View MAX673605_4904067.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-2531; Rev 2; 12/05
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits
General Description
The MAX6736-MAX6745 are low-power dual-/triplevoltage microprocessor (P) 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 components. The low supply current of 6A makes these devices ideal for portable equipment. The MAX6736/MAX6737 are dual fixed-voltage P 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 P supervisors with two fixed and one user-adjustable reset threshold inputs. The MAX6741/MAX6744 are dual-voltage P supervisors with a power-OK (POK) output ideal for powersupply sequencing. The MAX6742/MAX6745 monitor the primary V CC supply and have an independent power-fail comparator. The MAX6736-MAX6745 monitor I/O supply voltages (V CC1) 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 voltages down to 0.5V. A variety of push-pull or open-drain reset outputs along with manual reset input and power-fail input/output features are available (see the Selector Guide). The MAX6736-MAX6745 are offered in a space-saving 5-pin SC70 package and operate over the -40C to +85C temperature range.
Features
Dual-/Triple-Supply Reset Voltage Monitors Precision Factory-Set Reset Thresholds for Monitoring from 0.9V to 5.0V Adjustable Reset Input Down to 0.488V 150ms and 1200ms (min) Reset Timeout Period Options VCC1 Power-OK Output for Power-Supply Sequencing Applications (MAX6741/MAX6744) Power-Fail Input/Power-Fail Output (MAX6742/MAX6745) 6A Supply Current Tiny SC70 Package
MAX6736-MAX6745
Ordering Information
PART MAX6736XK_ _D_-T MAX6737XK_ _D_-T TEMP RANGE -40C to +85C -40C to +85C PIN-PACKAGE 5 SC70-5 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-voltage 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. Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing "-T" with "+T" when ordering. Ordering Information and Selector Guide continued at end of data sheet. Pin Configurations, Typical Application Circuits, and Functional Diagram appear at end of data sheet.
Applications
Portable/BatteryPowered Equipment Multivoltage Systems Notebook Computers Controllers PDAs GPS Equipment POS Equipment
Selector Guide
PART MAX6736 MAX6737 MAX6738 VOLTAGE MONITORS 2 fixed 2 fixed 1 fixed, 1 adj OPEN-DRAIN RESET X -- X PUSH-PULL RESET -- X -- MANUAL RESET X X X POWER-FAIL INPUT/ OUTPUT -- -- -- POK OUTPUT -- -- -- RSTIN INPUT -- -- X
*Manual reset detect on RESET output. ________________________________________________________________ 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.
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
ABSOLUTE MAXIMUM RATINGS
VCC1, VCC2, POK1 to GND ......................................-0.3V to +6V Open-Drain RESET, PFO to GND.............................-0.3V to +6V Push-Pull RESET to GND..........................-0.3V to (VCC1 + 0.3V) MR, RSTIN, PFI to GND............................-0.3V to (VCC1 + 0.3V) Input/Output Current, All Pins .............................................20mA Continuous Power Dissipation (TA = +70C) 5-Pin SC70 (derate 3.1mW/C above +70C) ..............247mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = 1.2V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Operating Voltage Range SYMBOL VCC1, VCC2 CONDITIONS TA = -40C to 0C TA = 0C to +85C VCC1 = 3.3V, VCC1 > VCC2, no load, reset not asserted VCC1 Supply Current ICC1 VCC1 = 1.8V, VCC1 < VCC2, no load, reset not asserted VCC2 = 1.8V, VCC2 < VCC1, no load, reset not asserted VCC2 Supply Current ICC2 VCC2 = 3.3V, VCC2 > VCC1, no load, reset not asserted MAX67_ _L MAX67_ _M MAX67_ _T MAX67_ _S Reset Threshold for VCC1 VTH1 MAX67_ _R MAX67_ _Z MAX67_ _Y MAX67_ _W MAX67_ _V TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C 4.500 4.425 4.250 4.175 3.000 2.950 2.850 2.800 2.550 2.505 2.250 2.213 2.125 2.088 1.620 1.593 1.530 1.503 1.575 1.665 2.188 2.313 2.625 2.925 3.075 4.375 MIN 1.2 1.0 5 5 1 10 4.625 TYP MAX 5.5 5.5 10 A 10 2 A 20 4.750 4.825 4.500 4.575 3.150 3.200 3.000 3.050 2.700 2.745 2.375 2.413 2.250 2.288 1.710 1.737 1.620 1.647 V UNITS V
