MAX806SEPA+ [ROCHESTER]
1-CHANNEL POWER SUPPLY MANAGEMENT CKT, PDIP8, 0.300 INCH, PLASTIC, DIP-8;
| 型号： | MAX806SEPA+ |
| 厂家： | 
Rochester Electronics |
| 描述： | 1-CHANNEL POWER SUPPLY MANAGEMENT CKT, PDIP8, 0.300 INCH, PLASTIC, DIP-8 光电二极管 |
| 文件： | 总13页 (文件大小：964K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0243; Rev 2; 12/05
3.0V/3.3V Microprocessor Supervisory Circuits
_______________General Description
____________________________Features
♦ RESET and RESET Outputs
♦ Manual Reset Input
♦ Precision Supply-Voltage Monitor
♦ 200ms Reset Time Delay
♦ Watchdog Timer (1.6s timeout)
–————–
These microprocessor (µP) supervisory circuits reduce
the complexity and number of components required for
power-supply monitoring and battery-control functions
in µP systems. They significantly improve system relia-
bility and accuracy compared to separate ICs or
discrete components.
These devices are designed for use in systems powered
by 3.0V or 3.3V supplies. See the selector guide in the
back of this data sheet for similar devices designed for
5V systems. The suffixes denote different reset threshold
voltages: 3.075V (T), 2.925V (S), and 2.625V (R) (see the
Reset Threshold section in the Detailed Description). All
these parts are available in 8-pin DIP and SO packages.
Functions offered in this series are as follows:
♦ Battery-Backup Power Switching—
Battery Can Exceed VCC in Normal Operation
♦ 40µA VCC Supply Current
♦ 1µA Battery Supply Current
♦ Voltage Monitor for Power-Fail or
Low-Battery Warning
–————–
♦ Guaranteed RESET Assertion to VCC = 1V
♦ 8-Pin DIP and SO Packages
______________Ordering Information
PART**
TEMP RANGE
0°C to +70°C
PIN-PACKAGE
8 Plastic DIP
8 SO
MAX690_CPA
MAX690_CSA
MAX690_C/D
MAX690_EPA
MAX690_ESA
MAX690_MJA
Part
0°C to +70°C
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
MAX690
MAX704
MAX802
MAX804
MAX805
MAX806
4ꢀ
4ꢀ
2ꢀ
2ꢀ
4ꢀ
2ꢀ
75mV
75mV
2ꢀ
0°C to +70°C
Dice*
✓
✓
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
8 Plastic DIP
8 SO
✓
✓
✓
✓
✓
8 CERDIP
2ꢀ
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
75mV
2ꢀ
✓
**These parts offer a choice of reset threshold voltage. Select
the letter corresponding to the desired nominal reset threshold
voltage (T = 3.075V, S = 2.925V, R = 2.625V) and insert it into
the blank to complete the part number.
Devices in PDIP and SO packages are available in both leaded
and lead-free packaging. Specify lead free by adding the +
symbol at the end of the part number when ordering. Lead free
not available for CERDIP package.
________________________Applications
Battery-Powered Computers and Controllers
Embedded Controllers
Intelligent Instruments
Automotive Systems
_________Typical Operating Circuits
Critical µP Power Monitoring
Portable Equipment
REGULATED +3.3V OR +3.0V
V
CC
UNREGULATED
DC
μP
__________________Pin Configuration
0.1μF
V
CC
RESET
RESET
(RESET)
R1
R2
TOP VIEW
NMI
PFO
MAX690T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
I/O LINE
GND
PFI
WDI
1
2
3
4
8
7
6
5
V
VBATT
OUT
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
3.6V
LITHIUM
BATTERY
BUS
RESET (RESET)
WDI <MR>
PFO
V
CC
V
OUT
VBATT
GND
PFI
GND
V
CC
CMOS RAM
GND
0.1μF
0.1μF
DIP/SO
( ) ARE FOR MAX804T/S/R, MAX805T/S/R
( ) ARE FOR MAX804T/S/R, MAX805T/S/R
< > ARE FOR MAX704T/S/R, MAX806T/S/R
See last page for MAX704T/S/R, MAX806T/S/R.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
3.0V/3.3V Microprocessor Supervisory Circuits
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
Continuous Power Dissipation (T = +70°C)
A
V
.........................................................................-0.3V to 6.0V
Plastic DIP (derate 9.09mW/°C above +70°C) ..............727mW
SO (derate 5.88mW/°C above +70°C)...........................471mW
CERDIP (derate 8.00mW/°C above +70°C)...................640mW
Operating Temperature Ranges
CC
VBATT....................................................................-0.3V to 6.0V
All Other Inputs ...................-0.3V to the higher of V or VBATT
Continuous Input Current
CC
V
..................................................................................100mA
MAX690_C_ _/MAX704_C_ _/MAX80_ _C_ _ ........0°C to +70°C
MAX690_E_ _/MAX704_E_ _/MAX80_ _E_ _. .....-40°C to +85°C
MAX690_M_ _/MAX704_M_ _/MAX80_ _M_ _...-55°C to +125°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
CC
VBATT ...............................................................................18mA
GND ..................................................................................18mA
Output Current
–————– –——–
RESET, PFO ....................................................................18mA
V
................................................................................100mA
OUT
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 = 3.17V to 5.5V for the MAX690T/MAX704T/MAX80_T, V = 3.02V to 5.5V for the MAX690S/MAX704S/MAX80_S, V = 2.72V to
CC
CC
CC
5.5V for the MAX690R/MAX704R/MAX80_R; VBATT = 3.6V; T = T
to T
; unless otherwise noted. Typical values are at T = +25°C.)
