MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN 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 (μP) systems. The devices significantly
improve system reliability and accuracy compared to other
ICs or discrete components. The MAX16033–MAX16040
provide μP 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 push-pull reset or an active-low
open-drain reset.
The MAX16033–MAX16040 are available in 2mm x 2mm,
8-pin or 10-pin μDFN packages and are fully specified
from -40°C to +85°C.
Applications
●● Portable/BatteryPowered Equipment
●● POS Equipment
●● Critical μP/μC Power
Monitoring
●● Set-Top Boxes
●●
●●
●●
●●
●●
●●
Controllers
Computers
Fax Machines
Industrial Control
Real-Time Clocks
Intelligent Instrument
Pin Configurations and Typical Operating Circuit appear at
end of data sheet
Selector Guide
PART
MR
MAX16033_
ü
MAX16034_
WATCHDOG
BATTON
MAX16039_
MAX16040_
TEMP RANGE
PIN-PACKAGE
MAX16033LLB_ _+T
PART*
-40°C to +85°C
10 µDFN
MAX16033PLB_ _+T
-40°C to +85°C
10 µDFN
MAX16034LLB_ _+T
-40°C to +85°C
10 µDFN
MAX16034PLB_ _+T
-40°C to +85°C
10 µDFN
*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 the
Selector Guide for a listing of device features.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Ordering Information continued on last page.
RESETIN
CEIN/CEOUT
PFI, PFO
ü
ü
10 µDFN-10
ü
ü
10 µDFN-10
ü
ü
10 µDFN-10
ü
ü
10 µDFN-10
ü
8 µDFN-8
ü
8 µDFN-8
ü
8 µDFN-8
ü
8 µDFN-8
ü
MAX16036_
MAX16038_
Ordering Information
ü
MAX16035_
MAX16037_
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 13μA 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 μDFN Paclages
ü
ü
ü
ü
ü
Note: Replace “_” with L for push-pull or P for open-drain RESET and PFO outputs.
19-0882; Rev 2; 5/19
PIN-PACKAGE
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Absolute Maximum Ratings
Output Current
OUT..................................Short-Circuit Protected for up to 5s
RESET, BATTON............................................................20mA
Continuous Power Dissipation (TA = +70°C)
8-Pin μDFN (derate 4.8mW/°C above +70°C)..........380.6mW
10-Pin μDFN (derate 5mW/°C above +70°C)...........402.8mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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
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 = -40°C to +85°C, for MAX16039PLA31+T, TA = -55°C to +85°C, unless
otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Operating Voltage Range
Supply Current
SYMBOL
CONDITIONS
VCC, VBATT No load (Note 2)
ICC
No load, VCC > VTH
Supply Current in Battery
Backup Mode
VBATT = 2.8V,
VCC = 0V,
excluding IOUT
BATT Standby Current (Note 3)
(VBATT + 0.2V) <
VCC < 5.5V
VCC to OUT On-Resistance
IBATT
RON
Output Voltage in Battery
Backup Mode
VOUT
Battery-Switchover Threshold
VSW
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MIN
TYP
0
MAX
UNITS
5.5
V
VCC = 2.8V
13
30
VCC = 3.6V
16
35
VCC = 5.5V
22
50
TA = +25°C
1
TA = -40°C to +85°C
2
TA = -55°C
(MAX16039PLA31+T
only)
10
µA
µA
TA = +25°C
-0.1
+0.02
TA = -40°C to +85°C
-0.3
+0.02
TA = -40°C to +125°C
µA
+0.06
VCC = 4.75V, VCC > VTH, IOUT = 150mA
VCC = 3.15V, VCC > VTH, IOUT = 65mA
3.1
VCC = 2.5V, VCC > VTH, IOUT = 25mA
VBATT = 4.50V, VCC = 0V, IOUT = 20mA
4.6
3.7
Ω
VBATT - 0.2
VBATT = 3.15V, VCC = 0V, IOUT = 10mA
VBATT - 0.15
