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PDF MAX6725 Data sheet ( Hoja de datos )
| Número de pieza | MAX6725 | |
| Descripción | Dual/Triple Ultra-Low-Voltage SOT23 P Supervisory Circuits | |
| Fabricantes | Maxim Integrated | |
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19-2325; Rev 3; 6/03
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
General Description
The MAX6715–MAX6729 are ultra-low-voltage microproces-
sor (µP) supervisory circuits designed to monitor two or three
system power-supply voltages. These devices assert a sys-
tem reset if any monitored supply falls below its factory-
trimmed or adjustable threshold and maintain reset for a
minimum timeout period after all supplies rise above their
thresholds. The integrated dual/triple supervisory circuits sig-
nificantly improve system reliability and reduce size com-
pared to separate ICs or discrete components.
These devices monitor primary supply voltages (VCC1) from
1.8V to 5.0V and secondary supply voltages (VCC2) from
0.9V to 3.3V with factory-trimmed reset threshold voltage
options (see Reset Voltage Threshold Suffix Guide). An
externally adjustable RSTIN input option allows customers to
monitor a third supply voltage down to 0.62V. These devices
are guaranteed to be in the correct reset output logic state
when either VCC1 or VCC2 remains greater than 0.8V.
A variety of push-pull or open-drain reset outputs along with
watchdog input, manual reset input, and power-fail input/out-
put features are available (see Selector Guide). Select reset
timeout periods from 1.1ms to 1120ms (min) (see Reset
Timeout Period Suffix Guide). The MAX6715–MAX6729 are
available in small 5, 6, and 8-pin SOT23 packages and oper-
ate over the -40°C to +85°C temperature range.
Applications
Multivoltage Systems
Telecom/Networking Equipment
Computers/Servers
Portable/Battery-Operated Equipment
Industrial Equipment
Printer/Fax
Set-Top Boxes
Typical Operating Circuit
UNREGULATED
DC
R1
R2
DC/DC OUT2
IN CONVERTER
OUT1
VCC1
VCC2
PUSHBUTTON
SWITCH
RSTIN/PFI
RST
WDI
MR PFO
MAX67_ _
1.8V 0.9V
I/O CORE
SUPPLY SUPPLY
RESET
I/O µP
NMI
Features
o VCC1 (primary supply) Reset Threshold Voltages
from 1.58V to 4.63V
o VCC2 (secondary supply) Reset Threshold
Voltages from 0.79V to 3.08V
o Externally Adjustable RSTIN Threshold for
Auxiliary/Triple-Voltage Monitoring
(0.62V internal reference)
o Watchdog Timer Option
35s (min) Long Startup Period
1.12s (min) Normal Timeout Period
o Manual Reset Input Option
o Power-Fail Input/Power-Fail Output Option
(Push-Pull and Open-Drain Active-Low)
o Guaranteed Reset Valid Down to VCC1 or
VCC2 = 0.8V
o Reset Output Logic Options
o Immune to Short VCC Transients
o Low Supply Current 14µA (typ) at 3.6V
o Small 5, 6, and 8-Pin SOT23 Packages
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX6715UT_ _D_ -T -40°C to +85°C 6 SOT23-6
MAX6716UT_ _D_ -T -40°C to +85°C 6 SOT23-6
MAX6717UK_ _D_ -T -40°C to +85°C 5 SOT23-5
MAX6718UK_ _D_ -T -40°C to +85°C 5 SOT23-5
MAX6719UT_ _D_ -T -40°C to +85°C 6 SOT23-6
MAX6720UT_ _D_ -T -40°C to +85°C 6 SOT23-6
Note: The first “_ _” are placeholders for the threshold voltage
levels of the devices. Desired threshold levels are set by the part
number suffix found in the Reset Voltage Threshold Suffix Guide.
The “_” after the D is a placeholder for the reset timeout delay
time. Desired delay time is set using the timeout period suffix
found in the Reset Timeout Period Suffix Guide. For example the
MAX6716UTLTD3-T is a dual-voltage supervisor VTH1 = 4.625V,
VTH2 = 3.075V, and 210ms (typ) timeout period.
Ordering Information continued at end of data sheet.
Pin Configurations appear at end of data sheet.
Selector Guide 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.
