MAX6365 [MAXIM]
SOT23, Low-Power レP Supervisory Circuits with Battery Backup and Chip-Enable Gating; SOT23封装，低功耗微处理器监控电路，带有备用电池和片选控制
| 型号： | MAX6365 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | SOT23, Low-Power レP Supervisory Circuits with Battery Backup and Chip-Enable Gating |
| 文件： | 总15页 (文件大小：221K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1658; Rev 1; 6/01
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
General Description
Features
The MAX6365–MAX6368 supervisory circuits simplify
power-supply monitoring, battery-backup control func-
tions, and memory write protection in microprocessor
(µP) systems. The circuits significantly improve the size,
accuracy, and reliability of modern systems with an ultra-
small integrated solution.
o Low +1.2V Operating Supply Voltage (V or V
o Precision Monitoring of +5.0V, +3.3V, +3.0V, and
+2.5V Power-Supply Voltages
)
CC
BATT
o On-Board Gating of Chip-Enable Signals, 1.5ns
Propagation Delay
o Debounced Manual Reset Input (MAX6365)
o Watchdog Timer, 1.6s Timeout (MAX6366)
o Battery-On Output Indicator (MAX6367)
o Auxiliary User-Adjustable RESET IN (MAX6368)
o Low 10µA Quiescent Supply Current
o Three Available Output Structures
These devices perform four basic system functions:
1) Provide a µP reset output during V
supply power-
CC
up, power-down, and brownout conditions.
2) Internally control V to backup-battery switching to
CC
maintain data or low-power operation for CMOS
RAM, CMOS µPs, real-time clocks, and other digital
logic when the main supply fails.
Push-Pull RESET
Open-Drain RESET
Open-Drain RESET
3) Provide memory write protection through internal
chip-enable gating during supply or processor faults.
o RESET/RESET Valid Down to 1.2V Guaranteed
4) Include one of the following options: a manual reset
input (MAX6365), a watchdog timer function
(MAX6366), a battery-on output (MAX6367), or an
auxiliary user-adjustable reset input (MAX6368).
(V
CC
or V
)
BATT
o Power-Supply Transient Immunity
o 150ms min Reset Timeout Period
o Miniature 8-Pin SOT23 Package
The MAX6365–MAX6368 operate from V
supply volt-
CC
ages as low as 1.2V. The factory preset reset threshold
voltages range from 2.32V to 4.63V (see Ordering
Information). In addition, each part is offered in three
reset output versions: push-pull active low, open-drain
active low, or open-drain active high (see Selector
Guide). The MAX6365–MAX6368 are available in minia-
ture 8-pin SOT23 packages.
Ordering Information
PIN-
PACKAGE
PART*
TEMP. RANGE
MAX6365LKA__-T
MAX6365PKA__-T
MAX6365HKA__-T
MAX6366LKA__-T
MAX6366PKA__-T
MAX6366HKA__-T
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
Applications
Critical µP/µC Power
Monitoring
Portable/Battery-
Powered Equipment
Fax Machines
Set-Top Boxes
POS Equipment
Industrial Control
Computers/Controllers
MAX6367LKA__-T
MAX6367PKA__-T
MAX6367HKA__-T
MAX6368LKA__-T
MAX6368PKA__-T
MAX6368HKA__-T
Pin Configurations
TOP VIEW
RESET, RESET
1
2
3
4
8
7
6
5
CE OUT
BATT
OUT
*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. SOT parts
come in tape-and-reel only and must be ordered in 2500-piece
increments. See Device Marking Codes for a complete parts list,
including SOT top marks and standard threshold versions. See
Selector Guide for a listing of device features.
CE IN
GND
MR
MAX6365
V
CC
SOT23
Pin Configurations continued at end of data sheet.
Typical Operating Circuit appears at end of data sheet.
