MAX16024

19-4249; Rev 0; 8/08 Battery-Backup Circuits with Regulated Output Voltage General Description The MAX16023/MAX16024 low-power battery-backup circuits with a regulated output are capable of delivering up to 100mA output current. The MAX16023/MAX16024 include a low-dropout regulator, a microprocessor (µP) reset circuit, and a battery switchover circuit. Additional available features include a manual reset, a power-fail comparator, and a battery-on indicator. These devices reduce the number of external components to minimize board space and improve reliability. The MAX16023/MAX16024 are ideally suited for providing power for backing up critical memory such as static random-access memory (SRAM) or real-time clocks (RTCs). The regulated output is powered by VCC when it is present and switches over to the backup power during brownout. The MAX16023/MAX16024 accept an input voltage from 1.53V to 5.5V and provide fixed standard output voltages of 1.2V, 1.8V, 2.5V, 3.0V, and 3.3V. The MAX16024 offers the ability to externally set the output voltage using a resistive divider. All outputs are available with push-pull or open-drain configurations. The MAX16023 offers a power-fail comparator for monitoring an additional voltage or for providing an early powerfail warning. Another feature includes a manual-reset input (MAX16023/MAX16024). The MAX16024 also features a battery-on indicator and chip-enable gating function. The MAX16023/MAX16024 are offered in 8- and 10-pin TDFN packages and are fully specified from -40°C to +85°C temperature range. ♦ 100mA Low-Dropout Regulator ♦ Factory-Trimmed and Adjustable Output Voltages ♦ 1.53V to 5.5V Operating Voltage Range ♦ Low-Power Consumption: 4µA (typ) ♦ Power-Fail Comparators for Monitoring Voltages Down to 0.6V ♦ Battery-On Indicator ♦ Battery Freshness Seal ♦ On-Board Gating of CE Signals, 1.5ns Propagation Delay (MAX16024) ♦ Debounced Manual-Reset Input ♦ 145ms (min) Reset Timeout Period ♦ Tiny 8-Pin and 10-Pin TDFN Packages ♦ UL® Certified to Conform to IEC 60950-1 Features ♦ System Monitoring for 5V, 3.3V, 3V, 2.5V, or 1.8V Power-Supply Voltages MAX16023/MAX16024 Ordering Information PART MAX16023_TA_ _ _+T MAX16024_TB_ _ _+T TEMP RANGE -40°C to +85°C -40°C to +85°C PIN-PACKAGE 8 TDFN-EP* 10 TDFN-EP* Applications Main/Backup Power for RTCs/SRAM Industrial Controls GPS Systems Set-Top Boxes Point-of-Sale Equipment Portable/Battery Equipment UL is a registered trademark of Underwriters Laboratories, Inc. The first placeholder “_” designates reset output options. A letter “L” in this placeholder indicates a push-pull output and letter “P” indicates an open-drain output. The next placeholder “_” designates the reset threshold (Table 1). The last two placeholders “_ _” designate output voltage (Table 2). For the MAX16024 with adjustable output voltage version, there are no last two placeholders. +Denotes a lead-free/RoHS-compliant package. T = Tape and reel. *EP = Exposed pad. Pin Configurations BATT ON 6 *EP 2 VCC 3 BATT 4 MR 5 SET CEOUT RESET RESET 8 GND GND 7 OUT OUT 9 PFO 5 8 7 6 10 MAX16023 MAX16024 *EP + 1 VCC 2 BATT 3 MR + 1 CEIN 4 PFI TDFN *EP = EXPOSED PAD TDFN ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 ABSOLUTE MAXIMUM RATINGS VCC, BATT, OUT to GND..........................................-0.3V to +6V RESET, PFO, BATT ON (all open drain) to GND..................................................................-0.3V to +6V RESET, PFO, BATT ON (all push-pull) to GND .................................................-0.3V to (VOUT + 0.3V) PFI, CEIN, CEOUT to GND.......................-0.3V to (VOUT + 0.3V) MR to GND .................................................