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19-0882; Rev 0; 7/07
Low-Power Battery Backup Circuits in Small DFN Packages
General Description
The MAX16033-MAX16040 supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery control functions in microprocessor (P) systems. The devices significantly improve system reliability and accuracy compared to other ICs or discrete components. The MAX16033-MAX16040 provide P reset, backup-battery switchover, power-fail warning, watchdog, and chip-enable gating features. The MAX16033-MAX16040 operate from supply voltages up to 5.5V. The factory-set reset threshold voltage ranges from 2.32V to 4.63V. The devices feature a manual-reset input (MAX16033/MAX16037), a watchdog timer input (MAX16034/MAX16038), a battery-on output (MAX16035/MAX16039), an auxiliary adjustable reset input (MAX16036/MAX16040), and chip-enable gating (MAX16033-MAX16036). Each device includes a power-fail comparator and offers an active-low pushpull reset or an active-low open-drain reset. The MAX16033-MAX16040 are available in 2mm x 2mm, 8-pin or 10-pin DFN packages and are fully specified from -40C to +85C.
Features
Low 1.2V Operating Supply Voltage Precision Monitoring of 5.0V, 3.3V, 3.0V, and 2.5V Power-Supply Voltages Independent Power-Fail Comparator Debounced Manual-Reset Input Watchdog Timer, 1.6s Timeout Battery-On Output Indicator Auxiliary User-Adjustable RESETIN Low 13A Quiescent Supply Current Two Available Output Structures: Active-Low Push-Pull Reset Active-Low Open-Drain Reset Active-Low Reset Valid Down to 1.2V Power-Supply Transient Immunity 140ms (min) Reset Timeout Period Small 2mm x 2mm, 8-Pin and 10-Pin DFN Packages
MAX16033-MAX16040
Ordering Information
PART* MAX16033LLB_ _+T MAX16033PLB_ _+T MAX16034LLB_ _+T MAX16034PLB_ _+T TEMP RANGE PINPACKAGE PKG CODE
Applications
Portable/BatteryPowered Equipment POS Equipment Critical P/C Power Monitoring Set-Top Boxes Controllers Computers Fax Machines Industrial Control Real-Time Clocks Intelligent Instrument
-40C to +85C 10 DFN-10 L1022-1 -40C to +85C 10 DFN-10 L1022-1 -40C to +85C 10 DFN-10 L1022-1 -40C to +85C 10 DFN-10 L1022-1
Pin Configurations and Typical Operating Circuit appear at end of data sheet.
Ordering Information continued on last page. *These parts offer a choice of reset threshold voltages. From the Reset Threshold Ranges table, insert the desired threshold voltage code in the blank to complete the part number. See Selector Guide for a listing of device features. +Denotes a lead-free package. T = Tape and reel.
Selector Guide
PART MAX16033_ MAX16034_ MAX16035_ MAX16036_ MAX16037_ MAX16038_ MAX16039_ MAX16040_ MR WATCHDOG BATTON RESETIN CEIN/CEOU PFI, PFO PIN-PACKAGE 10 DFN-10 10 DFN-10 10 DFN-10 10 DFN-10 8 DFN-8 8 DFN-8 8 DFN-8 8 DFN-8
Note: Replace "_" with L for push-pull or P for open-drain RESET and PFO outputs.
________________________________________________________________ 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.
Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
ABSOLUTE MAXIMUM RATINGS
Terminal Voltages (with respect to GND) VCC, BATT, OUT .......................................................-0.3V to +6V RESET (open drain), PFO (open drain) ....................-0.3V to +6V RESET (push-pull), PFO (push-pull), BATTON, RESETIN, WDI MR, CEIN, CEOUT, PFI ............................-0.3V to (VOUT + 0.3V) Input Current VCC Peak..............................................................................1A VCC Continuous ............................................................250mA BATT Peak ....................................................................250mA BATT Continuous ............................................................40mA GND ................................................................................75mA Output Current OUT ..................................Short-Circuit Protected for up to 5s RESET, BATTON .............................................................20mA Continuous Power Dissipation (TA = +70C) 8-Pin DFN (derate 4.8mW/C above +70C) ..........380.6mW 10-Pin DFN (derate 5mW/C above +70C) ...........402.8mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = 2.25V to 5.5V, VBATT = 3V, RESET not asserted, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Operating Voltage Range Supply Current SYMBOL VCC, VBATT ICC CONDITIONS No load (Note 2) VCC = 2.8V No load, VCC > VTH VBATT = 2.8V, VCC = 0V, excluding IOUT IBATT (VBATT + 0.2V) < VCC < 5.5V VCC = 3.6V VCC = 5.5V Supply Current in Battery Backup Mode BATT Standby Current (Note 3) TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C -0.1 -0.3 MIN 0 13 16 22 TYP MAX 5.5 30 35 50 1 A 2 +0.02 +0.02 3.1 3.7 4.6 VBATT - 0.2 VBATT - 0.15 VBATT - 0.15 0 -40 mV V A A UNITS V