________________________________________________________________ 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.
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
ABSOLUTE MAXIMUM RATINGS
Terminal Voltages (with respect to GND)
GND ...............................................................................75mA
Output Current
V
CC
, BATT, OUT.......................................................-0.3V to +6V
RESET (open drain), RESET (open drain)................-0.3V to +6V
BATT ON, RESET (push-pull), RESET IN,
OUT ...............................Short-Circuit Protected for up to 10s
RESET, RESET, BATT ON, CE OUT...............................20mA
WDI, CE IN, CE OUT ...........................-0.3V to (V
MR ..............................................................-0.3V to (V
+ 0.3V)
+ 0.3V)
Continuous Power Dissipation (T = +70°C)
OUT
CC
A
8-Pin SOT23 (derate 8.75mW/°C above +70°C)........700mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature .....................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Input Current
V
V
Peak ..............................................................................1A
Continuous .............................................................250mA
CC
CC
BATT Peak .....................................................................250mA
BATT Continuous .............................................................40mA
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
= +2.4V to +5.5V, V
= +3.0V, CE IN = V , reset not asserted, T = -40°C to +85°C. Typical values are at T = +25°C,
CC
BATT
CC
A
A
unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
, V
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Voltage Range
(Note 2)
V
No load
0
5.5
V
CC BATT
V
V
V
= 2.8V
= 3.6V
= 5.5V
10
12
15
30
35
CC
CC
CC
Supply Current
I
No load, V
> V
TH
µA
CC
CC
(Excluding I
)
OUT
50
T = +25°C
1
A
Supply Current in Battery-
Backup Mode (Excluding I
V
V
= 2.8V,
BATT
I
µA
µA
BACK
)
= 0
OUT
CC
T
= -40°C to +85°C
3
A
T = +25°C
A
-0.1
-1.0
0.02
0.02
3.1
3.7
4.6
5.5V > V
+ 0.2V)
> (V
BATT
CC
BATT Standby Current
I
BATT
T = -40°C to +85°C
A
V
V
V
= 4.75V, I
= 3.15V, I
= 2.38V, I
= 150mA
CC
CC
CC
OUT
OUT
OUT
V
to OUT On-Resistance
R
ON
= 65mA
= 25mA
Ω
CC
V
V
V
-
-
-
BATT
0.2
V
V
V
= 4.5V, I
= 20mA
= 10mA
BATT
BATT
BATT
OUT
OUT
Output Voltage in Battery-
Backup Mode
BATT
0.15
V
= 3.0V, I
V
OUT
BATT
0.15
= 2.25V, I
= 5mA
OUT
Power-up
Power-down
20
Battery-Switchover Threshold
(V - V
V
V
< V
CC
mV
SW
TH
)
CC
BATT
-20
MAX636__KA46
MAX636__KA44
MAX636__KA31
MAX636__KA29
MAX636__KA26
MAX636__KA23
4.50
4.25
3.00
2.85
2.55
2.25
4.63
4.38
3.08
2.93
2.63
2.32
4.75
4.50
3.15
3.00
2.70
2.38
Reset Threshold
V
V
TH
V
Falling Reset Delay
t
V falling at 10V/ms
CC
20
µs
CC
RD
2
