19-2531; Rev 1; 4/03 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits 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) ♦ 6µA Supply Current ♦ Tiny SC70 Package 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 -40°C to +85°C temperature range. Applications Portable/BatteryPowered Equipment Controllers Multivoltage Systems GPS Equipment Notebook Computers POS Equipment PDAs 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-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. 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 RESET PUSH-PULL RESET MANUAL RESET POWER-FAIL INPUT/ OUTPUT POK OUTPUT RSTIN INPUT MAX6736 2 fixed X — X — — — MAX6737 2 fixed — X X — — — MAX6738 1 fixed, 1 adj X — X — — X *Manual reset detect on RESET output. ________________________________________________________________ Maxim Integrated Products 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 MAX6736–MAX6745 General Description The MAX6736–MAX6745 are low-power dual-/triplevoltage 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 components. 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 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. MAX6736–MAX6745 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits 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 = +70°C) 5-Pin SC70 (derate 3.1mW/°C above +70°C) ..............247mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+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 = 1.2V to 5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Operating Voltage Range VCC1 Supply Current VCC2 Supply Current SYMBOL VCC1, VCC2 ICC1 ICC2 CONDITIONS TA = 0°C to +85°C 1.0 5.5 VCC1 = 3.3V, VCC1 > VCC2, no load, reset not asserted 5 10 VCC1 = 1.8V, VCC1 < VCC2, no load, reset not asserted 5 10 VCC2 = 1.8V, VCC2 < VCC1, no load, reset not asserted 1 2 VCC2 = 3.3V, VCC2 > VCC1, no load, reset not asserted 10 20 4.625 4.750 UNITS V µA µA MAX67_ _T MAX67_ _S MAX67_ _R MAX67_ _Z MAX67_ _Y MAX67_ _W MAX67_ _V 2 MAX 5.5 MAX67_ _M VTH1 TYP 1.2 MAX67_ _L Reset Threshold for VCC1 MIN TA = -40°C to 0°C TA = 0°C to +85°C 4.500 TA = -40°C to +85°C 4.425 TA = 0°C to +85°C 4.250 TA = -40°C to +85°C 4.175 TA = 0°C to +85°C 3.000 TA = -40°C to +85°C 2.950 TA = 0°C to +85°C 2.850 TA = -40°C to +85°C 2.800 TA = 0°C to +85°C 2.550 TA = -40°C to +85°C 2.505 TA = 0°C to +85°C 2.250 TA = -40°C to +85°C 2.213 TA = 0°C to +85°C 2.125 TA = -40°C to +85°C 2.088 TA = 0°C to +85°C 1.620 TA = -40°C to +85°C 1.593 TA = 0°C to +85°C 1.530 TA = -40°C to +85°C 1.503 4.825 4.375 4.500 4.575 3.075 3.150 3.200 2.925 3.000 3.050 2.625 2.700 2.745 2.313 2.375 2.413 2.188 2.250 2.288 1.665 1.710 1.737 1.575 _______________________________________________________________________________________ 1.620 1.647 V Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits (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 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) VTH-RSTIN Reset Threshold Hysteresis TYP 3.075 TA = 0°C to +85°C 3.000 TA = -40°C to +85°C 2.905 TA = 0°C to +85°C 2.850 TA = -40°C to +85°C 2.800 TA = 0°C to +85°C 2.550 TA = -40°C to +85°C 2.505 TA = 0°C to +85°C 2.250 TA = -40°C to +85°C 2.213 TA = 0°C to +85°C 2.125 TA = -40°C to +85°C 2.088 TA = 0°C to +85°C 1.620 TA = -40°C to +85°C 1.593 TA = 0°C to +85°C 1.530 TA = -40°C to +85°C 1.503 TA = 0°C to +85°C 1.350 TA = -40°C to +85°C 1.328 TA = 0°C to +85°C 1.275 TA = -40°C to +85°C 1.253 TA = 0°C to +85°C 1.080 TA = -40°C to +85°C 1.062 TA = 0°C to +85°C 1.020 TA = -40°C to +85°C 1.002 TA = 0°C to +85°C 0.810 TA = -40°C to +85°C 0.797 TA = 0°C to + 85°C 0.765 TA = -40°C to +85°C 0.752 RESET Output High (Push-Pull) VOL VOH 3.150 2.925 3.000 3.050 2.625 2.700 2.745 2.313 2.375 2.413 2.188 2.250 2.288 1.665 1.710 1.737 1.575 1.620 1.647 1.388 V 1.425 1.448 1.313 1.350 1.373 1.110 1.140 1.158 1.050 1.080 1.098 0.833 0.855 0.869 0.788 0.810 0.824 TA = -40°C to +85°C 0.468 0.507 -10 +10 VTH1, VTH2, RSTIN, PFI UNITS 3.050 0.476 0.488 0.500 0.5 VCC1 ≥ 1.0V, ISINK = 50µA, TA = 0°C to +85°C RESET, POK1 Output Low MAX TA = 0°C to +85°C VRSTIN ≥ 0.1V (Note 2) RSTIN Input Current MIN V nA % 0.3 VCC1 ≥ 1.2V, ISINK = 100µA 0.3 VCC1 ≥ 2.13V, ISINK = 1.2mA 0.3 VCC1 ≥ 4.25V, ISINK = 3.2mA, 0.4 VCC1 ≥ 2.38V, ISOURCE = 500µA, output deasserted 0.8 × VCC VCC1 ≥ 4.75V, ISOURCE = 800µA, output deasserted 0.8 × VCC V V _______________________________________________________________________________________ 3 MAX6736–MAX6745 ELECTRICAL CHARACTERISTICS (continued) MAX6736–MAX6745 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 RESET Output Open-Drain Leakage Current (MAX6736/MAX6738) SYMBOL ILKG POK1 Output Open-Drain Leakage VCC Reset Delay tRD VCC Reset Timeout Period (Note 3) tRP CONDITIONS MIN MAX UNITS Output not asserted low (Note 2) 500 nA Output not asserted low (Note 2) 500 nA VCC1, VCC2, or RSTIN falling at 10mV/µs from VTH + 100mV to VTH - 100mV TYP 35 µs MAX67_ _ _ _ XK_ _D3 150 225 300 MAX67_ _ _ _ XK_ _ D7 1200 1800 2400 0.75 1.5 3.00 kΩ 150 225 300 ms ms MANUAL RESET (MAX6736–MAX6739 only) MR to VCC1 Internal Pullup Impedance MR Timeout Period tMRP MR Minimum Input Pulse Width tMPW Both D3 and D7 timing options 1 MR Glitch Rejection µs 100 ns 0.3 × VCC1 VIL MR Input Voltage 0.8 × VCC1 VIH MR to RESET Delay 300 V ns VCC1 POWER-OK OUTPUT (MAX6741/MAX6744 only) POK1 Timeout Period tPOKP 37.5 56.25 75.0 ms 25 50 100 kΩ (Note 4) 37.5 56.25 75.0 ms MAX67_ _ _ _ XK_ _D3 150 225 300 MAX67_ _ _ _ XK_ _ D7 1200 1800 2400 PUSHBUTTON RESET (MAX6740/MAX6741/MAX6742 only) RESET to VCC1 Internal Pullup Impedance Manual Reset Detect Debounce Period tDEB Manual Reset Timeout Period (Note 3) tMRP Manual Reset Minimum Input Pulse Width tMPW (Note 4) 1 ms µs Manual Reset Release Detect Threshold (Note 4) 0.5 × VCC1 V Manual Reset Glitch Rejection (Note 4) 100 ns 300 ns Manual Reset to RESET Delay 4 _______________________________________________________________________________________ Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits (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 TA = 0°C to +85°C 0.476 0.488 0.500 TA = -40°C to +85°C 0.468 0.507 VPFI ≥ 0.1V (Note 2) -10 +10 UNITS POWER-FAIL COMPARATOR (MAX6742/MAX6745 only) Power Fail In Threshold (Note 5) VTH-PFI Power Fail In Current IPFI PFO Output Low VOL PFI to PFO Propagation Delay tP PFO Startup Delay VCC1 ≥ 1.53V, ISINK = 500µA 0.3 VCC1 ≥ 2.03V, ISINK = 1.2mA 0.3 VCC1 ≥ 4.25V, ISINK = 3.2mA 0.4 V nA V PFI falling at 10mV/µs from VTH-PFI + 100mV to VTH-PFI - 100mV or rising at 10mV/µs from VTH-PFI - 100mV to VTH-PFI + 100mV (Note 5) 35 µs To output valid (Note 5) 5 ms All devices are 100% tested at TA = +25°C. 