A
MIN
MAX A
PARAMETER
SYMBOL
CONDITIONS
MIN
1.0
TYP
MAX UNITS
MAX690_C, MAX704_C, MAX80_ _C
MAX690_E/M, MAX704_E/M, MAX80_ _E/M
MAX690_C/E, MAX704_C/E,
5.5
V
Operating Voltage Range,
V
, VBATT (Note 1)
CC
1.1
5.5
40
50
40
50
50
MAX80_ _C/E, V
< 3.6V
CC
MAX690_C/E, MAX704_C/E,
MAX80_ _C/E, V < 5.5V
–—–
MR = V
(MAX704_/
MAX806_)
65
µA
55
CC
CC
V
Supply Current
CC
I
SUPPLY
(excluding I
)
OUT
MAX690_M, MAX704_M,
MAX80_ _M, V < 3.6V
CC
MAX690_M, MAX704_M,
MAX80_ _M, V < 5.5V
70
CC
–—–
MR = V
CC
V
Supply Current in Battery-
CC
(MAX704_/
MAX806_)
V
CC
= 2.0V, VBATT = 2.3V
25
50
µA
Backup Mode (excluding I
)
OUT
MAX690_C/E, MAX704_C/E, MAX80_ _C/E
MAX690_M, MAX704_M, MAX80_ _M
MAX690_C/E, MAX704_C/E, MAX80_ _C/E
MAX690_M, MAX704_M, MAX80_ _M
MAX690_C/E, MAX704_C/E, MAX80_ _C/E,
0.4
0.4
1
10
0.5
5
VBATT Supply Current, Any Mode
(excluding I ) (Note 2)
µA
µA
OUT
0.01
0.01
Battery Leakage Current
(Note 3)
V
-
V
-
CC
CC
I
= 5mA (Note 4)
0.03
0.015
OUT
V
0.3
-
V
0.15
-
CC
MAX690_C/E, MAX704_C/E, MAX80_ _C/E
= 50mA
CC
I
OUT
V
-
V
-
CC
MAX690_M, MAX704_M, MAX80_ _M
= 5mA (Note 4)
CC
V
Output Voltage
V
OUT
I
0.035
0.015
OUT
V
-
V
-
CC
MAX690_M, MAX704_M, MAX80_ _M
CC
I
= 50mA
0.35
0.15
OUT
V
-
V
-
CC
CC
I
= 250µA, V
> 2.5V (Note 4)
OUT
CC
0.0015 0.0006
2
_______________________________________________________________________________________
3.0V/3.3V Microprocessor Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(V = 3.17V to 5.5V for the MAX690T/MAX704T/MAX80_T, V = 3.02V to 5.5V for the MAX690S/MAX704S/MAX80_S, V = 2.72V to
CC
CC
CC
5.5V for the MAX690R/MAX704R/MAX80_R; VBATT = 3.6V; T = T
to T
; unless otherwise noted. Typical values are at T = +25˚C.)
