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PDF MAX6740 Data sheet ( Hoja de datos )
| Número de pieza | MAX6740 | |
| Descripción | (MAX6736 - MAX6745) Low-Power Dual-/Triple-Voltage SC70 UP Supervisory Circuits | |
| Fabricantes | Maxim Integrated | |
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19-2531; Rev 1; 4/03
Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
General Description
The MAX6736–MAX6745 are low-power dual-/triple-
voltage microprocessor (µP) supervisors. These
devices assert a 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 significantly reduce size
and power compared to separate ICs or discrete com-
ponents. The low supply current of 6µA makes these
devices ideal for portable equipment.
The MAX6736/MAX6737 are dual fixed-voltage µP
supervisors with a manual reset input. The MAX6738/
MAX6739 have one fixed and one adjustable reset
threshold and a manual reset input. The MAX6740/
MAX6743 are triple-voltage µP supervisors with two
fixed and one user-adjustable reset threshold inputs.
The MAX6741/MAX6744 are dual-voltage µP supervi-
sors with a power-OK (POK) output ideal for power-
supply sequencing. The MAX6742/MAX6745 monitor
the primary VCC supply and have an independent
power-fail comparator.
The MAX6736–MAX6745 monitor I/O supply voltages
(VCC1) from 1.8V to 5.0V and core supply voltages
(VCC2) from 0.9V to 3.3V with factory-trimmed reset
threshold voltage options (Table 1). An external
adjustable RSTIN input option allows monitoring volt-
ages down to 0.5V.
A variety of push-pull or open-drain reset outputs along
with manual reset input and power-fail input/output fea-
tures are available (see the Selector Guide). The
MAX6736–MAX6745 are offered in a space-saving 5-pin
SC70 package and operate over the -40°C to +85°C
temperature range.
Applications
Portable/Battery-
Powered Equipment
Multivoltage Systems
Notebook Computers
Controllers
PDAs
GPS Equipment
POS Equipment
Features
o Dual-/Triple-Supply Reset Voltage Monitors
o Precision Factory-Set Reset Thresholds for
Monitoring from 0.9V to 5.0V
o Adjustable Reset Input Down to 0.488V
o 150ms and 1200ms (min) Reset Timeout Period
Options
o VCC1 Power-OK Output for Power-Supply
Sequencing Applications (MAX6741/MAX6744)
o Power-Fail Input/Power-Fail Output
(MAX6742/MAX6745)
o 6µA Supply Current
o Tiny SC70 Package
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX6736XK_ _D_-T -40°C to +85°C 5 SC70-5
MAX6737XK_ _D_-T -40°C to +85°C 5 SC70-5
Note: The first “_ _” or “_” are placeholders for the threshold
voltage levels of the devices. Desired threshold levels are set
by the part number suffix found in Tables 1 and 2. The “_” after
the D is a placeholder for the reset timeout period suffix found
in Table 3. For example, the MAX6736XKLTD3-T is a dual-volt-
age supervisor VTH1 = 4.625V, VTH2 = 3.075V, and a 150ms
minimum reset timeout period. All devices are available in
tape-and-reel only. There is a 2500-piece minimum order
increment for standard versions (see Table 1). Sample stock is
typically held on standard versions only. Nonstandard versions
require a minimum order increment of 10,000 pieces. Contact
factory for availability.
Ordering Information continued at end of data sheet.
Selector Guide continued at end of data sheet.
Pin Configurations appear at end of data sheet.
Typical Application Circuits appear at end of data sheet.
Functional Diagram appears at end of data sheet.
Selector Guide
PART
VOLTAGE
MONITORS
OPEN-DRAIN PUSH-PULL
RESET
RESET
MANUAL
RESET
POWER-FAIL
INPUT/
OUTPUT
POK
OUTPUT
RSTIN
INPUT
MAX6736
2 fixed
MAX6737
2 fixed
MAX6738
1 fixed, 1 adj
*Manual reset detect on RESET output.
X
—
X
—X
XX
—X
— ——
— ——
— —X
________________________________________________________________ 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  
Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 1.2V to 5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
POWER-FAIL COMPARATOR (MAX6742/MAX6745 only)
Power Fail In Threshold (Note 5)
VTH-PFI
TA = 0°C to +85°C
TA = -40°C to +85°C
Power Fail In Current
IPFI VPFI ≥ 0.1V (Note 2)
PFO Output Low
VCC1 ≥ 1.53V, ISINK = 500µA
VOL VCC1 ≥ 2.03V, ISINK = 1.2mA
VCC1 ≥ 4.25V, ISINK = 3.2mA
0.476
0.468
-10
0.488
0.500
0.507
+10
0.3
0.3
0.4
PFI to PFO Propagation Delay
PFI falling at 10mV/µs from VTH-PFI +
tP
100mV to VTH-PFI - 100mV or rising at
10mV/µs from VTH-PFI - 100mV to VTH-PFI +
100mV (Note 5)
35
PFO Startup Delay
To output valid (Note 5)
5
Note 1: All devices are 100% tested at TA = +25°C. All temperature limits are guaranteed by design.
