LTC1727/LTC1728 Micropower Precision Triple Supply Monitors in 8-Lead MSOP and 5-Lead SOT-23 Packages U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Monitors Three Inputs Simultaneously LTC1727-5: 5V, 3.3V and ADJ LTC1727-2.5: 2.5V, 3.3V and ADJ LTC1728-5: 5V, 3.3V and ADJ LTC1728-2.5: 2.5V, 3.3V and ADJ LTC1728-1.8: 3V, 1.8V and ADJ ±1.5% Threshold Accuracy Over Temperature Very Low Supply Current: 10µA Typ 200ms Reset Time Delay Active Low RESET Output Power Supply Glitch Immunity Guaranteed RESET for VCC3 ≥ 1V or VCC5 /VCC25/VCC18 ≥ 1V LTC1727 Includes Monitor Output for Each Supply LTC1727: 8-Lead MSOP and SO Packages LTC1728: 5-Lead SOT-23 Package U APPLICATIO S ■ ■ ■ ■ The LTC1728 is functionally identical to the LTC1727 without the individual monitor outputs. The RST output is guaranteed to be in the correct state for VCC5/VCC25/VCC18 or VCC3 down to 1V. The LTC1727/ LTC1728 may also be configured to monitor any one or two VCC inputs instead of three, depending on system requirements. Very low (10µA typical) supply current makes the LTC1727/ LTC1728 ideal for power conscious systems. The LTC1727 is available in an 8-lead MSOP or SO package and the LTC1728 is available in a 5-lead SOT-23 package. Desktop Computers Notebook Computers Intelligent Instruments Portable Battery-Powered Equipment Network Servers , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ The LTC®1727 is a triple supply monitor intended for systems with multiple supply voltages. Each supply monitor has its own open-drain output for individual supply monitoring. A common open-drain reset output remains low until all three supplies have been in compliance for 200ms. Tight 1.5% accuracy specifications and glitch immunity ensure reliable reset operation without false triggering. TYPICAL APPLICATIO DC/DC CONVERTER 3.3V 5V 1.8V SYSTEM LOGIC 5 VCC3 RST Triple Supply Monitor with Power Good Output (3.3V, 2.5V and Adjustable) LTC1727-2.5 1 3.3V LTC1728-5 0.1µF 0.1µF 4 VCC5 R1 61.9k 1% 3 VCCA R2 100k 1% 2.5V GND 1727/28 TA01 2 ADJUSTABLE SUPPLY R1 1 2 3 R2 4 VCC3 COMP3 VCC25 COMP25 VCCA RST GND COMPA 8 R3 10k R4 10k POWER GOOD 7 6 SYSTEM RESET 5 1727/28 TA08 1 LTC1727/LTC1728 W W W AXI U U ABSOLUTE RATI GS (Notes 1, 2) VCC3, VCC5/VCC25/VCC18, VCCA ................... – 0.3V to 7V RST ........................................................... – 0.3V to 7V COMPA, COMP3, COMP25/COMP5 (MS8 and SO-8 Only) ............................ – 0.3V to 7V Operating Temperature Range (Note 3) ............................................. – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................ 