MAXIM MAX7705

19-0151; Rev 0; 6/93
µP Power-Supply Monitor
with Reset
FEATURE
♦ No External Components
♦ Low Cost
♦ Precise Reset Threshold
♦ 280ms Power-On Reset Delay
♦ 8-Pin DIP and SO Packages
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX7705
TL7705
MAX7705CPA
0°C to +70°C
8 Plastic DIP
0
3
MAX7705CSA
0°C to +70°C
8 SO
MAX7705C/D
0°C to +70°C
MAX7705EPA
-40°C to +85°C
8 Plastic DIP
MAX7705ESA
-40°C to +85°C
8 SO
No. of External
Components Required
Operating Supply
Current
____________________________Features
+5V
65µA
1.8mA
+3V
35µA
1.8mA
Power-Supply Glitch
Immunity
Yes
No
Guaranteed Minimum
Reset Delay
Yes
No
Dice*
* Contact factory for dice specifications.
________________________Applications
Minimum Component Count, Low-Cost
Processor Systems
__________Typical Operating Circuit
__________________Pin Configuration
VCC
MAX7705
TOP VIEW
*
N.C. 1
8
VCC
N.C. 2
7
N.C.
6
N.C.
5
RESET
N.C. 3
MAX7705
GND 4
DIP/SO
*
1
N.C.
VCC 8
2
N.C.
N.C. 7
3
N.C.
N.C. 6
4
GND
RESET 5
µP
*
RESET
GND
* THE MAX7705 ELIMINATES THREE EXTERNAL
COMPONENTS REQUIRED BY THE TL7705.
________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
1
MAX7705
_______________General Description
In applications with microprocessors (µPs) that have a
RESET input, the MAX7705 is functionally and socket
compatible with the TL7705, but requires no external
components. It provides power-supply glitch immunity
and a guaranteed power-up reset delay, while typically
consuming 1/27th the power from a +5V supply.
The MAX7705 monitors the power supply in µP and digital
systems. The RESET output is valid for VCC down to 1V.
The device offers excellent circuit reliability and low cost
by eliminating external components and adjustments.
A system reset is provided during power-up, powerdown, and brownout conditions. When VCC is below the
reset threshold, RESET is low and holds the µP in reset.
RESET will go high 280ms after VCC rises above the
reset threshold. The MAX7705 is available in 8-pin DIP
and SO packages.
MAX7705
µP Power-Supply Monitor
with Reset
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
VCC ......................................................................-0.3V to 6.0V
RESET....................................................-0.3V to (VCC + 0.3V)
Input Current, VCC ..............................................................20mA
Output Current, RESET ......................................................20mA
Rate-of-Rise, VCC ............................................................100V/µs
Continuous Power Disipation (TA = +70°C)
Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW
SO (derate 5.88mW/°C above +70°C) .........................471mW
Operating Temperature Ranges:
MAX7705C_ _ .....................................................0°C to +70°C
MAX7705E_ _ ..................................................-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
(VCC = full range, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
MAX7705C
1.0
5.5
MAX7705E
1.2
5.5
VCC Range
V
MAX7705C, VCC < 5.5V
65
150
MAX7705E, VCC < 5.5V
65
200
4.65
4.75
Supply Current
µA
RESET Threshold
4.50
VCC to RESET Delay
VCC = reset threshold max to reset threshold min
Reset Active Timeout Period
VCC = reset threshold max, VCC rising
RESET Output Voltage
20
140
280
V
µs
560
ISINK = 3.2mA, VCC = reset threshold min
0.4
ISINK = 50µA, VCC ≥ 1.0V, MAX7705C
0.3
ISINK = 100µA, VCC ≥ 1.2V, MAX7705E
0.4
ISOURCE = 800µA, VCC ≥ reset threshold max
2
UNITS
ms
V
VCC - 1.5
_______________________________________________________________________________________
µP Power-Supply Monitor
with Reset
POWER-UP RESET DELAY
vs. TEMPERATURE
SUPPLY CURRENT
vs. TEMPERATURE
100
250
200
150
100
80
60
-60
-20
20
60
VCC = +5V
VCC = +4V
40
VCC = +3V
0
0
4.660
NO LOAD
20
50
4.665
NOTE: STEADY-STATE SUPPLY
CURRENT IS INDEPENDENT
OF RESET OUTPUT STATUS
100
VCC = +2V
4.650
4.645
4.640
4.630
-20
20
60
100
TEMPERATURE (°C)
TEMPERATURE (°C)
4.655
4.635
VCC = +1V
-60
RESET THRESHOLD (V)
VCC = RESET THRESHOLD MAX
VCC RISING
SUPPLY CURRENT (µA)
POWER-UP RESET DELAY (ms)
300
RESET THRESHOLD
vs. TEMPERATURE
-60
-20
20
60
100
TEMPERATURE (°C)
POWER-DOWN RESET DELAY
vs. TEMPERATURE
POWER-DOWN RESET DELAY (µs)
24
20
16
12
8
4
VCC STEPPED FROM RESET THRESHOLD
MAX TO RESET THRESHOLD MIN
0
-60
-20
20
60
100
TEMPERATURE (°C)
______________________________________________________________Pin Description
PIN
NAME
FUNCTION
1,2,3,6,7
N.C.
