MAX16037LLA46+ [MAXIM]
Low-Power Battery Backup Circuits in Small レDFN Packages; 小μDFN封装低功耗电池备份电路
| 型号： | MAX16037LLA46+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Low-Power Battery Backup Circuits in Small レDFN Packages |
| 文件： | 总21页 (文件大小：215K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0882; Rev 0; 7/07
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
General Description
Features
♦ Low 1.2V Operating Supply Voltage
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 signifi-
cantly improve system reliability and accuracy com-
pared to other ICs or discrete components. The
MAX16033–MAX16040 provide µP reset, backup-bat-
tery switchover, power-fail warning, watchdog, and
chip-enable gating features.
♦ 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
The MAX16033–MAX16040 operate from supply volt-
ages up to 5.5V. The factory-set reset threshold voltage
ranges from 2.32V to 4.63V. The devices feature a man-
ual-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.
♦ 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
Packages
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.
Ordering Information
PIN-
PKG
PART*
TEMP RANGE
Applications
PACKAGE
CODE
MAX16033LLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
MAX16033PLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
MAX16034LLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
MAX16034PLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
Portable/Battery-
Powered Equipment
Controllers
Computers
POS Equipment
Fax Machines
Industrial Control
Real-Time Clocks
Intelligent Instrument
Critical µP/µC Power
Monitoring
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 volt-
age code in the blank to complete the part number. See Selector
Guide for a listing of device features.
Set-Top Boxes
+Denotes a lead-free package.
T = Tape and reel.
Pin Configurations and Typical Operating Circuit appear at
end of data sheet.
Selector Guide
CEIN/CEOU
PART
MR
WATCHDOG
BATTON
RESETIN
PFI, PFO
PIN-PACKAGE
10 µDFN-10
10 µDFN-10
10 µDFN-10
10 µDFN-10
8 µDFN-8
MAX16033_
MAX16034_
MAX16035_
MAX16036_
MAX16037_
MAX16038_
MAX16039_
MAX16040_
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
8 µDFN-8
✓
8 µDFN-8
8 µDFN-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 µDFN Packages
ABSOLUTE MAXIMUM RATINGS
Terminal Voltages (with respect to GND)
Output Current
V
BATT, OUT.......................................................-0.3V to +6V
OUT ..................................Short-Circuit Protected for up to 5s
RESET, BATTON.............................................................20mA
CC,
RESET (open drain), PFO (open drain)....................-0.3V to +6V
RESET (push-pull), PFO (push-pull), BATTON, RESETIN, WDI
Continuous Power Dissipation (T = +70°C)
A
MR, CEIN, CEOUT, PFI ............................-0.3V to (V
+ 0.3V)
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
OUT
Input Current
V
V
Peak..............................................................................1A
Continuous ............................................................250mA
CC
CC
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
(V
= 2.25V to 5.5V, V = 3V, RESET not asserted, T = -40°C to +85°C, unless otherwise noted. Typical values are at T =
BATT A A
CC
+25°C.) (Note 1)
3–MAX1640
PARAMETER
SYMBOL
, V
CONDITIONS
No load (Note 2)
MIN
TYP
MAX
5.5
30
UNITS
Operating Voltage Range
Supply Current
V
0
V
CC BATT
V
V
V
= 2.8V
= 3.6V
= 5.5V
13
16
22
CC
CC
CC
I
No load, V
> V
TH
35
µA
CC
CC
50
V
V
= 2.8V,
= 0V,
BATT
T
T
= +25°C
1
2
A
A
Supply Current in Battery
Backup Mode
µA
µA
CC
= -40°C to +85°C
excluding I
OUT
T
T
= +25°C
-0.1
-0.3
+0.02
+0.02
3.1
A
(V
< 5.5V
+ 0.2V) < V
CC
BATT
BATT Standby Current (Note 3)