-0.3V to (VCC + 0.3V) Input Current VCC Peak Current.....................................................................1A VCC Continuous Current ...............................................250mA BATT Peak Current .......................................................500mA BATT Continuous Current ...............................................70mA Output Current OUT Short Circuit to GND Duration ....................................10s RESET, BATT ON, CEOUT..............................................20mA Continuous Power Dissipation (TA = +70°C) 8-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW 10-Pin TDFN (derate 24.4mW/°C above +70°C) .......1951mW Thermal Resistance (Note 1) θJA (8-Pin and 10-Pin TDFN)........................................41°C/W Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. 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 = 1.53V to 5.5V, VBATT = 3V, reset not asserted, TA = TJ = -40°C to +85°C, COUT = 10µF, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 2) PARAMETER Operating Voltage Range SYMBOL VCC, VBATT (Note 3) LDO = 1.2V LDO = 1.8V VCC = LDO + 0.5V, no load Supply Current ICC VCC = LDO + 0.5V, IOUT = 20mA LDO = 2.5V LDO = 3V LDO = 3.3V LDO = 1.2V LDO = 1.8V LDO = 2.5V LDO = 3V LDO = 3.3V Supply Current in Battery-Backup Mode BATT Standby Current SET Reference Voltage SET Input Leakage Current Output Voltage Range VOUT VSET IBATT VCC = 0, VBATT = 3V, no dropout, no load VCC > VBATT + 0.2V MAX16024_TB_, VCC = 2.2V MAX16024_TB_, SET = 1.2V MAX16024_TB_, VCC > VOUT LDO = 1.2V LDO = 1.8V Output Voltage Accuracy IOUT = 1mA LDO = 2.5V LDO = 3V LDO = 3.3V -0.01 1.144 -20 1.8 1.145 1.704 2.368 2.837 3.114 1.2 1.8 2.5 3 3.3 1.2 CONDITIONS MIN 1.53 4.3 4.7 5.2 5.5 5.7 16 16 16 17 17 3.5 TYP MAX 5.5 6 7 7.5 8 8 20 21 18.1 18.6 19 5.26 +0.01 1.272 +20 5.25 1.270 1.900 2.634 3.165 3.482 V µA µA V nA V µA UNITS V 2 _______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage ELECTRICAL CHARACTERISTICS (continued) (VCC = 1.53V to 5.5V, VBATT = 3V, reset not asserted, TA = TJ = -40°C to +85°C, COUT = 10µF, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 2) PARAMETER Line Regulation Load Regulation SYMBOL CONDITIONS VCC = (VOUT + 1V) to (VOUT + 2V), IOUT = 1mA VCC = VOUT + 1V, IOUT = 1mA to 2mA LDO = 1.2V LDO = 1.8V Dropout Voltage IOUT = 50mA (Note 4) LDO = 2.5V LDO = 3V LDO = 3.3V Output Current Limit Battery Freshness Leakage Current RESET OUTPUT (RESET) Reset Threshold VCC Falling to Reset Delay Reset Timeout Period RESET Output Low Voltage RESET Output High Voltage (Push-Pull Output) RESET Output Leakage Current (Open-Drain Output) POWER-FAIL COMPARATOR (PFI, PFO) PFI Input Threshold PFI Input Hysteresis PFI Input Current PFO Output Low Voltage PFO Output High Voltage (Push-Pull Output) PFO Leakage Current (Open-Drain Output) PFO Delay Time MANUAL RESET (MR) Input Low Voltage Input High Voltage Pullup Resistance Glitch Immunity MR to Reset Delay VIL VIH Pullup resistance to VCC 0.7 x VCC 20 30 100 120 0.3 x VCC V kΩ ns ns VPFT VPFI-HYS IPFI VOUT = 1.8V, ISINK = 1mA, PFO asserted VOUT =1.2V, ISINK = 100µA, PFO asserted ISOURCE = 100µA, PFO deasserted V PFO = 5.5V, PFO deasserted (VPFI + 100mV) to (VPFI - 100mV) 20 VOUT - 0.3V 1 -1 VPFI falling, 1.6V ≤ VCC ≤ 5.5V 0.570 0.590 30 +1 0.3 0.3 0.611 V mV µA V V µA µs VTH tRD tRP VOL VCC falling at 10V/ms VCC rising VOUT = 3.3V, ISINK = 3.2mA, RESET asserted VOUT = 1.8V, ISINK = 1mA, RESET asserted VOUT = 1.2V, ISINK = 100µA, RESET asserted VOH VCC ≥ 1.1 x VTH, ISOURCE = 100µA, RESET deasserted V RESET = 5.5V, reset deasserted VOUT - 0.3V 1 145 (See Table 1) 20 215 285 0.3 0.3 0.3 V µA V V µs ms VCC = 1.6V VCC ≥ 2V VBATT = 5.5V MIN TYP 0.2 0.15 500 200 180 150 150 75 150 10 mA nA mV MAX 1.0 1.0 UNITS %/V % MAX16023/MAX16024 _______________________________________________________________________________________ 3 Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 ELECTRICAL CHARACTERISTICS (continued) (VCC = 1.53V to 5.5V, VBATT = 3V, reset not asserted, TA = TJ = -40°C to +85°C, COUT = 10µF, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS VOUT = 1.2V, ISINK = 100µA, BATT ON deasserted Output Low Voltage VOL VOUT = 1.8V, ISINK = 1mA, BATT ON deasserted VOUT = 3.3V, ISINK = 3.2mA, BATT ON deasserted Output High Voltage (Push-Pull Output) Output Leakage Current (Open-Drain Output) Output Short-Circuit Current CE GATING (CEIN, CEOUT) CEIN Leakage Current CEIN to CEOUT Resistance CEOUT Short-Circuit Current CEIN to CEOUT Propagation Delay Output High Voltage Reset to CEOUT Delay VOH Reset asserted, VCC = 0.9 x VTH or 0 VCC = 5V, reset deasserted Reset asserted, CEOUT = 0 50Ω source, CLOAD = 50pF, VCC = 4.75V ISOURCE = 100µA, reset asserted VOUT - 0.3V 12 -1 8 0.75 1.5 +1 50 2 7 µA Ω mA ns V µs VOH ISOURCE = 100µA, BATT ON asserted VCC = 5.5V Sink current, VCC = 5V (Note 6) 60 VOUT - 0.3V 1 MIN TYP MAX UNITS BATTERY-ON INDICATOR (BATT ON) 0.3 0.3 0.3 V µA mA V Note 2: Note 3: Note 4: Note 5: Note 6: All devices are 100% production tested at TA = +25°C and TA = +85°C. Limits over temperature are guaranteed by design. VBATT can be 0 anytime or VCC can go down to 0 if VBATT is active (except at startup). Dropout voltage is defined as (VIN - VOUT) when VOUT is 2% below the value of VOUT when VIN = VOUT + 1V. CEIN to CEOUT resistance is tested with VCC = 5V and V CEIN = 0 or 5V. Use external current-limiting resistor to limit current to 20mA (max). 4 _______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 Table 1. Reset Threshold Ranges SUFFIX L M T S R Z Y W V RESET THRESHOLD RANGES (V) MIN 4.508 4.264 2.991 2.845 2.549 2.243 2.117 1.603 1.514 TYP 4.63 4.38 3.08 2.93 2.63 2.32 2.19 1.67 1.575 MAX 4.906 4.635 3.239 3.080 2.755 2.425 2.288 1.733 1.639 Table 2. Fixed Output Voltage SUFFIX 33 30 25 18 12 NOMINAL OUTPUT VOLTAGE (V) 3.3 3.0 2.5 1.8 1.2 Typical Operating Characteristics (VCC = 5V, VBATT = 0, IOUT = 0, TA = +25°C, unless otherwise noted.) VCC SUPPLY CURRENT vs. VCC SUPPLY VOLTAGE MAX16023 toc01 VCC SUPPLY CURRENT vs. TEMPERATURE MAX16023 toc02 BATT SUPPLY CURRENT vs. VCC SUPPLY VOLTAGE MAX16024PTBS25+ VOUT = 2.5V VTH = 2.93V MAX16023 toc03 25 MAX16024PTBS25+ VOUT = 2.5V VTH = 2.93V 10 9 VCC SUPPLY CURRENT (μA) 8 7 6 5 4 3 2 1 MAX16024PTBS25+ VOUT = 2.5V VTH = 2.93V 6 5 4 3 VBATT = 3.0V 2 VBATT = 2.8V 1 0 15 10 5 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VCC SUPPLY VOLTAGE (V) 0 -40 -15 10 35 60 85 TEMPERATURE (°C) BATT SUPPLY CURRENT (μA) VCC SUPPLY CURRENT (μA) 20 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 VCC SUPPLY VOLTAGE (V) BATTERY SUPPLY CURRENT vs. TEMPERATURE MAX16023 toc04 BATT STANDBY CURRENT vs. TEMPERATURE MAX16023 toc05 RESET OUTPUT VOLTAGE LOW vs. SINK CURRENT MAX16024PTBS25+ OUTPUT VOLTAGE LOW (V) 0.8 MAX16023 toc06 5 BATTERY SUPPLY CURRENT (μA) MAX16024PTBS25+ VBATT = +3.0V VCC = 0 10 8 BATT STANDBY CURRENT (nA) 6 4 2 0 -2 -4 -6 -8 VCC = 3.3V VBATT = 3.0V 1.0 4 3 0.6 2 0.4 1 0.2 0 -40 -15 10 35 60 85 TEMPERATURE (°C) -10 -40 -15 10 35 60 85 TEMPERATURE (°C) 0 0 2 4 6 8 10 12 14 16 18 20 SINK CURRENT (mA) _______________________________________________________________________________________ 5 Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 Typical Operating Characteristics (continued) (VCC = 5V, VBATT = 0, IOUT = 0, TA = +25°C, unless otherwise noted.) VCC FALLING TO RESET DELAY vs. TEMPERATURE MAX16023 toc07 RESET TIMEOUT PERIOD vs. TEMPERATURE MAX16023 toc08 NORMALIZED RESET THRESHOLD vs. TEMPERATURE 1.015 1.010 1.005 1.000 0.995 0.990 0.985 0.980 MAX16024PTBS25+ VOUT = 2.5V MAX16023 toc09 100 90 