2
_______________________________________________________________________________________
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 1.2V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL MAX67_ _T MAX67_ _S MAX67_ _R MAX67_ _Z MAX67_ _Y MAX67_ _W Reset Threshold for VCC2 VTH2 MAX67_ _V MAX67_ _I MAX67_ _H MAX67_ _G MAX67_ _F MAX67_ _E MAX67_ _D RSTIN Threshold (MAX6738/ MAX6739/MAX6740/MAX6743) RSTIN Input Current Reset Threshold Hysteresis VTH-RSTIN CONDITIONS TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to +85C TA = -40C to +85C TA = 0C to + 85C TA = -40C to +85C MIN 3.000 2.905 2.850 2.800 2.550 2.505 2.250 2.213 2.125 2.088 1.620 1.593 1.530 1.503 1.350 1.328 1.275 1.253 1.080 1.062 1.020 1.002 0.810 0.797 0.765 0.752 0.476 0.468 -10 0.5 0.3 0.3 0.3 0.4 0.8 x VCC 0.8 x VCC V 0.488 0.788 0.833 1.050 1.110 1.313 1.388 1.575 1.665 2.188 2.313 2.625 2.925 TYP 3.075 MAX 3.150 3.050 3.000 3.050 2.700 2.745 2.375 2.413 2.250 2.288 1.710 1.737 1.620 1.647 1.425 1.448 1.350 1.373 1.140 1.158 1.080 1.098 0.855 0.869 0.810 0.824 0.500 0.507 +10 V nA % V UNITS
MAX6736-MAX6745
TA = 0C to +85C TA = -40C to +85C VRSTIN 0.1V (Note 2) VTH1, VTH2, RSTIN, PFI VCC1 1.0V, ISINK = 50A, TA = 0C to +85C
RESET, POK1 Output Low
VOL
VCC1 1.2V, ISINK = 100A VCC1 2.13V, ISINK = 1.2mA VCC1 4.25V, ISINK = 3.2mA, VCC1 2.38V, ISOURCE = 500A, output deasserted
RESET Output High (Push-Pull)
VOH
VCC1 4.75V, ISOURCE = 800A, output deasserted
V
_______________________________________________________________________________________
3
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 1.2V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER RESET Output Open-Drain Leakage Current (MAX6736/MAX6738) POK1 Output Open-Drain Leakage VCC Reset Delay VCC Reset Timeout Period (Note 3) MR to VCC1 Internal Pullup Impedance MR Timeout Period MR Minimum Input Pulse Width MR Glitch Rejection VIL MR Input Voltage VIH MR to RESET Delay VCC1 POWER-OK OUTPUT (MAX6741/MAX6744 only) POK1 Timeout Period RESET to VCC1 Internal Pullup Impedance Manual Reset Detect Debounce Period Manual Reset Timeout Period (Note 3) Manual Reset Minimum Input Pulse Width Manual Reset Release Detect Threshold Manual Reset Glitch Rejection Manual Reset to RESET Delay tDEB tMRP tMPW (Note 4) MAX67_ _ _ _ XK_ _D3 MAX67_ _ _ _ XK_ _ D7 (Note 4) (Note 4) (Note 4) tPOKP 37.5 56.25 75.0 ms PUSHBUTTON RESET (MAX6740/MAX6741/MAX6742 only) 25 37.5 150 1200 1 0.5 x VCC1 100 300 50 56.25 225 1800 100 75.0 300 2400 k ms ms s V ns ns 0.8 x VCC1 300 tMRP tMPW Both D3 and D7 timing options tRD tRP SYMBOL ILKG CONDITIONS Output not asserted low (Note 2) MIN TYP MAX 500 UNITS nA
Output not asserted low (Note 2) VCC1, VCC2, or RSTIN falling at 10mV/s from VTH + 100mV to VTH - 100mV MAX67_ _ _ _ XK_ _D3 MAX67_ _ _ _ XK_ _ D7 150 1200 35 225 1800
500
nA s
300 2400
ms
MANUAL RESET (MAX6736-MAX6739 only) 0.75 150 1 100 0.3 x VCC1 1.5 225 3.00 300 k ms s ns
V
ns
4