VBATT = 2.5V, VCC = 0V, IOUT = 5mA
VCC rising
VCC - VBATT,
VCC < VTH
VCC falling
VBATT - 0.15
0
-40
V
mV
Maxim Integrated │ 2
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Electrical Characteristics (continued)
(VCC = 2.25V to 5.5V, VBATT = 3V, RESET not asserted, TA = -40°C to +85°C, for MAX16039PLA31+T, TA = -55°C to +85°C, unless
otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
MAX160_ _ _L_46
4.50
4.63
4.75
MAX160_ _ _L_44
4.25
4.38
4.50
MAX160_ _ _L_31
3.00
3.08
3.15
MAX160_ _ _L_29
2.85
2.93
3.00
MAX160_ _ _L_26
2.55
2.63
2.70
MAX160_ _ _L_23
2.25
2.32
2.38
UNITS
RESET OUTPUT
Reset Threshold
VTH
VCC Falling Reset Delay
VCC falling at 10V/ms
Reset Active Timeout Period
tRP
RESET Output Low Voltage
VOL
RESET asserted
RESET Output High Voltage
VOH
MAX160_ _L only (push-pull), RESET not
asserted, ISOURCE = 500µA, VCC > VTH(MAX)
RESET Output Leakage
Current
ILKG
MAX160_ _P only (open drain), not asserted
VPFI
VPFI falling
25
140
V
µs
280
ISINK = 1.6mA, VCC ≥ 2.1V
0.3
ISINK = 100µA, VCC > 1.2V
0.4
0.8 x
VCC
ms
V
V
1
µA
1.285
V
POWER-FAIL COMPARATOR
PFI Input Threshold
1.185
PFI Hysteresis
1.235
1
PFI Input Current
VPFI = 0V or VCC
PFO Output Low Voltage
VOL
VCC > 2.1V, ISINK = 1.6mA
Output asserted
VCC > 1.2V, ISINK = 100µA
PFO Output High Voltage
VOH
MAX160_ _L only (push-pull), VCC >
VTH(MAX), ISOURCE = 500µA, output not
asserted
PFO Leakage Current
MAX160_ _P only (open drain), VPFO = 5.5V,
not asserted
PFO Delay Time
VPFI + 100mV to VPFI - 100mV
-100
%
+100
0.3
0.4
0.8 x
VCC
nA
V
V
1
4
µA
µs
MANUAL RESET (MAX16033/MAX16037)
MR Input Voltage
VIL
0.3 x VCC
VIH
0.7 x VCC
20
Pullup Resistance to VCC
Minimum Pulse Width
Glitch Immunity
MR to Reset Delay
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165
1
VCC = 3.3V
V
kΩ
µs
100
ns
120
ns
Maxim Integrated │ 3
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Electrical Characteristics (continued)
(VCC = 2.25V to 5.5V, VBATT = 3V, RESET not asserted, TA = -40°C to +85°C, for MAX16039PLA31+T, TA = -55°C to +85°C, unless
otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
1.00
1.65
2.25
UNITS
WATCHDOG (MAX16034/MAX16038)
Watchdog Timeout Period
tWD
Minimum WDI Input Pulse Width
tWDI
WDI Input Voltage
(Note 4)
100
VIL
0.3 x VCC
VIH
0.7 x VCC
WDI Input Current
s
ns
-1.0
V
+1.0
µA
0.4
V
BATTON (MAX16035/MAX16039)
Output Voltage
VOL
Output Short-Circuit Current
ISINK = 3.2mA, VBATT = 2.1V
Sink current, VCC = 5V
Source current, VBATT > 2V
60
mA
10
30
120
µA
1.185
1.235
1.285
V
0.01
25
nA
RESETIN (MAX16036/MAX16040)
RESETIN Threshold
VRTH
RESETIN Input Current
RESETIN to Reset Delay
(VRTH + 100mV) to (VRTH - 100mV)
1.5
µs
CHIP-ENABLE GATING (MAX16033–MAX16036)
CEIN Leakage Current
RESET asserted
±1
µA
CEIN to CEOUT Resistance
RESET not asserted, VCC = VTH(MAX),
VCEIN = VCC/2, ISINK = 10mA
100
Ω
CEOUT Short-Circuit Current
RESET asserted, VCEOUT = 0V
mA
CEIN to CEOUT Propagation
Delay (Note 4)
50Ω source impedance driver, VCC = 4.75V
CLOAD = 50pF
VCC = 3.15V
CEOUT Output-Voltage High
VCC = 5V, VCC > VBATT, ISOURCE = 100µA
VCC = 0V, VBATT > 2.2V, ISOURCE = 1µA
RESET to CEOUT Delay
Note
Note
Note
Note
1
2.0
1.5
7
2
9
0.7 x VCC
VBATT - 0.1
ns
V
1
µs
1: All devices are 100% production tested at TA = +25°C. All overtemperature limits are guaranteed by design.
