MAX7705CSA+-MAX7705ESA+ Fast Delivery |IC PHOENIX CO.,LIMITED

MAX7705CSA+ ,µP Power Supply Monitor with ResetApplicationsMinimum Component Count, Low-Cost __________Typical Operating CircuitProcessor Systems_ ..
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MAX7705CSA+-MAX7705ESA+
µP Power Supply Monitor with Reset
_______________General Description
In applications with microprocessors (μPs) that have a
RESETinput, 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 1/27ththe power from a +5V supply.
The MAX7705 monitors the power supply in μP and digital
systems. The RESEToutput is valid for VCCdown 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, power-
down, and brownout conditions. When VCCis below the
reset threshold, RESETis low and holds the μP in reset.
RESETwill go high 280ms after VCCrises above the
reset threshold. The MAX7705 is available in 8-pin DIP
and SO packages.
________________________Applications
Minimum Component Count, Low-Cost
Processor Systems
____________________________FeaturesNo External ComponentsLow CostPrecise Reset Threshold280ms Power-On Reset Delay8-Pin DIP and SO Packages
______________Ordering Information
* Contact factory for dice specifications.
μP Power-Supply Monitorith Reset
________________________________________________________________Maxim Integrated Products1
VCC
N.C.
N.C.
RESETGND
N.C.
N.C.
N.C.AX7705
VCC
RESET
GND
*
* THE MAX7705 ELIMINATES THREE EXTERNAL
COMPONENTS REQUIRED BY THE TL7705.
__________________Pin Configuration
VCC
N.C.
N.C.
RESETGND
N.C.
N.C.
N.C.
MAX7705
DIP/SO
TOP VIEW
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.
19-0151; Rev 0; 6/93
PARTTEMP. RANGEPIN-PACKAGE
MAX7705CPA0°C to +70°C8 Plastic DIP
MAX7705CSA0°C to +70°C8 SO
MAX7705C/D0°C to +70°CDice*
FEATUREMAX7705TL7705
No. of External
Components Required03
Operating Supply
Current
65μA1.8mA
Power-Supply Glitch
ImmunityYesNo
Guaranteed Minimum
Reset Delay YesNo
+5V
+3V35μA1.8mA
MAX7705EPA-40°C to +85°C8 Plastic DIP
MAX7705ESA-40°C to +85°C8 SO
μP Power-Supply Monitorith 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
ELECTRICAL CHARACTERISTICS
(VCC= full range, TA= TMINto TMAX, unless otherwise noted.)
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.
PARAMETERCONDITIONSMINTYPMAXUNITS
MAX7705C1.05.5
VCCRange
MAX7705E1.25.5
MAX7705C, VCC< 5.5V65150
Supply Current
MAX7705E, VCC< 5.5V65200
RESETThreshold4.504.654.75V
VCCto RESETDelayVCC= reset threshold max to reset threshold min20μs
Reset Active Timeout PeriodVCC= reset threshold max, VCCrising140280560ms
ISINK= 3.2mA, VCC= reset threshold min0.4
ISINK= 50μA, VCC≥1.0V, MAX7705C0.3
RESETOutput Voltage
ISOURCE= 800μA, VCC≥reset threshold maxVCC - 1.5
ISINK= 100μA, VCC≥1.2V, MAX7705E0.4
μP Power-Supply Monitorith Reset
_______________________________________________________________________________________3
POWER-DOWN RESET DELAY
vs. TEMPERATURE
TEMPERATURE (°C)
(μ
VCC STEPPED FROM RESET THRESHOLD
MAX TO RESET THRESHOLD MIN
POWER-UP RESET DELAY
vs. TEMPERATURE
TEMPERATURE (°C)
(m
VCC = RESET THRESHOLD MAX
VCC RISING
SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
T (μ
NOTE: STEADY-STATE SUPPLY
CURRENT IS INDEPENDENT
OF RESET OUTPUT STATUS
NO LOAD
VCC = +5V
VCC = +4V
VCC = +3V
VCC = +2V
VCC = +1V
RESET THRESHOLD
vs. TEMPERATURE
TEMPERATURE (°C)
(V
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
______________________________________________________________Pin Description
PINNAMEFUNCTION
1,2,3,6,7N.C.No Connection. There is no internal connection to these pins.GNDGroundRESETReset Output remains low while VCCis below the reset threshold, and for 280ms after VCCrises above the
reset threshold.VCC+5V Supply Voltage
μP Power-Supply Monitorith Reset_______________________________________________________________________________________
__________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 RESETinput, simply plug the MAX7705 into the
same socket and omit the RESETpull-up resistor, reset
timing capacitor, and reference bypass capacitor (see
the Typical Operating Circuit).