_______________________________________________________________________________________
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 1.2V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS TA = 0C to +85C TA = -40C to +85C VPFI 0.1V (Note 2) VCC1 1.53V, ISINK = 500A PFO Output Low VOL VCC1 2.03V, ISINK = 1.2mA VCC1 4.25V, ISINK = 3.2mA PFI falling at 10mV/s from VTH-PFI + 100mV to VTH-PFI - 100mV or rising at 10mV/s from VTH-PFI - 100mV to VTH-PFI + 100mV (Note 5) To output valid (Note 5) MIN 0.476 0.468 -10 TYP 0.488 MAX 0.500 0.507 +10 0.3 0.3 0.4 V UNITS POWER-FAIL COMPARATOR (MAX6742/MAX6745 only) Power Fail In Threshold (Note 5) Power Fail In Current VTH-PFI IPFI V nA
MAX6736-MAX6745
PFI to PFO Propagation Delay
tP
35
s
PFO Startup Delay
5
ms
Note 1: Note 2: Note 3: Note 4: Note 5:
All devices are 100% tested at TA = +25C. All temperature limits are guaranteed by design. Guaranteed by design. tRD timeout period begins after POK1 timeout period (tPOKP) and VCC2 VTH2 (max) (MAX6741/MAX6744). Refers to the manual reset function obtained by forcing the RESET output low. VCC1 1.6V.
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX6736-45 toc01
SUPPLY CURRENT vs. TEMPERATURE
MAX6736-45 toc02
SUPPLY CURRENT vs. TEMPERATURE
9 8 SUPPLY CURRENT (A) 7 6 5 4 3 2 1 0 ICC2 ICC1 TOTAL VCC1 = 1.8V, VCC2 = 1.2V
MAX6736-45 toc03
10 9 8 SUPPLY CURRENT (A) 7 6 5 4 3 2 1 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) ICC2 TOTAL ICC1 VCC1 = 3.3V, VCC2 = 2.5V
10 9 8 SUPPLY CURRENT (A) 7 6 5 4 3 2 1 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) ICC2 TOTAL ICC1 VCC1 = 2.5V, VCC2 = 1.8V
10
-40
-20
0
20
40
60
80
TEMPERATURE (C)
_______________________________________________________________________________________
5
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
NORMALIZED VCC/POK1/MR TIMEOUT PERIOD vs. TEMPERATURE
MAXIMUM VCC1/VCC2 TRANSIENT DURATION (s) 1.019 NORMALIZED VCC/POK1/MR RESET TIMEOUT PERIOD 1.014 1.009 1.004 0.999 0.994 0.989 0.984 -40 -20 0 20 40 60 80 TEMPERATURE (C)
MAX6736-45 toc04
MAXIMUM VCC1/VCC2 TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE
MAX6736-45 toc05
10,000
1000
VCC1 RESET OCCURS ABOVE THESE LINES
100
10
VCC2
0 10 100 RESET THRESHOLD OVERDRIVE (mV) 1000
NORMALIZED VCC RESET THRESHOLD vs. TEMPERATURE
MAX6736-45 toc06
VCC TO RESET OUTPUT DELAY vs. TEMPERATURE
48.5 100mV OVERDRIVE
MAX6736-45 toc07
1.008 NORMALIZED VCC RESET THRESHOLD
1.003
VCC TO RESET OUTPUT DELAY (s)
43.5
0.998
38.5
0.993 NORMALIZED TO +25C 0.988 -40 -20 20 40 0 TEMPERATURE (C) 60 80
33.5
28.5 -40 -20 20 40 0 TEMPERATURE (C) 60 80
RESET INPUT TO RESET OUTPUT DELAY vs. TEMPERATURE
MAX6736-45 toc08
POWER-FAIL INPUT TO POWER-FAIL OUTPUT DELAY vs. TEMPERATURE
49 44 RISING EDGE 39 100mV OVERDRIVE
MAX6736-45 toc09
35 RSTIN TO RESET OUTPUT DELAY (s)
100mV OVERDRIVE
30
PFI TO PFO DELAY (s)
34
25
29 24 -40 -20 20 40 0 TEMPERATURE (C) 60 80
FALLING EDGE
20
-40
-20
20 40 0 TEMPERATURE (C)
60
80
6
_______________________________________________________________________________________
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
MR TO RESET OUTPUT DELAY
MAX6736-45 toc10
POWER-FAIL INPUT TO POWER-FAIL OUTPUT DELAY
MAX6736-45 toc11
VMR 2V/div
PFI 200mV/div
VRESET 2V/div
PFO 2V/div
100ns/div
10s/div
VCC TO RESET OUTPUT DELAY
MAX6736-45 toc12
OUTPUT LOW VOLTAGE vs. SINK CURRENT
VCC = 3.3V VCC 200mV/div AC-COUPLED OUTPUT LOW VOLTAGE (mV) 400
MAX6736-45 toc13
500
300
200
VRESET 2V/div
100
0 4s/div 0 1 2 3 4 5 6 7 8 9 10 SINK CURRENT (mA)
OUTPUT HIGH VOLTAGE vs. SOURCE CURRENT
VCC = 3.3V OUTPUT HIGH VOLTAGE (V) 3
MAX6736-45 toc14
4
2
1
0 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 SOURCING CURRENT (mA)