300°C W U U PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW TOP VIEW VCC3 VCC5 /VCC25 VCCA GND 1 2 3 4 8 7 6 5 COMP3 COMP25/COMP5 RST COMPA MS8 PACKAGE 8-LEAD PLASTIC MSOP VCC3 1 VCC5/ 2 VCC25 VCCA 3 8 GND 4 5 COMP3 COMP25/ COMP5 RST 7 6 RST 1 VCC5/ 4 VCC25 / VCC18 VCCA 3 COMPA S5 PACKAGE 5-LEAD PLASTIC SOT-23 S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 125°C, θJA = 200°C/W 5 VCC3 GND 2 TJMAX = 125°C, θJA = 250°C/W TJMAX = 125°C, θJA = 150°C/W ORDER PART NUMBER MS8 PART MARKING ORDER PART NUMBER S8 PART MARKING ORDER PART NUMBER S5 PART MARKING LTC1727EMS8-2.5 LTC1727EMS8-5 LTHY LTHX LTC1727ES8-2.5 LTC1727IS8-2.5 LTC1727ES8-5 LTC1727IS8-5 172725 727I25 17275 1727I5 LTC1728ES5-1.8 LTC1728ES5-2.5 LTC1728ES5-5 LTPH LTIA LTHZ Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS All except LTC1728-1.8. The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT3 Reset Threshold VCC3 VCC3 Input Threshold ● 3.036 3.086 3.135 V VRT5 Reset Threshold VCC5 VCC5 Input Threshold (5V Version) ● 4.600 4.675 4.750 V VRT25 Reset Threshold VCC25 VCC25 Input Threshold (2.5V Version) ● 2.300 2.338 2.375 V VRTA Reset Threshold VCCA VCCA Input Threshold ● 0.985 1.000 1.015 V VCCOP VCC3, VCC5/VCC25 Operating Voltage RST, COMP3, COMP5, COMP25 in Correct Logic State ● 1 7 V VCCOPA VCC3, VCC5/VCC25 Operating Voltage Minimum Supply Voltage to Guarantee COMPA in Correct Logic State ● 2 2.3 V IVCC3 VCC3 Supply Current VCC5/VCC25 > VCC3 VCC5/VCC25 < VCC3, VCC3 = 3.3V (Note 4) ● ● 1 10 2 20 µA µA IVCC25 VCC25 Supply Current VCC25 < VCC3, VCC25 = 2.5V (Note 4) ● 1 2 µA IVCC5 VCC5 Supply Current VCC5 = 5V, VCC3 < VCC5 ● 10 20 µA IVCCA VCCA Input Current VCCA = 1V ● – 15 0 15 nA tRST Reset Pulse Width RST Low with 10k Pull-Up to VCC3 (Note 5) ● 140 200 280 ms 2 LTC1727/LTC1728 ELECTRICAL CHARACTERISTICS All except LTC1728-1.8. The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless otherwise noted. SYMBOL PARAMETER CONDITIONS tUV VCC Undervoltage Detect to RST or COMPX VCC5, VCC25, VCC3 or VCCA Less Than Reset Threshold VRT by More Than 1% (Note 5) MIN VOL Output Voltage Low, RST, COMPX ISINK = 2.5mA, VCC3 = 3V, VCC5/VCC25 = 0V ISINK = 100µA, VCC3 = 1V, VCC5/VCC25 = 0V ISINK = 100µA, VCC3 = 0V, VCC5/VCC25 = 1V ISINK = 100µA, VCC3 = 1V, VCC5/VCC25 = 1V ● ● ● ● VOH Output Voltage High, RST, COMPX (Note 6) ISOURCE = 1µA ● VCC3 – 1 TYP MAX 0.15 0.05 0.05 0.05 UNITS µs 110 0.4 0.3 0.3 0.3 V V V V V LTC1727-5/LTC1728-5 Only VOVR VCC5 Reset Override Voltage (Note 7) VCC3 ±0.025 Override VCC5 Ability to Assert RST V LTC1728-1.8 The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC3 = 3V, VCC18 = 1.8V, VCCA = VCC3 unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT3 Reset Threshold VCC3 VCC3 Input Threshold ● 2.760 2.805 2.850 V VRT18 Reset Threshold VCC18 VCC18 Input Threshold ● 1.656 1.683 1.710 V VRTA Reset Threshold VCCA VCCA Input Threshold ● 0.985 1.000 1.015 V VCCOP VCC3, VCC18 Operating Voltage RST in Correct Logic State ● 1 7 V IVCC3 VCC3 Supply Current VCC18 > VCC3 VCC18 < VCC3, VCC3 = 3V (Note 4) ● ● 1 10 2 20 µA µA IVCC18 VCC18 Supply Current VCC18 < VCC3, VCC18 = 1.8V (Note 4) ● 1 2 µA IVCCA VCCA Input Current VCCA = 1V ● – 15 0 15 nA tRST Reset Pulse Width RST Low (Note 5) ● 140 200 280 ms tUV VCC Undervoltage Detect to RST VCC18, VCC3 or VCCA Less Than Reset (Note 5) Threshold VRT by More Than 1% VOL Output Voltage Low, RST ISINK = 2.5mA, VCC3 = 3V, VCC18 = 0V ISINK = 100µA, VCC3 = 1V, VCC18 = 0V ISINK = 100µA, VCC3 = 0V, VCC18 = 1V ISINK = 100µA, VCC3 = 1V, VCC18 = 1V ● ● ● ● VOH Output Voltage High, RST ISOURCE = 1µA (Note 6) ● VCC3 – 1 Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: All voltage values are with respect to GND. Note 3: The LTC1727E/LTC1728E are guaranteed to meet specified performance from 0°C to 70°C and are designed, characterized and assured to meet the extended temperature limits of – 40°C to 85°C but are not tested at these temperatures. Note 4: Both VCC3 and VCC5/VCC25/VCC18 can act as the supply depending on which pin has the greatest potential. µs 110 0.15 0.05 0.05 0.05 0.4 0.3 0.3 0.3 V V V V V Note 5: Measured from when input passes through the input threshold (VRTX) until RST or COMPX passes through 1.5V. Note 6: The output pins RST and COMPX have internal pull-ups to VCC3 of typically 6µA. However, external pull-up resistors may be used when faster rise times are required or for VOH voltages greater than VCC3. Note 7: The VCC5 reset override voltage is valid for an operating range less than approximately 4.15V. Above this point the override is turned off and the VCC5 pin functions normally. 3 LTC1727/LTC1728 U W TYPICAL PERFOR A CE CHARACTERISTICS VCCA Threshold Voltage vs Temperature VCCA Input Current vs Input Voltage 1.0 0.5 0 – 0.5 –1.0 –1.5 – 2.0 0.80 0.85 0.90 0.95 1 1.05 1.10 1.15 1.20 INPUT VOLTAGE (V) TYPICAL TRANSIENT DIRATION (µs) 1.5 1.010 1.005 1.000 0.995 0.990 0.985 –60 –40 –20 0 20 40 60 TEMPERATURE (°C) Reset Pulse Width vs Temperature 10 260 150 100 50 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VCC) 1727/28 G03 200 160 1.3 4 VOL = 0.2V 20 40 60 80 1.1 1.0 0.9 0.8 2 0.7 1 0.6 0 0 0 100 1 3 4 2 VCC3 OR VCC5 (V) 5 0.5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 6 1727/28 G05 1727/28 G04 1.5 VCC3 = 3.3V VCC25 = 2.5V VCCA = 3.3V 1.4 1.3 15 VCC5 = 5V VCC3 = 3.3V VCCA = 3.3V 14 13 1.2 12 1.1 11 IVCC3 (µA) 12 0.9 9 8 7 0.7 7 6 0.6 6 80 100 0.5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 1727/28 G08 VCC5 = 5V VCC3 = 3.3V VCCA = 3.3V 10 0.8 1727/28 G07 4 1.0 8 5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 IVCC5 vs Temperature (LTC1727-5/LTC1728-5) 11 9 80 1727/28 G06 IVCC3 vs Temperature (LTC1727-5/LTC1728-5) IVCC3 vs Temperature (LTC1727-2.5/LT1728-2.5) 10 VCC3 = 3.3V VCC25 = 2.5V VCCA = 3.3V 1.2 5 3 180 1.5 1.4 IVCC25 (µA) 220 IVCC25 vs Temperature (LTC1727-2.5/LT1728-2.5) 6 TEMPERATURE (°C) IVCC3 (µA) 200 VOL = 0.4V 7 240 13 250 TA = 25°C 8 ISINK (mA) RESET PULSE WIDTH, tRST (ms) 9 140 –60 –40 –20 RESET OCCURS ABOVE CURVE 300 RST, COMPX ISINK vs Supply Voltage 280 15 100 350 1727/28 G02 1727/28 G01 14 80 TA = 25°C 400 IVCC5 (µA) INPUT CURRENT (nA) 450 1.015 TA = 25°C VCCA THRESHOLD VOLTAGE, VRTA (V) 2.0 Typical Transient Duration vs Comparator Overdrive 5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 1727/28 G09 LTC1727/LTC1728 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC3 Threshold Voltage vs