A
MIN
MAX A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
VBATT VBATT
I
I
= 250µA, VBATT = 2.3V
OUT
OUT
- 0.1
- 0.034
V
OUT
in Battery-Backup Mode
V
VBATT
- 0.14
= 1mA, VBATT = 2.3V
VBATT - V
V
> V
> 1.75V (Note 5)
CC
65
25
mV
CC, SW
Battery Switch Threshold,
Falling
V
CC
V
SW
VBATT > V
(Note 6)
CC
2.30
2.40
2.50
V
Battery Switch Threshold,
Rising (Note 7)
This value is identical to the reset threshold,
V rising
CC
V
V
CC
V
V
V
V
V
V
V
V
V
V
V
V
falling
rising
falling
rising
falling
rising
falling
rising
falling
rising
falling
rising
3.00
3.00
3.00
3.00
2.85
2.85
2.88
2.88
2.55
2.55
2.59
2.59
140
3.075
3.085
3.075
3.085
2.925
2.935
2.925
2.935
2.625
2.635
2.625
2.635
200
3.15
3.17
3.12
3.14
3.00
3.02
3.00
3.02
2.70
2.72
2.70
2.72
280
CC
CC
CC
CC
CC
CC
CC
CC
CC
CC
CC
CC
MAX690T/704T/805T
MAX802T/804T/806T
MAX690S/704S/805S
MAX802S/804S/806S
MAX690R/704R/805R
MAX802R/804R/806S
Reset Threshold (Note 8)
V
V
RST
Reset Timeout Period
t
V
< 3.6V
CC
ms
V
WP
V
CC
V
CC
–——– –————–
PFO, RESET Output Voltage
V
I
= 50µA
SOURCE
OH
- 0.3
- 0.05
–——– –————–
PFO, RESET Output Short to
I
V
I
= 3.3V, V
= 0V
180
500
0.3
µV
V
OS
CC
OH
GND Current (Note 4)
= 1.2mA;
–——– –————–
SINK
PFO, RESET, RESET
V
MAX690_/704_/802_/806_, V
MAX804_/805_, V
= V min;
RST
max
0.06
OL
OL
CC
Output Voltage
= V
CC
RST
VBATT = 0V, V
MAX690_C, MAX704_C, MAX80_ _C
= 1.0V, I
= 40µA,
SINK
CC
0.13
0.17
0.3
–——– –————–
PFO, RESET Output Voltage
V
V
VBATT = 0V, V = 1.2V, I = 200µA,
MAX690_E/M, MAX704_E/M, MAX80_ _E/M
CC
SINK
0.3
+1
MAX804_C,
MAX805_C
-1
VBATT = 0V,
V
V
RESET Output Leakage Current
(Note 9)
= V
min;
µA
CC
RST
MAX804_E/M,
MAX805_E/M
= 0V, V
RESET
CC
-10
+10
_______________________________________________________________________________________
3
3.0V/3.3V Microprocessor Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(V = 3.17V to 5.5V for the MAX690T/MAX704T/MAX80_T, V = 3.02V to 5.5V for the MAX690S/MAX704S/MAX80_S, V = 2.72V to
CC
CC
CC
5.5V for the MAX690R/MAX704R/MAX80_R; VBATT = 3.6V; T = T
to T
; unless otherwise noted. Typical values are at T = +25˚C.)
A
MIN
MAX A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
MAX802_C/E, MAX804_C/E,
MAX806_C/E
1.212
1.237
1.262
V
V
V
< 3.6V
falling
CC
PFI
PFI Input Threshold
V
PFT
PFH
MAX690_/MAX704_/MAX805_
1.187
-25
1.237
1.287
MAX690_C/E, MAX704_C/E, MAX80_ _C/E
MAX690_M, MAX704_M, MAX80_ _M
MAX690_C/E, MAX704_C/E,
2
2
25
nA
PFI Input Current
-500
500
10
20
MAX80_ _C/E
PFI Hysteresis, PFI Rising
PFI Input Current
V
V
CC
< 3.6V
mV
MAX690_M, MAX704_M, MAX80_ _M
10
2
25
MAX690_C/E, MAX704_C/E, MAX80_ _C/E
MAX690_M, MAX704_M, MAX80_ _M
-25
25
nA
-500
2
500
V
0.7 x V
CC
IH
–—–
MR Input Threshold
MAX704_/MAX806_ only
MAX704_/MAX806_ only
V
V
0.3 x V
100
IL
MR
MD
CC
CC
–—–
MR Pulse Width
t
t
20
60
60
ns
ns
µA
–—–
MR to Reset Delay
MAX704_/MAX806_ only
–—–
500
350
0.7 x V
–—–
MR Pull-Up Current
MAX704_/MAX806_ only, MR = 0V, V
= 3V
20
CC
V
IH
CC
WDI Input Threshold
WDI Input Current
MAX690_/MAX802_/MAX804_/MAX805_ only
V
V
0.3 x V
-1
IL
MAX690_C/E, MAX802_C/E,
MAX804_C/E, MAX805_C/E
+0.01
+0.01
+1
0V< V
< 5.5V
µA
CC
MAX690_M, MAX802_M,
MAX804_M, MAX805_M
-10
+10
2.24
MAX690/MAX802/MAX804/
MAX805 only
Watchdog Timeout Period
WDI Pulse Width
t
V
CC
< 3.6V
1.12
100
1.60
20
s
WD
MAX690_/MAX802_/MAX804_/MAX805_ only
ns
–—–
Note 1: V supply current, logic input leakage, watchdog functionality (MAX690_/802_/805_/804_), MR functionality
CC
–————–
(MAX704_/806_), PFI functionality, state of RESET (MAX690_/704_/802_/806_), and RESET (MAX804_/805_) tested at
–————–
–——–
VBATT = 3.6V, and V = 5.5V. The state of RESET or RESET and PFO is tested at V = V min.