VCC = 4.75V, VCC > VTH, IOUT = 150mA VCC to OUT On-Resistance RON VCC = 3.15V, VCC > VTH, IOUT = 65mA VCC = 2.5V, VCC > VTH, IOUT = 25mA VBATT = 4.50V, VCC = 0V, IOUT = 20mA Output Voltage in Battery Backup Mode VOUT VBATT = 3.15V, VCC = 0V, IOUT = 10mA VBATT = 2.5V, VCC = 0V, IOUT = 5mA Battery-Switchover Threshold VSW VCC - VBATT, VCC < VTH VCC rising VCC falling
2
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Low-Power Battery Backup Circuits in Small DFN Packages
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 2.25V to 5.5V, VBATT = 3V, RESET not asserted, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER RESET OUTPUT MAX160_ _ _L_46 MAX160_ _ _L_44 Reset Threshold VTH MAX160_ _ _L_31 MAX160_ _ _L_29 MAX160_ _ _L_26 MAX160_ _ _L_23 VCC Falling Reset Delay Reset Active Timeout Period RESET Output Low Voltage RESET Output High Voltage RESET Output Leakage Current POWER-FAIL COMPARATOR PFI Input Threshold PFI Hysteresis PFI Input Current PFO Output Low Voltage PFO Output High Voltage PFO Leakage Current PFO Delay Time MANUAL RESET (MAX16033/MAX16037) VIL MR Input Voltage VIH Pullup Resistance to VCC Minimum Pulse Width Glitch Immunity MR to Reset Delay VCC = 3.3V 0.7 x VCC 20 1 100 120 165 k s ns ns 0.3 x VCC VOL VOH VPFI = 0V or VCC Output asserted VCC > 2.1V, ISINK = 1.6mA VCC > 1.2V, ISINK = 100A 0.8 x VCC 1 4 -100 VPFI VPFI falling 1.185 1.235 1 +100 0.3 0.4 1.285 V % nA V V A s tRP VOL VOH ILKG RESET asserted ISINK = 1.6mA, VCC > 2.1V ISINK = 100A, VCC > 1.2V 0.8 x VCC 1 VCC falling at 10V/ms 140 4.50 4.25 3.00 2.85 2.55 2.25 4.63 4.38 3.08 2.93 2.63 2.32 25 280 0.3 0.4 4.75 4.50 3.15 3.00 2.70 2.38 s ms V V A V SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX16033-MAX16040
MAX160_ _L only (push-pull), RESET not asserted, ISOURCE = 500A, VCC > VTH(MAX) MAX160_ _P only (open drain), not asserted
MAX160_ _L only (push-pull), VCC > VTH(MAX), ISOURCE = 500A, output not asserted MAX160_ _P only (open drain), VPFO = 5.5V, not asserted VPFI + 100mV to VPFI - 100mV
V
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3
Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 2.25V to 5.5V, VBATT = 3V, RESET not asserted, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Watchdog Timeout Period Minimum WDI Input Pulse Width SYMBOL tWD tWDI VIL WDI Input Voltage VIH WDI Input Current BATTON (MAX16035/MAX16039) Output Voltage Output Short-Circuit Current RESETIN (MAX16036/MAX16040) RESETIN Threshold RESETIN Input Current RESETIN to Reset Delay CEIN Leakage Current CEIN to CEOUT Resistance CEOUT Short-Circuit Current CEIN to CEOUT Propagation Delay (Note 4) (VRTH + 100mV) to (VRTH - 100mV) RESET asserted RESET not asserted, VCC = VTH(MAX), VCEIN = VCC / 2, ISINK = 10mA RESET asserted, VCEOUT = 0V 50 source impedance driver, CLOAD = 50pF VCC = 4.75V VCC = 3.15V 0.7 x VCC VBATT - 0.1 1 s 1 1.5 2 CHIP-ENABLE GATING (MAX16033-MAX16036) 1 100 2.0 7 9 A mA ns VRTH 1.185 1.235 0.01 1.5 1.285 25 V nA s VOL ISINK = 3.2mA, VBATT = 2.1V Sink current, VCC = 5V Source current, VBATT > 2V 10 60 30 120 0.4 V mA A 0.7 x VCC -1.0 +1.0 A (Note 4) CONDITIONS MIN 1.00 100 0.3 x VCC TYP 1.65 MAX 2.25 UNITS s ns
WATCHDOG (MAX16034/MAX16038)
V
VCC = 5V, VCC > VBATT, ISOURCE = 100A CEOUT Output-Voltage High VCC = 0V, VBATT > 2.2V, ISOURCE = 1A RESET to CEOUT Delay
V
Note 1: Note 2: Note 3: Note 4:
All devices are 100% production tested at TA = +25C. All overtemperature limits are guaranteed by design. VBATT can be 0V any time, or VCC can go down to 0V if VBATT is active (except at startup). Positive current flows into BATT. Guaranteed by design.