I
BATT
= -40°C to +85°C
A
V
V
V
= 4.75V, V
= 3.15V, V
> V , I
= 150mA
> V , I = 65mA
TH OUT
CC
CC
CC
CC
TH OUT
V
to OUT On-Resistance
R
3.7
Ω
CC
ON
CC
= 2.5V, V
> V , I
= 25mA
4.6
CC
TH OUT
V
BATT
- 0.2
V
V
V
V
= 4.50V, V
= 3.15V, V
= 0V, I
= 0V, I
= 20mA
= 10mA
BATT
BATT
BATT
CC
OUT
Output Voltage in Battery
Backup Mode
V
BATT
- 0.15
V
V
OUT
CC
OUT
V
BATT
= 2.5V, V
= 0V, I
= 5mA
CC
OUT
- 0.15
V
V
rising
falling
0
CC
CC
Battery-Switchover Threshold
V
- V
, V
< V
TH
mV
SW
CC
BATT CC
-40
2
_______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
ELECTRICAL CHARACTERISTICS (continued)
(V
= 2.25V to 5.5V, V
= 3V, RESET not asserted, T = -40°C to +85°C, unless otherwise noted. Typical values are at T
A
=
CC
BATT
A
+25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RESET OUTPUT
MAX160_ _ _L_46
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
4.75
4.50
3.15
3.00
2.70
2.38
MAX160_ _ _L_44
MAX160_ _ _L_31
MAX160_ _ _L_29
MAX160_ _ _L_26
MAX160_ _ _L_23
Reset Threshold
V
V
TH
V
Falling Reset Delay
V
falling at 10V/ms
CC
µs
CC
Reset Active Timeout Period
t
140
280
0.3
0.4
ms
RP
I
I
= 1.6mA, V
= 100µA, V
> 2.1V
> 1.2V
SINK
CC
CC
RESET Output Low Voltage
V
RESET asserted
V
V
OL
SINK
MAX160_ _L only (push-pull), RESET not
asserted, I = 500µA, V > V
0.8 x
V
CC
RESET Output High Voltage
V
OH
SOURCE
CC
TH(MAX)
RESET Output Leakage
Current
I
MAX160_ _P only (open drain), not asserted
1
µA
LKG
POWER-FAIL COMPARATOR
PFI Input Threshold
PFI Hysteresis
V
V
V
falling
1.185
-100
1.235
1
1.285
V
PFI
PFI
PFI
%
PFI Input Current
= 0V or V
+100
0.3
nA
CC
V
V
> 2.1V, I
> 1.2V, I
= 1.6mA
= 100µA
CC
CC
SINK
SINK
PFO Output Low Voltage
PFO Output High Voltage
V
Output asserted
V
V
OL
0.4
MAX160_ _L only (push-pull), V > V
0.8 x
V
CC
CC
TH(MAX),
V
OH
I
= 500µA, output not asserted
SOURCE
MAX160_ _P only (open drain), V
not asserted
= 5.5V,
PFO
PFO Leakage Current
PFO Delay Time
1
µA
µs
V
+ 100mV to V
- 100mV
4
PFI
PFI
MANUAL RESET (MAX16033/MAX16037)
0.3 x
V
IL
V
CC
MR Input Voltage
V
0.7 x
V
IH
V
CC
Pullup Resistance to V
Minimum Pulse Width
Glitch Immunity
20
1
165
kΩ
µs
ns
ns
CC
V
= 3.3V
100
120
CC
MR to Reset Delay
_______________________________________________________________________________________
3
Low-Power Battery Backup
Circuits in Small µDFN Packages
ELECTRICAL CHARACTERISTICS (continued)
(V
= 2.25V to 5.5V, V = 3V, RESET not asserted, T = -40°C to +85°C, unless otherwise noted. Typical values are at T =
BATT A A
CC
+25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
2.25
0.3 x
UNITS
WATCHDOG (MAX16034/MAX16038)
Watchdog Timeout Period
t
1.00
100
1.65
s
WD
Minimum WDI Input Pulse Width
t
(Note 4)
ns
WDI
V
IL
V
CC
WDI Input Voltage
V
0.7 x
V
IH
V
CC
WDI Input Current
-1.0
+1.0
0.4
µA
BATTON (MAX16035/MAX16039)
Output Voltage
V
I
= 3.2mA, V = 2.1V
BATT
V
OL
SINK
Sink current, V
= 5V
BATT
60
30
mA
µA
CC
Output Short-Circuit Current
Source current, V
> 2V
10
120
RESETIN (MAX16036/MAX16040)
RESETIN Threshold
3–MAX1640
V
1.185
1.235
0.01
1.5
1.285
25
V
RTH
RESETIN Input Current
nA
µs
RESETIN to Reset Delay
(V
RTH
+ 100mV) to (V
- 100mV)
RTH
CHIP-ENABLE GATING (MAX16033–MAX16036)
CEIN Leakage Current
RESET asserted
1
µA
Ω
RESET not asserted, V
= V
= 10mA
CC
TH(MAX),
CEIN to CEOUT Resistance
CEOUT Short-Circuit Current
100
V
= V
/ 2, I
CEIN
CC
SINK
RESET asserted, V
= 0V
1
1.5
2
2.0
7
mA
ns
CEOUT
V
V
= 4.75V
= 3.15V
CC
CC
CEIN to CEOUT Propagation
Delay (Note 4)
50Ω source impedance driver,
C
= 50pF
LOAD
9
0.7 x
V
V
= 5V, V
> V
, I
BATT SOURCE
= 100µA
= 1µA
CC
CC
V
CC
CEOUT Output-Voltage High
RESET to CEOUT Delay
V
V
BATT
= 0V, V
> 2.2V, I
SOURCE
CC
BATT
- 0.1
1
µs
Note 1: All devices are 100% production tested at T = +25°C. All overtemperature limits are guaranteed by design.