CC
CC
CC
Note 2: Tested at VBATT = 3.6V, V = 3.5V and 0V. The battery current will rise to 10µA over a narrow transition window around
CC
V
= 1.9V.
CC
Note 3: Leakage current into the battery is tested under the worst-case conditions at V = 5.5V, VBATT = 1.8V and at V = 1.5V,
CC
CC
VBATT= 1.0V.
Note 4: Guaranteed by design.
Note 5: When V > V > VBATT, V
remains connected to V until V drops below VBATT. The V -to-VBATT comparator
CC CC CC
SW
CC
OUT
has a small 25mV typical hysteresis to prevent oscillation. For V < 1.75V (typ), V
switches to VBATT regardless of the
CC
OUT
voltage on VBATT.
Note 6: When VBATT > V > V , V
remains connected to V until V drops below the battery switch threshold (V ).
CC CC SW
CC
SW OUT
Note 7: V
switches from VBATT to V when V rises above the reset threshold, independent of VBATT. Switchover back to
occurs at the exact voltage that causes RESET to go high (on the MAX804_/805_, RESET goes low); however
OUT
CC CC
–————–
V
CC
switchover occurs 200ms prior to reset.
Note 8: The reset threshold tolerance is wider for V rising than for V falling to accommodate the 10mV typical hysteresis, which
CC
CC
prevents internal oscillation.
Note 9: The leakage current into or out of the RESET pin is tested with RESET asserted (RESET output high impedance).
4
_______________________________________________________________________________________
3.0V/3.3V Microprocessor Supervisory Circuits
__________________________________________Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
V
-to-V
vs. TEMPERATURE
ON-RESISTANCE
VBATT-to-V
ON-RESISTANCE
OUT
SUPPLY CURRENT
vs. TEMPERATURE
CC
OUT
vs. TEMPERATURE
5
180
140
50
V
CC
= 0V
VBATT = 3.0V
VBATT = 2V
V
CC
= 5V
4
3
2
1
0
45
40
35
30
25
V
= 2.5V
CC
VBATT = 3V
V
= 3.3V
CC
V
= 3.3V
= 2.5V
CC
100
60
VBATT = 3V
PFI = GND
MR/WDI FLOATING
VBATT = 3.3V
V
= 5V
CC
VBATT = 5V
V
CC
20
–60 –40 –20
0
20 40 60 80 100 120 140
–60 –40 –20
0
20 40 60 80 100 120 140
–60 –40 –20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET TIMEOUT PERIOD
vs. TEMPERATURE
RESET-COMPARATOR PROPAGATION
DELAY vs. TEMPERATURE
BATTERY SUPPLY CURRENT
vs. TEMPERATURE
216
30
10,000
VBATT = 3.0V
100mV OVERDRIVE
V
= 0V
CC
PFI = GND
VBATT = 5V
212
208
204
200
196
26
22
18
14
10
1000
100
10
V
= 5V
CC
VBATT = 3.0V
VBATT = 3V
1
VBATT = 2V
V
= 3.3V
CC
0.1
–60 –40 –20
0
20 40 60 80 100 120 140
–60 –40 –20
0
20 40 60 80 100 120 140
–60 –40 –20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
PFI THRESHOLD
vs. TEMPERATURE
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
1.240
1.004
V
CC
= 3.3V
1.238
1.236
1.234
1.232
1.230
1.002
1.000
0.998
0.996
0.994
V
= 5V
CC
V
= 2.5V
CC
VBATT = 3.0V
VBATT = 3.0V
–60 –40 –20
0
20 40 60 80 100 120 140
–60 –40 –20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
3.0V/3.3V Microprocessor Supervisory Circuits
______________________________________________________________Pin Description
PIN
NAME
FUNCTION
MAX690 MAX704 MAX804
MAX802 MAX806 MAX805
Supply Output for CMOS RAM. When V is above the reset threshold, V
is
OUT
CC
1
1
1
V
OUT
connected to V
through a p-channel MOSFET switch. When V
falls below V
and
SW
CC
CC
VBATT, VBATT connects to V
Main Supply Input
Ground
. Connect to V
if no battery is used.
OUT
CC
2
3
2
3
2
3
V
CC
GND
–——–
falls below V , PFO goes
Power-Fail Input. When PFI is less than V
or when V
PFT
CC
SW
4
5
4
5
4
5
PFI
–——–
low; otherwise, PFO remains high. Connect to ground if unused.
–——–
Power-Fail Output. When PFI is less than V , or V falls below V , PFO goes low;
–——–
PFO
PFT
CC
SW
–——–
otherwise, PFO remains high. Leave open if unused.
Watchdog Input. If WDI remains high or low for 1.6s, the internal watchdog timer runs out
and reset is triggered. The internal watchdog timer clears while reset is asserted or when
WDI sees a rising or falling edge. The watchdog function cannot be disabled.
