch only if VCC is below the resetthreshold volt-age and VBATT is greater than VCC. When VCC exceeds
MAX704 substrate, regardless of the voltage applied to VBATT (Figure 3). During this time, diode D1 (between VBATT and the substrate) conducts current from VBATT to VCC if VBATT ≥ (VCC + 0.6V).
When the battery-backup mode is activated, VBATT con-nects to VOUT. In this mode, the substrate connects to VBATT and internal circuitry is powered from the battery (Figure 3). Table 1 shows the status of the MAX703/ MAX704 inputs and outputs in battery-backup mode.
When VCC is below, but within, 1V of VBATT, the internal switchover comparator draws about 30μA. Once VCC
Table 1. Input and Output Status in
Battery-Backup Mode
SIGNALSTATUS
VCCDisconnected from VOUT.
VOUTConnected to VBATT through an internal 80Ωp-channel MOSFET switch.
VBATTConnected to VOUT. Supply current is < 1µA when VCC < (VBATT - 1V).
RESETLogic-low.
PFIPower-fail comparator is disabled.
PFOLogic-low.Disabled.S2S4
VBATT
SUBSTRATE
VOUT
VCC
MAX703
MAX704
CONDITIONS1/S2S1/S2
VCC > Reset ThresholdOpenClosed
VCC < Reset Threshold and VCC > VBATTOpenClosed
VCC < Reset Threshold and VCC < VBATTClosedOpen
MAX703/MAX704Low-Cost Microprocessor Supervisory
Circuits with Battery Backup
drops to more than 1V below VBATT, the internal switcho-ver comparator shuts off and the supply current falls to less than 1μA.
Manual Reset
The manual reset input (MR) allows RESET to be acti-vated by a pushbutton switch. The switch is effectively debounced by the 140ms minimum reset pulse width. Because it is TTL/CMOS compatible, MR can be driven by an external logic line.
Applications Information
Using a Supercap as a
Backup Power Source
Supercaps are capacitors with extremely high capaci-tance values (on the order of 0.1 Farad). When using supercaps, if VCC exceeds the MAX703/MAX704 reset thresholds (4.65V and 4.40V, respectively), VBATT may not exceed VCC by more than 0.6V. Thus, with a 5% tolerance on VCC, VBATT should not exceed VCC (min) + 0.6V = 5.35V. Similarly, with a 10% tolerance on VCC, VBATT should not exceed 5.1V.
Figure 4’s supercap circuit uses the MAX703 with a ±5% tolerance voltage supply. In this circuit, the supercap rapidly charges to within a diode drop of VCC. However, the diode leakage current with trickle charge the super-cap voltage to VCC. If VBATT = 5.25V and the power is suddenly removed and then reapplied with VCC = 4.75V, VBATT - VCC does not exceed the allowable 0.6V differ-ence voltage.
Figure 5’s circuit uses the MAX704 with a ±10% tolerance voltage supply. Note that if VCC = 5.5V and VBATT ≤ 5.1V, the power can be suddenly removed and reapplied with VCC = 4.5V, and VBATT - VCC will not exceed the allow-able 0.6V voltage difference.
Batteries and Power Supplies as
Backup Power Sources
Lithium batteries work well as backup batteries because they have very low self-discharge rates and high-energy density. Single lithium batteries with opencircuit volt-ages of 3.0V to 3.6V are ideal for use with the MAX703/MAX704. Batteries with an open-circuit voltage less than the minimum reset threshold plus 0.3V can be directly connected to the MAX703/MAX704 VBATT input with no additional circuitry (see the Typical Operating Circuit).
However, batteries with open-circuit voltages greater than the reset threshold plus 0.3V cannot be used as backup batteries, since they source current into the substrate through diode D1 (Figure 3) when VCC is close to the reset threshold.
Using the MAX703/MAX704 without a
Backup Power Source
If a backup power source is not used, ground VBATT and connect VCC to VOUT. A direct connection to VCC eliminates any voltage drop across the internal switch, which would otherwise appear at VOUT. Alternatively, use the MAX705–MAX708, which do not have batterybackup capabilities.
Figure 4. Using a Supercap as a Backup Power Source with a
MAX703 and a +5V ±5% Supply
Figure 5. Using a Supercap as a Backup Power Source with
the MAX704 and a +5V ±10% Supply
Table 2. Allowable Backup-Battery
Voltages
PARTMAXIMUM BACKUP-BATTERY VOLTAGE (V)
MAX7034.80
MAX7044.55
+5V
VCC
0.1F
VOUT
VBATT
GND
RESETTOP
TO STATIC RAM
MAX703
+5V
VCC
0.1F
VOUT
VBATT
GND
RESETTOP
TO STATIC RAM
100kΩ
MAX704
MAX703/MAX704Low-Cost Microprocessor Supervisory
Circuits with Battery Backup

Partno	Mfg	Dc	Qty	Available	Descript
MAX703		N/a	616	avai	µP Reset IC with Battery-Backup