_______________________________________________________________________________________
7
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
Pin Description
PIN MAX6736 MAX6738 MAX6740 MAX6741 MAX6742 MAX6737 MAX6739 MAX6743 MAX6744 MAX6745 NAME FUNCTION Reset Output, Push-Pull or Open Drain Active Low. RESET changes from high to low when any monitored power-supply input (VCC1, VCC2, RSTIN) drops below its selected reset threshold. It remains low until all monitored power-supply inputs exceed their selected reset thresholds for the VCC reset timeout period. RESET is forced low if MR is low for at least the MR minimum input pulse width. It remains low for the MR reset timeout period after MR goes high. The pushpull output is referenced to VCC1. The MAX6736/MAX6738 open-drain outputs require an external pullup resistor. The MAX6740/MAX6741/MAX6742 open-drain outputs have an internal 50k pullup resistor to VCC1 and provide a manual reset function. Ground Manual Reset, Active Low. Pull low for at least MR minimum input pulse width to force RESET low. Reset remains active as long as MR is low and for the MR reset timeout period after MR goes high. There is an internal 1.5k pullup resistor to VCC1. Voltage Input 1. Power supply and input for the secondary P voltage reset monitor. Adjustable Reset Threshold Input. RESET is asserted when RSTIN is below the internal 0.488V reference level. Set the adjustable reset threshold with an external resistor-divider network. Connect RSTIN to VCC1 if unused. Voltage Input 2. Power supply and input for the primary P voltage reset monitor. Power-Fail Comparator Input. PFO is asserted when PFI is below 0.488V. PFO is deasserted without any reset timeout period when PFI goes above 0.488V. Connect PFI to an external resistor network to set the desired monitor threshold. Power-Fail Comparator Output, Open Drain Active Low. PFO is asserted when PFI is below 0.488V. VCC1 Power-OK Output, Open Drain Active High. POK1 remains low as long as VCC1 is below VTH1. POK1 output goes high after VCC1 exceeds VTH1 for the POK1 timeout period. POK1 logic is independent of the MR or VCC2 inputs. The output can be used to control VCC1-to-VCC2 supply sequencing.
1
1
1
1
1
RESET
2
2
2
2
2
GND
3
3
--
--
--
MR
4
--
4
4
--
VCC2
--
4
3
--
--
RSTIN
5
5
5
5
5
VCC1
--
--
--
--
4
PFI
--
--
--
--
3
PFO
--
--
--
3
--
POK1
8
_______________________________________________________________________________________
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
Table 1. Reset Voltage Threshold Suffix Guide for MAX6736/MAX6737/MAX6740/ MAX6741/MAX6743/MAX6744
PART NO. SUFFIX (__) LT MS MR TZ TW TI TG TE SY SV SH SF SD RY RV RH RF VCC1 NOMINAL VOLTAGE THRESHOLD (V) 4.625 4.375 4.375 3.075 3.075 3.075 3.075 3.075 2.925 2.925 2.925 2.925 2.925 2.625 2.625 2.625 2.625 VCC2 NOMINAL VOLTAGE THRESHOLD (V) 3.075 2.925 2.625 2.313 1.665 1.388 1.110 0.833 2.188 1.575 1.313 1.050 0.788 2.188 1.575 1.313 1.050 PART NO. SUFFIX (__) RD ZW ZI ZG ZE YV YH YF YD WT WI WG WE VR VH VF VD VCC1 NOMINAL VOLTAGE THRESHOLD (V) 2.625 2.313 2.313 2.313 2.313 2.188 2.188 2.188 2.188 1.665 1.665 1.665 1.665 1.575 1.575 1.575 1.575 VCC2 NOMINAL VOLTAGE THRESHOLD (V) 0.788 1.665 1.388 1.110 0.833 1.575 1.313 1.050 0.788 3.075 1.388 1.110 0.833 2.625 1.313 1.050 0.788
Note: Standard versions, shown in bold, are available in the D3 timeout option only. Samples are typically held on standard versions only. There is a 10,000-piece order increment on nonstandard versions. Other threshold voltage combinations may be available; contact factory for availability.