6
—
6
6
WDI
–—–
Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as
–—–
–—–
MR is low and for 200ms after MR returns high. This active-low input has an internal
70µA pullup current. It can be driven from a TTL or CMOS logic line, or shorted to ground
with a switch. Leave open if unused.
–—–
MR
—
—
Active-Low Reset Output. Pulses low for 200ms when triggered, and stays low whenever
–—–
V
is below the reset threshold or when MR is a logic low. It remains low for 200ms after
–————–
RESET
CC
7
7
—
–—–
either V
rises above the reset threshold, the watchdog triggers a reset, or MR goes
CC
from low to high.
RESET Active-High, Open-Drain Reset Output is the inverse of RESET.
Backup-Battery Input. When V falls below V and VBATT, V
–————–
—
8
—
8
7
8
switches from V to
CC
CC
SW
OUT
VBATT VBATT. When V
rises above the reset threshold, V reconnects to V . VBATT may
OUT CC
CC
exceed V . Connect to V
if no battery is used.
CC
CC
Reset Threshold
_______________Detailed Description
The MAX690T/MAX704T/MAX805T are intended for
3.3V systems with a 5ꢀ power-supply tolerance and a
10ꢀ system tolerance. Except for watchdog faults,
reset will not assert as long as the power supply
remains above 3.15V (3.3V - 5ꢀ). Reset is guaranteed
to assert before the power supply falls below 3.0V.
Reset Output
A microprocessor’s (µP’s) reset input starts the µP in a
known state. These µP supervisory circuits assert reset to
prevent code execution errors during power-up, power-
down, brownout conditions, or a watchdog timeout.
–————–
RESET is guaranteed to be a logic low for 0V < VCC
<
The MAX690S/MAX704S/MAX805S are designed for
3.3V 10ꢀ power supplies. Except for watchdog
faults, they are guaranteed not to assert reset as long
as the supply remains above 3.0V (3.3V - 10ꢀ). Reset
is guaranteed to assert before the power supply falls
below 2.85V (VCC - 14ꢀ).
VRST, provided that VBATT is greater than 1V. Without
–————–
a backup battery, RESET is guaranteed valid for VCC
> 1V. Once VCC exceeds the reset threshold, an
–————–
internal timer keeps RESET low for the reset timeout
–————–
period; after this interval, RESET goes high (Figure 2).
If a brownout condition occurs (VCC dips below the
The MAX690R/MAX704R/MAX805R are optimized for
monitoring 3.0V 10ꢀ power supplies. Reset will not
occur until VCC falls below 2.7V (3.0V - 10ꢀ), but is
guaranteed to occur before the supply falls below
2.59V (3.0V - 14ꢀ).
–————–
–————–
reset threshold), RESET goes low. Each time RESET
is asserted, it stays low for the reset timeout period.
Any time VCC goes below the reset threshold, the
internal timer restarts.
The watchdog timer can also initiate a reset. See the
The MAX802R/S/T, MAX804R/S/T, and MAX806R/S/T
are respectively similar to the MAX690R/S/T,
MAX805R/S/T, and MAX704R/S/T, but with tightened
reset and power-fail threshold tolerances.
Watchdog Input section.
The MAX804_/MAX805_ active-high RESET output is
open drain, and the inverse of the MAX690_/MAX704_/
–————–
MAX802_/MAX806_ RESET output.
6
_______________________________________________________________________________________
3.0V/3.3V Microprocessor Supervisory Circuits
3.0V OR 3.3V
VBATT
BATTERY
SWITCHOVER
CIRCUITRY
V
V
RST
V
OUT
V
CC
V
CC
SW
BATTERY
SWITCHOVER
COMPARATOR
0V
3.0V OR 3.3V
V
OUT
VBATT = 3.6V
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
1.237V
RESET
t
WP
V
SW
COMPARATOR
3.0V OR 3.3V
RESET
1.237V
*
RESET
GENERATOR
WATCHDOG
TIMER
*
WDI
RESET
(RESET)
(RESET)
**
MR
PFI
PFO
POWER-FAIL
COMPARATOR
V
PFT
PFO
VBATT = PFI = 3.6V
= 0mA
I
OUT
( ) MAX804T/S/R, MAX805T/S/R ONLY, RESET EXTERNALLY PULLED UP TO V
* MAX690T/S/R, MAX802T/S/R, MAX804T/S/R, MAX805T/S/R ONLY
** MAX704T/S/R, MAX806T/S/R ONLY
CC
( ) MAX804T/S/R, MAX805T/S/R ONLY
Figure 1. Block Diagram
Figure 2. Timing Diagram
Watchdog Input
Power-Fail Comparator
The PFI input is compared to an internal reference. If
(MAX690_/802_/804_/805_)
–——–
PFI is less than VPFT, PFO goes low. The power-fail
The watchdog circuit monitors the µP’s activity. If the µP
does not toggle the watchdog input (WDI) within 1.6sec,
a reset pulse is triggered. The internal 1.6sec timer is
cleared by either a reset pulse or by a transition (low-to-
high or high-to-low) at WDI. If WDI is tied high or low, a
RESET pulse is triggered every 1.8sec (tWD plus tRS).
comparator is intended for use as an undervoltage
detector to signal a failing power supply. However, the
comparator does not need to be dedicated to this
function because it is completely separate from the rest
of the circuitry.