Temperature (All But LTC1728-1.8) 3.125 2.3600 2.3525 2.3450 2.3375 2.3300 2.3225 2.3150 2.3075 2.3000 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 VCC5 Threshold Voltage vs Temperature (LTC1727-5/LTC1728-5) 4.750 VCC5 THESHOLD VOLTAGE, VRT5 (V) 3.135 2.3675 VCC3 THRESHOLD VOLTAGE, VRT3 (V) 2.3750 4.725 3.115 3.105 4.700 3.095 3.085 4.675 3.075 4.650 3.065 3.055 4.625 3.045 3.035 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 1727/28 G10 1.5 1.4 100 4.600 20 40 60 –60 –40 –20 0 TEMPERATURE (°C) 1727/28 G12 15 VCC3 = 3V VCC18 = 1.8V VCCA = 3V VCC3 = 3V 14 VCC18 = 1.8V VCCA = 3V 13 1.2 12 1.1 11 1.0 0.9 10 9 0.8 8 0.7 7 0.6 6 0.5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 80 100 1727/28 G14 1727/28 G13 VCC3 Threshold Voltage vs Temperature (LTC1728-1.8) VCC18 Threshold Voltage vs Temperature (LTC1728-1.8) 2.845 VCC3 THRESHOLD VOLTAGE, VRT3 (V) 1.710 1.700 1.690 1.680 1.670 1.660 1.650 –60 –40 –20 0 20 40 60 TEMPERATURE (°C) 80 100 IVCC3 vs Temperature (LTC1728-1.8) IVCC3 (µA) IVCC18 (µA) 1.3 80 1727/28 G11 IVCC18 vs Temperature (LTC1728-1.8) VCC18 THRESHOLD VOLTAGE, VRT18 (V) VCC25 THRESHOLD VOLTAGE, VRT25 (V) VCC25 Threshold Voltage vs Temperature (LTC1727-2.5/LTC1728-2.5) 80 100 1727/28 G15 2.835 2.825 2.815 2.805 2.795 2.785 2.775 2.765 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 1727/28 G16 5 LTC1727/LTC1728 U U U PI FU CTIO S (LTC1727/LTC1728) VCC3 (Pin 1/Pin 5): 3.3V Sense Input and Power Supply Pin. (3V Sense Input and Power Supply Pin for LTC1728-1.8.) This pin provides power to the part when the voltage on VCC3 is greater than the voltage on VCC5/VCC25/VCC18. Bypass to ground with a ≥ 0.1µF ceramic capacitor. VCC5 (Pin 2/Pin 4): 5V Sense Input and Power Supply Pin. This pin is used on the LTC1727-5/LTC1728-5 to provide power to the part when the voltage on VCC5 is greater than the voltage on VCC3. Bypass to ground with a ≥ 0.1µF ceramic capacitor. COMPA (Pin 5): VCCA Comparator Output for the LTC1727. Active high, open-drain logic output with weak pull-up to VCC3. Asserted when VCCA is above VRTA. Deasserted when VCCA is below VRTA or if both the VCC3 and VCC5 supply pins are too low to power the internal bandgap reference (typically < 2.0V). Can be pulled greater than VCC3 using an external pull-up. RST (Pin 6/Pin 1): Reset Logic Output. Active low, opendrain logic output with weak pull-up to VCC3. Can be pulled up greater than VCC3 when interfacing to 5V logic. Asserted when one or all of the supplies are below trip thresholds and held for 200ms after all supplies become valid. VCC25 (Pin 2/Pin 4): 2.5V Sense Input and Power Supply Pin. This pin is used on the LTC1727-2.5/LTC1728-2.5 to provide power to the part when the voltage on VCC25 is greater than the voltage on VCC3. Bypass to ground with a ≥ 0.1µF ceramic capacitor. COMP5 (Pin 7): VCC5 Comparator Output for the LTC1727-5. Active high, open-drain logic output with weak pull-up to VCC3. Asserted when VCC5 is above VRT5. Can be pulled greater than VCC3 using an