2: VBATT can be 0V any time, or VCC can go down to 0V if VBATT is active (except at startup).
3: Positive current flows into BATT.
4: Guaranteed by design.
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Maxim Integrated │ 4
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
17
16
15
14
13
12
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-15
10
35
60
85
10
35
60
1.0
VCC = 0V
9
8
VBATT = 2V
7
6
5
4
3
2
1
0
85
VBATT = 5V
VBATT = 3V
-40
-15
10
35
60
85
RESET TIMEOUT PERIOD
vs. TEMPERATURE
VCC-TO-RESET PROPAGATION DELAY
vs. TEMPERATURE
VCC = 2.5V
IOUT = 25mA
1.0
0.8
VCC = 4.5V
IOUT = 150mA
VCC = 3V
IOUT = 65mA
0.4
VCC = 5V
225
0.2
220
215
210
205
200
195
190
185
5
20
35
50
65
80
-40
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
-15
10
35
60
-20
0
20
40
TEMPERATURE (°C)
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0.25V/ms
90
75
60
1V/ms
45
30
15
0
85
10V/ms
-40
-20
60
80
0
20
40
60
80
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
-40
VCC FALLING
105
TEMPERATURE (°C)
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
MAX16033 toc07
NORMALIZED RESET THRESHOLD
TEMPERATURE (°C)
300
MAXIMUM TRANSIENT DURATION (µs)
-40 -25 -10
180
120
MAX16033 toc08
0.6
230
MAX16033 toc06
VCC-TO-OUT ON-RESISTANCE
vs. TEMPERATURE
VCC-TO-RESET PROPAGATION DELAY (µs)
TEMPERATURE (°C)
MAX16033 toc05
TEMPERATURE (°C)
MAX16033 toc04
TEMPERATURE (°C)
1.2
0
-15
-40
BATT-TO-OUT ON-RESISTANCE
vs. TEMPERATURE
MAX16033 toc03
0.8
10
1.4
VCC-TO-OUT ON-RESISTANCE (Ω)
0.9
11
-40
VBATT = 3V
VCC = 0V
BATTERY-TO-OUT ON-RESISTANCE (Ω)
18
1.0
RESET TIMEOUT PERIOD (ms)
SUPPLY CURRENT (µA)
19
BATTERY SUPPLY CURRENT
(BACKUP MODE) vs. TEMPERATURE
MAX16033 toc02
VCC = 5V
BATTERY SUPPLY CURRENT (µA)
20
MAX16033 toc01
SUPPLY CURRENT
vs. TEMPERATURE
RESET OCCURS
ABOVE CURVE
250
MAX160_ _-46
(VTH = 4.63V)
200
150
MAX160_ _-29
(VTH = 2.93V)
100
50
0
1
10
100
1000
10,000
RESET THRESHOLD OVERDRIVE (VTH - VCC) (mV)
Maxim Integrated │ 5
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
1.235
VBATT = 2.5V
1.00
1.230
VBATT = 2.3V
0.75
1.225
0.50
1.220
0.25
1.215
0
-0.25
0
1.210
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE (V)
-40
CEIN PROPAGATION DELAY
vs. CEOUT LOAD CAPACITANCE
2.0
VCC = 3V
1.5
VCC = 5V
1.0
0.5
0
0
25
50
75
100
125
150
35
60
175
2.5
2.3
2.0
1.8
1.5
1.3
1.0
VCC = 3V
15
10
VCC = 5V
5
2.0
VCC = 5V
1.9
85
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
-40
-15
10
35
60
85
1.0
-40
-15
10
35
60
85
TEMPERATURE (°C)
PFI THRESHOLD
vs. TEMPERATURE
1.250
1.245
1.240
PFI THRESHOLD (V)
4.25
4.00
3.75
3.50
60
MAX16033 toc16
VOD = 30mV
35
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
20
MAX16033 toc15
5.00
10
CEIN TO CEOUT ON-RESISTANCE
vs. TEMPERATURE
PFI-TO-PFO DELAY
vs. TEMPERATURE
PFI-TO-PFO DELAY (s)
-15
-40