–————–
–——–
The power-fail comparator turns off and PFO goes low
As long as reset is asserted, the timer remains cleared
and does not count. As soon as reset is deasserted,
the timer starts counting. Unlike the 5V MAX690 family,
the watchdog function cannot be disabled.
when VCC falls below VSW on power-down. The power-
fail comparator turns on as VCC crosses VSW on
power-up. If the comparator is not used, connect PFI to
–——–
–——–
ground and leave PFO unconnected. PFO may be
–—–
connected to MR on the MAX704_/MAX806_ so that a
low voltage on PFI will generate a reset (Figure 5b).
_______________________________________________________________________________________
7
3.0V/3.3V Microprocessor Supervisory Circuits
Backup-Battery Switchover
__________Applications Information
In the event of a brownout or power failure, it may be
These µP supervisory circuits are not short-circuit
necessary to preserve the contents of RAM. With a
protected. Shorting VOUT to ground—excluding power-
backup battery installed at VBATT, the devices auto-
up transients such as charging a decoupling
matically switch RAM to backup power when VCC
capacitor—destroys the device. Decouple both VCC
falls.
and VBATT pins to ground by placing 0.1µF capacitors
as close to the device as possible.
This family of µP supervisors (designed for 3.3V and 3V
systems) doesn’t always connect VBATT to VOUT when
VBATT is greater than VCC. VBATT connects to VOUT
(through a 140Ω switch) when VCC is below VSW and
VBATT is greater than VCC, or when VCC falls below
1.75V (typ) regardless of the VBATT voltage. This is
done to allow the backup battery (e.g., a 3.6V lithium
Using a SuperCap
as a Backup Power Source
SuperCaps™ are capacitors with extremely high
capacitance values (e.g., order of 0.47F) for their size.
Figure 3 shows two ways to use a SuperCap as a
backup power source. The SuperCap may be
connected through a diode to the 3V input (Figure 3a)
or, if a 5V supply is also available, the SuperCap may
be charged up to the 5V supply (Figure 3b) allowing a
longer backup period. Since VBATT can exceed VCC
while VCC is above the reset threshold, there are no
special precautions when using these µP supervisors
with a SuperCap.
cell) to have a higher voltage than VCC
.
Switchover at VSW (2.40V) ensures that battery-backup
mode is entered before VOUT gets too close to the 2.0V
minimum required to reliably retain data in CMOS RAM.
Switchover at higher VCC voltages would decrease
backup-battery life. When VCC recovers, switchover is
deferred until VCC rises above the reset threshold
(VRST) to ensure a stable supply. VOUT is connected to
V
CC through a 3Ω PMOS power switch.
Operation without a Backup
Power Source
These µP supervisors were designed for battery-
backed applications. If a backup battery is not used,
connect both VBATT and VOUT to VCC, or use a
different µP supervisor such as the MAX706T/S/R or
MAX708T/S/R.
Manual Reset
–—–
A logic low on MR asserts reset. Reset remains asserted
–—–
–—–
while MR is low, and for tWP (200ms) after MR returns
high. This input has an internal 70µA pull-up current, so
–—–
it can be left open if it is not used. MR can be driven with
TTL or CMOS logic levels, or with open-drain/collector
outputs. Connect a normally open momentary switch
Replacing the Backup Battery
The backup power source can be removed while VCC
remains valid, if VBATT is decoupled with a 0.1µF
–—–
from MR to GND to create a manual-reset function;
external debounce circuitry is not required.
capacitor to ground, without danger of triggering
–————–
RESET/R E S E T. As long as VCC stays above VSW
battery-backup mode cannot be entered.
,
Table 1. Input and Output Status in
Battery-Backup Mode
Adding Hysteresis
to the Power-Fail Comparator
The power-fail comparator has a typical input
hysteresis of 10mV. This is sufficient for most applica-
tions where a power-supply line is being monitored
through an external voltage divider (see the Monitoring
an Additional Power Supply section).