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. Note 1: Note 2: Note 3: Note 4: Note 5: Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) TOTAL 6 ICC1 5 4 3 2 8 7 6 TOTAL 5 ICC1 4 3 2 ICC2 1 0 -20 0 20 40 TEMPERATURE (°C) 60 80 8 7 6 TOTAL 5 4 ICC1 3 ICC2 1 0 -40 VCC1 = 1.8V, VCC2 = 1.2V 9 2 ICC2 1 10 SUPPLY CURRENT (µA) 7 SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) 8 VCC1 = 2.5V, VCC2 = 1.8V 9 SUPPLY CURRENT vs. TEMPERATURE MAX6736-45 toc02 MAX6736-45 toc01 VCC1 = 3.3V, VCC2 = 2.5V 9 SUPPLY CURRENT vs. TEMPERATURE 10 MAX6736-45 toc03 SUPPLY CURRENT vs. TEMPERATURE 10 0 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 -40 -20 0 20 40 60 80 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX6736–MAX6745 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAXIMUM VCC1/VCC2 TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE 1.009 1.004 0.999 0.994 0.989 0.984 -40 -20 0 20 40 60 MAX6736-45 toc05 RESET OCCURS ABOVE THESE LINES 100 VCC2 10 0 10 80 100 1000 TEMPERATURE (°C) RESET THRESHOLD OVERDRIVE (mV) NORMALIZED VCC RESET THRESHOLD vs. TEMPERATURE VCC TO RESET OUTPUT DELAY vs. TEMPERATURE MAX6736-45 toc06 1.008 NORMALIZED VCC RESET THRESHOLD VCC1 1000 1.003 0.998 0.993 MAX6736-45 toc07 1.014 10,000 VCC TO RESET OUTPUT DELAY (µs) NORMALIZED VCC/POK1/MR RESET TIMEOUT PERIOD 1.019 MAXIMUM VCC1/VCC2 TRANSIENT DURATION (µs) MAX6736-45 toc04 NORMALIZED VCC/POK1/MR TIMEOUT PERIOD vs. TEMPERATURE 100mV OVERDRIVE 48.5 43.5 38.5 33.5 NORMALIZED TO +25°C 0.988 28.5 -20 20 40 0 TEMPERATURE (°C) 60 80 -40 30 25 60 80 100mV OVERDRIVE 44 RISING EDGE 39 34 29 FALLING EDGE 24 20 -40 6 49 PFI TO PFO DELAY (µs) MAX6736-45 toc08 100mV OVERDRIVE 20 40 0 TEMPERATURE (°C) POWER-FAIL INPUT TO POWER-FAIL OUTPUT DELAY vs. TEMPERATURE RESET INPUT TO RESET OUTPUT DELAY vs. TEMPERATURE 35 -20 MAX6736-45 toc09 -40 RSTIN TO RESET OUTPUT DELAY (µs) MAX6736–MAX6745 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits -20 20 40 0 TEMPERATURE (°C) 60 80 -40 -20 20 40 0 TEMPERATURE (°C) 60 _______________________________________________________________________________________ 80 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits POWER-FAIL INPUT TO POWER-FAIL OUTPUT DELAY MR TO RESET OUTPUT DELAY MAX6736-45 toc11 MAX6736-45 toc10 PFI 200mV/div VMR 2V/div PFO 2V/div 100ns/div 10µs/div VCC TO RESET OUTPUT DELAY OUTPUT LOW VOLTAGE vs. SINK CURRENT MAX6736-45 toc12 500 VCC 200mV/div AC-COUPLED VRESET 2V/div OUTPUT LOW VOLTAGE (mV) VCC = 3.3V 400 MAX6736-45 toc13 VRESET 2V/div 300 200 100 0 4µs/div 0 1 2 3 4 5 6 7 8 9 10 SINK CURRENT (mA) 4 OUTPUT HIGH VOLTAGE (V) VCC = 3.3V 3 MAX6736-45 toc14 OUTPUT HIGH VOLTAGE vs. SOURCE CURRENT 2 1 0 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 SOURCING CURRENT (mA) _______________________________________________________________________________________ 7 MAX6736–MAX6745 Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX6736–MAX6745 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits Pin Description PIN MAX6736 MAX6738 MAX6740 MAX6741 MAX6742 MAX6737 MAX6739 MAX6743 MAX6744 MAX6745 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 50kΩ pullup resistor to VCC1 and provide a manual reset function. 1 1 1 1 1 RESET 2 2 2 2 2 GND 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 1.5kΩ pullup resistor to VCC1. 3 3 — — — MR 4 — 4 4 — VCC2 Voltage Input 1. Power supply and input for the secondary µP voltage reset monitor. — 4 3 — — RSTIN 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. 