Table 2. Reset Voltage Threshold Suffix Guide for MAX6738/MAX6739/MAX6742/ MAX6745
PART NO. SUFFIX (_) L M T S R Z Y W V VCC1 NOMINAL VOLTAGE THRESHOLD (V) 4.625 4.375 3.075 2.925 2.625 2.313 2.188 1.665 1.575
Table 3. VCC Timeout Period Suffix Guide
TIMEOUT PERIOD SUFFIX D3 D7 ACTIVE TIMEOUT PERIOD MIN (ms) 150 1200 MAX (ms) 300 2400
Note: Standard versions, shown in bold, are available in the D3 timeout option only. Samples are typically held on standard versions only. There is a 10,000-piece order increment on nonstandard versions. Other threshold voltages may be available; contact factory for availability. _______________________________________________________________________________________ 9
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
VCC1 VTH1
GND
POK1 tPOKP
GND
VCC2 VTH2
GND
MR
SWITCH BOUNCE
SWITCH BOUNCE
GND
RESET tRP GND
tMRP
Figure 1. Timing Diagram
Detailed Description
Supply Voltages
The MAX6736-MAX6745 P supervisory circuits maintain system integrity by alerting the P to fault conditions. These devices are optimized for systems that monitor two or three supply voltages. The reset output state is guaranteed to remain valid while either VCC1 or VCC2 is above 1.2V.
Reset Output
The MAX6736-MAX6745 provide an active-low reset output (RESET). RESET is asserted when the voltage at either VCC1 or VCC2 falls below the voltage threshold level, RSTIN drops below the threshold, or MR is pulled low. Once reset is asserted, it stays low for the reset timeout period. If VCC1, VCC2, or RSTIN goes below the reset threshold before the reset timeout period is completed, the internal timer restarts. The MAX6736/MAX6738/ MAX6740/MAX6741/MAX6742 have open-drain reset outputs, while the MAX6737/MAX6739/MAX6743/MAX6744/ MAX6745 have push-pull reset outputs (Figure 1). The MAX6740/MAX6741/MAX6742 include a RESET output with a manual reset detect function. The opendrain RESET output has an internal 50k pullup to V CC 1. The RESET output is low while the output is pulled to GND and remains low for at least the manual reset timeout period after the external GND pulldown is
Threshold Levels
The MAX6736/MAX6737/MAX6740/MAX6741/MAX6743/ MAX6744 input voltage threshold combinations are indicated by a two-letter code in Table 1. The MAX6738/ MAX6739/MAX6742/MAX6745 input voltage thresholds are indicated by a one-letter code in Table 2. Contact the factory for the availability of other voltage thresholds.
10
______________________________________________________________________________________
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
SWITCH BOUNCE OPEN PUSHBUTTON SWITCH CLOSED SWITCH BOUNCE SWITCH BOUNCE SWITCH BOUNCE
VCC1 tDEB RESET GND tMRP tDEB tMRP
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 technician, or external logic circuitry to initiate a reset while the monitored supplies remain above their reset thresholds. 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 1.5k pullup resistor to VCC1 and can be left unconnected if not used. MR can be driven with CMOS logic levels, open-drain/open-collector outputs, or a momentary pushbutton switch to GND to create a manual reset function.
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 largevalued resistors, resulting in reduced power consumption 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 external resistor-divider network as shown in Figure 4 to set the desired trip threshold. Connect PFI to VCC1 if unused.