PIN NAME
STATUS
Connected to VBATT through an internal
140Ω switch
V
OUT
V
Disconnected from V
OUT
CC
The power-fail comparator is disabled when
< V
PFI
V
If additional noise margin is desired, connect a resistor
–——–
CC
SW
–——–
PFO
between PFO and PFI as shown in Figure 4a. Select
Logic low when V
< V
or PFI < V
SW PFT
CC
the ratio of R1 and R2 such that PFI sees 1.237V (VPFT
)
WDI
The watchdog timer is disabled
Disabled
when VIN falls to its trip point (VTRIP). R3 adds the
hysteresis and will typically be more than 10 times the
value of R1 or R2. The hysteresis window extends both
above (VH) and below (VL) the original trip point (VTRIP).
–—–
MR
–————–
RESET
Low logic
RESET
VBATT
High impedance
Connected to V
OUT
SuperCap is a trademark of Baknor Industries.
8
_______________________________________________________________________________________
3.0V/3.3V Microprocessor Supervisory Circuits
3.0V OR 3.3V
+5V
3.0V OR
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
V
OUT
V
TO STATIC
RAM
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
V
3.3V
V
TO STATIC
RAM
CC
CC
OUT
1N4148
1N4148
0.47F
VBATT
RESET
(RESET)
TO μP
VBATT
RESET
(RESET)
TO μP
0.47F
GND
GND
(
) ARE FOR MAX804T/S/R, MAX805T/S/R ONLY
a
b
(
) ARE FOR MAX804T/S/R, MAX805T/S/R ONLY
Figure 3. Using a SuperCap as a Backup Power Source
–————–
Connecting an ordinary signal diode in series with R3,
as shown in Figure 4b, causes the lower trip point (VL)
to coincide with the trip point without hysteresis (VTRIP),
example, the RESET output is driven high and the µP
wants to pull it low, indeterminate logic levels may
result. To correct this, connect a 4.7kΩ resistor
–————–
so the entire hysteresis window occurs above VTRIP
.
between the RESET output and the µP reset I/O, as in
–————–
This method provides additional noise margin without
compromising the accuracy of the power-fail threshold
when the monitored voltage is falling. It is useful for
accurately detecting when a voltage falls past a
threshold.
Figure 6. Buffer the RESET output to other system
components.
Negative-Going V
Transients
CC
While issuing resets to the µP during power-up, power-
down, and brownout conditions, these supervisors are
relatively immune to short-duration negative-going VCC
transients (glitches). It is usually undesirable to reset
the µP when VCC experiences only small glitches.
The current through R1 and R2 should be at least 1µA to
ensure that the 25nA (max over extended temperature
range) PFI input current does not shift the trip point. R3
should be larger than 10kΩ so it does not load down the
–——–
Figure 7 shows maximum transient duration vs. reset-
comparator overdrive, for which reset pulses are not
generated. The graph was produced using negative-
going VCC pulses, starting at 3.3V and ending below
the reset threshold by the magnitude indicated (reset
comparator overdrive). The graph shows the maximum
pulse width a negative-going VCC transient may
typically have without causing a reset pulse to be
issued. As the amplitude of the transient increases
(i.e., goes farther below the reset threshold), the
maximum allowable pulse width decreases. Typically,
a VCC transient that goes 100mV below the reset
threshold and lasts for 40µs or less will not cause a
reset pulse to be issued.
PFO pin. Capacitor C1 adds additional noise rejection.
Monitoring an Additional Power Supply
These µP supervisors can monitor either positive or
negative supplies using a resistor voltage divider to
–——–
PFI. PFO can be used to generate an interrupt to the
–—–
–——–
µP (Figure 5). Connecting PFO to MR on the MAX704
and MAX806 causes reset to assert when the
monitored supply goes out of tolerance. Reset remains
–—–
–——–
asserted as long as PFO holds MR low, and for 200ms
–——–
after PFO goes high.
Interfacing to µPs
with Bidirectional Reset Pins
µPs with bidirectional reset pins, such as the Motorola
A 100nF bypass capacitor mounted close to the VCC
pin provides additional transient immunity.
