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68HC11/Bidirectional-Compatible
µP Reset Circuit
General Description
The MAX6314 low-power CMOS microprocessor (µP)
supervisory circuit is designed to monitor power
supplies in µP and digital systems. The MAX6314’s
RESET
output is bidirectional, allowing it to be directly
connected to µPs with bidirectional reset inputs, such
as the 68HC11. It provides excellent circuit reliability
and low cost by eliminating external components and
adjustments. The MAX6314 also provides a debounced
manual reset input.
This device performs a single function: it asserts a reset
signal whenever the V
CC
supply voltage falls below a
preset threshold or whenever manual reset is asserted.
Reset remains asserted for an internally programmed
interval (reset timeout period) after V
CC
has risen above
the reset threshold or manual reset is deasserted.
The MAX6314 comes with factory-trimmed reset
threshold voltages in 100mV increments from 2.5V
to 5V. Preset timeout periods of 1ms, 20ms, 140ms,
and 1120ms (minimum) are also available. The device
comes in a SOT143 package.
For a µP supervisor with an open-drain reset pin, see
the MAX6315 data sheet.
Features
♦
Small SOT143 Package
♦
RESET
Output Simplifies Interface to
Bidirectional Reset I/Os
♦
Precision Factory-Set V
CC
Reset Thresholds:
100mV Increments from 2.5V to 5V
♦
±1.8% Reset Threshold Accuracy at T
A
= +25°C
♦
±2.5% Reset Threshold Accuracy Over Temp.
♦
Four Reset Timeout Periods Available:
1ms, 20ms, 140ms, or 1120ms (minimum)
♦
Immune to Short V
CC
Transients
♦
5µA Supply Current
♦
Pin-Compatible with MAX811
MAX6314*
Ordering Information
PART
†
MAX6314US50D1-T
MAX6314US49D1-T
MAX6314US48D1-T
MAX6314US47D1-T
MAX6314US46D1-T
MAX6314US45D1-T
NOMINAL
V
TH
(V)
5.00
4.90
4.80
4.70
4.63
4.50
MIN t
RP
(ms)
1
1
1
1
1
1
TOP
MARK
††
AA_ _
AB_ _
AC_ _
AD_ _
AE_ _
AF_ _
________________________Applications
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
†
The MAX6314 is available in a SOT143 package, -40°C to
+85°C temperature range.
††
The first two letters in the package top mark identify the part,
while the remaining two letters are the lot tracking code.
Typical Operating Circuit
V
CC
V
CC
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Ordering Information continued at end of data sheet.
LASER-
TRIMMED
RESISTORS
V
CC
68HC11**
Pin Configuration
TOP VIEW
µP
4.7kΩ
RESET
MR
RESET
CIRCUITRY
GND
1
4
V
CC
MAX6314
RESET
RESET
MAX6314
GND
2
3
MR
SOT143
**OR OTHER
µC/µP
WITH BIDIRECTIONAL RESET I/O PIN.
*Patents
Pending
1
________________________________________________________________
Maxim Integrated Products
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.
68HC11/Bidirectional-Compatible
µP Reset Circuit
MAX6314
ABSOLUTE MAXIMUM RATINGS
V
CC
........................................................................-0.3V to +6.0V
All Other Pins..............................................-0.3V to (V
CC
+ 0.3V)
Input Current (V
CC
) .............................................................20mA
Output Current (RESET)......................................................20mA
Rate of Rise (V
CC
) ...........................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
SOT143 (derate 4mW/°C above +70°C) .......................320mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
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
CC
= +2.5V to +5.5V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Operating Voltage Range
V
CC
Supply Current
Reset Threshold (Note 1)
Reset Threshold Tempco
V
CC
to Reset Delay
Reset Timeout Period
SYMBOL
V
CC
I
CC
V
TH
∆V
TH
/°C
V
CC
= falling at 1mV/µs
MAX6314US_ _D1-T
MAX6314US_ _D2-T
MAX6314US_ _D3-T
MAX6314US_ _D4-T
1
20
140
1120
0.8
2.4
0.3 x V
CC
0.7 x V
CC
1
100
500
32
V
CC
> 4.25V, I
SINK
= 3.2mA
RESET
Output Voltage
V
OL
V
CC
> 2.5V, I
SINK
= 1.2mA
V
CC
> 1.2V, I
SINK
= 0.5mA
V
CC
> 1.0V, I
SINK
= 80µA
RESET
INTERNAL PULLUP
Transition Flip-Flop Setup Time (Note 2)
Active Pullup Enable Threshold
RESET
Active Pullup Current
RESET
Pullup Resistance
RESET
Output Rise Time
(Note 3)
t
S
V
CC
= 5V
V
CC
= 5V
C
LOAD
= 120pF
C
LOAD
= 250pF
C
LOAD
= 200pF
C
LOAD
= 400pF
0.4
4.2
V
CC
= 3V
t
R
V
CC
= 5V
20
4.7
400
0.9
5.2
333
666
333
666
63
100
0.4
0.3
0.3
0.3
ns
V
mA
kΩ
V
µs
ns
ns
kΩ
V
CONDITIONS
T
A
= 0°C to +70°C
V
CC
= 5.5V, no load
V
CC
= 3.6V, no load
T
A
= +25°C
T
A
= -40°C to +85°C
MIN
1.0
5
4
V
TH
60
35
1.4
28
200
1570
TYP
MAX
5.5
12
10
V
TH
+ 1.8%
V
TH
+ 2.5%
UNITS
V
µA
V
ppm/°C
µs
2
40
280
2240
ms
V
TH
- 1.8%
V
TH
- 2.5%
t
RP
MANUAL RESET INPUT
MR
Input Threshold
MR
Minimum Input Pulse
MR
Glitch Rejection
MR
to Reset Delay
MR
Pullup Resistance
V
IL
V
IH
V
IL
V
IH
V
TH
> 4.0V
V
TH
< 4.0V
ns
V
Note 1:
The MAX6314 monitors V
CC
through an internal, factory-trimmed voltage divider that programs the nominal reset threshold.