external pull-up. VCC18 (Pin 2/Pin 4): 1.8V Sense Input and Power Supply Pin. This pin is used on the LTC1728-1.8 to provide power to the part when the voltage on VCC18 is greater than the voltage on VCC3. Bypass to ground with a ≥ 0.1µF ceramic capacitor. COMP25 (Pin 7): VCC25 Comparator Output for the LTC1727-2.5. Active high, open-drain logic output with weak pull-up to VCC3. Asserted when VCC25 is above VRT25. Can be pulled greater than VCC3 using an external pull-up. VCCA (Pin 3/Pin 3): 1V Sense, High Impedance Input. If unused, it can be tied to either VCC3 or VCC5 /VCC25/VCC18. COMP3 (Pin 8): VCC3 Comparator Output for the LTC1727. Active high, open-drain logic output with weak pull-up to VCC3. Asserted when VCC3 is above VRT3. Can be pulled greater than VCC3 using an external pull-up. GND (Pin 4/Pin 2): Ground. 6 LTC1727/LTC1728 W BLOCK DIAGRA S LTC1727-5/LTC1727-2.5 VCC3 6µA – VCC3 1 8 COMP3 + VCC3 POWER DETECT 6µA VCC INTERNAL VCC5 / 2 VCC25 7 COMP25/ COMP5 – VCC3 + 6µA VCCA 3 GND 4 – + 200ms PULSE GENERATOR 6 RST 200ms DELAY VCC3 6µA 5 COMPA BANDGAP REFERENCE 1727 BD1 7 LTC1727/LTC1728 W BLOCK DIAGRA S LTC1728-5/LTC1728-2.5/LTC1728-1.8 – VCC3 5 + POWER DETECT VCC INTERNAL VCC3 VCC5/ VCC25 / 4 VCC18 6µA – 200ms PULSE GENERATOR 1 200ms DELAY + – VCCA 3 + GND 2 BANDGAP REFERENCE 1727 BD2 WU W TI I G DIAGRA VCC Monitor Timing VCCX VRTX tUV RST tRST 1.5V COMPX 1727 TD01 8 RST LTC1727/LTC1728 U W U U APPLICATIO S I FOR ATIO Supply Monitoring Power-Down The LTC1727 is a low power, high accuracy triple supply monitoring circuit with three monitor outputs and a 200ms microprocessor reset output. On power-down, once any of the VCC inputs drop below its threshold, RST is held at a logic low. A logic low of 0.3V is guaranteed until both VCC3 and VCC5/VCC25/VCC18 drop below 1V. All three VCC inputs must be above predetermined thresholds for reset not to be invoked. The LTC1727/LTC1728 will assert reset during power-up, power-down and brownout conditions on any one or all of the VCC inputs. Power Detect The LTC1727/LTC1728 are powered from the 3.3V/3V input pin (VCC3), the 1.8V input pin (VCC18), the 2.5V input pin (VCC25) or the 5V input pin (VCC5), whichever pin has the highest potential. This ensures the part pulls the RST pin low as soon as either input pin is ≥ 1V. Power-Up Upon power-up, either the VCC5 /VCC25/VCC18 or VCC3 pin, can power the part. This ensures that RST will be low when either VCC5 /VCC25/VCC18 or VCC3 reaches 1V. As long as any one of the VCC inputs is below its predetermined threshold, RST will stay a logic low. Once all of the VCC inputs rise above their thresholds, an internal timer is started and RST is released after 200ms. RST is reasserted whenever any one of the VCC inputs drops below its predetermined threshold and remains asserted until 200ms after all of the VCC inputs are above their thresholds. On the LTC1727, each of the comparator outputs will be low until the VCC input that is monitored by that comparator rises above the