A
Note 2: V
can be 0V any time, or V
can go down to 0V if V
is active (except at startup).
BATT
CC
BATT
Note 3: Positive current flows into BATT.
Note 4: Guaranteed by design.
4
_______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
SUPPLY CURRENT
vs. TEMPERATURE
BATTERY SUPPLY CURRENT
(BACKUP MODE) vs. TEMPERATURE
BATT-TO-OUT ON-RESISTANCE
vs. TEMPERATURE
20
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1.0
9
V
= 5V
V
V
= 3V
= 0V
V
= 0V
CC
CC
BATT
CC
19
18
17
16
15
14
13
12
11
10
8
V
= 2V
BATT
7
6
5
4
3
V
= 5V
BATT
2
V
= 3V
10
BATT
1
0
-40
-15
10
35
60
85
-40
-15
10
35
60
85
-40
-15
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
V
CC
-TO-OUT ON-RESISTANCE
vs. TEMPERATURE
RESET TIMEOUT PERIOD
vs. TEMPERATURE
V
CC
-TO-RESET PROPAGATION DELAY
vs. TEMPERATURE
120
105
90
75
60
45
30
15
0
230
225
220
215
210
205
200
195
190
185
180
V
FALLING
0.25V/ms
V
= 5V
CC
CC
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
I
= 2.5V
= 25mA
CC
OUT
1V/ms
V
= 4.5V
= 150mA
CC
V
= 3V
= 65mA
CC
I
OUT
I
OUT
10V/ms
-40 -25 -10
5
20 35 50 65 80
-40
-20
0
20
40
60
80
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
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
300
RESET OCCURS
ABOVE CURVE
250
200
150
100
50
MAX160_ _-46
(V = 4.63V)
TH
MAX160_ _-29
(V = 2.93V)
TH
0
-40
-20
0
20
40
60
80
1
10
100
1000
10,000
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (V - V ) (mV)
TH
CC
_______________________________________________________________________________________
5
Low-Power Battery Backup
Circuits in Small µDFN Packages
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
BATTERY SUPPLY CURRENT
RESETIN THRESHOLD
vs. TEMPERATURE
RESETIN-TO-RESET PROPAGATION
DELAY vs. TEMPERATURE
vs. SUPPLY VOLTAGE
2.00
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
3.0
2.8
2.5
2.3
2.0
1.8
1.5
1.3
1.0
V
= 2.93V
MAX16036/
MAX16040
MAX16036/
MAX16040
V
= 50mV
OD
TH
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
V
= 2.8V
BATT
V
= 2.5V
BATT
V
= 2.3V
BATT
-0.25
0
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
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
CEIN PROPAGATION DELAY
vs. CEOUT LOAD CAPACITANCE
CEIN TO CEOUT ON-RESISTANCE
vs. TEMPERATURE
3–MAX1640
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
3.0
2.5
2.0
1.5
1.0
0.5
0
35
30
25
20
15
10
5
V
= 5V
CC
V
= 3V
CC
V
= 3V
CC
V
= 5V
CC
V
= 5V
CC
0
-40
-15
10
35
60
85
0
25
50
75 100 125 150 175
-40
-15
10
35
60
85
TEMPERATURE (°C)
CEOUT LOAD CAPACITANCE (pF)
TEMPERATURE (°C)
PFI-TO-PFO DELAY
vs. TEMPERATURE
PFI THRESHOLD
vs. TEMPERATURE
5.00
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
V
= 30mV
OD
4.75
4.50
4.25
4.00
3.75
3.50
3.25
3.00
2.75
2.50
2.25
2.00
FALLING EDGE
-15
-40
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
6
_______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
Pin Description
PIN
MAX16033–
MAX16036
MAX16037–
MAX16040
NAME
FUNCTION
(10-pin µDFN) (8-pin µDFN)
Active-Low Reset Output. RESET remains low when V
is below the reset
CC
threshold (V ), the manual-reset input is low, or RESETIN is low. It asserts low in
TH
pulses when the internal watchdog times out. RESET remains low for the reset
1
1
RESET
timeout period (t ) after V
rises above the reset threshold, after the manual-reset
RP
CC
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.