TEMPERATURE (°C)
4.75
4.50
VOD = 50mV
TEMPERATURE (°C)
25
CEOUT LOAD CAPACITANCE (pF)
1.235
1.230
3.25
3.00
2.75
2.50
2.25
2.00
MAX16036/
MAX16040
TEMPERATURE (°C)
30
0
2.8
85
MAX16033 toc13
CEIN TO CEOUT ON-RESISTANCE (Ω)
2.5
10
35
MAX16033 toc12
CEIN PROPAGATION DELAY (ns)
3.0
-15
3.0
MAX16033 toc11
1.240
1.25
RESETIN-TO-RESET PROPAGATION DELAY (µs)
1.245
WATCHDOG TIMEOUT PERIOD (s)
VBATT = 2.8V
1.50
MAX16036/
MAX16040
RESETIN THRESHOLD (V)
1.75
1.250
RESETIN-TO-RESET PROPAGATION
DELAY vs. TEMPERATURE
MAX16033 toc10
VTH = 2.93V
MAX16033 toc09
BATTERY SUPPLY CURRENT (µA)
2.00
RESETIN THRESHOLD
vs. TEMPERATURE
MAX16033 toc14
BATTERY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
1.225
1.220
1.215
FALLING EDGE
-40
-15
10
35
TEMPERATURE (°C)
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60
85
1.210
-40
-15
10
35
60
85
TEMPERATURE (°C)
Maxim Integrated │ 6
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Pin Description
PIN
MAX16033–
MAX16036
(10-pin µDFN)
MAX16037–
MAX16040
(8-pin µDFN)
NAME
FUNCTION
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.
1
1
RESET
2
—
CEIN
3
2
PFI
4
3
GND
5
4
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
MR
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 20kΩ pullup to VCC.
WDI
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).
BATTON
Battery-On Output (MAX16035/MAX16039). BATTON goes high during battery
backup mode.
RESETIN
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.
6
5
PFO
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.
7
6
VCC
Supply Voltage, 1.2V to 5.5V
8
7
OUT
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.
9
8
BATT
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.
10
—
CEOUT
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.
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Maxim Integrated │ 7
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Pin Description (continued)
BATTON (MAX16035/MAX16039 ONLY)
1.235V
MAX16033
MAX16040
VCC
OUT
CHIP-ENABLE
OUTPUT
CONTROL
BATT
CEIN
(MAX16033–MAX16036 ONLY)
CEOUT
RESET
GENERATOR
MR
(MAX16033/MAX16037 ONLY)
WATCHDOG
TRANSITION
DETECTOR
WDI
(MAX16034/MAX16038 ONLY)
RESET
WATCHDOG
TIMER
RESETIN
(MAX16036/MAX16040 ONLY)
PFO
1.235V
1.235V
GND
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PFI
Maxim Integrated │ 8
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Detailed Description
The Typical Operating Circuit shows a typical connection for the MAX16033–MAX16040. OUT powers the
static random-access memory (SRAM). If VCC 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 on-resistance
of the MOSFET is a function of the backup-battery voltage and temperature and is shown in the BATT-to-OUT
On-Resistance vs. Temperature graph in the Typical
Operating Characteristics.