Adjustable Input Voltage
The MAX6738/MAX6739 and MAX6740/MAX6743 provide an additional input to monitor a second or third system voltage. The threshold voltage at RSTIN is typi-
Applications Information
VEXT_TH R1 RSTIN R2 GND
MAX6738 MAX6739 MAX6740 MAX6743
Interfacing to the P 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 4.7k resistor between RESET and the P's reset I/O port as shown in Figure 5.
Figure 3. Monitoring an Additional Voltage ______________________________________________________________________________________ 11
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
A) VIN IS POSITIVE
VEXT_TH R1 PFI R2
MAX6742 MAX6745
PFO
VEXT_TH = VTH-PFI
(
R1 + R2 R2
)
GND
B) VIN IS NEGATIVE
shown in Figure 6. Select the values of R1, R2, and R3 such that PFI sees VTH-PFI (488mV) when VEXT falls to its power-fail trip point (VFAIL) and when VEXT 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 the PFO output 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 1A to ensure that the 10nA (max) PFI input current does not significantly shift the trip points. Therefore, for most applications: R2 < VTH-PFI / 1mA < 0.488V / 1mA < 488k PFO is an open-drain output requiring an external pullup resistor, R4. Select R4 to be less than 1% of R3.
VCC R1 PFI R2
MAX6742 MAX6745
PFO
VEXT_TH = R2
(
(VTH-PFI)
)(
V 1+1 - CC R1 R1 R2
)
VPFI = 488mV
VGOOD = DESIRED VEXT GOOD VOLTAGE THRESHOLD VFAIL = DESIRED VEXT FAIL VOLTAGE THRESHOLD VPU = VPULLUP (FOR OPEN-DRAIN PFO) R2 = 488k (FOR >1A R2 CURRENT)
VEXT_TH
GND
Figure 4. Using Power-Fail Input to Monitor an Additional Power Supply
R1 = R2
(VGOOD - VTH-PFI ) -
(VTH- PFI (VGOOD - VFAIL )
VPU
VTH - PFI
Adding Hysteresis to the Power-Fail Comparator
The power-fail comparator has a typical input hysteresis of 2.5mV. This is sufficient for most applications in which a power-supply line is being monitored through an external voltage-divider. If additional noise margin is desired, connect a resistor between PFO and PFI, as
R3 = (R1 x VPU) / (VGOOD - VFAIL) R4 0.01 x R3
Power Sequencing Applications
Many dual-voltage processors/ASICs require specific power-up/power-down sequences for the I/O and core supplies.
VCC1 VCC2
RESET TO OTHER SYSTEM COMPONENTS
R3
VPULLUP
VGOOD VFAIL
VIN
VCC2 VCC1
MAX6737 MAX6739 MAX6743 MAX6744 RESET MAX6745
VEXT
MAX6742 MAX6745
R1 PFI R2 PFO R4
PFO
4.7k RESET
P
GND
GND
GND
VGOOD = DESIRED VEXT GOOD VOLTAGE THRESHOLD VFAIL = DESIRED VEXT FAIL VOLTAGE THRESHOLD VOH = VCC1 (FOR PUSH-PULL PFO) R2 = 200k (FOR > 2.5A R2 CURRENT) R1 = R2 ((VGOOD - VTH-PFI) - (VTH-PFI)(VGOOD - VFAIL) / VPU) / VTH-PFI R3 = (R1 x VOH) / (VGOOD - VFAIL)
Figure 5. Interfacing to Ps with Bidirectional Reset I/O 12
Figure 6. Adding Hysteresis to Power Fail for Push-Pull PFO
______________________________________________________________________________________
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits
The MAX6741/MAX6744 offer a VCC1 POK (POK1) ideal for VCC1-to-VCC2 sequencing. POK1 remains low as long as VCC1 is below its VTH1 threshold. When VCC1 exceeds VTH1 for the POK1 timeout period (tPOKP), the open-drain POK1 output is deasserted. The POK1 output can then enable the VCC2 power supply (use an external POK1 pullup resistor). RESET is deasserted when both VCC1 and VCC2 remain above their selected thresholds for the reset timeout period (tRP). The POK1 output can be used for I/O before core or core before I/O sequencing, depending on the selected VCC1/VCC2 thresholds. See the Typical Application Circuit and Figure 1.