_______________________________________________________________________________________
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
ELECTRICAL CHARACTERISTICS (continued)
(V
= +2.4V to +5.5V, V
= +3.0V, CE IN = V , reset not asserted, T = -40°C to +85°C. Typical values are at T = +25°C,
CC
BATT
CC
A
A
unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
Reset Active Timeout Period
t
150
280
ms
V
RP
I
V
= 1.6mA,
> 2.1V
SINK
0.3
CC
Reset asserted,
V
OL
V
= 0
BATT
I
V
= 100µA,
SINK
> 1.2V
RESET Output Voltage
0.4
0.3
CC
✕
Reset not asserted
(MAX636_L only)
I
V
= 500µA,
TH(MAX)
0.8
SOURCE
V
OH
> V
V
CC
CC
I
V
= 1.6mA,
SINK
V
Reset not asserted
OL
> V
CC
TH (MAX)
✕
I
V
= 1mA,
> 1.8V
0.7
V
SOURCE
Reset not asserted,
RESET Output Voltage
V
µA
V
CC
CC
V
= 0
BATT
V
OH
(MAX636_H only)
(Note 3)
✕
I
V
= 200µA,
> 1.2V
0.8
V
SOURCE
CC
CC
RESET Output Leakage Current
I
MAX636_P and MAX636_H only
1
LKG
MANUAL RESET (MAX6365 only)
✕
0.3
V
IL
V
CC
MR Input Voltage
✕
0.7
V
V
IH
CC
Pullup Resistance
20
1
kΩ
µs
ns
ns
Minimum Pulse Width
Glitch Immunity
V
V
= 3.3V
= 3.3V
100
120
CC
CC
MR to Reset Delay
WATCHDOG (MAX6366 only)
Watchdog Timeout Period
Minimum WDI Input Pulse Width
t
1.00
100
1.65
2.25
s
WD
t
ns
WDI
✕
0.3
V
IL
V
CC
WDI Input Voltage
V
✕
0.7
V
V
IH
CC
WDI Input Current
BATT ON (MAX6367 only)
Output Voltage
-1.0
1.0
0.4
µA
V
I
= 3.2mA, V = 2.1V
BATT
V
OL
SINK
Sink current, V
= 5V
60
30
mA
CC
Output Short-Circuit Current
Source current, V
> 2V
10
100
µA
BATT
_______________________________________________________________________________________
3
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
ELECTRICAL CHARACTERISTICS (continued)
(V
= +2.4V to +5.5V, V
= +3.0V, CE IN = V , reset not asserted, T = -40°C to +85°C. Typical values are at T = +25°C,
CC
BATT
CC
A
A
unless otherwise noted.) (Note 1)
PARAMETER
RESET IN (MAX6368 only)
RESET IN Threshold
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
V
1.185
1.235 1.285
V
RTH
RESET IN Leakage Current
RESET IN to Reset Delay
CHIP-ENABLE GATING
CE IN Leakage Current
CE IN to CE OUT Resistance
0.01
1.5
25
nA
µs
V
= 50mV, RESET IN falling
OD
Reset asserted
1
100
2.0
7
µA
Ω
Reset not asserted (Note 4)
Reset asserted, CE OUT = 0
20
0.75
1.5
2
CE OUT Short-Circuit Current
mA
V
V
= 4.75V
= 3.15V
CC
CC
CE IN to CE OUT Propagation
Delay
50Ω source,
C
ns
= 50pF
LOAD
9
✕
V
V
= 5V, V
> V
, I
= 100µA
0.8
V
CC
CC
BATT SOURCE
CC
CE OUT Output Voltage High
Reset-to-CE OUT Delay
V
V
-
BATT
0.1
= 0, V
> 2.2V, I
SOURCE
= 1µA
CC
BATT
12
µs
Note 1: All devices are 100% production tested at T = +25°C. Limits over temperature are guaranteed by design.
A
Note 2: V
can be 0 anytime, or V
can go down to 0 if V
is active (except at startup).
BATT
CC
BATT
Note 3: RESET is pulled up to OUT. Specifications apply for OUT = V
or OUT = BATT.
CC
Note 4: The chip-enable resistance is tested with V
= V and CE IN = V /2.