2
—
CEIN
3
4
2
3
PFI
Power-Fail Input. PFO goes low when V
falls below 1.235V.
PFI
GND
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 (t ) after
RP
MR
MR transitions from low to high. Leave unconnected, or connect to V
if not used.
CC
MR has an internal 20kΩ pullup to V
.
CC
Watchdog Input (MAX16034/MAX16038). If WDI remains high or low for longer than
the watchdog timeout period (t ), the internal watchdog timer runs out and a reset
pulse is triggered for the reset timeout period (t ). The internal watchdog clears
RP
WD
WDI
5
4
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.
BATTON
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 t
RP
after RESETIN goes high.
Active-Low Power-Fail Output. PFO goes low when V
falls below 1.235V. PFO
PFI
stays low until V
goes above 1.235V. PFO also goes low when V falls below
CC
6
5
PFO
PFI
the reset threshold voltage.
7
8
6
7
V
Supply Voltage, 1.2V to 5.5V
Output. OUT sources from V
CC
when RESET is not asserted and from the greater of
CC
OUT
V
or BATT when V
is below the reset threshold voltage.
CC
CC
Backup Battery Input. When V
falls below the reset threshold, OUT switches to
CC
BATT if V
is 40mV greater than V . When V
rises above V
, OUT
BATT
CC
CC
BATT
9
8
BATT
switches to V . The 40mV hysteresis prevents repeated switching if V
CC
falls
CC
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.
10
—
CEOUT
_______________________________________________________________________________________
7
Low-Power Battery Backup
Circuits in Small µDFN Packages
Functional Diagram
BATTON (MAX16035/MAX16039 ONLY)
1.235V
MAX16033–
MAX16040
V
CC
OUT
CHIP-ENABLE
OUTPUT
CONTROL
BATT
3–MAX1640
CEIN
CEOUT
RESET
(MAX16033–MAX16036 ONLY)
RESET
GENERATOR
MR
(MAX16033/MAX16037 ONLY)
WATCHDOG
TRANSITION
DETECTOR
WATCHDOG
TIMER
WDI
(MAX16034/MAX16038 ONLY)
RESETIN
(MAX16036/MAX16040 ONLY)
PFO
1.235V
1.235V
GND
PFI
8
_______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
these devices to be used with most µPs and high-
Detailed Description
speed DSPs.
The Typical Operating Circuit shows a typical connec-
tion for the MAX16033–MAX16040. OUT powers the
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.
static random-access memory (SRAM). If V
is
CC
is lower
greater than the reset threshold (V ), or if V
TH
CC
than V
but higher than V
, V
is connected to
is less than
CC
TH
OUT. If V
BATT CC
is lower than V
and V
CC
TH
V
BATT
, BATT is connected to OUT. OUT supplies up to
If CEIN is low when RESET is asserted, CEOUT is held
low for 1µs to allow completion of the read/write opera-
tion (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.
200mA from V . In battery-backup mode, an internal
CC
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.
The propagation delay through the chip-enable circuit-
ry 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
50Ω driver and 50pF load capacitance. Minimize the
capacitive load at CEOUT and use a low output-imped-
ance driver to minimize propagation delay.
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
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 resis-
tor in series with the load at CEOUT.
V
CC
V
TH
CEIN
CEOUT
*
RESET-TO-CEOUT DELAY
t
t
RD
RD
t
t
RP
RP
RESET
PFO
PFI > V
PFI
* IF CEIN GOES HIGH BEFORE RESET ASSERTS,
CEOUT GOES HIGH WITHOUT DELAY AS CEIN GOES HIGH.