Transient Immunity
The MAX6736-MAX6745 supervisors are relatively immune to short-duration falling VCC transients (glitches). It is usually undesirable to reset the P when VCC experiences only small glitches. The Typical Operating Characteristics show Maximum VCC1/VCC2 Transient Duration vs. Reset Threshold Overdrive, for which reset pulses are not generated. The graph shows the maximum pulse width that a falling VCC transient might typically have without causing a reset pulse to be issued. As the amplitude of the transient increases, the maximum allowable pulse width decreases. A 0.1F bypass capacitor mounted close to the VCC pin provides additional transient immunity.
MAX6736-MAX6745
Monitoring a Negative Voltage
The power-fail comparator can be used to monitor a negative supply voltage using the circuit shown in Figure 4. When the negative supply is valid, PFO is low. When the negative supply voltage drops, PFO goes high. The circuit's accuracy is affected by the PFI threshold tolerance, VCC, R1, and R2.
Chip Information
TRANSISTOR COUNT: 249 PROCESS: BiCMOS
Functional Diagram
VCC1
MAX6736- MAX6745
PFO POK1 VCC1 VCC2
DELAY
RSTIN/PFI
RESET TIMEOUT PERIOD
RESET OUTPUT RESET
VCC2 VCC1
MR PULLUP
0.488V
VCC1 1.23V
MR
______________________________________________________________________________________
13
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
Selector Guide (continued)
PART MAX6739 MAX6740 MAX6741 MAX6742 MAX6743 MAX6744 MAX6745 VOLTAGE MONITORS 1 fixed, 1 adj 2 fixed, 1 adj 2 fixed 1 fixed 2 fixed, 1adj 2 fixed 1 fixed OPEN-DRAIN RESET -- X* X* X* -- -- -- PUSH-PULL RESET X -- -- -- X X X MANUAL RESET X X* X* X* -- -- -- POWER-FAIL INPUT/ OUTPUT -- -- -- X -- -- X POK OUTPUT -- -- X -- -- X -- RSTIN INPUT X X -- -- X -- --
*Manual reset detect on RESET output.
Typical Application Circuits
DC/DC CONVERTER UNREGULATED DC IN OUT VBATT IN OUT DC/DC CONVERTER VCC
IN
OUT DC/DC CONVERTER SHDN VCC2 VCC1 CORE I/O SUPPLY SUPPLY
P
VCC1 MAX6742 PFI GND
PFO
P
RESET
MAX6741
RESET GND
POK1
GND
RESET
RESET GND
PUSHBUTTON SWITCH
PUSHBUTTON SWITCH
14
______________________________________________________________________________________
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits
Pin Configurations
TOP VIEW
RESET 1 5 VCC1 RESET 1 5 VCC1
MAX6736-MAX6745
RESET 1
5
VCC1
GND 2
MAX6736 MAX6737
4 VCC2
GND 2
MAX6738 MAX6739
4 RSTIN
GND 2
MAX6740 MAX6743
4 VCC2
MR 3
MR 3
RSTIN 3
SC70
RESET 1 5 VCC1
SC70
SC70
RESET 1
5
VCC1
GND 2
MAX6741 MAX6744
4 VCC2
GND 2
MAX6742 MAX6745
4 PFI
POK1 3
PFO 3
SC70
SC70
Ordering Information (continued)
PART MAX6738XK_D_-T MAX6739XK_D_-T MAX6740XK_ _D_-T MAX6741XK_ _D_-T MAX6742XK_D_-T MAX6743XK_ _D_-T MAX6744XK_ _D_-T MAX6745XK_D_-T TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 5 SC70-5 5 SC70-5 5 SC70-5 5 SC70-5 5 SC70-5 5 SC70-5 5 SC70-5 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-voltage 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. Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing "-T" with "+T" when ordering.
______________________________________________________________________________________
15
Low-Power Dual-/Triple-Voltage SC70 P Supervisory Circuits MAX6736-MAX6745
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
SC70, 5L.EPS
PACKAGE OUTLINE, 5L SC70
21-0076
C
1
1
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

▲Up To Search▲

Price & Availability of MAX673605

	To Download MAX673605 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .