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MAX805LCSA+T

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MAX805LCSA+T

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Part Number MAX805LCSA+T
Manufacturer Maxim Integrated
Description IC SUPERVISOR MPU 8-SOIC
Datasheet MAX805LCSA+T Datasheet
Package 8-SOIC (0.154", 3.90mm Width)
In Stock 363 piece(s)
Unit Price $ 3.8311 *
Lead Time Can Ship Immediately
Estimated Delivery Time Oct 23 - Oct 28 (Choose Expedited Shipping)
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Part Number # MAX805LCSA+T (PMIC - Supervisors) is manufactured by Maxim Integrated and distributed by Heisener. Being one of the leading electronics distributors, we carry many kinds of electronic components from some of the world’s top class manufacturers. Their quality is guaranteed by its stringent quality control to meet all required standards.

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MAX805LCSA+T Specifications

ManufacturerMaxim Integrated
CategoryIntegrated Circuits (ICs) - PMIC - Supervisors
Datasheet MAX805LCSA+TDatasheet
Package8-SOIC (0.154", 3.90mm Width)
Series-
TypeBattery Backup Circuit
Number of Voltages Monitored1
OutputPush-Pull, Totem Pole
ResetActive High
Reset Timeout140 ms Minimum
Voltage - Threshold4.65V
Operating Temperature0°C ~ 70°C (TA)
Mounting TypeSurface Mount
Package / Case8-SOIC (0.154", 3.90mm Width)
Supplier Device Package8-SOIC

MAX805LCSA+T Datasheet

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General Description The MAX690A/MAX692A/MAX802L/MAX802M/MAX805L reduce the complexity and number of components required for power-supply monitoring and battery- control functions in microprocessor (μP) systems. They significantly improve system reliability and accuracy compared to separate ICs or discrete components. These parts provide four functions: 1) A reset output during power-up, power-down, and brownout conditions. 2) Battery-backup switching for CMOS RAM, CMOS μP, or other low-power logic. 3) A reset pulse if the optional watchdog timer has not been toggled within 1.6s. 4) A 1.25V threshold detector for power-fail warning or low-battery detection, or to monitor a power supply other than +5V. The parts differ in their reset-voltage threshold levels and reset outputs. The MAX690A/MAX802L/MAX805L generate a reset pulse when the supply voltage drops below 4.65V, and the MAX692A/MAX802M generate a reset below 4.40V. The MAX802L/MAX802M guarantee power-fail accuracies to ±2%. The MAX805L is the same as the MAX690A except that RESET is provided instead of RESET. All parts are available in 8-pin DIP and SO packages. The MAX690A/MAX802L are pin compatible with the MAX690 and MAX694. The MAX692A/MAX802M are pin compatible with the MAX692. Applications ● Battery-Powered Computers and Controllers ● Intelligent Instruments ● Critical μP Power Monitoring Features ● Precision Supply Voltage Monitor: 4.65V for MAX690A/MAX802L/MAX805L 4.40V for MAX692A/MAX802M ● Reset Time Delay: 200ms ● Watchdog Timer: 1.6s Timeout ● Battery-Backup Power Switching ● 200μA Quiescent Supply Current ● 50nA Quiescent Supply Current in Battery- Backup Mode ● Voltage Monitor for Power-Fail or Low-Battery Warning ● Power-Fail Accuracy Guaranteed to ±2% (MAX802L/M) ● Guaranteed RESET Assertion to VCC = 1V ● 8-Pin SO and DIP Packages 19-4333; Rev 5; 4/15 Ordering Information continued at end of data sheet. *Dice are specified at TA = +25°C **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 free by adding the + symbol at the end of the part number when ordering. Lead free not available for CERDIP package. PART TEMP RANGE PIN-PACKAGE MAX690ACPA 0°C to +70°C 8 Plastic DIP MAX690ACSA 0°C to +70°C 8 SO MAX690AC/D 0°C to +70°C Dice* MAX690AEPA -40°C to +85°C 8 Plastic DIP MAX690AESA -40°C to +85°C 8 SO MAX690AMJA -55°C to +125°C 8 CERDIP** VCC VCC NMI I/O LINE GND GND BUS CMOS RAM UNREGULATED DC REGULATED +5V RESET PFO WDI VOUT GND VBATT VCC PFI R1 R2 0.1µF 3.6V LITHIUM BATTERY MAX690A MAX802L µPRESET MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits Typical Operating Circuit Pin Configurations Ordering Information 1 2 3 4 8 7 6 5 VBATT RESET (RESET) WDI PFOPFI GND VCC VOUT DIP/SO TOP VIEW MAX690A MAX692A MAX802L MAX802M MAX805L ( ) ARE FOR MAX805L ONLY.