80 70 DELAY (µs) 60 50 40 30 20 10 0 -40 -15 10 35 60 VCC FALLING 10V/ms 220 215 RESET TIMEOUT PERIOD (ms) 210 205 200 195 190 185 180 -40 -15 10 35 60 1.020 NORMALIZED RESET THRESHOLD 85 85 -40 -15 10 35 60 85 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE MAX16023 toc10 DROPOUT VOLTAGE vs. LOAD CURRENT MAX16023 toc11 OUTPUT VOLTAGE vs. LOAD CURRENT 2.66 2.62 OUTPUT VOLTAGE (V) 2.58 2.54 2.50 2.46 2.42 2.38 2.34 2.30 TA = +85°C 0 10 20 30 40 50 60 70 80 90 100 LOAD CURRENT (mA) TA = -40°C TA = +25°C MAX16024PTBS25+ VOUT = 2.5V MAX16023 toc12 200 175 TRANSIENT DURATION (ms) 150 125 100 75 50 25 0 0 200 400 600 800 RESET THRESHOLD OVERDRIVE (mV) RESET OCCURS ABOVE THE CURVE 500 450 DROPOUT VOLTAGE (mV) 400 350 300 250 200 150 100 50 0 MAX16024PTBS25+ 2.70 1000 0 10 20 30 40 50 60 70 80 90 100 LOAD CURRENT (mA) 6 _______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage Typical Operating Characteristics (continued) (VCC = 5V, VBATT = 0, IOUT = 0, TA = +25°C, unless otherwise noted.) MAX16023/MAX16024 OUTPUT VOLTAGE vs. VCC VOLTAGE 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 0 1 2 3 MAX16024PTBS25+ IOUT = 0 MAX16023 toc13 LOAD-TRANSIENT RESPONSE MAX16023 toc14 STARTUP RESPONSE MAX16023 toc15 COUT = 10µF OUT AC-COUPLED 100mV/div 50mA IOUT 20mA/div 10mA OUT 1V/div MAX16024PTBS25+ IOUT = 0 2ms/div VCC 2V/div OUTPUT VOLTAGE (V) MAX16024PTBS25+ 4 5 6 1ms/div VCC VOLTAGE (V) MR FALLING TO RESET DELAY MAX16023 toc16 CHIP-ENABLE LOCKING OUT SIGNAL DURING RESET MAX16023 toc17 MR 5V/div RESET 5V/div CEIN 2V/div RESET 5V/div CEOUT 2V/div 200ns/div 40µs/div _______________________________________________________________________________________ 7 Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 Pin Description PIN MAX16023 1 2 MAX16024 2 3 NAME VCC BATT FUNCTION Supply Voltage Input. Bypass VCC to GND with a 0.1µF capacitor. Backup Battery Input. If VCC falls below its reset threshold (VTH), VBATT ≥ VCC, and if the regulator enters dropout, the regulator is powered from BATT. If VBATT < VCC, the regulator is powered from VCC. Bypass BATT to GND with a 0.1µF capacitor. Active-Low, Manual-Reset Input. RESET asserts when MR is pulled low. RESET remains low for the duration of reset timeout period after MR transitions from low to high. Connect MR to OUT or leave unconnected if not used. MR is internally connected to VCC through a 30kΩ pullup resistor. Power-Fail Comparator Input. Connect PFI to a resistive divider to set the desired PFI threshold. The PFI input is referenced to an internal VPFT threshold. A VPFI-HYS internal hysteresis provides noise immunity. The power-fail comparator is powered from OUT. Active-Low, Power-Fail Comparator Output. PFO goes low when VPFI falls below the internal VPFT threshold and goes high when VPFI rises above VPFT + VPFI-HYS hysteresis. Ground Active-Low Reset Output. RESET asserts when VCC falls below the reset threshold or MR is pulled low. RESET remains low for the duration of the reset timeout period after VCC rises above the reset threshold and MR goes high. RESET is available in pushpull and open-drain options. Linear Regulator Output Voltage. Available in the following factory-fixed voltages of 1.2V, 1.8V, 2.5V, 3.0V, or 3.3V for all devices. The MAX16024 is also available with an adjustable output voltage (1.8V to 5.25V). Bypass OUT to GND with a 10µF capacitor. Chip-Enable Input. The input to CE gating circuitry. Connect to GND or OUT if not used. Set Output Voltage Input. For the fixed output voltage versions (MAX16024_TB_ _ _), SET is not used. Connect SET to GND. For MAX16024_TB_, connect SET to an external resistive divider to set the desired output voltage between 1.8V and 5.25V. Active-High, Battery-On Output. BATT ON goes high when in the battery backup mode. Active-Low, Chip-Enable Output. CEOUT goes low only when CEIN is low and reset is not asserted. If CEIN is low when reset is asserted, CEOUT stays low for 12µs (typ) or until CEIN goes high, whichever occurs first. Exposed Pad. Internally connected to GND. Connect EP to a large ground plane to aid heat dissipation. Do not use EP as the only ground connection for the device. 