No Connection. There is no internal connection to these pins.
4
GND
Ground
5
RESET
8
VCC
Reset Output remains low while VCC is below the reset threshold, and for 280ms after VCC rises above the
reset threshold.
+5V Supply Voltage
_______________________________________________________________________________________
3
MAX7705
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAXIMUM TRANSIENT DURATION (µs)
MAX7705
µP Power-Supply Monitor
with Reset
150
TA = +25°C
100
50
10ns
0
10
100
1k
10k
RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)
Figure 1. Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
__________Applications Information
Replacing the TL7705 with a MAX7705
in an Existing Design
The MAX7705 has only three active pins: VCC, GND,
and RESET. When using a TL7705 with a µP that has
a RESET input, simply plug the MAX7705 into the
same socket and omit the RESET pull-up resistor, reset
timing capacitor, and reference bypass capacitor (see
the Typical Operating Circuit).
The MAX7705 monitors the VCC voltage and asserts
reset whenever VCC falls below the reset threshold.
The reset power-up delay is created by an internal
fixed oscillator. This delay is 100% tested and guaranteed over the full temperature range. The RESET output both sources and sinks current (see RESET Output
Voltage in the Electrical Characteristics).
Negative-Going VCC Transients
The MAX7705 asserts RESET during power-up,
power-down, and brownout conditions. However, it is
relatively immune to short-duration negative-going VCC
transients (glitches).
Figure 1 shows typical transient duration vs. reset comparator overdrive for which the MAX7705 does not generate a reset pulse. The graph was generated using a
fast-edge, negative-going pulse applied to VCC, starting
1.5V above the actual reset threshold and ending below
the reset threshold by the magnitude indicated (reset
comparator overdrive). It indicates the typical maxi-
4
mum pulse width a negative-going VCC transient may
have without causing a reset pulse to be issued. As
the magnitude of the transient increases (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 40µs
or less will not cause a reset pulse to be issued.
A 0.1µF bypass capacitor mounted as close as possible
to pin 2 (VCC) provides additional transient immunity.
Ensuring a Valid RESET Output
Down to VCC = 0V
When VCC falls below 1V, the MAX7705 RESET output
no longer sinks current; it becomes high impedance.
Therefore, high-impedance CMOS logic inputs connected to the RESET output can drift to indeterminate
voltages. In most applications this presents no problem, as µP and other circuitry is generally inoperative
with VCC below 1V. In applications where the RESET
output must be valid down to 0V, adding a pull-down
resistor to the RESET pin (as shown in Figure 2) will
cause any stray leakage currents to flow to ground,
holding RESET low. The resistance value of R1 is not
critical. It should be about 100kΩ, which is large
enough not to load RESET and small enough to pull
RESET to ground.
VCC
MAX7705
RESET
R1
GND
Figure 2. RESET Valid to VCC = Ground Circuit
_______________________________________________________________________________________
µP Power-Supply Monitor
with Reset
µPs with bidirectional reset pins, such as Motorola’s
68HC11 series, can contend with the MAX7705 reset
output. If, for example, the MAX7705 RESET output is
asserted high and the µP wants to pull it low, an indeterminate logic level may result. To correct this, connect a 4.7kΩ resistor between the MAX7705 RESET
output and the µP reset I/O, as in Figure 3. Buffer the
RESET signal to other system components.
BUFFER
BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS
VCC
VCC
MAX7705
RESET
GND
___________________Chip Topography
V CC
RESET
0.045"
(1.143mm)
GND
0.056"
(1.422mm)
µP
4.7k
RESET
TRANSISTOR COUNT = 380;
SUBSTRATE CONNECTED TO VCC.