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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 (VCC + 0.3V) Input Current VCC ...............................................................................200mA VBATT .............................................................................50mA GND ................................................................................20mA Output Current VOUT .............................. Short-Circuit Protected for up to 10s All Other Outputs ............................................................20mA Rate of Rise, VCC, VBATT ..............................................100V/μs Continuous Power Dissipation Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW SO (derate 5.88mW/°C above +70°C) ....................... 471mW CERDIP (derate 8.00mW/°C above +70°C) ................640mW Operating Temperature Ranges: MAX69_AC_ _, MAX80_ _ C_ _ ........................0°C to +70°C MAX69_AE_ _, MAX80_ _ E_ _ ................... -40°C to +85°C MAX69_AMJA, MAX805LMJA ..................... -55°C to +125°C Storage Temperature Range ............................ -65°C to +160°C Lead Temperature (soldering, 10s) ................................ +300°C (VCC = 4.75V to 5.5V for MAX690A/MAX802L/MAX805L, VCC = 4.5V to 5.5V for MAX692A/MAX802M, VBATT = 2.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Operating Voltage Range, VCC, VBATT (Note 2) MAX69_AC, MAX802_C 1.0 5.5 VMAX805LC 1.1 5.5 MAX69_AE/M, MAX80_ _E 1.2 5.5 Supply Current (Excluding IOUT) ISUPPLY MAX69_AC, MAX802_C 200 350 µA MAX69_AE/M, MAX802_E, MAX805LE/M 200 500 ISUPPLY in Battery-Backup Mode (Excluding IOUT) VCC = 0V, VBATT = 2.8V TA = +25°C 0.05 1.0 µA TA = TMIN to TMAX 5.0 VBATT Standby Current (Note 3) 5.5V > VCC > VBATT +0.2V TA = +25°C -0.1 0.02 µA TA = TMIN to TMAX -1.0 0.02 VOUT Output IOUT = 5mA VCC - 0.05 VCC - 0.025 V IOUT = 50mA VCC - 0. 5 VCC - 0. 25 VOUT in Battery-Backup Mode IOUT = 250μA, VCC < VBATT - 0.2V VBATT - 0.1 VBATT - 0.02 V Battery Switch Threshold, VCC to VBATT VCC < VRT Power-up 20 mV Power-down -20 Battery Switchover Hysteresis 40 mV Reset Threshold VRT MAX690A, MAX802L, MAX805L 4.50 4.65 4.75 V MAX692A, MAX802M 4.25 4.40 4.50 MAX802L, TA = +25°C, VCC falling 4.55 4.70 MAX802M, TA = +25°C, VCC falling 4.30 4.45 Reset Threshold Hysteresis 40 mV Reset Pulse Width tRS 140 200 280 ms MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits www.maximintegrated.com Maxim Integrated │ 2 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 Note 1: The input voltage limits on PFI and WDI may be exceeded if the current into these pins is limited to less than 10mA.