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 these devices to be used
with most μPs and high-speed 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 1μs to allow completion of the read/write operation
(Figure 1). After the 1μs 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 chipenable propagation delay is specified from the 50% point
of CEIN to the 50% point of CEOUT, using a 50Ω 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
±1μA (max) over temperature. In low-impedance mode,
the impedance of CEIN appears as a 75Ω resistor in
series with the load at CEOUT.
VCC
VTH
CEIN
CEOUT
*
RESET-TO-CEOUT DELAY
tRD
RESET
tRD
tRP
tRP
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
www.maximintegrated.com
Maxim Integrated │ 9
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 batterybackup mode. The devices do not power up if the only
voltage source is VBATT. OUT only powers up from VCC
at startup.
Table 1. Input and Output Status in
Battery-Backup Mode
PIN
STATUS
VCC
Disconnected from OUT
OUT
Connected to BATT
BATT
Connected to OUT. Current drawn from the
battery is less than 1µA (at VBATT = 2.8V,
excluding IOUT) when VCC = 0V.
RESET
Asserted
BATTON
High state
MR, RESETIN,
Inputs ignored
CEIN, and WDI
CEOUT
PFO
Low-Power Battery-Backup
Circuits in Small μDFN Packages
high. MR has an internal 20kΩ (min) pullup resistor to
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 0.1μF capacitor from MR to GND to provide additional
noise immunity.
Watchdog Input
(MAX16034/MAX16038 Only)
The watchdog monitors μP activity through the watchdog
input (WDI). RESET asserts when the μP fails to toggle
WDI. Connect WDI to a bus line or μP 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.
WDI
Connected to OUT
tRP
Asserted
Manual-Reset Input
(MAX16033/MAX16037 Only)
Many μP-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
www.maximintegrated.com
RESET
tWD
tRP
tWD
tWD = WATCHDOG TIMEOUT PERIOD
tRP = RESET TIMEOUT PERIOD
Figure 2. MAX16034/MAX16038 Watchdog Timeout Period and
Reset Active Time
Maxim Integrated │ 10
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
BATTON Indicator
(MAX16035/MAX16039 Only)
Power-Fail Comparator
The MAX16033–MAX16040 issue an interrupt (nonmaskable or regular) to the μP 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
(Figure 1). The MAX160_ _L devices provide push-pull
PFO outputs. The MAX160_ _P devices provide opendrain PFO outputs.
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 10μA from OUT. Use
BATTON to indicate battery-switchover status or to supply
base drive to an external pass transistor for higher current
applications (Figure 3).
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.
VCC
Use the following equations to set the reset threshold voltage (VRTH) of the secondary power supply (see Figure 4):
VIN
VRTH = VREF (R1/R2 + 1)
where VREF = 1.235V. To simplify the resistor selection,
choose a value for R2 and calculate R1:
MAX16036
MAX16040
R1
RESETIN
R1 = R2 [(VRTH/VREF) - 1]
R2
Since the input current at RESETIN is 25nA (max), large
values (up to 1MΩ) can be used for R2 with no significant
loss in accuracy.
Figure 4. Setting RESETIN Voltage for the MAX16036/
MAX16040
2.4V TO 5.5V
0.1µF
VCC
BATTON
BATT
OUT
(CEOUT)
CE
CMOS RAM
MAX16035
MAX16039
(CEIN)
ADDRESS
DECODE
A0–A15
µP
GND
RESET
RESET
( ) FOR MAX16035 ONLY
Figure 3. MAX16035/MAX16039 BATTON Driving an External Pass Transistor
www.maximintegrated.com
Maxim Integrated │ 11
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
RESET
A μP’s reset input puts the μP in a known state.