5 5 5 5 5 VCC1 Voltage Input 2. Power supply and input for the primary µP voltage reset monitor. — — — — 4 PFI 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. — — — — 3 PFO Power-Fail Comparator Output, Open Drain Active Low. PFO is asserted when PFI is below 0.488V. POK1 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. — 8 NAME — — 3 — _______________________________________________________________________________________ Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits PART NO. SUFFIX (__) VCC1 NOMINAL VOLTAGE THRESHOLD (V) VCC2 NOMINAL VOLTAGE THRESHOLD (V) PART NO. SUFFIX (__) VCC1 NOMINAL VOLTAGE THRESHOLD (V) VCC2 NOMINAL VOLTAGE THRESHOLD (V) LT MS 4.625 4.375 3.075 2.925 RD 2.625 0.788 ZW 2.313 1.665 MR 4.375 2.625 TZ 3.075 2.313 ZI ZG 2.313 2.313 1.388 1.110 TW TI 3.075 3.075 1.665 1.388 ZE 2.313 0.833 YV 2.188 1.575 TG 3.075 1.110 TE 3.075 0.833 YH YF 2.188 2.188 1.313 1.050 SY SV 2.925 2.925 2.188 1.575 YD 2.188 0.788 WT 1.665 3.075 WI WG 1.665 1.665 1.388 1.110 SH 2.925 1.313 SF 2.925 1.050 SD RY 2.925 2.625 0.788 2.188 WE 1.665 0.833 VR 1.575 2.625 RV 2.625 1.575 RH 2.625 1.313 VH VF 1.575 1.575 1.313 1.050 RF 2.625 1.050 VD 1.575 0.788 MAX6736–MAX6745 Table 1. Reset Voltage Threshold Suffix Guide for MAX6736/MAX6737/MAX6740/ MAX6741/MAX6743/MAX6744 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 (_) VCC1 NOMINAL VOLTAGE THRESHOLD (V) L 4.625 M 4.375 T 3.075 S 2.925 R 2.625 Z 2.313 Y 2.188 W 1.665 V 1.575 Table 3. VCC Timeout Period Suffix Guide TIMEOUT PERIOD SUFFIX ACTIVE TIMEOUT PERIOD MIN (ms) MAX (ms) D3 150 300 D7 1200 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 MAX6736–MAX6745 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits VCC1 VTH1 GND POK1 tPOKP GND VCC2 VTH2 GND SWITCH BOUNCE MR SWITCH BOUNCE GND RESET tRP GND tMRP Figure 1. Timing Diagram Detailed Description Supply Voltages The MAX6736–MAX6745 µP supervisory circuits maintain system integrity by alerting the µP 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. 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 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 50kΩ 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 ______________________________________________________________________________________ Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits SWITCH BOUNCE SWITCH BOUNCE SWITCH BOUNCE PUSHBUTTON SWITCH CLOSED VCC1 tMRP tDEB tDEB tMRP RESET 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 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 1.5kΩ pullup resistor to VCC1 and can be left unconnected if not used. MR can be driven with CMOS logic levels, open-drain/open-collector outputs, or a momentary pushbutton switch to GND to create a manual reset function. 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- 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. Applications Information VEXT_TH R1 RSTIN MAX6738 MAX6739 MAX6740 MAX6743 R2 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. GND Figure 3. Monitoring an Additional Voltage ______________________________________________________________________________________ 11 MAX6736–MAX6745 SWITCH BOUNCE OPEN MAX6736–MAX6745 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits A) VIN IS POSITIVE VEXT_TH MAX6742 MAX6745 R1 PFI VEXT_TH = VTH-PFI ( R1 + R2 R2 ) PFO R2 GND B) VIN IS NEGATIVE VCC VEXT_TH = R2 MAX6742 MAX6745 R1 PFI ( )( (VTH-PFI) ) V 1 + 1 - CC R1 R1 R2 VPFI = 488mV 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 1µA 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 < 488kΩ PFO is an open-drain output requiring an external pullup resistor, R4. Select R4 to be less than 1% of R3. VGOOD = DESIRED VEXT GOOD VOLTAGE THRESHOLD VFAIL = DESIRED VEXT FAIL VOLTAGE THRESHOLD VPU = VPULLUP (FOR OPEN-DRAIN PFO) R2 = 488kΩ (FOR >1µA R2 CURRENT) PFO R2 GND VEXT_TH Figure 4. Using Power-Fail Input to Monitor an Additional Power Supply 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 