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(VCC = 4.75V to 5.5V for MAX690A/MAX802L/MAX805L, VCC = 4.5V to 5.5V for MAX692A/MAX802M, 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. Note 4: WDI is guaranteed to be in an intermediate, non-logic level state if WDI is floating and VCC is in the operating voltage range. WDI is internally biased to 35% of VCC with an input impedance of 50kΩ. PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS RESET Output Voltage ISOURCE = 800μA V ISINK = 3.2mA 0.4 MAX69_AC, MAX802_C, VCC = 1.0V ISINK = 50μA 0.3 MAX69_AE/M, MAX802_E, VCC = 1.2V, ISINK = 100μA 0.3 RESET Output Voltage MAX805LC, ISOURCE = 4μA, VCC = 1.1V 0.8 V MAX805LE/M, ISOURCE = 4μA, VCC = 1.2V 0.9 MAX805L, ISOURCE = 800μA VCC - 1.5 MAX805L, ISINK = 3.2mA 0.4 Watchdog Timeout tWD 1.00 1.60 2.25 s WDI Pulse Width tWP VIL = 0.4V, VIH = (0.8) (VCC) 50 ns WDI Input Threshold (Note 4) VCC = 5V Logic low 0.8 V Logic high 3.5 WDI Input Current WDI = VCC 50 150 µA WDI = 0V -150 -50 PFI Input Threshold MAX69_A, MAX805L, VCC = 5V 1.20 1.25 1.30 V MAX802_C/E, VCC = 5V 1.225 1.250 1.275 PFI Input Current -25 0.01 25 nA PFO Output Voltage ISOURCE = 800μA VCC - 1.5 V ISINK = 3.2mA 0.4 MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits www.maximintegrated.com Maxim Integrated │ 3 Electrical Characteristics (continued)

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4.75 0 OUTPUT VOLTAGE vs. LOAD CURRENT 4.80 5.00 IOUT (mA) V O UT (V ) 40 4.90 4.85 10 30 50 4.95 20 VCC = +5V VBATT = +2.8V TA = +25°C SLOPE = 5Ω M AX 69 0A -M AX 80 5L to c0 1 MAX690A RESET RESPONSE TIME 2µs/div VCC +5V RESET +5V +4V 1V/div 0V TA = +25°C VCC VCC GND RESET 10k RESET 30pF MAX690A-MAX805L toc04 MAX805L RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE 500ms/div 0V VCC +5V 1V/div RESET 0V +5V 1V/div 10k 330 pF VCC RESET GND VBATT MAX690A-MAX805L toc07 MAX805L RESET RESPONSE TIME 2µs/div 0V VCC +4V 0V +4V +5V GND RESET VCC 330pF 10k MAX690A-MAX805L toc08 2.70 0 OUTPUT VOLTAGE vs. LOAD CURRENT 2.72 2.80 IOUT (mA) V O UT (V ) 0.8 2.76 2.74 0.2 0.6 1.0 2.78 0.4 VCC = 0V VBATT = +2.8V TA = +25°C SLOPE = 80Ω M AX 69 0A -M AX 80 5L to c0 2 POWER-FAIL COMPARATOR RESPONSE TIME 400ns/div PFI +1.30V PFO +5V +0V +1.2V +5V PFO 30pF 1k +1.25V PFI VCC = +5V TA = +25°C M AX 69 0A -M AX 80 5L to c0 5 MAX690A RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE 500ms/div VCC 0V RESET 0V +5V 1V/div +5V 1V/div TA = +25°C VBATT = OV VCC VCC GND RESET 2k RESET 330pF MAX690A-MAX805L toc03 POWER-FAIL COMPARATOR RESPONSE TIME 400ns/div PFI +1.20V PFO 0V +3V +1.3V VCC = +5V TA = +25°C +5V PFO 30pF 1k +1.25V PFI MAX690A-MAX805L toc06 MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits Maxim Integrated │ 4www.maximintegrated.com Typical Operating Characteristics

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PIN NAME FUNCTIONMAX690A/MAX692A MAX802L/MAX802M MAX805L 1 1 VOUT Supply 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 will be connected to VOUT. 2 2 VCC +5V Supply Input 3 3 GND Ground 4 4 PFI Power-Fail Comparator Input. When PFI is less than 1.25V, PFO goes low. Connect PFI to GND or VCC when not used. 5 5 PFO Power-Fail Output. When PFI is less than 1.25V, PFO goes low; otherwise PFO stays high. 6 6 WDI Watchdog Input. If WDI remains high or low for 1.6sec, the internal watchdog timer runs out and reset is triggered. If WDI is left floating or connected to a high-impedance three-state buffer, the watchdog feature is disabled. The internal watchdog timer clears whenever reset is asserted, WDI is three-stated, or WDI sees a rising or falling edge. 7 7 RESET Reset Output. Whenever RESET is triggered, it pulses low for 200ms. It stays low when VCC is below the reset threshold (4.65V in the MAX690A/MAX802L and 4.4V in the MAX692A/MAX802M) and remains low for 200ms after VCC rises above the reset threshold. A watchdog timeout also triggers RESET. — — RESET Active-High Reset Output is the inverse of RESET. When RESET is asserted, the RESET output voltage = VCC or VBATT, whichever is higher. 8 8 VBATT Backup-Battery Input. When VCC falls below the reset threshold, VBATT will be switched to VOUT if VBATT is 20mV greater than VCC. When VCC rises to 20mV above VBATT, VOUT will be reconnected to VCC. The 40mV hysteresis prevents repeated switching if VCC falls slowly. MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits www.maximintegrated.com Maxim Integrated │ 5 Pin Description