4
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Low-Power Battery Backup Circuits in Small DFN Packages
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX16033 toc01
MAX16033-MAX16040
BATTERY SUPPLY CURRENT (BACKUP MODE) vs. TEMPERATURE
MAX16033 toc02
BATT-TO-OUT ON-RESISTANCE vs. TEMPERATURE
BATTERY-TO-OUT ON-RESISTANCE () 9 8 7 6 5 4 3 2 1 0 -40 -15 VBATT = 3V VBATT = 5V VCC = 0V VBATT = 2V
MAX16033 toc03
20 19 18 SUPPLY CURRENT (A) 17 16 15 14 13 12 11 10 -40
VCC = 5V
1.0 0.9 BATTERY SUPPLY CURRENT (A) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
VBATT = 3V VCC = 0V
1.0
-15
10
35
60
85
-40
-15
10
35
60
85
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
VCC-TO-OUT ON-RESISTANCE vs. TEMPERATURE
MAX16033 toc04
RESET TIMEOUT PERIOD vs. TEMPERATURE
MAX16033 toc05
VCC-TO-RESET PROPAGATION DELAY vs. TEMPERATURE
VCC-TO-RESET PROPAGATION DELAY (s) VCC FALLING 0.25V/ms 90 75 60 1V/ms 45 30 15 10V/ms 0 -40 -20 0 20 40 60 80 105
MAX16033 toc06 MAX16033 toc08
230 225 RESET TIMEOUT PERIOD (ms) 220 215 210 205 200 195 190 185 180
1.4 VCC-TO-OUT ON-RESISTANCE () 1.2 1.0 0.8 0.6 0.4 0.2 0
VCC = 5V
120
VCC = 2.5V IOUT = 25mA
VCC = 3V IOUT = 65mA
VCC = 4.5V IOUT = 150mA
-40 -25 -10
5
20
35
50
65
80
-40
-15
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
NORMALIZED RESET THRESHOLD vs. TEMPERATURE
1.003 1.002 1.001 1.000 0.999 0.998 0.997 0.996 0.995 0.994 0.993 0.992 0.991 0.990 -40 -20 0 20 40 60 80 TEMPERATURE (C)
MAX16033 toc07
MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE
300 MAXIMUM TRANSIENT DURATION (s) 250 200 150 100 50 0 1 10 100 1000 10,000 RESET THRESHOLD OVERDRIVE (VTH - VCC) (mV) MAX160_ _-29 (VTH = 2.93V) MAX160_ _-46 (VTH = 4.63V) RESET OCCURS ABOVE CURVE
NORMALIZED RESET THRESHOLD
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Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
BATTERY SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX16033 toc09
RESETIN THRESHOLD vs. TEMPERATURE
MAX16033 toc10
RESETIN-TO-RESET PROPAGATION DELAY vs. TEMPERATURE
RESETIN-TO-RESET PROPAGATION DELAY (s) 2.8 2.5 2.3 2.0 1.8 1.5 1.3 1.0 -40 -15 10 35 60 85 MAX16036/ MAX16040 VOD = 50mV
MAX16033 toc11
2.00 1.75 BATTERY SUPPLY CURRENT (A) 1.50 1.25 1.00 0.75 0.50 0.25 0 -0.25 0
VTH = 2.93V VBATT = 2.8V
1.250 1.245 RESETIN THRESHOLD (V) 1.240 1.235 1.230 1.225 1.220 1.215 1.210
MAX16036/ MAX16040
3.0
VBATT = 2.5V VBATT = 2.3V
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V)
-40
-15
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
CEIN PROPAGATION DELAY vs. CEOUT LOAD CAPACITANCE
MAX16033 toc12
CEIN TO CEOUT ON-RESISTANCE vs. TEMPERATURE
MAX16033 toc13
WATCHDOG TIMEOUT PERIOD vs. TEMPERATURE
1.9 WATCHDOG TIMEOUT PERIOD (s) 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 VCC = 5V
MAX16033 toc14
3.0 CEIN PROPAGATION DELAY (ns) 2.5 2.0 1.5 1.0 0.5 0 0 25 50 75 100 125 150 VCC = 5V
35 CEIN TO CEOUT ON-RESISTANCE () 30 25 20 15 10 VCC = 5V 5 0 VCC = 3V
2.0
VCC = 3V
175
-40
-15
10
35
60
85
-40
-15
10
35
60
85
CEOUT LOAD CAPACITANCE (pF)
TEMPERATURE (C)
TEMPERATURE (C)
PFI-TO-PFO DELAY vs. TEMPERATURE
MAX16033 toc15
PFI THRESHOLD vs. TEMPERATURE
1.245 1.240 PFI THRESHOLD (V) 1.235 1.230 1.225 1.220 1.215
MAX16033 toc16
5.00 4.75 4.50 PFI-TO-PFO DELAY (s) 4.25 4.00 3.75 3.50 3.25 3.00 2.75 2.50 2.25 2.00 -40 FALLING EDGE VOD = 30mV
1.250
1.210 -15 10 35 60 85 -40 -15 10 35 60 85 TEMPERATURE (C) TEMPERATURE (C)
6
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Low-Power Battery Backup Circuits in Small DFN Packages
Pin Description
PIN MAX16033- MAX16036 (10-pin DFN) MAX16037- MAX16040 (8-pin DFN) NAME FUNCTION
MAX16033-MAX16040
1
1
RESET
Active-Low Reset Output. RESET remains low when VCC is below the reset threshold (VTH), the manual-reset input is low, or RESETIN is low. It asserts low in pulses when the internal watchdog times out. RESET remains low for the reset timeout period (tRP) after VCC rises above the reset threshold, after the manual-reset input goes from low to high, after RESETIN goes high, or after the watchdog triggers a reset event. The MAX160_ _L is an active-low push-pull output, while the MAX160_ _P is an active-low open-drain output. Chip-Enable Input. The input to the chip-enable gating circuit. Connect to GND or OUT if not used. Power-Fail Input. PFO goes low when VPFI falls below 1.235V. Ground Manual-Reset Input (MAX16033/MAX16037). Driving MR low asserts RESET. RESET remains asserted as long as MR is low and for the reset