appropriate predetermined threshold. The COMP3, and COMP5/COMP25 outputs are guaranteed to be in the correct logic state for either VCC3 or VCC5/VCC25 greater than 1V. The COMPA output requires the internal bandgap reference to be valid before the correct logic state can be output. Therefore, the COMPA output will be held low until VCCA is above 1V and VCC3 or VCC5/VCC25 is greater than 2V (typ). Glitch Immunity The RST output of the LTC1727/LTC1728 have two forms of glitch immunity built in. First, the input monitors require the input voltage to transition at least 10% of the input threshold (0.1 • VRTH) below the input threshold for approximately 50µs in order to force the monitor output low. The duration of the transition must be longer for voltage transitions of lesser magnitude (see Figure 1). Secondly, the reset pulse width of approximately 200ms acts to debounce the RST output ensuring that the RST output will always be in the correct state. The individual monitor outputs of the LTC1727 do not have hysteresis and will track the monitor inputs relative to the monitor’s input threshold (VRTA, VRT25, VRT3 and VRT5). A very slow moving input voltage with ripple riding on it may cause the individual monitor outputs (COMPA, COMP25, COMP3 and COMP5) to toggle on the ripple as the input voltage passes the input threshold. The slow response time of the LTC1727’s input monitors has a tendency to integrate signals on the inputs improving their immunity to noise and ripple. 450 400 TRANSIENT DURATION (µs) The LTC1728 is a low power, high accuracy triple supply monitoring circuit with a single 200ms microprocessor reset output. 350 300 250 200 150 100 50 0 1 10 100 0.1 RESET MONITOR OVERDRIVE VOLTAGE (% OF VCC) 1727/28 F01 Figure 1. Transient Duration vs Comparator Overdrive 9 LTC1727/LTC1728 U W U U APPLICATIO S I FOR ATIO When monitoring either 3.3V or 5V with VCC3 strapped to VCC5 (see Figure 2), the part determines which is the appropriate range. The part handles this situation as shown in Figure 3. Above 1V and below VRT3, RST is held low. From VRT3 to approximately 4.15V the part assumes 3.3V supply monitoring and RST is deasserted. Above approximately 4.15V the part operates as a 5V monitor. In most systems the 5V supply will pass through the 3.1V to 4.15V region in < 200ms during power-up, and the RST output will behave as desired. Table 1 summarizes the state of RST at various operating voltages with VCC3 = VCC5. Override Functions (5V Versions Only) The VCCA pin, if unused, can be tied to either VCC3 or VCC5. This is an obvious solution since the trip points for VCC3 and VCC5 will always be greater than the trip point for VCCA. The VCC5 input trip point is disabled if its voltage is equal to the voltage on VCC3 ±25mV and the voltage on VCC5 is less than 4.15V. In this manner, the LTC1727-5/ LTC1728-5 will behave as a 3.3V monitor and VCC5 reset capability will be disabled. The VCC5 trip point is reenabled when the voltage on VCC5 is equal to the voltage