Figure 1. RESET and Chip-Enable Timing
_______________________________________________________________________________________
9
Low-Power Battery Backup
Circuits in Small µDFN Packages
V
. This input can be driven from TTL/CMOS logic
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:
CC
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 cir-
cuitry is not required. When driving MR from long
cables or when using the device in a noisy environ-
ment, connect a 0.1µF capacitor from MR to GND to
provide additional noise immunity.
1) V
2) V
falls below the reset threshold voltage.
CC
CC
is below V
.
BATT
Table 1 lists the status of the inputs and outputs in bat-
tery-backup mode. The devices do not power-up if the
Watchdog Input
(MAX16034/MAX16038 Only)
only voltage source is V
. OUT only powers up from
BATT
The watchdog monitors µP activity through the watch-
dog 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
V
CC
at startup.
Table 1. Input and Output Status in
Battery-Backup Mode
(t ), the internal watchdog timer runs out and triggers
PIN
STATUS
Disconnected from OUT
WD
a reset pulse for the reset timeout period (t ). The
RP
V
CC
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
OUT
Connected to BATT
Connected to OUT. Current drawn from the
3–MAX1640
BATT
battery is less than 1µA (at V
= 2.8V,
BATT
period (t ); see Figure 2.
WD
excluding I
) when V
= 0V.
OUT
CC
RESET
Asserted
BATTON
High state
MR, RESETIN,
CEIN, and WDI
Inputs ignored
CEOUT
Connected to OUT
Asserted
WDI
PFO
t
RP
t
RP
t
t
WD
WD
RESET
Manual-Reset Input
(MAX16033/MAX16037 Only)
t = WATCHDOG TIMEOUT PERIOD
WD
t = RESET TIMEOUT PERIOD
RP
Many µP-based products require manual-reset capabil-
ity, 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 (t ) after it returns
RP
high. MR has an internal 20kΩ (min) pullup resistor to
Figure 2. MAX16034/MAX16038 Watchdog Timeout Period and
Reset Active Time
10 ______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
BATTON Indicator
(MAX16035/MAX16039 Only)
Power-Fail Comparator
The MAX16033–MAX16040 issue an interrupt (nonmask-
able or regular) to the µP when a power failure occurs.
The power line is monitored by two external resistors con-
nected 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 warn-
ing 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
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 (see Figure 3).
RESETIN Comparator
(MAX16036/MAX16040 Only)
An internal 1.235V reference sets the RESETIN thresh-
old voltage. RESET asserts when the voltage at
RESETIN is below 1.235V. Use the RESETIN function to
monitor a secondary power supply.
PFO low when V
falls below the reset threshold volt-
CC
age (see Figure 1). The MAX160_ _L devices provide
push-pull PFO outputs. The MAX160_ _P devices provide
open-drain PFO outputs.
V
CC
Use the following equations to set the reset threshold
voltage (V
Figure 4):
) of the secondary power supply (see
RTH
V
IN
V
= V
(R1 / R2 + 1)
RTH
REF
MAX16036
MAX16040
R1
R2
where V
= 1.235V. To simplify the resistor selection,
choose a value for R2 and calculate R1.
REF
RESETIN
R1 = R2 [(V / V ) - 1]
RTH
REF
Since the input current at RESETIN is 25nA (max), large
values (up to 1MΩ) can be used for R2 with no signifi-
cant loss in accuracy.
Figure 4. Setting RESETIN Voltage for the
MAX16036/MAX16040
2.4V TO 5.5V
0.1µF
V
CC
BATTON
BATT
OUT
(CEOUT)
CE
CMOS RAM
MAX16035
MAX16039
ADDRESS
A0–A15
(CEIN)
RESET
DECODE
µP
GND
RESET
( ) FOR MAX16035 ONLY
Figure 3. MAX16035/MAX16039 BATTON Driving an External Pass Transistor
______________________________________________________________________________________ 11
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
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 V
.
CC
asserts when V
is below the reset threshold voltage
CC
and for at least 140ms (t ) after V
rises above the
CC
RP
Using a Super Cap as a
Backup Power Source
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.
Super caps are capacitors with extremely high capaci-
tance, 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, allow-
ing a longer backup period. Since V
can be higher
BATT
than V
while V
is above the reset threshold volt-
CC
CC
age, there are no special precautions required when
using these µP supervisors with a super cap.