TH(MAX) CC
CC
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
BATTERY SUPPLY CURRENT
(BACKUP MODE) vs. TEMPERATURE
SUPPLY CURRENT
vs. TEMPERATURE (NO LOAD)
16
BATT-TO-OUT ON-RESISTANCE
vs. TEMPERATURE
1.2
1.0
0.8
0.6
0.4
0.2
0
8
7
6
5
4
3
2
1
0
V
= 0
CC
V
V
= 5.0V
CC
= 0
15
14
13
12
11
10
9
BATT
V
= 2.0V
BATT
V
BATT
= 2.8V
V
= 2.8V
= 5.0V
BATT
V
= 2.0V
BATT
V
BATT
I
= 25mA
= 0
OUT
CC
V
8
-40 -20
0
20
40
60
80
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
V
TO OUT ON-RESISTANCE
vs. TEMPERATURE
RESET TIMEOUT PERIOD
vs. TEMPERATURE
V
TO RESET PROPAGATION DELAY
vs. TEMPERATURE
CC
CC
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
210
205
200
195
190
135
120
105
90
75
60
45
30
15
0
V
FALLING
CC
V
I
= 2.3V
CC
= 25mA
OUT
0.25V/ms
V
OUT
= 3.0V
= 65mA
CC
I
1V/ms
20
V
I
= 4.5V
CC
= 150mA
OUT
10V/ms
0
-40 -20
0
20
40
60
80
-40
-20
0
20
40
60
80
-40 -20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET THRESHOLD
vs. TEMPERATURE
BATTERY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
5.0
4.5
4.0
3.5
3.0
2.5
2.0
400
350
300
250
200
150
100
50
10
9
8
7
6
5
4
3
2
1
0
V
= 2.93V
TH
MAX636_ 46 (V = 4.63V)
TH
V
= 2.8V
= 2.5V
BATT
MAX636_ 46
(V = 4.63V)
TH
V
BATT
RESET OCCURS
ABOVE CURVE
V
= 2.3V
BATT
MAX636_ 26 (V = 2.63V)
TH
MAX636_ 26
(V = 2.63V)
TH
0
-40 -20
0
20
40
60
80
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5
(V)
1
10
100
1000
10,000
TEMPERATURE (°C)
V
RESET THRESHOLD OVERDRIVE V - V (mV)
CC
TH CC
_______________________________________________________________________________________
5
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
MAX6368
MAX6368
RESET IN THRESHOLD
vs. TEMPERATURE
1.236
RESET IN TO RESET PROPAGATION DELAY
vs. TEMPERATURE
CHIP-ENABLE PROPAGATION DELAY
vs. CE OUT LOAD CAPACITANCE
5
4
3
2
1
0
V
= 50mV
OD
CE IN = 0 TO V
CC
2.8
2.5
2.2
1.9
1.6
1.3
1.0
DRIVER SOURCE
IMPEDANCE = 50Ω
V
V
= 3V
= 5V
CC
1.235
1.234
CC
0
50
100
(pF)
150
200
-40 -20
0
20
40
60
80
-40 -20
0
20
40
60
80
TEMPERATURE (°C)
C
TEMPERATURE (°C)
LOAD
MAX6366
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
CE IN TO CE OUT ON-RESISTANCE
vs. TEMPERATURE
25
20
15
10
5
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
V
= 3.0V
= 5.0V
CC
V
CC
V
V
= 5.0V
BATT
CC
V
V
= V /2
CC
= 0
CE IN
BATT
= 0
0
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
6
_______________________________________________________________________________________
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Pin Description
PIN
NAME
FUNCTION
Active-High Reset Output. RESET asserts high continuously when V is below the reset threshold (V ),
CC
TH
MR is low, or RESET IN is low. It asserts in pulses when the internal watchdog times out. RESET remains
asserted for the reset timeout period (t ) after V rises above the reset threshold, after the manual reset
RESET
RP
CC
input goes from low to high, after RESET IN goes high, or after the watchdog triggers a reset event.
RESET is an open-drain active-high reset output.
1
Active-Low Reset Output. RESET asserts low continuously when V
is below the reset threshold
CC
(V ), the manual reset input is low, or RESET IN is low. It asserts low in pulses when the internal
TH
watchdog times out. RESET remains asserted low for the reset timeout period (t ) after V
RP
CC
RESET
rises above the reset threshold, after the manual reset input goes from low to high, after RESET
IN goes high, or after the watchdog triggers a reset event. The MAX636_L is an active-low push-
pull output, while the MAX636_P is an active-low open-drain output.
2
3
CE IN
Chip-Enable Input. The input to chip-enable gating circuitry. Connect to GND or OUT if not used.
Ground
GND
MAX6365 Manual-Reset Input. Maintaining logic low on MR asserts a reset. Reset output
remains asserted as long as MR is low and for the reset timeout period (t ) after MR transitions
RP
MR
from low to high. Leave unconnected, or connect to V if not used. MR has an internal 20kΩ
CC
pullup to V
.
CC
MAX6366 Watchdog Input. 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 whenever reset asserts or whenever WDI sees
RP
WD
WDI
4
a rising or falling edge (Figure 2).