The MAX16033–MAX16040 μP supervisory circuits
assert a reset to prevent code-execution errors during
power-up, 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.
3V OR 3.3V
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 μP
supervisors with a super cap.
3V OR 3.3V
VCC
VCC
5V
1N4148
MAX16033
MAX16040
MAX16033
MAX16040
1N4148
BATT
BATT
0.47F
0.47F
(a)
(b)
Figure 5. Using a Super Cap as a Backup Source
www.maximintegrated.com
Maxim Integrated │ 12
MAX16033–MAX16040
START
Low-Power Battery-Backup
Circuits in Small μDFN Packages
VCC
SUBROUTINE
OR PROGRAM LOOP
SET
WDI HIGH
RESET
VCC
SET
WDI
LOW
MAX16033
MAX16040
V+
MR
R1
PFI
RETURN
TO µP
R2
PFO
GND
END
Figure 6. Watchdog Flow Diagram
Figure 7. Monitoring an Additional Power Supply
Watchdog Software Considerations
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.
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 μP.
Replacing the Backup Battery
Decouple BATT to GND with a 0.1μF capacitor. The
backup power source can be removed while VCC 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.
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 10μA to ensure that the
100nA (max) PFI input current does not shift the trip point.
Set R3 to be higher than 10kΩ to reduce the load at PFO.
Capacitor C1 adds additional noise rejection.
To simplify the resistor selection, choose a value for R2
and calculate R1:
R1 = R2 [(VTH(PFI)/1.235) - 1]
www.maximintegrated.com
Maxim Integrated │ 13
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
(a)
(b)
VCC
VIN
VCC
VIN
MAX16033
MAX16040
R1
MAX16033
MAX16040
R1
PFI
R2
PFI
R3
C1
R2
C1
R3
PFO (PUSH-PULL)
PFO (PUSH-PULL)
GND
GND
TO µP
TO µP
PFO
PFO
0V
VL
VTRIP
VH
R1
=
VTRIP VPFT1 +
R2
R1 R1
= (VPFT + VPFH)1 +
+
VH
R2 R3
R1 R1 R1
V=
+
VCC
L VPFT1 +
−
R2 R3 R3
VPFT = 1.235V
VPFH = 12mV
VIN
0V
VTRIP
VH
VIN
R1
=
VTRIP VPFT1 +
R2
R1 R1 R1
= (VPFT + VPFH)1 +
+
VH
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
www.maximintegrated.com
Maxim Integrated │ 14
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Monitoring a Negative Voltage
3.0V OR 3.3V
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.
VCC
Negative-Going VCC Transients
The MAX16033–MAX16040 are relatively immune to
short-duration, negative-going VCC transients. Resetting
the μP when VCC 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 25μs does not trigger a reset pulse.
A 0.1μF bypass capacitor mounted close to VCC provides
additional transient immunity.