1 page  
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
(VCC1 = 5V, VCC2 = 3.3V, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
SUPPLY CURRENT vs. TEMPERATURE
VCC1 = 5V, VCC2 = 3.3V
18
16
TOTAL
14
12 ICC1
10
8
6
4 ICC2
2
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
SUPPLY CURRENT vs. TEMPERATURE
VCC1 = 1.8V, VCC2 = 1.2V
18
16
14
12
10
TOTAL
8
6 ICC1
4
2 ICC2
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
NORMALIZED VCC RESET THRESHOLD
vs. TEMPERATURE
1.004
1.003
1.002
1.001
1.000
0.999
0.998
0.997
0.996
-40
-15 10 35 60
TEMPERATURE (°C)
85
SUPPLY CURRENT vs. TEMPERATURE
VCC1 = 3.3V, VCC2 = 2.5V
18
16
14
12 TOTAL
10
8 ICC1
6
4 ICC2
2
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
NORMALIZED RESET/WATCHDOG
TIMEOUT PERIOD vs. TEMPERATURE
1.007
1.006
1.005
1.004
1.003
1.002
1.001
1.000
0.999
0.998
-40
-15 10 35 60
TEMPERATURE (°C)
85
RESET INPUT AND POWER-FAIL INPUT
THRESHOLD vs. TEMPERATURE
631
630
629
628
627
626
625
-40
-15 10 35 60
TEMPERATURE (°C)
85
SUPPLY CURRENT vs. TEMPERATURE
VCC1 = 2.5V, VCC2 = 1.8V
18
16
14
12
10 TOTAL
8
6 ICC1
4
2 ICC2
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
MAXIMUM VCC TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
10,000
RESET OCCURS ABOVE
THIS LINE
1000
100
10
1
10 100 1000
RESET THRESHOLD OVERDRIVE (mV)
54
53
52
51
50
49
48
47
46
45
44
-40
VCC TO RESET DELAY
vs. TEMPERATURE
100mV OVERDRIVE
-15 10 35 60
TEMPERATURE (°C)
85
_______________________________________________________________________________________ 5
5 Page 
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
A
VIN
R1
MAX6728/
MAX6729
PFI PFO
R2
GND
B
VCC
R1
MAX6728/
MAX6729
PFI PFO
R2
VIN
GND
( )VTRIP = VPFI
R1 + R2
R2
[ ( ) ]VTRIP = R2
(VPFI)
1+
R1
1
R2
- VCC
R1
VPFI = 626.5mV
Figure 3. Using Power-Fail Input to Monitor an Additional
Power-Supply a) VIN is Positive b) VIN is Negative
providing an early power-fail warning so software can
conduct an orderly system shutdown. It can also be
used to monitor supplies other than VCC1 or VCC2 by
setting the power-fail threshold with a resistor-divider, as
shown in Figure 3. PFI is the input to the power-fail com-
parator. The typical comparator delay is 2µs from PFI to
PFO. Connect PFI to ground of VCC1 if unused.
Ensuring a Valid Reset Output
Down to VCC = 0
The MAX6715–MAX6729 are guaranteed to operate
properly down to VCC = 0.8V. In applications that
require valid reset levels down to VCC = 0 use a pull-
down resistor at RST to ground. The resistor value used
is not critical, but it must be large enough not to load
the reset output when VCC is above the reset threshold.
For most applications, 100kΩ is adequate. This config-
uration does not work for the open-drain outputs of the
MAX6715/MAX6717/MAX6719/MAX6721/MAX6723/
MAX6725/MAX6727/MAX6728. For push-pull, active-
high RST output connect the external resistor as a
pullup from RST to VCC1.
VCC1 VCC2
RESET TO OTHER SYSTEM COMPONENTS
MAX6715–
MAX6729
VCC2 RST
VCC1
4.7kΩ
µP
RESET
GND GND
Figure 4. Interfacing to µPs with Bidirectional Reset I/O
Applications Information
Interfacing to µPs with Bidirectional
Reset Pins
Most microprocessors with bidirectional reset pins can
interface directly to open-drain RST output options.
Systems simultaneously requiring a push-pull RST out-
put and a bidirectional reset interface can be in logic
contention. To prevent contention, connect a 4.7kΩ
resistor between RST and the µP’s reset I/O port as
shown in Figure 4.
Adding Hysteresis to the Power-Fail
Comparator
The power-fail comparator has a typical input hysteresis
of 3mV. This is sufficient for most applications where a
power-supply line is being monitored through an external
voltage-divider (see the Power-Fail Comparator section).
If additional noise margin is desired, connect a resistor
between PFO and PFI as shown in Figure 5. Select the
values of R1, R2, and R3 so PFI sees VPFI (626mV) when
VEXT falls to its power-fail trip point (VFAIL) and when VIN
rises to its power-good trip point (VGOOD). The hysteresis
window extends between the specified VFAIL and VGOOD
thresholds. R3 adds the additional hysteresis by sinking
current from the R1/R2 divider network when PFO is logic
low and sourcing current into the network when PFO is
logic high. R3 is typically an order of magnitude greater
than R1 or R2.
The current through R2 should be at least 2.5µA to
ensure that the 25nA (max) PFI input current does not
significantly shift the trip points. Therefore, R2 <
VPFI/2.5µA < 248kΩ for most applications. R3 will provide
additional hysteresis for PFO push-pull (VOH = VCC1) or
open-drain (VOH = VPULLUP) applications.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet MAX6725.PDF ] | |
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