The MAX7705 monitors the VCCvoltage and asserts
reset whenever VCCfalls below the reset threshold.
The reset power-up delay is created by an internal
fixed oscillator. This delay is 100% tested and guaran-
teed over the full temperature range. The RESETout-
put both sources and sinks current (see RESETOutput
Voltage in the Electrical Characteristics).
Negative-Going VCCTransients
The MAX7705 asserts RESETduring 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 com-
parator overdrive for which the MAX7705 does notgen-
erate a reset pulse. The graph was generated using a
fast-edge, negative-going pulse applied to VCC, starting1.5V above the actual reset threshold and ending below
the reset threshold by the magnitude indicated (reset
comparator overdrive). It indicates the typical maxi-
mum pulse width a negative-going VCCtransient 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 VCCtransient 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
RESETOutput
Down to VCC= 0V
When VCCfalls below 1V, the MAX7705 RESEToutput
no longer sinks current; it becomes high impedance.
Therefore, high-impedance CMOS logic inputs con-
nected to the RESEToutput can drift to indeterminate
voltages. In most applications this presents no prob-
lem, as μP and other circuitry is generally inoperative
with VCCbelow 1V. In applications where the RESET
output must be valid down to 0V, adding a pull-down
resistor to the RESETpin (as shown in Figure 2) will
cause any stray leakage currents to flow to ground,
holding RESETlow. The resistance value of R1 is not
critical. It should be about 100kΩ, which is large
enough not to load RESETand small enough to pull
RESETto ground.
15010010k
RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)
(μ
TA = +25°C
10ns
VCC
GND
MAX7705
RESET
Figure 1.Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
Figure 2.RESETValid to VCC= Ground Circuit
___________________Chip Topography
TRANSISTOR COUNT = 380;
SUBSTRATE CONNECTED TO VCC.
μP Power-Supply Monitorith Reset
_______________________________________________________________________________________5
4.7k
VCC
GND
RESET
MAX7705
RESET
VCC
GND
BUFFER
BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS
Figure 3.Interfacing to μPs with Bidirectional Reset I/O
Interfacing to μPs with
Bidirectional Reset Inputs
μPs with bidirectional reset pins, such as Motorola’s
68HC11 series, can contend with the MAX7705 reset
output. If, for example, the MAX7705 RESEToutput is
asserted high and the μP wants to pull it low, an inde-
terminate logic level may result. To correct this, con-
nect a 4.7kΩresistor between the MAX7705 RESET
output and the μP reset I/O, as in Figure 3. Buffer the
RESETsignal to other system components.
RESETVCC
GND
0.045"
(1.143mm)
0.056"
(1.422mm)
μP Power-Supply Monitorith Reset_______________________________________________________________________________________A2D
DIM-
MIN
MAX
15˚
MIN
MAX
15˚
INCHESMILLIMETERS
2.54 BSC
7.62 BSC
0.100 BSC
0.300 BSCL
21-324Aα
8-PIN PLASTIC
DUAL-IN-LINE
PACKAGE
_______________________________________________________Package Information

Partno	Mfg	Dc	Qty	Available	Descript
MAX7705CSA+ \|MAX7705CSA	MAXIM	N/a	20	avai	µP Power Supply Monitor with Reset
MAX7705ESA+ \|MAX7705ESA	MAXIM	N/a	20	avai	µP Power Supply Monitor with Reset