3–MAX1640
3V OR 3.3V
3V OR 3.3V
V
CC
V
CC
5V
MAX16033–
MAX16040
MAX16033–
MAX16040
1N4148
0.47F
1N4148
0.47F
BATT
BATT
(a)
(b)
Figure 5. Using a Super Cap as a Backup Source
12 ______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
V
CC
START
V
CC
RESET
TO µP
SET
WDI
LOW
MAX16033–
MAX16040
SUBROUTINE
OR PROGRAM LOOP
SET
V+
MR
WDI HIGH
R1
R2
PFI
PFO
GND
RETURN
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 soft-
ware 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 watch-
dog 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 watch-
dog would timeout and reset the µP.
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
Replacing the Backup Battery
such that V
falls to 1.235V when V drops to its trip
IN
PFI
Decouple BATT to GND with a 0.1µF capacitor. The
point, V
. R3 adds hysteresis and is typically more
TRIP
backup power source may be removed while V
CC
than 10 times the value of R1 or R2. The hysteresis win-
dow extends above (V ) and below (V ) the original trip
remains valid without the danger of triggering a reset
pulse. The device does not enter battery-backup mode
H
L
point, V
. Connecting an ordinary signal diode in
TRIP
when V
stays above the reset threshold voltage.
series with R3 as shown in Figure 8b causes the lower
trip point (V ) to coincide with the trip point without hys-
CC
L
TRIP
Power-Fail Comparator
teresis (V
). 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.
Monitoring an Additional Power Supply
Monitor another voltage by connecting a resistive divider
to PFI as shown in Figure 7. The threshold voltage is:
V
= 1.235 (R1 / R2 + 1)
TH(PFI)
where V
is the threshold at which the monitored
TH(PFI)
voltage will trip PFO.
To simplify the resistor selection, choose a value for R2
and calculate R1.
R1 = R2 [(V
/ 1.235) - 1]
TH(PFI)
______________________________________________________________________________________ 13
Low-Power Battery Backup
Circuits in Small µDFN Packages
(a)
(b)
V
CC
V
CC
V
IN
V
IN
MAX16033–
MAX16040
MAX16033–
MAX16040
R1
R2
R1
R2
PFI
PFI
R3
R3
C1
C1
PFO (PUSH-PULL)
GND
PFO (PUSH-PULL)
GND
TO µP
TO µP
PFO
0V
PFO
0V
3–MAX1640
V
IN
V
IN
V
TRIP
V
V
H
V
H
L
V
TRIP
R1
R2
⎛
⎞
R1
R2
⎛
⎞
V
V
V
= V
1 +
V
V
= V
1 +
⎜
PFT
⎜
⎝
⎟
⎠
TRIP
PFT
⎟
⎠
TRIP
⎝
R1
R2
R1
R3
⎛
⎞
R1
R2
R1
R3
R1
R3
⎛
⎞
= (V
+ V
) 1 +
+
= (V
+ V
) 1 +
+
−
V
D
⎜
⎟
⎠
H
L
PFT
PFH
⎜
⎟
⎠
H
PFT
PFH
⎝
⎝
V
V
V
V
= V
TRIP
R1
R2
R1
R3
R1
⎛
⎞
L
= V
1 +
+
−
⎟
V
CC
⎜
PFT
⎝
⎠
R3
= 1.235V
= 12mV
PFT
PFH
V
V
= 1.235V
= 12mV
PFT
= DIODE FORWARD VOLTAGE
PFH
D
Figure 8. (a) Adding Additional Hysteresis to the Power-Fail Comparator. (b) Shifting the Additional Hysteresis above V
TRIP
14 ______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
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
3.0V OR 3.3V
PFI to be above +1.235V, PFO goes high. Ensure V
CC
V
CC
comes up before the negative supply.
Negative-Going V
Transients
CC
The MAX16033–MAX16040 are relatively immune to
short-duration, negative-going V transients.
MAX16033–
MAX16040
R1
R2
CC
PFI
PFO
Resetting the µP when V
experiences only small
CC
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
GND
V-
width of a negative-going V
transient that would not
CC
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 decreas-
PFO
V-
V
TRIP
V
L
0V
es. Typically, a V
transient that goes 100mV below
CC
the reset threshold and lasts for 25µs does not trigger a
reset pulse.