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Detailed Description Reset Output A microprocessor’s (μP’s) reset input starts the μP in a known state. When the μP is in an unknown state, it should be held in reset. The MAX690A/MAX692A/ MAX802L/MAX802M assert reset during power-up and prevent code execution errors during power-down or brownout conditions. On power-up, once VCC reaches 1V, RESET is guaranteed to be a logic low. As VCC rises, RESET remains low. When VCC exceeds the reset threshold, an internal timer keeps RESET low for a time equal to the reset pulse width; after this interval, RESET goes high (Figure 2). If a brownout condition occurs (if VCC dips below the reset threshold), RESET is triggered. Each time RESET is triggered, it stays low for the reset pulse width interval. Any time VCC goes below the reset threshold, the internal timer restarts the pulse. If a brownout condition interrupts a previously initiated reset pulse, the reset pulse continues for another 200ms. On power- down, once VCC goes below the threshold, RESET is guaranteed to be logic low until VCC droops below 1V. RESET is also triggered by a watchdog timeout. If a high or low is continuously applied to the WDI pin for 1.6sec, RESET pulses low. As long as RESET is asserted, the watchdog timer remains clear. When RESET comes high, the watchdog resumes timing and must be serviced within 1.6sec. If WDI is tied high or low, a RESET pulse is triggered every 1.8s (tWD plus tRS). The MAX805L active-high RESET output is the inverse of the MAX690A/MAX692A/MAX802L/MAX802M RESET output, and is guaranteed to be valid with VCC down to 1.1V. Some μPs, such as Intel’s 80C51, require an active- high reset pulse. Watchdog Input The watchdog circuit monitors the μP’s activity. If the μP does not toggle the watchdog input (WDI) within 1.6sec, a reset pulse is triggered. The internal 1.6sec timer is cleared by either a reset pulse or by open circuiting the WDI input. As long as reset is asserted or the WDI input is open circuited, the timer remains cleared and does not count. As soon as reset is released or WDI is driven high or low, the timer starts counting. It can detect pulses as short as 50ns. Power-Fail Comparator The PFI input is compared to an internal 1.25V reference. If PFI is less than 1.25V, PFO goes low. The power- fail comparator is intended for use as an undervoltage detector to signal a failing power supply; it need not be Figure 1. Block Diagram Figure 2. Timing Diagram 0.8V WATCHDOG TIMER PFO RESET (RESET) VOUT RESET GENERATOR BATTERY-SWITCHOVER CIRCUITRY 1.25V 3.5V VBATT VCC PFI WDI MAX690A MAX692A MAX802L MAX802M MAX805L ( ) ARE FOR MAX805L ONLY. GND 1.25V tRS +5V 0V VCC 0V +5V 0V RESET +5V 0V (RESET) 3.0V 3.0V VOUT +5V 0V PFO VBATT = PFI = 3.0V IOUT = 0mA( ) ARE FOR MAX805L ONLY. MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits www.maximintegrated.com Maxim Integrated │ 6

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dedicated to this function though, as it is completely separate from the rest of the circuitry. The external volt- age divider drives PFI to sense the unregulated DC input to the +5V regulator (see Typical Operating Circuit). The voltage-divider ratio can be chosen such that the voltage at PFI falls below 1.25V just before the +5V regulator drops out. PFO then triggers an interrupt which signals the μP to prepare for power-down. To conserve backup-battery power, the power-fail detector comparator is turned off and PFO is forced low when VBATT connects to VOUT. Backup-Battery Switchover In the event of a brownout or power failure, it may be necessary to preserve the contents of RAM. With a back- up battery installed at VBATT, the devices automatically switch RAM to backup power when VCC fails. As long as VCC exceeds the reset threshold, VOUT connects to VCC through a 5Ω PMOS power switch. Once VCC falls below the reset threshold, VCC or VBATT (whichever is higher) switches to VOUT. Unlike the MAX690/MAX692, the MAX690A/MAX692A/MAX802L/ MAX802M/MAX805L don’t always connect VBATT to VOUT when VBATT is greater than VCC. VBATT connects to VOUT (through an 80Ω switch) only when VCC is below the reset threshold and VBATT is greater than VCC. When VCC exceeds the reset threshold, it is connected to the MAX690A/MAX692A/MAX802L/MAX802M/MAX805L substrate, regardless of the voltage applied to VBATT (Figure 3). During this time, the diode (D1) between VBATT and the substrate will conduct current from VBATT to VCC if VBATT is 0.6V or greater than VCC. Figure 3. Backup-Battery Switchover Block Diagram Figure 4. Using a SuperCap as a Backup Power Source with a MAX690A/MAX802L/MAX805L and a +5V ±5% Supply Table 1. Wiper Position and Attenuation SIGNAL STATUS VCC Disconnected from VOUT VOUT Connected to VBATT through an internal 80Ω PMOS switch VBATT Connected to VOUT. Current drawn from the battery is less than 1μA, as long as VCC < VBATT - 1V. PFI Power-fail comparator is disabled. PFO Logic low RESET Logic low RESET Logic high (MAX805L only) WDI Watchdog timer is disabled SW1/SW2 SW3/SW4CONDITION VCC > Reset Threshold Open Closed ClosedOpen OpenClosed VCC < Reset Threshold and VCC > VBATT VCC < Reset Threshold and VCC < VBATT RESET THRESHOLD = 4.65V IN MAX690A/MAX802L/MAX805L. RESET THRESHOLD = 4.4V IN MAX692A/MAX802M VOUT D3 SUBSTRATE D1 D2 SW2SW1 SW4SW3 VBATT VCC MAX690A MAX692A MAX802L MAX802M MAX805L VBATT VCC VOUT RESET (RESET) GND TO STATIC RAM TO µP 0.1F MAX690A MAX802L MAX805L +5V + ( ) ARE FOR MAX805L ONLY. MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits www.maximintegrated.com Maxim Integrated │ 7

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When VBATT connects to VOUT, backup mode is activated and the internal circuitry is powered from the battery (Table 1). When VCC is just below VBATT, the current drawn from VBATT is typically 30μA. When VCC drops to more than 1V below VBATT, the internal switchover comparator shuts off and the supply current falls to less than 1μA. Applications Information Using a SuperCap as a Backup Power Source SuperCaps are capacitors with extremely high capacitance values, on the order of 0.1F. Figure 4 shows a SuperCap used as a backup power source. Do not allow the SuperCap’s voltage to exceed the maximum reset threshold by more than 0.6V. In Figure 4’s circuit, the SuperCap rapidly charges to within a diode drop of VCC. However, after a long time, the diode leakage current will pull the SuperCap voltage up to VCC. When using a SuperCap with the MAX690A/MAX802L/MAX805L, VCC may not exceed 4.75V + 0.6V = 5.35V. Use the SuperCap circuit of Figure 5 with a MAX692A or MAX802M and a ±10% supply. This circuit ensures that the SuperCap only charges to VCC - 0.5V. At the maximum VCC of 5.5V, the SuperCap charges up to 5.0V, only 0.5V above the maximum reset threshold—well within the requisite 0.6V. Allowable Backup Power-Source Batteries Lithium batteries work very well as backup batteries due to very low self-discharge rates and high energy density. Single lithium batteries with open-circuit volt- ages of 3.0V to 3.6V are ideal. Any battery with an open- circuit voltage less than the minimum reset threshold plus 0.3V can be connected directly to the VBATT input of the MAX690A/MAX692A/MAX802L/MAX802M/MAX805L with no additional circuitry (see the Typical Operating Circuit). However, batteries with open-circuit voltages that are greater cannot be used for backup, as current is sourced into the substrate through the diode (D1 in Figure 3) when VCC is close to the reset threshold. Figure 5. Using a SuperCap as a Backup Power Source with the MAX692A/MAX802M and a +5V ±10% Supply Figure 6. Adding Hysteresis to the Power-Fail Comparator Table 2. Allowable Backup-Battery Voltages (see Using a SuperCap as a Backup Power Source section for use with a SuperCap) PART NO. MAXIMUM BACKUP-BATTERY VOLTAGE (V) MAX690A/ MAX802L/MAX805L 4.80 MAX692A/ MAX802M 4.55 VBATT VCC VOUT RESET GND TO STATIC RAM TO µP 0.1F MAX692A MAX802M +5V +100kΩ PFO VCC GND TO µP MAX690 MAX692A MAX802L MAX802M MAX805L +5V R2 R1 R3 PFI *OPTIONAL +5V 0V PFO VL VHVTRIP VIN 0V VIN C1* VTRIP = 1.25/ R2 R1 + = R2 + R2( ( VIH = 1.25/ R2 || R3 R1 + R2 || R3( ( VL - 1.25 R3 5 - 1.25 R2 1.25 MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits www.maximintegrated.com Maxim Integrated │ 8