BATT ON
RESET IN
MAX6367 Battery-On Output. BATT ON goes high when in battery backup mode.
MAX6368 Reset Input. When RESET IN falls below 1.235V, reset asserts. Reset output remains
asserted as long as RESET IN is low and for at least t after RESET IN goes high.
RP
Supply Voltage, 1.2V to 5.5V. Reset asserts when V
drops below the reset threshold voltage
CC
5
6
V
(V ). Reset remains asserted until V
rises above V and for at least t after V
rises
CC
CC
TH
CC
TH
RP
above V .
TH
Output. OUT sources from V
is below the reset threshold.
when not in reset and from the greater of V
or BATT when V
CC CC
CC
OUT
Backup-Battery Input. When V
falls below the reset threshold, OUT switches to BATTif V
BATT
CC
is 20mV greater than V . When V
hysteresis prevents repeated switching if V
rises 20mV above V
, OUT switches to V . The 40mV
BATT CC
7
8
BATT
CC
CC
falls slowly.
CC
Chip-Enable Output. CE OUT goes low only when CE IN is low and reset is not asserted. If CE
IN is low when reset is asserted, CE OUT will stay low for 12µs (typ) or until CE IN goes high,
whichever occurs first.
CE OUT
_______________________________________________________________________________________
7
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Functional Diagram
BATT ON (MAX6367 ONLY)
1.235V
MAX6365
MAX6366
MAX6367
MAX6368
V
CC
OUT
CHIP-ENABLE
OUTPUT
CONTROL
BATT
CE IN
CE OUT
20k
RESET
GENERATOR
MR
RESET
(RESET)
(MAX6365 ONLY)
WATCHDOG
TRANSITION
DETECTOR
WDI
WATCHDOG
TIMER
(MAX6366 ONLY)
RESET IN
(MAX6368 ONLY)
1.235V
GND
CMOS RAM in the event of a power failure. During nor-
mal 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. All of these devices use a series trans-
mission gate from CE IN to CE OUT. The 2ns propaga-
tion delay from CE IN to CE OUT allows the devices to
be used with most µPs and high-speed DSPs.
Detailed Description
The Typical Operating Circuit shows a typical connec-
tion for the MAX6365–MAX6368. OUT powers the static
random-access memory (SRAM). If V
is greater than
CC
the reset threshold (V ), or if V
is lower than V
TH
CC
TH
but higher than V
, V
is connected to OUT. If
BATT
CC
V
is lower than V
and V
is less than V
,
BATT
CC
TH
CC
BATT is connected to OUT. OUT supplies up to 150mA
from V . In battery-backup mode, an internal MOSFET
CC
During normal operation, CE IN is connected to CE
OUT through a low on-resistance transmission gate.
This is valid when reset is not asserted. If CE IN is high
when reset is asserted, CE OUT remains high regard-
less of any subsequent transitions on CE IN during the
reset event.
connects the backup battery to OUT. The on-resistance
of the MOSFET is a function of backup-battery voltage
and is shown in the BATT-to-OUT On-Resistance vs.
Temperature graph in the Typical Operating Char-
acteristics.
If CE IN is low when reset is asserted, CE OUT is held
low for 12µs to allow completion of the read/write oper-
ation (Figure 1). After the 12µs delay expires, the CE
Chip-Enable Signal Gating
The MAX6365–MAX6368 provide internal gating of CE
signals to prevent erroneous data from being written to
8
_______________________________________________________________________________________
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
OUT goes high and stays high regardless of any sub-
Table 1. Input and Output Status in
Battery-Backup Mode
sequent transitions on CE IN during the reset event.
When CE OUT is disconnected from CE IN, CE OUT is
actively pulled up to OUT.
PIN
STATUS
Disconnected from OUT
The propagation delay through the chip-enable circuit-
ry depends on both the source impedance of the drive
to CE IN and the capacitive loading at CE OUT. The
chip-enable propagation delay is production tested
from the 50% point of CE IN to the 50% point of CE
OUT, using a 50Ω driver and 50pF load capacitance.