⎡
⎤
⎥
⎦
1
R1
1
R2
V
R1
⎛
⎞
CC
V
V
= R2 V
+ V
+
−
(
)
⎜
⎝
⎟
⎠
TRIP
⎢
PFT
PFH
A 0.1µF bypass capacitor mounted close to V
vides additional transient immunity.
pro-
CC
⎣
⎡
(
⎤
1
1
V
CC
R1
⎛
⎞
= R2 V
+
−
)
⎜
⎟
⎠
L
⎢
PFT
⎥
⎝
R1
R2
⎣
⎦
V
V
= 1.235V
= 12mV
PFT
PFH
Figure 9. Monitoring a Negative Voltage
______________________________________________________________________________________ 15
Low-Power Battery Backup
Circuits in Small µDFN Packages
Device Marking Codes
TOP
MARK
TOP
MARK
TOP
MARK
TOP
MARK
PART
PART
PART
PART
MAX16033LLB23+T
MAX16033LLB26+T
MAX16033LLB29+T
MAX16033LLB31+T
MAX16033LLB44+T
MAX16033LLB46+T
MAX16033PLB23+T
MAX16033PLB26+T
MAX16033PLB29+
MAX16033PLB31+
+ABE
+ABF
+ABG
+ABH
+ABI
MAX16035LLB23+T
MAX16035LLB26+T
MAX16035LLB29+
MAX16035LLB31+
+ACC
+ACD
+ACE
+ACF
+ACG
+ACH
+ACI
MAX16037LLA23+T
MAX16037LLA26+T
MAX16037LLA29+
MAX16037LLA31+
+ABX
+ABY
+ABZ
MAX16039LLA23+T
MAX16039LLA26+T
MAX16039LLA29+T
+ACV
+ACW
+ACX
+ACY
+ACZ
+ADA
+ADB
+ADC
+ADD
+ADE
+ADF
+ADG
+ADH
+ADI
+ACA MAX16039LLA31+T
MAX16035LLB44+T
MAX16037LLA44+T
+ACB
+ACC
+ACD
+ACE
+ACF
+ACG
+ACH
+ACI
MAX16039LLA44+T
MAX16039LLA46+T
MAX16039PLA23+T
MAX16039PLA26+T
MAX16039PLA29+
MAX16039PLA31+
MAX16035LLB46+
MAX16037LLA46+
+ABJ
+ABK
+ABL
+ABM
+ABN
+ABO
+ABP
+ABQ
+ABR
+ABS
+ABT
+ABU
+ABV
+ABW
+ABX
+ABY
ABZ
MAX16035PLB23+T
MAX16035PLB26+T
MAX16035PLB29+
MAX16035PLB31+
MAX16037PLA23+T
MAX16037PLA26+T
MAX16037PLA29+
MAX16037PLA31+
+ACJ
+ACK
+ACL
+ACM
+ACN
+ACO
+ACP
+ACQ
+ACR
+ACS
+ACT
+ACU
+ACV
+ACW
+ACX
+ACY
+ACZ
MAX16033PLB44+T
MAX16035PLB44+T
MAX16037PLA44+T
MAX16039PLA44+T
MAX16033PLB46+
MAX16035PLB46+
MAX16037PLA46+
MAX16039PLA46+
MAX16034LLB23+T
MAX16034LLB26+T
MAX16034LLB29+T
MAX16034LLB31+T
MAX16034LLB44+T
MAX16034LLB46+T
MAX16034PLB23+T
MAX16034PLB26+T
MAX16034PLB29+
MAX16034PLB31+
MAX16036LLB23+T
MAX16036LLB26+T
MAX16036LLB29+
MAX16036LLB31+
MAX16038LLA23+T
MAX16038LLA26+T
MAX16038LLA29+
MAX16038LLA31+
+ACJ
+ACK
+ACL
MAX16040LLA23+T
MAX16040LLA26+T
MAX16040LLA29+T
3–MAX1640
+ADJ
+ADK
+ADL
+ADM
+ADN
+ADO
+ADP
+ADQ
+ADR
+ADS
+ACM MAX16040LLA31+T
+ACN MAX16040LLA44+T
+ACO MAX16040LLA46+T
MAX16036LLB44+T
MAX16038LLA44+T
MAX16036LLB46+
MAX16038LLA46+
MAX16036PLB23+T
MAX16036PLB26+T
MAX16036PLB29+
MAX16036PLB31+
MAX16038PLA23+T
MAX16038PLA26+T
MAX16038PLA29+
MAX16038PLA31+
+ACP
+ACQ
+ACR
+ACS
+ACT
+ACU
MAX16040PLA23+T
MAX16040PLA26+T
MAX16040PLA29+
MAX16040PAL31+
MAX16034PLB44+T
+ACA
+ACB
MAX16036PLB44+T
MAX16038PLA44+T
MAX16040PLA44+T
MAX16034PLB46+
MAX16036PLB46+
MAX16038PLA46+
MAX16040PLA46+
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 µDFN Packages
3–MAX1640
Pin Configurations
TOP VIEW
10
9
8
7
6
10
9
8
7
6
MAX16035
MAX16036
MAX16033
MAX16034
+
+
1
2
3
4
5
1
2
3
4
5
10-µDFN
( ) FOR MAX16036 ONLY
10-µDFN
( ) FOR MAX16034 ONLY
8
1
7
6
5
4
8
1
7
6
5
4
MAX16037
MAX16038
MAX16039
MAX16040
+
+
2
3
2
3
8-µDFN
( ) FOR MAX16038 ONLY
8-µDFN
( ) FOR MAX16040 ONLY
+ DENOTES A LEAD-FREE PACKAGE.