timeout period (tRP) after MR transitions from low to high. Leave unconnected, or connect to VCC if not used. MR has an internal 20k pullup to VCC. Watchdog Input (MAX16034/MAX16038). If WDI remains high or low for longer than the watchdog timeout period (tWD), the internal watchdog timer runs out and a reset pulse is triggered for the reset timeout period (tRP). The internal watchdog clears whenever RESET asserts or whenever WDI sees a rising or falling edge (Figure 2). Battery-On Output (MAX16035/MAX16039). BATTON goes high during battery backup mode. Reset Input (MAX16036/MAX16040). When RESETIN falls below 1.235V, RESET asserts. RESET remains asserted as long as RESETIN is low and for at least tRP after RESETIN goes high. Active-Low Power-Fail Output. PFO goes low when VPFI falls below 1.235V. PFO stays low until VPFI goes above 1.235V. PFO also goes low when VCC falls below the reset threshold voltage. Supply Voltage, 1.2V to 5.5V Output. OUT sources from VCC when RESET is not asserted and from the greater of VCC or BATT when VCC is below the reset threshold voltage. Backup Battery Input. When VCC falls below the reset threshold, OUT switches to BATT if VBATT is 40mV greater than VCC. When VCC rises above VBATT, OUT switches to VCC. The 40mV hysteresis prevents repeated switching if VCC falls slowly. Chip-Enable Output. CEOUT goes low only when CEIN is low and reset is not asserted. When CEOUT is disconnected from CEIN, CEOUT is actively pulled up to OUT.
2 3 4
-- 2 3
CEIN PFI GND
MR
5
4
WDI
BATTON
RESETIN
6 7 8
5 6 7
PFO VCC OUT
9
8
BATT
10
--
CEOUT
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Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
Functional Diagram
BATTON (MAX16035/MAX16039 ONLY)
1.235V
MAX16033- MAX16040
VCC
OUT
BATT
CHIP-ENABLE OUTPUT CONTROL
CEIN (MAX16033-MAX16036 ONLY)
CEOUT
MR (MAX16033/MAX16037 ONLY)
RESET GENERATOR
RESET
WDI (MAX16034/MAX16038 ONLY) RESETIN (MAX16036/MAX16040 ONLY)
WATCHDOG TRANSITION DETECTOR
WATCHDOG TIMER
PFO 1.235V 1.235V
GND
PFI
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Low-Power Battery Backup Circuits in Small DFN Packages
Detailed Description
The Typical Operating Circuit shows a typical connection for the MAX16033-MAX16040. OUT powers the static random-access memory (SRAM). If V CC is greater than the reset threshold (VTH), or if VCC is lower than VTH but higher than VBATT, VCC is connected to OUT. If VCC is lower than VTH and VCC is less than VBATT, BATT is connected to OUT. OUT supplies up to 200mA from VCC. In battery-backup mode, an internal MOSFET connects the backup battery to OUT. The onresistance of the MOSFET is a function of the backupbattery voltage and temperature and is shown in the BATT-to-OUT On-Resistance vs. Temperature graph in the Typical Operating Characteristics. these devices to be used with most Ps and highspeed DSPs. When RESET is deasserted, CEIN is connected to CEOUT through a low on-resistance transmission gate. If CEIN is high when RESET is asserted, CEOUT remains high regardless of any subsequent transitions on CEIN during the reset event. If CEIN is low when RESET is asserted, CEOUT is held low for 1s to allow completion of the read/write operation (Figure 1). After the 1s 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. The chip-enable propagation delay is specified from the 50% point of CEIN to the 50% point of CEOUT, using a 50 driver and 50pF load capacitance. Minimize the capacitive load at CEOUT and use a low output-impedance driver to minimize propagation delay. In high-impedance mode, the leakage current at CEIN is 1A (max) over temperature. In low-impedance mode, the impedance of CEIN appears as a 75 resistor in series with the load at CEOUT.
MAX16033-MAX16040
Chip-Enable Signal Gating (MAX16033-MAX16036 Only)
The MAX16033-MAX16036 provide internal gating of chip-enable (CE) signals to prevent erroneous data from being written to CMOS RAM in the event of a power failure or brownout condition. During normal operation, the CE gate is enabled and passes all CE transitions. When reset asserts, this path becomes disabled, preventing erroneous data from corrupting the CMOS RAM. The MAX16033-MAX16036 provide a series transmission gate from CEIN to CEOUT. A 2ns (typ) propagation delay from CEIN to CEOUT allows
VCC VTH
CEIN
CEOUT RESET-TO-CEOUT DELAY tRD tRP tRD tRP
*
RESET
PFO PFI > VPFI
* IF CEIN GOES HIGH BEFORE RESET ASSERTS,
CEOUT GOES HIGH WITHOUT DELAY AS CEIN GOES HIGH.
Figure 1. RESET and Chip-Enable Timing
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Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
Backup Battery Switchover
To preserve the contents of the RAM in a brownout or power failure, the MAX16033-MAX16040 automatically switch to back up the battery installed at BATT when the following two conditions are met: 1) VCC falls below the reset threshold voltage. 2) VCC is below VBATT. Table 1 lists the status of the inputs and outputs in battery-backup mode. The devices do not power-up if the only voltage source is VBATT. OUT only powers up from VCC at startup. VCC. This input can be driven from TTL/CMOS logic outputs or with open-drain/collector outputs. Connect a normally-open momentary switch from MR to GND to create a manual-reset function; external debounce circuitry is not required. When driving MR from long cables or when using the device in a noisy environment, connect a 0.1F capacitor from MR to GND to provide additional noise immunity.
Watchdog Input (MAX16034/MAX16038 Only)
The watchdog monitors P activity through the watchdog input (WDI). RESET asserts when the P fails to toggle WDI. Connect WDI to a bus line or P I/O line. A change of state (high to low, low to high, or a minimum 100ns pulse) resets the watchdog timer. If WDI remains high or low for longer than the watchdog timeout period (tWD), the internal watchdog timer runs out and triggers a reset pulse for the reset timeout period (tRP). The internal watchdog timer clears whenever reset is asserted or whenever WDI sees a rising or falling edge. If WDI remains in either a high or low state, a reset pulse periodically asserts after every watchdog timeout period (tWD); see Figure 2.
Table 1. Input and Output Status in Battery-Backup Mode
PIN VCC OUT BATT RESET BATTON MR, RESETIN, CEIN, and WDI CEOUT PFO STATUS Disconnected from OUT Connected to BATT Connected to OUT. Current drawn from the battery is less than 1A (at VBATT = 2.8V, excluding IOUT) when VCC = 0V. Asserted High state Inputs ignored Connected to OUT Asserted
WDI tRP RESET tWD tWD tRP
Manual-Reset Input (MAX16033/MAX16037 Only)
Many P-based products require manual-reset capability, allowing the user or external logic circuitry to initiate a reset. For the MAX16033/MAX16037, a logic-low on MR asserts RESET. RESET remains asserted while MR is low and for a minimum of 140ms (tRP) after it returns high. MR has an internal 20k (min) pullup resistor to
tWD = WATCHDOG TIMEOUT PERIOD tRP = RESET TIMEOUT PERIOD
Figure 2. MAX16034/MAX16038 Watchdog Timeout Period and Reset Active Time
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Low-Power Battery Backup Circuits in Small DFN Packages
BATTON Indicator (MAX16035/MAX16039 Only)
BATTON is a push-pull output that asserts high when in battery-backup mode. BATTON typically sinks 3.2mA at a 0.4V saturation voltage. In battery-backup mode, this terminal sources approximately 10A from OUT. Use BATTON to indicate battery-switchover status or to supply base drive to an external pass transistor for higher current applications (see Figure 3).
Power-Fail Comparator
The MAX16033-MAX16040 issue an interrupt (nonmaskable or regular) to the P when a power failure occurs. The power line is monitored by two external resistors connected to the power-fail input (PFI). When the voltage at PFI falls below 1.235V, the power-fail output (PFO) drives the processor's NMI input low. An earlier power-fail warning can be generated if the unregulated DC input of the regulator is available for monitoring. The MAX16033- MAX16040 turn off the power-fail comparator and force PFO low when VCC falls below the reset threshold voltage (see Figure 1). The MAX160_ _L devices provide push-pull PFO outputs. The MAX160_ _P devices provide open-drain PFO outputs.
VCC
MAX16033-MAX16040
RESETIN Comparator (MAX16036/MAX16040 Only)
An internal 1.235V reference sets the RESETIN threshold voltage. RESET asserts when the voltage at RESETIN is below 1.235V. Use the RESETIN function to monitor a secondary power supply. Use the following equations to set the reset threshold voltage (VRTH) of the secondary power supply (see Figure 4): VRTH = VREF (R1 / R2 + 1) where VREF = 1.235V. To simplify the resistor selection, choose a value for R2 and calculate R1. R1 = R2 [(VRTH / VREF) - 1] Since the input current at RESETIN is 25nA (max), large values (up to 1M) can be used for R2 with no significant loss in accuracy.
VIN R1
MAX16036 MAX16040
RESETIN
R2
Figure 4. Setting RESETIN Voltage for the MAX16036/MAX16040
2.4V TO 5.5V 0.1F
VCC BATT
BATTON OUT (CEOUT) CE CMOS RAM
MAX16035 MAX16039
(CEIN) ADDRESS DECODE A0-A15 P GND ( ) FOR MAX16035 ONLY RESET RESET
Figure 3. MAX16035/MAX16039 BATTON Driving an External Pass Transistor
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Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
RESET
A P's reset input puts the P in a known state. The MAX16033-MAX16040 P supervisory circuits assert a reset to prevent code-execution errors during powerup, power-down, and brownout conditions. RESET asserts when VCC is below the reset threshold voltage and for at least 140ms (tRP) after VCC rises above the reset threshold. RESET also asserts when MR is low (MAX16033/MAX16037) or when RESETIN is below 1.235V (MAX16036/MAX16040). The MAX16034/ MAX16038 watchdog function causes RESET to assert in pulses following a watchdog timeout (Figure 2). The MAX160_ _L devices provide push-pull RESET outputs. The MAX160_ _P devices provide open-drain RESET outputs.
Applications Information
Operation Without a Backup Power Source
The MAX16033-MAX16040 provide a battery backup function. If a backup power source is not used, connect BATT to GND and OUT to VCC.
Using a Super Cap as a Backup Power Source
Super caps are capacitors with extremely high capacitance, such as 0.47F. Figure 5 shows two methods to use a super cap as a backup power source. Connect the super cap through a diode to the 3V input (Figure 5a) or connect the super cap through a diode to 5V (Figure 5b) if a 5V supply is available. The 5V supply charges the super cap to a voltage close to 5V, allowing a longer backup period. Since VBATT can be higher than VCC while VCC is above the reset threshold voltage, there are no special precautions required when using these P supervisors with a super cap.
3V OR 3.3V
3V OR 3.3V
VCC 5V 1N4148
VCC
MAX16033- MAX16040
1N4148
MAX16033- MAX16040
BATT 0.47F 0.47F
BATT
(a)
(b)
Figure 5. Using a Super Cap as a Backup Source
12
______________________________________________________________________________________
Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
START VCC VCC SET WDI LOW RESET TO P
SUBROUTINE OR PROGRAM LOOP SET WDI HIGH
V+
MAX16033- MAX16040
MR R1 PFI PFO GND R2
RETURN
END
Figure 6. Watchdog Flow Diagram
Figure 7. Monitoring an Additional Power Supply
Watchdog Software Considerations
One way to help the watchdog timer to monitor software execution more closely is to set and reset the watchdog at different points in the program, rather than pulsing the watchdog input periodically. Figure 6 shows a flow diagram where the I/O driving the watchdog is set low in the beginning of the program, set high at the beginning of every subroutine or loop, and set low again when the program returns to the beginning. If the program should hang in any subroutine, the watchdog would timeout and reset the P.
Connect PFO to MR in applications that require RESET to assert when the second voltage falls below its threshold. RESET remains asserted as long as PFO holds MR low, and for 140ms (min) after PFO goes high.
Replacing the Backup Battery
Decouple BATT to GND with a 0.1F capacitor. The backup power source may be removed while V CC remains valid without the danger of triggering a reset pulse. The device does not enter battery-backup mode when VCC stays above the reset threshold voltage.
Power-Fail Comparator
Monitoring an Additional Power Supply Monitor another voltage by connecting a resistive divider to PFI as shown in Figure 7. The threshold voltage is: VTH(PFI) = 1.235 (R1 / R2 + 1) where VTH(PFI) is the threshold at which the monitored voltage will trip PFO. To simplify the resistor selection, choose a value for R2 and calculate R1. R1 = R2 [(VTH(PFI) / 1.235) - 1]
Adding Hysteresis to the Power-Fail Comparator The power-fail comparator provides a typical hysteresis of 12mV, which is sufficient for most applications where a power-supply line is being monitored through an external voltage-divider. Connect a voltage-divider between PFI and PFO as shown in Figure 8a to provide additional noise immunity. Select the ratio of R1 and R2 such that VPFI falls to 1.235V when VIN drops to its trip point, VTRIP. R3 adds hysteresis and is typically more than 10 times the value of R1 or R2. The hysteresis window extends above (VH) and below (VL) the original trip point, VTRIP. Connecting an ordinary signal diode in series with R3 as shown in Figure 8b causes the lower trip point (VL) to coincide with the trip point without hysteresis (VTRIP). This method provides additional noise margin without compromising the accuracy of the power-fail threshold when the monitored voltage is falling. Set the current through R1 and R2 to be at least 10A to ensure that the 100nA (max) PFI input current does not shift the trip point. Set R3 to be higher than 10k to reduce the load at PFO. Capacitor C1 adds additional noise rejection.
______________________________________________________________________________________
13
Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
(a) VCC (b) VCC
VIN
VIN
R1 PFI R2 C1 R3
MAX16033- MAX16040
R1 PFI R2 C1 R3
MAX16033- MAX16040
PFO (PUSH-PULL) GND TO P TO P
PFO (PUSH-PULL) GND
PFO 0V VL VH VIN
PFO 0V VTRIP VH VIN
VTRIP
R1 VTRIP = VPFT1 + R2 R1 R1 VH = (VPFT + VPFH)1 + + R2 R3 R1 R1 R1 VL = VPFT1 + VCC + - R2 R3 R3 VPFT = 1.235V VPFH = 12mV
R1 VTRIP = VPFT1 + R2 R1 R1 R1 VH = (VPFT + VPFH)1 + + VD - R2 R3 R3 VL = VTRIP VPFT = 1.235V VPFH = 12mV VD = DIODE FORWARD VOLTAGE
Figure 8. (a) Adding Additional Hysteresis to the Power-Fail Comparator. (b) Shifting the Additional Hysteresis above VTRIP
14
______________________________________________________________________________________
Low-Power Battery Backup Circuits in Small DFN Packages
Monitoring a Negative Voltage Connect the circuit as shown in Figure 9 to use the power-fail comparator to monitor a negative supply rail. PFO stays low when V- is good. When V- rises to cause PFI to be above +1.235V, PFO goes high. Ensure VCC comes up before the negative supply.
MAX16033-MAX16040
3.0V OR 3.3V
VCC
Negative-Going VCC Transients The MAX16033-MAX16040 are relatively immune to short-duration, negative-going V CC transients. Resetting the P when V CC experiences only small glitches is not usually desired. The Typical Operating Characteristics section contains a Maximum Transient Duration vs. Reset Threshold Overdrive graph. The graph shows the maximum pulse width of a negative-going VCC transient that would not trigger a reset pulse. As the amplitude of the transient increases (i.e., goes further below the reset threshold voltage), the maximum allowable pulse width decreases. Typically, a VCC transient that goes 100mV below the reset threshold and lasts for 25s does not trigger a reset pulse. A 0.1F bypass capacitor mounted close to VCC provides additional transient immunity.
R1 PFI R2
MAX16033- MAX16040
PFO
V-
GND
PFO VL VTRIP V0V
VCC 1 1 VTRIP = R2( VPFT + VPFH) + - R1 R2 R1 VCC 1 1 VL = R2( VPFT) + - R1 R2 R1 VPFT = 1.235V VPFH = 12mV
Figure 9. Monitoring a Negative Voltage
______________________________________________________________________________________
15
Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
Device Marking Codes
PART MAX16033LLB23+T MAX16033LLB26+T MAX16033LLB29+T MAX16033LLB31+T MAX16033LLB44+T MAX16033LLB46+T MAX16033PLB23+T MAX16033PLB26+T MAX16033PLB29+ MAX16033PLB31+ MAX16033PLB44+T MAX16033PLB46+ MAX16034LLB23+T MAX16034LLB26+T MAX16034LLB29+T MAX16034LLB31+T MAX16034LLB44+T MAX16034LLB46+T MAX16034PLB23+T MAX16034PLB26+T MAX16034PLB29+ MAX16034PLB31+ MAX16034PLB44+T MAX16034PLB46+ TOP MARK +ABE +ABF +ABG +ABH +ABI +ABJ +ABK +ABL +ABM +ABN +ABO +ABP +ABQ +ABR +ABS +ABT +ABU +ABV +ABW +ABX +ABY ABZ +ACA +ACB PART MAX16035LLB23+T MAX16035LLB26+T MAX16035LLB29+ MAX16035LLB31+ MAX16035LLB44+T MAX16035LLB46+ MAX16035PLB23+T MAX16035PLB26+T MAX16035PLB29+ MAX16035PLB31+ MAX16035PLB44+T MAX16035PLB46+ MAX16036LLB23+T MAX16036LLB26+T MAX16036LLB29+ MAX16036LLB31+ MAX16036LLB44+T MAX16036LLB46+ MAX16036PLB23+T MAX16036PLB26+T MAX16036PLB29+ MAX16036PLB31+ MAX16036PLB44+T MAX16036PLB46+ TOP MARK +ACC +ACD +ACE +ACF +ACG +ACH +ACI +ACJ +ACK +ACL +ACM +ACN +ACO +ACP +ACQ +ACR +ACS +ACT +ACU +ACV +ACW +ACX +ACY +ACZ PART MAX16037LLA23+T MAX16037LLA26+T MAX16037LLA29+ MAX16037LLA31+ MAX16037LLA44+T MAX16037LLA46+ MAX16037PLA23+T MAX16037PLA26+T MAX16037PLA29+ MAX16037PLA31+ MAX16037PLA44+T MAX16037PLA46+ MAX16038LLA23+T MAX16038LLA26+T MAX16038LLA29+ MAX16038LLA31+ MAX16038LLA44+T MAX16038LLA46+ MAX16038PLA23+T MAX16038PLA26+T MAX16038PLA29+ MAX16038PLA31+ MAX16038PLA44+T MAX16038PLA46+ TOP MARK +ABX +ABY +ABZ +ACA +ACB +ACC +ACD +ACE +ACF +ACG +ACH +ACI +ACJ +ACK +ACL +ACM +ACN +ACO +ACP +ACQ +ACR +ACS +ACT +ACU PART MAX16039LLA23+T MAX16039LLA26+T MAX16039LLA29+T MAX16039LLA31+T MAX16039LLA44+T MAX16039LLA46+T MAX16039PLA23+T MAX16039PLA26+T MAX16039PLA29+ MAX16039PLA31+ MAX16039PLA44+T MAX16039PLA46+ MAX16040LLA23+T MAX16040LLA26+T MAX16040LLA29+T MAX16040LLA31+T MAX16040LLA44+T MAX16040LLA46+T MAX16040PLA23+T MAX16040PLA26+T MAX16040PLA29+ MAX16040PAL31+ MAX16040PLA44+T MAX16040PLA46+ TOP MARK +ACV +ACW +ACX +ACY +ACZ +ADA +ADB +ADC +ADD +ADE +ADF +ADG +ADH +ADI +ADJ +ADK +ADL +ADM +ADN +ADO +ADP +ADQ +ADR +ADS
Note: 48 standard versions shown in bold are available. Sample stock is generally held on standard versions only. Contact factory for nonstandard versions availability.
16
______________________________________________________________________________________
Low-Power Battery Backup Circuits in Small DFN Packages
Pin Configurations
TOP VIEW
CEOUT CEOUT
MAX16033-MAX16040
BATT
BATT
OUT
OUT
PFO
VCC
10
9
8
7
6
10
9
8
VCC 7 4 GND VCC 6 3 GND
MAX16033 MAX16034 +
1 RESET 2 CEIN 3 PFI 4 GND 5 MR (WDI)
MAX16035 MAX16036 +
1 RESET 2 CEIN 3 PFI 5 BATTON (RESETIN) BATTON (RESETIN) PFO 5 4
10-DFN ( ) FOR MAX16034 ONLY
10-DFN ( ) FOR MAX16036 ONLY
BATT
BATT
OUT
8
7
6
5
8
7
MAX16037 MAX16038 +
1 RESET 2 PFI 3 GND 4 MR (WDI)
MAX16039 MAX16040 +
1 RESET 2 PFI
8-DFN ( ) FOR MAX16038 ONLY
8-DFN ( ) FOR MAX16040 ONLY
+ DENOTES A LEAD-FREE PACKAGE.
______________________________________________________________________________________
OUT
VCC
PFO
PFO 6
17
Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
Typical Operating Circuit
2.4V TO 5.5V 0.1F CMOS RAM VCC ADDITIONAL DC VOLTAGE BATT OUT 0.1F CE
REALTIME CLOCK
R3
MAX16033- MAX16040
RESETIN*
R4
ADDITIONAL DC VOLTAGE RESET R1 PFI R2 CEIN** GND ADDRESS DECODE PFO WDI*** CEOUT**
A0-A15 RESET I/O P I/O
* RESETIN APPLIES TO MAX16035/MAX16039 ONLY. **CEIN AND CEOUT APPLY TO MAX16033-MAX16036 ONLY. ***WDI APPLIES TO MAX16034/MAX16038 ONLY.
18
______________________________________________________________________________________
Low-Power Battery Backup Circuits in Small DFN Packages
Ordering Information (continued)
PART* MAX16035LLB_ _+T MAX16035PLB_ _+T MAX16036LLB_ _+T MAX16036PLB_ _+T MAX16037LLA_ _+T MAX16037PLA_ _+T MAX16038LLA_ _+T MAX16038PLA_ _+T MAX16039LLA_ _+T MAX16039PLA_ _+T MAX16040LLA_ _+T MAX16040PLA_ _+T TEMP RANGE PINPACKAGE PKG CODE SUFFIX 46 44 31 29 26 23
Reset Threshold Ranges
RESET THRESHOLD VOLTAGE (V) MIN 4.50 4.25 3.00 2.85 2.55 2.25 TYP 4.63 4.38 3.08 2.93 2.63 2.32 MAX 4.75 4.50 3.15 3.00 2.70 2.38
MAX16033-MAX16040
-40C to +85C 10 DFN-10 L1022-1 -40C to +85C 10 DFN-10 L1022-1 -40C to +85C 10 DFN-10 L1022-1 -40C to +85C 10 DFN-10 L1022-1 -40C to +85C 8 DFN-8 -40C to +85C 8 DFN-8 -40C to +85C 8 DFN-8 -40C to +85C 8 DFN-8 -40C to +85C 8 DFN-8 -40C to +85C 8 DFN-8 -40C to +85C 8 DFN-8 -40C to +85C 8 DFN-8 L822-1 L822-1 L822-1 L822-1 L822-1 L822-1 L822-1 L822-1
Chip Information
PROCESS: BiCMOS
*These parts offer a choice of reset threshold voltages. From the Reset Threshold Ranges table, insert the desired threshold voltage code in the blank to complete the part number. See Selector Guide for a listing of device features. +Denotes a lead-free package. T = Tape and reel.
______________________________________________________________________________________
19
Low-Power Battery Backup Circuits in Small DFN Packages MAX16033-MAX16040
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
D
A
e
b
N
XXXX XXXX XXXX
SOLDER MASK COVERAGE
E
PIN 1 0.10x45
L
PIN 1 INDEX AREA SAMPLE MARKING 7 1 A A
L1
(N/2 -1) x e)
C L
C L
b A A2 A1
L e
EVEN TERMINAL
L e
ODD TERMINAL
PACKAGE OUTLINE, 6, 8, 10L uDFN, 2x2x0.80 mm
-DRAWING NOT TO SCALE-
21-0164
A
1
2
20
______________________________________________________________________________________
6, 8, 10L UDFN.EPS
Low-Power Battery Backup Circuits in Small DFN Packages
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
MAX16033-MAX16040
COMMON DIMENSIONS SYMBOL A A1 A2 D E L L1 MIN. 0.70 0.15 0.020 1.95 1.95 0.30 NOM. 0.75 0.20 0.025 2.00 2.00 0.40 0.10 REF. MAX. 0.80 0.25 0.035 2.05 2.05 0.50
PACKAGE VARIATIONS PKG. CODE L622-1 L822-1 L1022-1 N 6 8 10 e 0.65 BSC 0.50 BSC 0.40 BSC b 0.300.05 0.250.05 0.200.03 (N/2 -1) x e 1.30 REF. 1.50 REF. 1.60 REF.
PACKAGE OUTLINE, 6, 8, 10L uDFN, 2x2x0.80 mm
-DRAWING NOT TO SCALE-
21-0164
A
2
2
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 ____________________ 21
(c) 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Heaney

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