Minimize the capacitive load at CE OUT to minimize
propagation delay, and use a low-output-impedance
driver.
V
CC
OUT
Connected to BATT
Connected to OUT. Current drawn from
BATT
the battery is less than 1µA (at V
=
BATT
2.8V, excluding I
) when V = 0.
OUT
CC
RESET/RESET
BATT ON
Asserted
High state
MR, RESET IN,
CE IN, WDI
Inputs ignored
CE OUT
Connected to OUT
Backup-Battery Switchover
In a brownout or power failure, it may be necessary to
preserve the contents of the RAM. With a backup bat-
tery installed at BATT, the MAX6365–MAX6368 auto-
Manual Reset Input (MAX6365 Only)
Many µP-based products require manual reset capabili-
ty, allowing the user or external logic circuitry to initiate a
reset. For the MAX6365, a logic low on MR asserts reset.
Reset remains asserted while MR is low and for a mini-
mum of 150ms (t ) after it returns high. MR has an inter-
nal 20kΩ pullup resistor to V . This input can be driven
with TTL/CMOS logic levels or with open-drain/collector
outputs. Connect a normally open momentary switch
from MR to GND to create a manual reset function; exter-
nal debounce circuitry is not required. If MR is driven
from long cables or the device is used in a noisy environ-
ment, connect a 0.1µF capacitor from MR to GND to pro-
vide additional noise immunity.
matically switch the RAM to backup power when V
CC
falls. The MAX6367 has a BATT ON output that goes
high in battery-backup mode. These devices require
two conditions before switching to battery-backup
mode:
RP
CC
1) V
2) V
must be below the reset threshold.
CC
CC
must be 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
only voltage source is on BATT. OUT only powers up
from V
at startup.
CC
V
OR BATT
RESET
CC
THRESHOLD V
TH
CE IN
CE OUT
*
RESET-TO-CE OUT DELAY (12µs)
t
t
RD
RD
t
t
RP
RP
RESET
RESET
*
IF CE IN GOES HIGH BEFORE RESET ASSERTS,
CE OUT GOES HIGH WITHOUT DELAY AS
CE IN GOES HIGH.
Figure 1. Reset and Chip-Enable Timing
_______________________________________________________________________________________
9
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
WDI
t
t
RP
RP
t
t
WD
WD
RESET
t
t
= WATCHDOG TIMEOUT PERIOD
WD
= RESET TIMEOUT PERIOD
RP
Figure 2. MAX6366 Watchdog Timeout Period and Reset Active Time
R1 = R2 [(V
/ V
) - 1]
Watchdog Input (MAX6366 Only)
The watchdog monitors µP activity through the watch-
dog input (WDI). If the µP becomes inactive, reset
asserts. To use the watchdog function, 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
RTH
REF
Since the input current at RESET IN is 25nA (max),
large values (up to 1MΩ) can be used for R2 with no
significant loss in accuracy. For example, in the Typical
Operating Circuit, the MAX6368 monitors two supply
voltages. To monitor the secondary 5V logic or analog
supply with a 4.60V nominal programmed reset thresh-
old, choose R2 = 100kΩ, and calculate R1 = 273kΩ.
than the watchdog timeout period (t ), the internal
WD
watchdog timer runs out and a reset pulse is triggered
for the reset timeout period (t ). The internal watchdog
RP
timer clears whenever reset asserts or whenever WDI
sees a rising or falling edge. If WDI remains in either a
high or low state, a reset pulse asserts periodically after
Reset Output
A µP’s reset input starts the µP in a known state. The
MAX6365–MAX6368 µP supervisory circuits assert a
reset to prevent code-execution errors during power-
up, power-down, and brownout conditions. RESET is
guaranteed to be a logic low or logic high, depending
on the device chosen (see Ordering Information).
RESET or RESET asserts when V
threshold and for at least 150ms (t ) after V
above the reset threshold. RESET or RESET also
asserts when MR is low (MAX6365) and when RESET IN
is less than 1.235V (MAX6368). The MAX6366 watch-
dog function will cause RESET (or RESET) to assert in
pulses following a watchdog timeout (Figure 2).
every t
(Figure 2). Leave WDI unconnected to dis-
WD
able the watchdog function.