Factory-trimmed reset thresholds are available in 100mV increments from 2.5V to 5V (see
Ordering and Marking Information).
Note 2:
This is the minimum time
RESET
must be held low by an external pull-down source to set the active pull-up flip-flop.
Note 3:
Measured from
RESET
V
OL
to (0.8 x V
CC
), R
LOAD
=
∞.
2
_______________________________________________________________________________________
68HC11/Bidirectional-Compatible
µP Reset Circuit
MAX6314
__________________________________________Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
PULLUP CHARACTERISTICS
MAX6314-01
+5V
4.7kΩ
74HC05
SUPPLY CURRENT vs. TEMPERATURE
MAX6314-02
6
4.7kΩ PULL-UP
2V/div
5
SUPPLY CURRENT (µA)
4
3
V
CC
= 3V
2
1
0
V
CC
= 1V
V
CC
= 5V
100pF
+5V
74HC05
V
CC
RESET
MAX6314
MAX6314 PULL-UP
2V/div
100pF
MR
GND
INPUT
5V/div
200ns/div
-50
-30
-10
10
30
50
70
90
TEMPERATURE (°C)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6314-03
POWER-DOWN RESET DELAY
vs. TEMPERATURE
MAX6314-04
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE (V
CC
RISING)
NORMALIZED RESET TIMEOUT PERIOD
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
MAX6314-05
6
5
SUPPLY CURRENT (µA)
4
3
T
A
= +25°C
2
T
A
= -40°C
1
0
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
50
POWER-DOWN RESET DELAY (µs)
V
CC
FALLING AT 1mV/µs
40
V
TH
= 4.63V
30
V
TH
= 3.00V
1.04
T
A
= +85°C
20
10
0
-50
-30
-10
10
30
50
70
90
TEMPERATURE (°C)
-50
-30
-10
10
30
50
70
90
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE (V
CC
FALLING)
MAX6314-06
MAXIMUM TRANSIENT DURATION
vs. RESET COMPARATOR OVERDRIVE
MAX6314-07
RESET PULLUP TIME
vs. TEMPERATURE
MAX6314-08
1.006
NORMALIZED RESET THRESHOLD
1.004
1.002
1.000
0.998
0.996
0.994
-50
-30
-10
10
30
50
70
100
MAXIMUM TRANSIENT DURATION (µs)
T
A
= +25°C
RESET OCCURS
ABOVE CURVE
600
500
RESET PULL-UP-TIME (ns)
C
L
= 390pF
400
300
200
C
L
= 100pF
100
80
60
V
TH
= 4.63V
40
20
V
TH
= 3.00V
0
0
10
100
1000
-50
-30
-10
10
30
50
70
90
RESET COMP. OVERDRIVE, V
TH
- V
CC
(mV)
TEMPERATURE (°C)
90
TEMPERATURE (°C)
_______________________________________________________________________________________
3
68HC11/Bidirectional-Compatible
µP Reset Circuit
MAX6314
______________________________________________________________Pin Description
PIN
1
2
NAME
GND
RESET
Ground
Active-Low Complementary Output. In addition to the normal n-channel pulldown,
RESET
has a p-channel
pullup transistor in parallel with a 4.7kΩ resistor to facilitate connection to µPs with bidirectional resets. See
the
Reset Output
section.
Manual Reset Input. A logic low on
MR
asserts reset. Reset remains asserted as long as
MR
is low, and for
the reset timeout period (t
RP
) after the reset conditions are terminated. Connect to V
CC
if not used.
Supply Voltage and Reset Threshold Monitor Input
FUNCTION
3
4
MR
V
CC
V
CC
LASER-
TRIMMED
RESISTORS
MAX6314
VREF
V
CC
63kΩ
RESET
GENERATOR
V
CC
2µs ONE-SHOT
TRANSITION
FLIP-FLOP
R
FF
S
Q
4.7kΩ
MR
RESET
ACTIVE PULLUP
ENABLE COMPARATOR
0.5V
GND
Figure 1. Functional Diagram
4
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