3 4 MR 4 — PFI 5 6 — 7 PFO GND RESET 7 8 8 9 OUT — 1 CEIN — 5 SET — 6 BATT ON CEOUT — 10 — — EP 8 _______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage Functional Diagrams BATT MAX16023/MAX16024 LDO VCC OUT LOGIC MR DROPOUT RESET DELAY RESET OUT REF OUT PFO PFI MAX16023 GND _______________________________________________________________________________________ 9 Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 Functional Diagrams (continued) BATT OUT LDO VCC SET LOGIC MR DROPOUT BATT ON RESET DELAY RESET VCC REF CE OUTPUT CONTROL CEIN CEOUT MAX16024 GND 10 ______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage Detailed Description The Typical Applications Circuit shows a typical connection using the MAX16024. OUT powers the SRAM. If VCC is higher than the reset threshold (VTH), or if VCC is lower than VTH but higher than VBATT, the regulator is powered from VCC. If VCC < VTH, VCC < VBATT, and the regulator is in dropout, the regulator is powered from BATT (see the Functional Diagrams). OUT supplies up to 100mA from VCC. Chip-Enable Signal Gating (MAX16024) The MAX16024 provides internal gating of CE signals to prevent erroneous data from being written to CMOS RAM in the event of a power failure or brownout. During normal operation, the CE gate enables and passes all CE transitions. When the reset output asserts, this path becomes disabled, preventing erroneous data from corrupting the CMOS RAM and CEOUT is pulled up to OUT through an internal current source. The 1.5ns propagation delay from CEIN to CEOUT allows the devices to be used with most µPs and high-speed DSPs. During normal operation (reset not asserted), CEIN is connected to C E OUT through a low on-resistance transmission gate. If CEIN is high when a reset asserts, CEOUT remains high regardless of any subsequent transition on CEIN during the reset event. If CEIN is low when reset asserts, CEOUT is held low for 12µs to allow completion of the read/write operation. After the 12µs delay expires, CEOUT goes high and stays high regardless of any subsequent transitions on CEIN during the reset event. When CEOUT is disconnected from CEIN, CEOUT is actively pulled up to OUT. The propagation delay through the chip-enable circuitry depends on both the source impedance of the drive to CEIN and the capacitive loading at CEOUT. Minimize the capacitive load at CEOUT to minimize propagation delay, and use a low-output-impedance driver. MAX16023/MAX16024 Backup-Battery Switchover In a brownout or power failure, it may be necessary to preserve the contents of the RAM. With a backup-battery installed at BATT, the MAX16023/MAX16024 automatically switch the RAM to backup power when VCC falls. The MAX16024 has a BATT ON output that goes high when in battery-backup mode. Three conditions must be met for these devices to switch to battery backup mode: 1) VCC is lower than the reset threshold. 2) VCC is lower than VBATT. 3) The regulator is in dropout (except for the 1.2V output version). VCC RESET THRESHOLD VTH CEIN CEOUT RESET-TO-CEOUT DELAY (12µs) tRD RESET tRP tRD tRP * * IF CEIN GOES HIGH BEFORE RESET ASSERTS, CEOUT GOES HIGH WITHOUT DELAY AS CEIN GOES HIGH. Figure 1. Reset and Chip-Enable Timing ______________________________________________________________________________________ 11 Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 Manual-Reset Input (MAX16023/MAX16024) Many µP-based products require manual-reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. For the MAX16023/ MAX16024, a logic-low on MR asserts RESET. RESET remains asserted while MR is low. When MR goes high, RESET deasserts after a minimum of 145ms (tRP). MR has an internal 30kΩ pullup resistor to VCC. MR can be driven with TTL/CMOS logic levels or with opendrain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manualreset function; external debounce circuitry is not required. If MR is driven from a long cable or the device is used in a noisy environment, connect a 0.1µF capacitor from MR to GND to provide additional noise immunity. above the reset threshold. RESET also asserts when MR is low. RESET is available in both push-pull and open-drain configurations. Power-Fail Comparator (MAX16023) The MAX16023 offers an additional undervoltage comparator. The output PFO goes low when the voltage at PFI falls below its VPFT threshold. Common uses for the power-fail comparator include monitoring the input of the power supply (such as a battery) before any voltage regulation to provide an early power-fail warning, so software can conduct an orderly system shutdown. The power-fail comparator has a typical input hysteresis of VPFI-HYS and is powered from OUT, making it independent of the reset circuit. Connect PFI to GND, if not used. Regulator Output Fixed output voltages of 1.2V, 1.8V, 2.5V, 3.0V, and 3.3V are available for all devices. The regulator output delivers up to 100mA of load current. The MAX16024 is available with both fixed and adjustable output-voltage options. Use an external resistive divider network connected between OUT, SET, and GND (Figure 2) to set the adjustable output voltage from 1.8V to 5.25V. Connect SET to GND for parts with fixed output voltage option. Battery-On Indicator (MAX16024) The MAX16024’s BATT ON output goes high when in battery-backup mode. Use BATT ON to indicate battery-switchover status. Battery Freshness Seal The MAX16023/MAX16024 battery freshness seal disconnects the backup battery from internal circuitry and OUT until VCC is applied. This ensures the backup battery connected to BATT is fresh when the final product is used for the first time. The internal freshness seal latch prevents BATT from powering OUT until VCC has come up for the first time, setting the latch. When VCC subsequently turns off, BATT begins to power OUT. To reenable the freshness seal (MAX16023/ MAX16024): 1) Connect a battery to BATT. 2) Bring VCC to 0. 3) Drive MR higher than VBATT + 1.2V for at least 3µs. 4) Pull OUT to 0. 1.53 TO 5.5V 0.1µF VCC OUT 1.8V TO 5.25V 10µF MAX16024 R1 TO µP RESET SET R2 GND Reset Output (MAX16023/MAX16024) A µP’s reset input starts the µP in a known state. The MAX16023/MAX16024 µP supervisory circuits assert a reset to prevent code-execution errors during powerup, power-down, and brownout conditions. R ESET asserts when V CC is below the reset threshold and remains low for at least 145ms (tRP) after VCC rises VOUT = VSET (1 + R1/R2) VSET = 1.2V Figure 2. Setting the Adjustable Output Voltage (MAX16024 Only) 12 ______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage Applications Information The MAX16023/MAX16024 are protected for typical short-circuit conditions of 10s or less. Shorting OUT to ground for longer than 10s might damage the device. Bypass VCC and BATT to GND with a 0.1µF capacitor each. Connect a 10µF low-ESR capacitor from OUT to GND. All capacitors should be mounted as close as possible to the device. Adding Hysteresis to PFI The power-fail comparators have a typical input hysteresis of VPFI-HYS. This is sufficient for most applications where a power-supply line is being monitored through an external voltage-divider (see the Monitoring an Additional Supply section). Figure 5 shows how to add hysteresis to the power-fail comparator. Select the ratio of R1 and R2 such that PFI sees VPFT when VIN falls to the desired trip point (VTRIP). Resistor R3 adds hysteresis. R3 is typically an order of magnitude greater than R1 or R2. The current through R1 and R2 should be at least 100µA to ensure that the 1µA (max) PFI input current does not shift the trip point. R3 should be larger than 50kΩ to prevent it from loading down PFO. Capacitor C1 adds additional noise rejection. MAX16023/MAX16024 Monitoring an Additional Supply The MAX16023 power-fail comparator can monitor either positive or negative supplies using a resistive divider to PFI (Figures 3 and 4). PFO can be used to generate an interrupt to the µP or to trigger a reset. To monitor a negative supply, connect the top of the resistive divider to VCC. Connect the bottom of the resistive divider to the negative voltage to be monitored. V1 5V 0.1μF R1 VCC RESET RESET µP PFI PFO 0.1µF V2 VCC R1 PFI MAX16023L R2 PFO MR R2 MAX16023 VGND VTRIP = VPFT - R2 5 - VPFT R1 VTRIP IS NEGATIVE GND ( ) ADDITIONAL SUPPLY RESET VOLTAGE V2(RESET) = VPFT x R1 + R2 R2 ( ) PFO +5V 0 VTRIP 0 V- Figure 3. Monitoring an Additional Supply by Connecting PFO to MR Figure 4. Monitoring a Negative Supply ______________________________________________________________________________________ 13 Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 +5V VIN 0.1µF R1 PFI R2 C1* R3 VCC VTRIP = VPFT x R1 + R2 R2 VH = VPFT + VPFI - HYS MAX16023 VL = R1 x VPFT - VCC R2 Replacing the Backup Battery When VCC is above VTH, the backup power source can be removed without danger of triggering a reset pulse. The device does not enter battery-backup mode when VCC stays above the reset threshold voltage. R1 + 1 R3 ( ( ( ) ) x ( R1 + R2 -V )+V R3 PFT ) PFT PFO GND WHERE VPFT IS THE POWER-FAIL THRESHOLD VOLTAGE. Negative-Going VCC Transients The MAX16023/MAX16024 are relatively immune to short duration, negative-going V CC transients. Resetting the µP when V CC experiences only small glitches is usually not desirable. A 0.1µF bypass capacitor mounted close to the VCC pin provides additional transient immunity. Capacitor Selection and Regulator Stability TO µP +5V PFO 0 VL VTRIP VH VIN *OPTIONAL Figure 5. Adding Hysteresis to the Power-Fail Comparator For stable operation, connect a low-ESR 10µF (min) output capacitor from OUT to GND. To reduce noise and improve load-transient response and power-supply rejection, use larger output capacitor values. Operation Without a Backup Power Source The MAX16023/MAX16024 provide battery-backup functions. If a backup power source is not used, connect BATT to GND. Part Number Table PART OUTPUT TYPE RESET REGULATED THRESHOLD OUTPUT VOLTAGE VOLTAGE (V) (V) 4.63 4.63 4.63 4.63 4.38 4.38 4.38 4.38 3.08 3.08 3.08 2.93 2.93 2.93 2.63 2.63 2.63 2.32 1.2 1.8 2.5 3.3 1.2 1.8 2.5 3.3 1.2 1.8 2.5 1.2 1.8 2.5 1.2 1.8 2.5 1.2 PART OUTPUT TYPE RESET REGULATED THRESHOLD OUTPUT VOLTAGE VOLTAGE (V) (V) 4.63 4.63 4.63 4.63 4.38 4.38 4.38 4.38 3.08 3.08 3.08 2.93 2.93 2.93 2.63 2.63 2.63 2.32 1.2 1.8 2.5 3.3 1.2 1.8 2.5 3.3 1.2 1.8 2.5 1.2 1.8 2.5 1.2 1.8 2.5 1.2 MAX16023LTAL12+T MAX16023LTAL18+T MAX16023LTAL25+T MAX16023LTAL33+T MAX16023LTAM12+T MAX16023LTAM18+T MAX16023LTAM25+T MAX16023LTAM33+T MAX16023LTAT12+T MAX16023LTAT18+T MAX16023LTAT25+T MAX16023LTAS12+T MAX16023LTAS18+T MAX16023LTAS25+T MAX16023LTAR12+T MAX16023LTAR18+T MAX16023LTAR25+T MAX16023LTAZ12+T Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull MAX16024LTBL12+T MAX16024LTBL18+T MAX16024LTBL25+T MAX16024LTBL33+T MAX16024LTBM12+T MAX16024LTBM18+T MAX16024LTBM25+T MAX16024LTBM33+T