R1 = R2 (VGOOD - VTH−PFI ) − VPU VTH - PFI 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. VPULLUP R3 RESET TO OTHER SYSTEM COMPONENTS VCC1 VCC2 (VTH- PFI (VGOOD - VFAIL ) VIN VCC2 MAX6737 MAX6739 MAX6743 MAX6744 RESET MAX6745 VEXT µP 4.7kΩ R1 R4 PFI PFO R2 GND Figure 5. Interfacing to µPs with Bidirectional Reset I/O 12 PFO MAX6742 MAX6745 RESET VCC1 GND VGOOD VFAIL GND VGOOD = DESIRED VEXT GOOD VOLTAGE THRESHOLD VFAIL = DESIRED VEXT FAIL VOLTAGE THRESHOLD VOH = VCC1 (FOR PUSH-PULL PFO) R2 = 200kΩ (FOR > 2.5µA R2 CURRENT) R1 = R2 ((VGOOD - VTH-PFI) - (VTH-PFI)(VGOOD - VFAIL) / VPU) / VTH-PFI R3 = (R1 x VOH) / (VGOOD - VFAIL) Figure 6. Adding Hysteresis to Power Fail for Push-Pull PFO ______________________________________________________________________________________ Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits 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. Transient Immunity The MAX6736–MAX6745 supervisors are relatively immune to short-duration falling VCC transients (glitches). It is usually undesirable to reset the µP 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 0.1µF bypass capacitor mounted close to the VCC pin provides additional transient immunity. Chip Information TRANSISTOR COUNT: 249 PROCESS: BiCMOS Functional Diagram VCC1 MAX6736– MAX6745 PFO POK1 DELAY VCC1 RSTIN/PFI RESET TIMEOUT PERIOD VCC2 RESET OUTPUT RESET VCC2 VCC1 MR PULLUP 0.488V VCC1 1.23V MR ______________________________________________________________________________________ 13 MAX6736–MAX6745 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. MAX6736–MAX6745 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits Selector Guide (continued) MANUAL RESET POWER-FAIL INPUT/ OUTPUT POK OUTPUT RSTIN INPUT X X — — X — X* — — X — X* — X — X* — X* X — — — X — — — X 2 fixed — X — — X — 1 fixed — X — X — — PART VOLTAGE MONITORS OPEN-DRAIN RESET MAX6739 1 fixed, 1 adj — MAX6740 2 fixed, 1 adj X* MAX6741 2 fixed X* MAX6742 1 fixed MAX6743 2 fixed, 1adj MAX6744 MAX6745 PUSH-PULL RESET *Manual reset detect on RESET output. Typical Application Circuits DC/DC CONVERTER UNREGULATED DC IN OUT VBATT IN OUT DC/DC CONVERTER SHDN IN OUT DC/DC CONVERTER VCC1 VCC2 VCC1 MAX6741 POK1 GND RESET CORE I/O SUPPLY SUPPLY µP RESET GND PFO MAX6742 µP RESET PFI GND PUSHBUTTON SWITCH PUSHBUTTON SWITCH 14 VCC ______________________________________________________________________________________ RESET GND Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits TOP VIEW RESET 1 5 RESET 1 VCC1 MAX6736 MAX6737 GND 2 MR 3 GND 2 4 5 MAX6738 MAX6739 MR 3 VCC2 VCC1 RESET 1 GND 2 4 RSTIN RESET 1 GND 2 5 VCC1 MAX6741 MAX6744 POK1 3 RSTIN 3 VCC2 SC70 4 VCC2 SC70 RESET 1 GND 2 4 VCC1 MAX6740 MAX6743 SC70 SC70 5 5 VCC1 4 PFI MAX6742 MAX6745 PFO 3 SC70 Ordering Information (continued) PART TEMP RANGE PIN-PACKAGE MAX6738XK_D_-T -40°C to +85°C 5 SC70-5 MAX6739XK_D_-T -40°C to +85°C 5 SC70-5 MAX6740XK_ _D_-T -40°C to +85°C 5 SC70-5 MAX6741XK_ _D_-T -40°C to +85°C 5 SC70-5 MAX6742XK_D_-T -40°C to +85°C 5 SC70-5 MAX6743XK_ _D_-T -40°C to +85°C 5 SC70-5 MAX6744XK_ _D_-T -40°C to +85°C 5 SC70-5 MAX6745XK_D_-T -40°C to +85°C 5 SC70-5 ______________________________________________________________________________________ 15 MAX6736–MAX6745 Pin Configurations 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 MAX6736–MAX6745 Low-Power Dual-/Triple-Voltage SC70 µP Supervisory Circuits 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 © 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.