______________________________________________________________________________________ 17
Low-Power Battery Backup
Circuits in Small µDFN Packages
Typical Operating Circuit
2.4V TO 5.5V
0.1µF
REAL-
TIME
CLOCK
CMOS
RAM
CE
V
CC
BATT
ADDITIONAL
DC VOLTAGE
OUT
0.1µF
MAX16033–
MAX16040
R3
R4
RESETIN*
ADDITIONAL
DC VOLTAGE
A0–A15
RESET
PFO
RESET
I/O
3–MAX1640
R1
µP
PFI
I/O
WDI***
CEOUT**
CEIN**
R2
GND
ADDRESS
DECODE
* 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 µDFN Packages
3–MAX1640
Ordering Information (continued)
Reset Threshold Ranges
PIN-
PACKAGE
PKG
CODE
RESET THRESHOLD VOLTAGE (V)
PART*
TEMP RANGE
SUFFIX
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
MAX16035LLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
MAX16035PLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
MAX16036LLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
MAX16036PLB_ _+T -40°C to +85°C 10 µDFN-10 L1022-1
46
44
31
29
26
23
MAX16037LLA_ _+T -40°C to +85°C 8 µDFN-8
MAX16037PLA_ _+T -40°C to +85°C 8 µDFN-8
MAX16038LLA_ _+T -40°C to +85°C 8 µDFN-8
MAX16038PLA_ _+T -40°C to +85°C 8 µDFN-8
MAX16039LLA_ _+T -40°C to +85°C 8 µDFN-8
MAX16039PLA_ _+T -40°C to +85°C 8 µDFN-8
MAX16040LLA_ _+T -40°C to +85°C 8 µDFN-8
MAX16040PLA_ _+T -40°C to +85°C 8 µDFN-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 volt-
age 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 µDFN Packages
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.)
A
b
D
e
N
XXXX
XXXX
XXXX
SOLDER
MASK
COVERAGE
E
PIN 1
0.10x45∞
L
L1
1
SAMPLE
MARKING
PIN 1
INDEX AREA
A
A
7
(N/2 -1) x e)
3–MAX1640
C
L
C
L
b
L
L
A
e
e
A2
EVEN TERMINAL
ODD TERMINAL
A1
PACKAGE OUTLINE,
6, 8, 10L uDFN, 2x2x0.80 mm
1
-DRAWING NOT TO SCALE-
21-0164
A
2
20 ______________________________________________________________________________________
Low-Power Battery Backup
Circuits in Small µDFN Packages
3–MAX1640
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.)
COMMON DIMENSIONS
SYMBOL
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
MAX.
0.80
0.25
0.035
2.05
2.05
0.50
A
A1
A2
D
-
E
L
L1
0.10 REF.
PACKAGE VARIATIONS
PKG. CODE
L622-1
N
6
e
b
(N/2 -1) x e
0.65 BSC
0.50 BSC
0.40 BSC
0.30±0.05 1.30 REF.
0.25±0.05 1.50 REF.
0.20±0.03 1.60 REF.
L822-1
8
L1022-1
10
PACKAGE OUTLINE,
6, 8, 10L uDFN, 2x2x0.80 mm
2
21-0164
A
-DRAWING NOT TO SCALE-
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
© 2007 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
Heaney
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