MAX16024LTBT12+T MAX16024LTBT18+T MAX16024LTBT25+T MAX16024LTBS12+T MAX16024LTBS18+T MAX16024LTBS25+T MAX16024LTBR12+T MAX16024LTBR18+T MAX16024LTBR25+T MAX16024LTBZ12+T Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull 14 ______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage Part Number Table (continued) PART OUTPUT TYPE Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain RESET REGULATED THRESHOLD OUTPUT VOLTAGE VOLTAGE (V) (V) 2.32 2.19 2.19 1.67 1.575 4.63 4.63 4.63 4.63 4.38 4.38 4.38 4.38 3.08 3.08 3.08 2.93 2.93 2.93 2.63 2.63 2.63 2.32 2.32 2.19 2.19 1.67 1.575 4.63 4.38 3.08 2.93 2.63 2.32 2.19 1.67 1.575 1.8 1.2 1.8 1.2 1.2 1.2 1.8 2.5 3.3 1.2 1.8 2.5 3.3 1.2 1.8 2.5 1.2 1.8 2.5 1.2 1.8 2.5 1.2 1.8 1.2 1.8 1.2 1.2 Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable PART OUTPUT TYPE Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull Push-Pull RESET REGULATED THRESHOLD OUTPUT VOLTAGE VOLTAGE (V) (V) 2.32 2.19 2.19 1.67 1.575 4.63 4.63 4.63 4.63 4.38 4.38 4.38 4.38 3.08 3.08 3.08 2.93 2.93 2.93 2.63 2.63 2.63 2.32 2.32 2.19 2.19 1.67 1.575 4.63 4.38 3.08 2.93 2.63 2.32 2.19 1.67 1.575 1.8 1.2 1.8 1.2 1.2 1.2 1.8 2.5 3.3 1.2 1.8 2.5 3.3 1.2 1.8 2.5 1.2 1.8 2.5 1.2 1.8 2.5 1.2 1.8 1.2 1.8 1.2 1.2 Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable Adjustable MAX16023/MAX16024 MAX16023LTAZ18+T MAX16023LTAY12+T MAX16023LTAY18+T MAX16023LTAW12+T MAX16023LTAV12+T MAX16023PTAL12+T MAX16023PTAL18+T MAX16023PTAL25+T MAX16023PTAL33+T MAX16023PTAM12+T MAX16023PTAM18+T MAX16023PTAM25+T MAX16023PTAM33+T MAX16023PTAT12+T MAX16023PTAT18+T MAX16023PTAT25+T MAX16023PTAS12+T MAX16023PTAS18+T MAX16023PTAS25+T MAX16023PTAR12+T MAX16023PTAR18+T MAX16023PTAR25+T MAX16023PTAZ12+T MAX16023PTAZ18+T MAX16023PTAY12+T MAX16023PTAY18+T MAX16023PTAW12+T MAX16023PTAV12+T MAX16024PTBL+T MAX16024PTBM+T MAX16024PTBT+T MAX16024PTBS+T MAX16024PTBR+T MAX16024PTBZ+T MAX16024PTBY+T MAX16024PTBW+T MAX16024PTBV+T MAX16024LTBZ18+T MAX16024LTBY12+T MAX16024LTBY18+T MAX16024LTBW12+T MAX16024LTBV12+T MAX16024PTBL12+T MAX16024PTBL18+T MAX16024PTBL25+T MAX16024PTBL33+T MAX16024PTBM12+T MAX16024PTBM18+T MAX16024PTBM25+T MAX16024PTBM33+T MAX16024PTBS12+T MAX16024PTBS18+T MAX16024PTBS25+T MAX16024PTBT12+T MAX16024PTBT18+T MAX16024PTBT25+T MAX16024PTBR12+T MAX16024PTBR18+T MAX16024PTBR25+T MAX16024PTBZ12+T MAX16024PTBZ18+T MAX16024PTBY12+T MAX16024PTBY18+T MAX16024PTBW12+T MAX16024PTBV12+T MAX16024LTBL+T MAX16024LTBM+T MAX16024LTBT+T MAX16024LTBS+T MAX16024LTBR+T MAX16024LTBZ+T MAX16024LTBY+T MAX16024LTBW+T MAX16024LTBV+T Bold parts denote standard versions. Samples are generally available on standard versions. Contact factory for availability of nonstandard versions. ______________________________________________________________________________________ 15 Battery-Backup Circuits with Regulated Output Voltage MAX16023/MAX16024 Selector Guide PART MAX16023L MAX16023P MAX16024L MAX16024P OUTPUTS (RESET, PFO, BATT ON ) Push-Pull Open Drain Push-Pull Open Drain RESET √ √ √ √ MR √ √ √ √ POWER-FAIL COMPARATOR √ √ — — CE GATE — — √ √ BATT ON — — √ √ REGULATOR OUTPUT VOLTAGE Fixed Fixed Fixed/adjustable Fixed/adjustable Typical Applications Circuit 3.3V 0.1µF VCC VCC BATT 3V 0.1µF BATT ON RESET RST µP 0.1µF A0–A15 MAX16024L OUT MR PUSHBUTTON CEOUT CE 10µF RAM RTC SET GND CEIN ADDRESS DECODE 16 ______________________________________________________________________________________ Battery-Backup Circuits with Regulated Output Voltage Chip Information PROCESS: BiCMOS Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 8 TDFN 10 TDFN PACKAGE CODE T833-2 T1033-1 DOCUMENT NO. 21-0137 21-0137 MAX16023/MAX16024 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17 © 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.