MAX16033
MAX16040
R1
PFI
PFO
R2
GND
V-
PFO
VL
VTRIP
0V
V-
1 VCC
1
VTRIP
= R2(VPFT + VPFH) +
− R1
R1
R2
1
1
V
CC
VL R2(VPFT) +
=
−
R1 R2 R1
VPFT = 1.235V
VPFH = 12mV
Figure 9. Monitoring a Negative Voltage
www.maximintegrated.com
Maxim Integrated │ 15
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Device Marking Codes
PART
TOP
MARK
PART
TOP
MARK
PART
TOP
MARK
PART
TOP
MARK
MAX16033LLB23+T
+ABE
MAX16035LLB23+T
+ACC
MAX16037LLA23+T
+ABX
MAX16039LLA23+T
+ACV
MAX16033LLB26+T
+ABF
MAX16035LLB26+T
+ACD
MAX16037LLA26+T
+ABY
MAX16039LLA26+T
+ACW
MAX16033LLB29+T
+ABG
MAX16035LLB29+T
+ACE
MAX16037LLA29+T
+ABZ
MAX16039LLA29+T
+ACX
MAX16033LLB31+T
+ABH
MAX16035LLB31+T
+ACF
MAX16037LLA31+T
+ACA
MAX16039LLA31+T
+ACY
MAX16033LLB44+T
+ABI
MAX16035LLB44+T
+ACG
MAX16037LLA44+T
+ACB
MAX16039LLA44+T
+ACZ
MAX16033LLB46+T
+ABJ
MAX16035LLB46+T
+ACH
MAX16037LLA46+T
+ACC
MAX16039LLA46+T
+ADA
MAX16033PLB23+T
+ABK
MAX16035PLB23+T
+ACI
MAX16037PLA23+T
+ACD
MAX16039PLA23+T
+ADB
MAX16033PLB26+T
+ABL
MAX16035PLB26+T
+ACJ
MAX16037PLA26+T
+ACE
MAX16039PLA26+T
+ADC
MAX16033PLB29+T
+ABM
MAX16035PLB29+T
+ACK
MAX16037PLA29+T
+ACF
MAX16039PLA29+T
+ADD
MAX16033PLB31+T
+ABN
MAX16035PLB31+T
+ACL
MAX16037PLA31+T
+ACG
MAX16039PLA31+T
+ADE
MAX16033PLB44+T
+ABO
MAX16035PLB44+T
+ACM
MAX16037PLA44+T
+ACH
MAX16039PLA44+T
+ADF
MAX16033PLB46+T
+ABP
MAX16035PLB46+T
+ACN
MAX16037PLA46+T
+ACI
MAX16039PLA46+T
+ADG
MAX16034LLB23+T
+ABQ
MAX16036LLB23+T
+ACO
MAX16038LLA23+T
+ACJ
MAX16040LLA23+T
+ADH
MAX16034LLB26+T
+ABR
MAX16036LLB26+T
+ACP
MAX16038LLA26+T
+ACK
MAX16040LLA26+T
+ADI
MAX16034LLB29+T
+ABS
MAX16036LLB29+T
+ACQ
MAX16038LLA29+T
+ACL
MAX16040LLA29+T
+ADJ
MAX16034LLB31+T
+ABT
MAX16036LLB31+T
+ACR
MAX16038LLA31+T
+ACM
MAX16040LLA31+T
+ADK
MAX16034LLB44+T
+ABU
MAX16036LLB44+T
+ACS
MAX16038LLA44+T
+ACN
MAX16040LLA44+T
+ADL
MAX16034LLB46+T
+ABV
MAX16036LLB46+T
+ACT
MAX16038LLA46+T
+ACO
MAX16040LLA46+T
+ADM
MAX16034PLB23+T
+ABW
MAX16036PLB23+T
+ACU
MAX16038PLA23+T
+ACP
MAX16040PLA23+T
+ADN
MAX16034PLB26+T
+ABX
MAX16036PLB26+T
+ACV
MAX16038PLA26+T
+ACQ
MAX16040PLA26+T
+ADO
MAX16034PLB29+T
+ABY
MAX16036PLB29+T
+ACW
MAX16038PLA29+T
+ACR
MAX16040PLA29+T
+ADP
MAX16034PLB31+T
ABZ
MAX16036PLB31+T
+ACX
MAX16038PLA31+T
+ACS
MAX16040PAL31+T
+ADQ
MAX16034PLB44+T
+ACA
MAX16036PLB44+T
+ACY
MAX16038PLA44+T
+ACT
MAX16040PLA44+T
+ADR
MAX16034PLB46+T
+ACB
MAX16036PLB46+T
+ACZ
MAX16038PLA46+T
+ACU
MAX16040PLA46+T
+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.