on VCC3 ±25mV and the two inputs are greater than approximately 4.15V. In this manner, the part can function as a 5V monitor with the 3.3V monitor disabled. VCC 3.3V OR 5V Table 1. Override Truth Table (VCC3 = VCC5) INPUTS (VCC3 = VCC5 = VCC) — 1V ≤ VCC ≤ VRT3 0 VRT3 ≤ VCC ≤ 4.15V 1 4.15V ≤ VCC ≤ VRT5 0 VRT5 ≤ VCC 1 LTC1728-5 5 4 3 2 R1 10k VCC3 VCC5 VCCA RST 1 TO SYSTEM RESET GND 1727/28 F02 Figure 2. Single Supply Monitor with Others Disabled 5 RST OUTPUT VOLTAGE (V) VCC3 = VCC5 = VCCA = 0V TO 5V 10k PULL-UP FROM RST TO VCC3 4 3 2 1 0 0 1 3 4 2 SUPPLY VOLTAGE (V) 5 1727/28 F03 Figure 3. RST Voltage vs Supply Voltage 10 RST 0V ≤ VCC ≤ 1V LTC1727/LTC1728 U W U U APPLICATIO S I FOR ATIO Figure 4 contains a simple circuit for 5V systems that can’t risk the RST output going high in the 3.1V to 4.15V range (possibly due to very slow rise time on the 5V supply). Diode D1 powers the LTC1728-5 while dropping ≈ 0.6V from the VCC5 pin to the VCC3 pin. This prevents the part’s internal override circuit from being activated. Without the override circuit active, the RST pin stays low until VCC5 reaches VRT5 ≅ 4.675V. (See Figure 5.) LTC1727-2.5/LTC1728-2.5/LTC1728-1.8 Override Functions The VCCA pin, if unused, can be tied to either VCC3 or VCC25/ VCC18. This is an obvious solution since the trip points for VCC3 and VCC25/VCC18 will always be greater than the trip point for VCCA. Likewise, the VCC25/VCC18, if unused, can be tied to VCC3. VCC3 must always be used. Tying VCC3 to VCC25/VCC18 and operating off of a 2.5V/1.8V supply will result in the continuous assertion of RST. 5V D1 LTC1728-5 5 4 3 2 0.1µF R1 10k VCC3 VCC5 VCCA RST 1 TO SYSTEM RESET GND D1: MMBD914 OR EQUIVALENT 1727/28 F04 Figure 4. LTC1728-5 Monitoring a Single 5V Supply. D1 Used to Avoid RST High Near 3.1V to 4V (See Figure 3). RST OUTPUT VOLTAGE (V) 5 VCC5 = VCCA = 0V TO 5V 10k PULL-UP FROM RST TO VCC5 TA = 25°C 4 3 2 1 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VCC5 (V) 1727/28 F05 Figure 5. RST Output Voltage Characteristics of the Circuit in Figure 4 11 LTC1727/LTC1728 U TYPICAL APPLICATIO S Triple Supply Monitor (3.3V, 5V and Adjustable) LTC1728-5 3.3V ADJUSTABLE SUPPLY OR DC/DC FEEDBACK DIVIDER R1* 5V 5 4 3 R2* 2 VCC3 RST 1 SYSTEM RESET VCC5 VCCA GND 1727/28 TA03 *TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL COMBINATION OF R1 AND R2 ≤ 66.5k Dual Supply Monitor (3.3V and 5V, Defeat VCCA Input) LTC1728-5 5 3.3V 4 5V 3 2 VCC3 RST 1 SYSTEM RESET VCC5 VCCA GND 1727/28 TA04 Dual Supply Monitor (3.3V or 5V Plus Adjustable) 3.3V OR 5V LTC1728-5 5 4 ADJUSTABLE SUPPLY R1* 3 R2* 2 VCC3 RST 10k 1 SYSTEM RESET VCC5 VCCA GND 1727/28 TA05 *TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL COMBINATION OF R1 AND R2 ≤ 66.5k REFER TO LTC1728-5 OVERRIDE FUNCTIONS IN THE APPLICATIONS INFORMATION SECTION 12 LTC1727/LTC1728 U TYPICAL APPLICATIO S Dual Supply Monitor (3.3V Plus Adjustable) 3.3V LTC1728-2.5 5 4 ADJUSTABLE SUPPLY R1* 3 2 R2* VCC3 RST 10k 1 SYSTEM RESET VCC25 VCCA GND 1727/28 TA06 *TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL COMBINATION OF R1 AND R2 ≤ 66.5k Using VCCA Tied to DC/DC Feedback Divider 2.9V LTC1435 VOSENSE ADJUSTABLE RESET TRIP THRESHOLD 2.74V 6 35.7k 1% 3.3V 2.8k 5V 1% 22.1k 1% LTC1728-5 5 4 3 2 VCC3 RST 1 SYSTEM RESET VCC5 VCCA GND 1727/28 TA07 13 LTC1727/LTC1728 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.15) 1 2 3 4 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.034 ± 0.004 (0.86 ± 0.102) 0° – 6° TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC 0.021 ± 0.006 (0.53 ± 0.015) 0.006 ± 0.004 (0.15 ± 0.102) MSOP (MS8) 1098 * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE S5 Package 5-Lead Plastic SOT-23 (LTC DWG # 05-08-1633) 2.80 – 3.00 (0.110 – 0.118) (NOTE 3) 2.60 – 3.00 (0.102 – 0.118) 1.50 – 1.75 (0.059 – 0.069) 0.35 – 0.55 (0.014 – 0.022) 1.90 (0.074) REF 0.00 – 0.15 (0.00 – 0.006) 0.09 – 0.20 (0.004 – 0.008) (NOTE 2) 0.90 – 1.45 (0.035 – 0.057) 0.35 – 0.50 0.90 – 1.30 (0.014 – 0.020) (0.035 – 0.051) FIVE PLACES (NOTE 2) S5 SOT-23 0599 NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DIMENSIONS ARE INCLUSIVE OF PLATING 3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 4. MOLD FLASH SHALL NOT EXCEED 0.254mm 5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ) 14 0.95 (0.037) REF LTC1727/LTC1728 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. SO8 1298 15 LTC1727/LTC1728 U TYPICAL APPLICATIO Triple Supply Monitor with Manual Reset Button 12V (± 5%) VTRIP = 11.2V (± 0.17V) 5V 3.3V 5 100nF R3* 10k 5% R1 1.07M 0.1% RST 1 LTC1728-5 4 VCC5 100nF R2 105k 0.1% MANUAL RESET BUTTON (NORMALLY OPEN) VCC3 *OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE 3 VCCA GND 2 1727/28 TA02 V VTRIP = CCA (R1 + R2) R2 V R1 = R2 TRIP – 1 VCCA ( ) RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65V Threshold LTC694-3.3 3.3V Supply Monitor, Watchdog Timer and Battery Backup 2.9V Threshold LTC699 5V Supply Monitor and Watchdog Timer 4.65V Threshold LTC1232 5V Supply Monitor, Watchdog Timer and Push-Button Reset 4.37V/4.62V Threshold LTC1326 Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ 4.725V, 3.118V, 1V Thresholds (±0.75%) LTC1326-2.5 Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (±0.75%) LTC1443/LTC1444 LTC1445 Micropower Quad Comparators with 1% Reference LTC1443 Has 1.182V Reference, LTC1444/LTC1445 Have 1.221V Reference and Adjustable Hysteresis LTC1536 Precision Triple Supply Monitor for PCI Applications Meets PCI tFAIL Timing Specifications LTC1540 Nanopower Comparator with 2% Reference 1.182V Reference, 300nA Supply Current, 8-Pin MSOP LTC1726-2.5 Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ Adjustable RESET and Watchdog Time Outs LTC1726-5 Micropower Triple Supply Monitor for 5V, 3.3V and ADJ Adjustable RESET and Watchdog Time Outs LTC1985-1.8 Micropower Triple Supply Monitor for 3.3V, 1.8V and ADJ Push-Pull RESET Output, SOT-23 16 Linear Technology Corporation 17278f LT/TP 0400 4K • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1999