BATT ON Indicator (MAX6367 Only)
is below the reset
CC
BATT ON is a push-pull output that drives high when in
battery-backup mode. BATT ON typically sinks 3.2mA
at 0.1V saturation voltage. In battery-backup mode, this
terminal sources approximately 10µA from OUT. Use
BATT ON to indicate battery-switchover status or to
supply base drive to an external pass transistor for
higher current applications (Figure 3).
rises
CC
RP
Applications Information
RESET IN Comparator (MAX6368 Only)
RESET IN is compared to an internal 1.235V reference.
If the voltage at RESET IN is less than 1.235V, reset
asserts. Use the RESET IN comparator as an undervolt-
age detector to signal a failing power supply or as a
secondary power-supply reset monitor.
Operation Without
a Backup Power Source
The MAX6365–MAX6368 provide battery-backup func-
tions. If a backup power source is not used, connect
BATT to GND and OUT to V
.
CC
To program the reset threshold (V
power supply, use the following (see Typical Operating
Circuit):
) of the secondary
RTH
Watchdog Software Considerations
One way to help the watchdog timer monitor the 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 4
shows a flow diagram in which the I/O driving the
V
RTH
= V
(R1 / R2 + 1)
REF
where V
= 1.235V. To simplify the resistor selection,
REF
choose a value for R2 and calculate R1:
10 ______________________________________________________________________________________
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
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 subrou-
tine, the problem would be quickly corrected.
starting at V
and ending below the reset threshold by
CC
the magnitude indicated (reset threshold overdrive).
The graph shows the maximum pulse width that a neg-
ative-going V
transient can typically have without
CC
triggering a reset pulse. As the amplitude of the tran-
sient increases (i.e., goes further below the reset
threshold), the maximum allowable pulse width
Replacing the Backup Battery
is above V , the backup power source can
TH
When V
CC
decreases. Typically, a V
below the reset threshold and lasts for 30µs will not trig-
ger a reset pulse.
transient that goes 100mV
CC
be removed without danger of triggering a reset pulse.
The device does not enter battery-backup mode when
V
CC
stays above the reset threshold voltage.
A 0.1µF bypass capacitor mounted close to the V
pin provides additional transient immunity.
CC
Negative-Going V
CC
Transients
These supervisors are relatively immune to short-dura-
tion, negative-going V transients. Resetting the µP
CC
desirable.
CC
when V
experiences only small glitches is usually not
The Typical Operating Characteristics section has a
Maximum Transient Duration vs. Reset Threshold
Overdrive graph for which reset is not asserted. The
graph was produced using negative-going V
pulses,
CC
+2.4V TO +5.5V
START
0.1µF
SET
WDI
LOW
BATT ON
OUT
V
CC
BATT
CE OUT
CE
MAX6367
SUBROUTINE
OR PROGRAM LOOP
SET WDI
CMOS RAM
ADDRESS
DECODE
CE IN
HIGH
A0–A15
µP
GND
RESET
RESET
RETURN
Figure 3. MAX6367 BATT ON Driving an External Pass
Transistor
END
Figure 4. Watchdog Flow Diagram
______________________________________________________________________________________ 11
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Reset Threshold Ranges