www.maximintegrated.com
Maxim Integrated │ 16
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Pin Configurations
CEOUT
BATT
OUT
VCC
PFO
CEOUT
BATT
OUT
VCC
PFO
TOP VIEW
10
9
8
7
6
10
9
8
7
6
MAX16035
MAX16036
MAX16033
MAX16034
10-µDFN
( ) FOR MAX16034 ONLY
10-µDFN
( ) FOR MAX16036 ONLY
PFO
CEIN
GND
GND
PFI
PFI
5
VCC
CEIN
4
OUT
RESET
3
RESET
2
BATT
1
MR (WDI)
5
PFO
4
VCC
3
OUT
2
BATT
1
BATTON
(RESETIN)
+
+
8
7
6
5
8
7
6
5
MAX16037
MAX16038
MAX16039
MAX16040
MR (WDI)
2
3
4
BATTON
(RESETIN)
GND
8-µDFN
( ) FOR MAX16038 ONLY
1
GND
4
PFI
3
RESET
2
PFI
+
1
RESET
+
8-µDFN
( ) FOR MAX16040 ONLY
+ DENOTES A LEAD(Pb)-FREE PACKAGE.
www.maximintegrated.com
Maxim Integrated │ 17
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Typical Operating Circuit
2.4V TO 5.5V
0.1µF
VCC
BATT
ADDITIONAL
DC VOLTAGE
CMOS
RAM
CE
OUT
0.1µF
MAX16033
MAX16040
R3
REALTIME
CLOCK
RESETIN*
R4
ADDITIONAL
DC VOLTAGE
A0–A15
RESET
R1
PFI
R2
RESET
PFO
I/O
WDI***
I/O
µP
CEOUT**
CEIN**
GND
ADDRESS
DECODE
* RESETIN APPLIES TO MAX16035/MAX16039 ONLY.
**CEIN AND CEOUT APPLY TO MAX16033–MAX16036 ONLY.
***WDI APPLIES TO MAX16034/MAX16038 ONLY.
www.maximintegrated.com
Maxim Integrated │ 18
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Ordering Information (continued)
PART*
Reset Threshold Ranges
TEMP RANGE
PIN-PACKAGE
MAX16035LLB_ _+T
-40°C to +85°C
10 µDFN
MIN
TYP
MAX
MAX16035PLB_ _+T
-40°C to +85°C
10 µDFN
46
4.50
4.63
4.75
MAX16036LLB_ _+T
-40°C to +85°C
10 µDFN
MAX16036PLB_ _+T
-40°C to +85°C
10 µDFN
44
4.25
4.38
4.50
MAX16037LLA_ _+T
-40°C to +85°C
8 µDFN
31
3.00
3.08
3.15
MAX16037PLA_ _+T
-40°C to +85°C
8 µDFN
29
2.85
2.93
3.00
MAX16038LLA_ _+T
-40°C to +85°C
8 µDFN
26
2.55
2.63
2.70
MAX16038PLA_ _+T
-40°C to +85°C
8 µDFN
23
2.25
2.32
2.38
MAX16039LLA_ _+T
-40°C to +125°C
8 µDFN
MAX16039PLA_ _+T
-40°C to +85°C
8 µDFN
8 µDFN
MAX16039PLA31+T
-55°C to +85°C
MAX16040LLA_ _+T
-40°C to +85°C
8 µDFN
MAX16040PLA_ _+T
-40°C to +85°C
8 µDFN
*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 the
Selector Guide for a listing of device features.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
www.maximintegrated.com
SUFFIX
RESET-THRESHOLD VOLTAGE (V)
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 μDFN
L822+1
21-0164
90-0005
10 μDFN
L1022+1
21-0164
90-0006
Maxim Integrated │ 19
MAX16033–MAX16040
Low-Power Battery-Backup
Circuits in Small μDFN Packages
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
1
5/14
Data sheet rebranded; updated Electrical Characteristics and Ordering Information
tables to support MAX16039PLA31+T option at -55°C
2, 19
2
5/19
Updated Electrical Characteristics and Ordering Information
2, 19
DESCRIPTION
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2019 Maxim Integrated Products, Inc. │ 20
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