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Operation Without a Backup Power Source If a backup power source is not used, ground VBATT and connect VOUT to VCC. Since there is no need to switch over to any backup power source, VOUT does not need to be switched. A direct connection to VCC eliminates any voltage drops across the switch which may push VOUT below VCC. Replacing the Backup Battery The backup battery can be removed while VCC remains valid, without danger of triggering RESET/RESET. As long as VCC stays above the reset threshold, battery- backup mode cannot be entered. In other switchover ICs where battery-backup mode is entered whenever VBATT gets close to VCC, an unconnected VBATT pin accumu- lates leakage charge and triggers RESET/RESET in error. Adding Hysteresis to the Power-Fail Comparator Hysteresis adds a noise margin to the power-fail comparator and prevents repeated triggering of PFO when VIN is close to its trip point. Figure 6 shows how to add hysteresis to the power-fail comparator. Select the ratio of R1 and R2 such that PFI sees 1.25V when VIN falls to its trip point (VTRIP). R3 adds the hysteresis. It will typically be an order of magnitude greater than R1 or R2 (about 10 times either R1 or R2). The current through R1 and R2 should be at least 1μA to ensure that the 25nA (max) PFI input current does not shift the trip point. R3 should be larger than 10kΩ so it does not load down the PFO pin. Capacitor C1 adds additional noise rejection. Monitoring a Negative Voltage The power-fail comparator can be used to monitor a negative supply rail using the circuit of Figure 7. When the negative rail is good (a negative voltage of large mag- nitude), PFO is low. When the negative rail is degraded (a negative voltage of lesser magnitude), PFO goes high. This circuit’s accuracy is affected by the PFI threshold tolerance, the VCC line, and the resistors. Interfacing to μPs with Bidirectional Reset Pins μPs with bidirectional reset pins, such as the Motorola 68HC11 series, can contend with the MAX690A/MAX692A/ MAX802L/MAX802M RESET output. If, for example, the RESET output is driven high and the μP wants to pull it low, indeterminate logic levels may result. To correct this, connect a 4.7kΩ resistor between the RESET output and the μP reset I/O, as in Figure 8. Buffer the RESET output to other system components. Figure 7. Monitoring a Negative Voltage PFO VCC GND MAX690A MAX692A MAX802L MAX802M MAX805L +5V R2 R1 PFI +5V 0V PFO VTRIP V- 0V V- NOTE: VTRIP IS NEGATIVE R1 + VL - 1.25 R2 1.25 - VTRIP MAX690A/MAX692A/ MAX802L/MAX802M/ MAX805L Microprocessor Supervisory Circuits www.maximintegrated.com Maxim Integrated │ 9

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Hen***** Muni

August 20, 2020

Superb pricing and super fast delivery.

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August 19, 2020

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August 15, 2020

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August 13, 2020

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August 5, 2020

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August 3, 2020

Tested one of them and works good.

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August 3, 2020

They work great and I hope to find more used for the extra ones.

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MAX805LCSA+T

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Heisener's commitment to quality has shaped our processes for sourcing, testing, shipping, and every step in between. This foundation underlies each component we sell.

ISO9001:2015, ICAS, IAF, UKAS

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