68HC11 series, can contend with the MAX690_/
–————–
MAX704_/MAX802_/MAX806_ RESET output. If, for
_______________________________________________________________________________________
9
3.0V/3.3V Microprocessor Supervisory Circuits
V
IN
V
IN
R
R
1
2
V
V
CC
R
R
CC
1
2
PFI
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
PFI
R
3
R
3
C1*
C1*
PFO
PFO
GND
GND
*OPTIONAL
*OPTIONAL
TO μP
TO μP
PFO
V
PFO
0V
V
0V
V
IN
IN
V
V
H
V
V
TRIP
L
H
0V
0V
V
TRIP
R + R
1
2
(
)
R + R
1
= V
2
TRIP
PFT
R
V
= V
PFT
2
(
)
TRIP
WHERE V
V
= 1.237V
= 10mV
R
2
PFT
PFH
1
1
1
(V
V )
D
CC -
R
+
+
–
V
= R (V + V
)
PFH
1
1
1
(
)
H
1
PFT
V
= (V + V ) (R )
H
PFT
PFH
1
R
R
R
+
+
(
)
1
2
3
3
R
R
R
3
1
2
WHERE V
V
= 1.237V
= 10mV
PFT
PFH
1
1
1
V
CC
+
+
–
V = R
L
V
(
)
1
PFT
R
R
R
R
3
1
2
3
V
= DIODE FORWARD VOLTAGE DROP
D
L
a
b
V
= V
TRIP
Figure 4. a) Adding Additional Hysteresis to the Power-Fail Comparator b) Shifting the Additional Hysteresis above V
PFT
V
IN
3.0V OR 3.3V
3.0V OR 3.3V
V
V
CC
CC
R
R
R
R
1
2
1
2
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
GND
PFI
PFO
PFI
PFO
MR
*
GND
V-
V
CC
V
CC
PFO
PFO
V
V-
IN
V
V
TRIP
V
V
H
L
0V
TRIP
1
1
V
CC
R + R
1
2
+
–
V
= R (V + V
PFT
)
* MAX704T/S/R,
MAX806T/S/R ONLY
TRIP
2
PFH
1
V
V
= V
PFT
(
)
CC
TRIP
(
)
1
R
R
R
1
1
2
R
2
WHERE V
V
= 1.237V
= 10mV
PFT
PFH
1
V
R + R
2
+
–
V = R (V )
PFT
L
2
= (V + V
PFT
)
(
)
H
PFH
(
)
R
1
R
R
1
2
NOTE: V
TRIP
IS NEGATIVE
R
2
a
b
Figure 5. Using the Power-Fail Comparator to Monitor an Additional Power Supply
10 ______________________________________________________________________________________
3.0V/3.3V Microprocessor Supervisory Circuits
_Typical Operating Circuits (cont.)
BUFFERED RESET TO OTHER SYSTEM COMPONENTS
3.0V OR 3.3V
V
V
OUT
RAM
CC
V
V
CC
CC
VBATT
μP
0.1µF
3.6V
0.1µF
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX806T/S/R
0.1µF
MAX704T/S/R
MAX806T/S/R
4.7kΩ
RESET
RESET
MR
RESET
GND PFI
μP
GND
GND
Figure 6. Interfacing to µPs with Bidirectional Reset I/O
100
80
V
CC
= 3.3V
T
= +25°C
A
60
40
20
0
10
100
1000
- V ) (mV)
RESET COMPARATOR OVERDRIVE (V
RST
CC
Figure 7. Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
______________________________________________________________________________________ 11
3.0V/3.3V Microprocessor Supervisory Circuits
_Ordering Information (continued)
___________________Chip Topography
V
VBATT
PART**
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
OUT
MAX704_CPA
MAX704_CSA
MAX704_C/D
MAX704_EPA
MAX704_ESA
MAX704_MJA
MAX802_CPA
MAX802_CSA
MAX802_C/D
MAX802_EPA
MAX802_ESA
MAX802_MJA
MAX804_CPA
MAX804_CSA
MAX804_C/D
MAX804_EPA
MAX804_ESA
MAX804_MJA
MAX805_CPA
MAX805_CSA
MAX805_C/D
MAX805_EPA
MAX805_ESA
MAX805_MJA
MAX806_CPA
MAX806_CSA
MAX806_C/D
MAX806_EPA
MAX806_ESA
MAX806_MJA
Dice*
V
CC
8 Plastic DIP
8 SO
0.110"
(2.794mm)
8 CERDIP
8 Plastic DIP
8 SO
GND
RESET
(RESET)
Dice*
WDI
[MR]
8 Plastic DIP
8 SO
8 CERDIP
8 Plastic DIP
8 SO
Dice*
PFI PFO
0.080"
8 Plastic DIP
8 SO
8 CERDIP
8 Plastic DIP
8 SO
(2.032mm)
( ) ARE FOR MAX804T/S/R, MAX805T/S/R.
[ ] ARE FOR MAX704T/S/R, MAX806T/S/R.
Dice*
8 Plastic DIP
8 SO
TRANSISTOR COUNT: 802;
8 CERDIP
8 Plastic DIP
8 SO
SUBSTRATE IS CONNECTED TO THE HIGHER OF
VCC OR VBATT, AND MUST BE FLOATED IN ANY
HYBRID DESIGN.
Dice*
8 Plastic DIP
8 SO
8 CERDIP
*Contact factory for dice specifications.
**These parts offer a choice of reset threshold voltage. Select
the letter corresponding to the desired nominal reset threshold
voltage (T = 3.075V, S = 2.925V, R = 2.625V) and insert it into
the blank to complete the part number.
Devices in PDIP and SO packages are available in both leaded
and lead-free packaging. Specify lead free by adding the +
symbol at the end of the part number when ordering. Lead free
not available for CERDIP package.
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.
12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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