RESET THRESHOLD RANGES (V)
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
46
44
31
29
26
23
Device Marking Codes
PART
TOP MARK
AAAM
AAAL
AAAK
AAAJ
PART
TOP MARK
AABK
AABJ
PART
TOP MARK
MAX6365LKA23
MAX6365LKA26
MAX6365LKA29*
MAX6365LKA31
MAX6365LKA44
MAX6365LKA46*
MAX6365PKA23
MAX6365PKA26
MAX6365PKA29*
MAX6365PKA31
MAX6365PKA44
MAX6365PKA46*
MAX6365HKA23
MAX6365HKA26
MAX6365HKA29
MAX6365HKA31
MAX6365HKA44
MAX6365HKA46*
MAX6366LKA23
MAX6366LKA26
MAX6366LKA29*
MAX6366LKA31
MAX6366LKA44
MAX6366LKA46*
MAX6366PKA23
MAX6366PKA26
MAX6366PKA29*
MAX6366PKA31
MAX6366PKA44
MAX6366PKA46*
MAX6366HKA23
MAX6366HKA26
MAX6366HKA29
MAX6366HKA31
MAX6366HKA44
MAX6366HKA46*
MAX6367LKA23
MAX6367LKA26
MAX6367LKA29*
MAX6367LKA31
MAX6367LKA44
MAX6367LKA46*
MAX6367PKA23
MAX6367PKA26
MAX6367PKA29*
MAX6367PKA31
MAX6367PKA44
MAX6367PKA46*
MAX6367HKA23
MAX6367HKA26
MAX6367HKA29
MAX6367HKA31
MAX6367HKA44
MAX6367HKA46*
MAX6368LKA23
MAX6368LKA26
MAX6368LKA29*
MAX6368LKA31
MAX6368LKA44
MAX6368LKA46*
MAX6368PKA23
MAX6368PKA26
MAX6368PKA29*
MAX6368PKA31
MAX6368PKA44
MAX6368PKA46*
MAX6368HKA23
MAX6368HKA26
MAX6368HKA29
MAX6368HKA31
MAX6368HKA44
MAX6368HKA46*
AACI
AACH
AACG
AACF
AACE
AACD
AACO
AACN
AACM
AACL
AACK
AACJ
AABI
AABH
AABG
AABF
AABQ
AABP
AABO
AABN
AABM
AABL
AABW
AABV
AABU
AABT
AABS
AABR
AACC
AACB
AACA
AABZ
AABY
AABX
AAAI
AAAH
AAAS
AAAR
AAAQ
AAAP
AAAO
AAAN
AAAY
AAAX
AAAW
AAAV
AAAU
AAAT
AABE
AABD
AABC
AABB
AABA
AAAZ
AACU
AACT
AACS
AACR
AACQ
AACP
AADA
AACZ
AACY
AACX
AACW
AACV
*These standard versions are available in small quantities through Maxim Distribution. Sample stock is generally held on
standard versions only. Contact factory for availability of nonstandard versions.
12 ______________________________________________________________________________________
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Selector Guide
MANUAL
RESET
INPUT
RESET
RESET
WATCH-
DOG
INPUT
CHIP-
ENABLE
GATING
RESET
OPEN-
DRAIN
BATT
ON
RESET
IN
PART
PUSH-
PULL
OPEN-
DRAIN
MAX6365LKA__
MAX6365PKA__
MAX6365HKA__
MAX6366LKA__
MAX6366PKA__
MAX6366HKA__
MAX6367LKA__
MAX6367PKA__
MAX6367HKA__
MAX6368LKA__
MAX6368PKA__
MAX6368HKA__
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Pin Configurations (continued)
TOP VIEW
RESET, RESET
CE IN
1
2
3
4
8
7
6
5
CE OUT
BATT
OUT
RESET, RESET
CE IN
1
2
3
4
8
7
6
5
CE OUT
BATT
OUT
MAX6367
MAX6366
GND
GND
BATT ON
V
WDI
V
CC
CC
SOT23
SOT23
RESET, RESET
1
2
3
4
8
7
6
5
CE OUT
BATT
OUT
CE IN
GND
MAX6368
RESET IN
V
CC
SOT23
______________________________________________________________________________________ 13
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Typical Operating Circuit
+2.4V TO +5.5V
CMOS
RAM
REAL-
TIME
CLOCK
0.1µF
CE
V
CC
OUT
BATT
0.1µF
MAX6366
MAX6368
SECONDARY
DC VOLTAGE
A0–A15
RESET
RESET
R1
R2
µP
I/O
WDI**
RESET IN*
CE IN
CE OUT
ADDRESS
DECODE
GND
*RESET IN APPLIES TO MAX6368 ONLY.
**WDI APPLIES TO MAX6366 ONLY.
Chip Information
TRANSISTOR COUNT: 729
PROCESS: CMOS
14 ______________________________________________________________________________________
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
Package Information
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 ____________________ 15
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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