Note 2: Guaranteed by design.
Note 3: tRD timeout period begins after POK1 timeout period (tPOKP) and VCC2 ≥ VTH2 (max) (MAX6741/MAX6744).
Note 4: Refers to the manual reset function obtained by forcing the RESET output low.
Note 5: VCC1 ≥ 1.6V.
UNITS
V
nA
V
µs
ms
(TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
10
VCC1 = 3.3V, VCC2 = 2.5V
9
8
7
TOTAL
6
5 ICC1
4
3
2 ICC2
1
0
-40
-20 0 20 40 60
TEMPERATURE (°C)
80
Typical Operating Characteristics
SUPPLY CURRENT vs. TEMPERATURE
10
9 VCC1 = 2.5V, VCC2 = 1.8V
8
7
6 TOTAL
5
ICC1
4
3
2
ICC2
1
0
-40
-20 0 20 40 60
TEMPERATURE (°C)
80
SUPPLY CURRENT vs. TEMPERATURE
10
9 VCC1 = 1.8V, VCC2 = 1.2V
8
7
6
5 TOTAL
4
3 ICC1
2
1 ICC2
0
-40
-20 0 20 40 60
TEMPERATURE (°C)
80
_______________________________________________________________________________________ 5
5 Page 
Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
PUSHBUTTON
SWITCH
OPEN
CLOSED
SWITCH
BOUNCE
SWITCH
BOUNCE
SWITCH
BOUNCE
SWITCH
BOUNCE
VCC1
RESET
tDEB
tMRP tDEB tMRP
GND
Figure 2. MAX6740/MAX6741/MAX6742 Manual Reset Timing Diagram
released. The manual reset detect function is internally
debounced for the tDEB timeout period, so the output
can be connected directly to a momentary pushbutton
switch, if desired (Figure 2).
Manual Reset Input
Many microprocessor-based products require manual
reset capability, allowing the operator, a test techni-
cian, or external logic circuitry to initiate a reset while
the monitored supplies remain above their reset thresh-
olds. The MAX6736–MAX6739 have a dedicated
active-low MR input. The RESET is asserted low while
MR is held low and remains asserted for the manual
reset timeout period after MR returns high. The MR
input has an internal 1.5kΩ pullup resistor to VCC1 and
can be left unconnected if not used. MR can be driven
with CMOS logic levels, open-drain/open-collector out-
puts, or a momentary pushbutton switch to GND to cre-
ate a manual reset function.
Adjustable Input Voltage
The MAX6738/MAX6739 and MAX6740/MAX6743 pro-
vide an additional input to monitor a second or third
system voltage. The threshold voltage at RSTIN is typi-
VEXT_TH
R1
R2
MAX6738
MAX6739
MAX6740
MAX6743
RSTIN
GND
cally 488mV. Connect a resistor-divider network to the
circuit as shown in Figure 3 to establish an externally
controlled threshold voltage, VEXT_TH.
VEXT_TH = 0.488V((R1 + R2) / R2)
Low leakage current at RSTIN allows the use of large-
valued resistors, resulting in reduced power consump-
tion of the system.
Power-Fail Comparator
PFI is the noninverting input to an auxiliary comparator. A
488mV internal reference (VTH-PFI) is connected to the
inverting input of the comparator. If PFI is less than
488mV, PFO is asserted low. PFO deasserts without a
timeout period when PFI rises above the externally set
threshold. Common uses for the power-fail comparator
include monitoring for low battery conditions or a failing
DC-DC converter input voltage (see the Typical
Application Circuits). The asserted PFO output can place
a system in a low-power suspend mode or support an
orderly system shutdown before monitored VCC voltages
drop below the reset thresholds. Connect PFI to an exter-
nal resistor-divider network as shown in Figure 4 to set
the desired trip threshold. Connect PFI to VCC1 if unused.
Applications Information
Interfacing to the µP with
Bidirectional Reset Pins
Most microprocessors with bidirectional reset pins can
interface directly to open-drain RESET output options.
Systems simultaneously requiring a push-pull RESET
output and a bidirectional reset interface can be in
logic contention. To prevent contention, connect a
4.7kΩ resistor between RESET and the µP’s reset I/O
port as shown in Figure 5.
Figure 3. Monitoring an Additional Voltage
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX6740.PDF ] | |
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