GND
Figure 3. Interfacing to µPs with Bidirectional Reset I/O
_______________________________________________________________________________________
5
MAX7705
Interfacing to µPs with
Bidirectional Reset Inputs
MAX7705
µP Power-Supply Monitor
with Reset
_______________________________________________________Package Information
DIM
D1
A
A1
A2
A3
B
B1
C
D
D1
E
E1
e
eA
eB
L
α
E
E1
D
A3
A
A2
L
A1
MILLIMETERS
MIN
MAX
–
5.08
0.38
–
3.18
4.45
1.40
2.03
0.41
0.56
1.27
1.65
0.20
0.30
8.84
9.91
0.13
0.89
7.62
8.26
6.10
7.11
2.54 BSC
7.62 BSC
–
10.16
2.92
3.81
0˚
15˚
21-324A
α
C
e
B1
B
6
INCHES
MAX
MIN
0.200
–
–
0.015
0.175
0.125
0.080
0.055
0.022
0.016
0.065
0.050
0.012
0.008
0.390
0.348
0.035
0.005
0.325
0.300
0.280
0.240
0.100 BSC
0.300 BSC
0.400
–
0.150
0.115
15˚
0˚
eA
8-PIN PLASTIC
DUAL-IN-LINE
PACKAGE
eB
_______________________________________________________________________________________
µP Power-Supply Monitor
with Reset
DIM
E
A
A1
B
C
D
E
e
H
h
L
α
H
INCHES
MAX
MIN
0.069
0.053
0.010
0.004
0.019
0.014
0.010
0.007
0.197
0.189
0.157
0.150
0.050 BSC
0.244
0.228
0.020
0.010
0.050
0.016
8˚
0˚
MILLIMETERS
MIN
MAX
1.35
1.75
0.10
0.25
0.35
0.49
0.19
0.25
4.80
5.00
3.80
4.00
1.27 BSC
5.80
6.20
0.25
0.50
0.40
1.27
0˚
8˚
21-325A
h x 45˚
D
α
A
0.127mm
0.004in.
e
A1
C
L
8-PIN PLASTIC
SMALL-OUTLINE
PACKAGE
B
_______________________________________________________________________________________
7
MAX7705
__________________________________________ Package Information (continued)
MAX7705
µP Power-Supply Monitor
with Reset
µ P Supervisory Circuits
Part
Number
Minimum
Nominal
Reset
Reset
Pulse
Threshold Width
(V)
(ms)
Nominal
Watchdog
Timeout Backup- CE Period
Battery Write
(sec)
Switch Protect
MAX690A/692A
4.65/4.40
140
1.6
✔
MAX691A/693A
4.65/4.40
140/adj.
1.6/adj.
✔
MAX696
Adj.
35/adj.
1.6/adj.
✔
MAX697
Adj.
35/adj.
1.6/adj.
MAX700
4.65/adj.
200
-
MAX703/704
4.65/4.40
140
-
MAX705/706
4.65/4.40
140
MAX706P
2.63
140
MAX706R/S/T
2.63/2.93/
3.08
MAX707/708
MAX708R/S/T
MAX709L/M/
R/S/T
PowerFail
Comparator
Manual- Watch- LowReset
dog
Line
Input
Output Output
Active- BatteryHigh
On
Reset
Output
✔
✔/10ns
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
1.6
✔
✔
✔
1.6
✔
✔
✔
140
1.6
✔
✔
✔
4.65/4.40
140
-
✔
✔
✔
2.63/2.93/
3.08
140
-
✔
✔
✔
4.65/4.40/
140
2.63/2.93/3.08
✔
✔
✔/10ns
✔
✔
✔
✔
✔
✔/10ns
✔
✔
✔
✔
✔
✔/10ns
✔/±2%
✔
✔
✔
MAX791
4.65
140
1
MAX792L/M/
R/S/T
4.65/4.40/
140
2.63/2.93/3.08
1
MAX800L/M
4.60/4.40
140
1.6/adj.
✔
MAX802L/M
4.60/4.40
140
1.6
✔
✔/±2%
MAX805L
4.65
140
1.6
✔
✔
MAX813L
4.65
140
1.6
MAX820L/M/
R/S/T
4.65/4.40/
140
2.63/2.93/3.08
1
MAX1232
4.37/4.62
250
0.15/0.60/1.2
MAX1259
-
-
-
✔/10ns
✔
✔
✔
✔
✔
✔
✔/±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.
8 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1993 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.