LTC2910 Octal Positive/Negative Voltage Monitor DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LTC®2910 is an octal input voltage monitor intended for monitoring multiple voltages in a variety of applications. Each input has a nominal 0.5V threshold, featuring 1.5% tight threshold accuracy over the entire operating temperature range. Glitch filtering ensures reliable reset operation without false or noisy triggering. 8 Low Voltage Adjustable Inputs (0.5V) Guaranteed Threshold Accuracy: ±1.5V Input Glitch Rejection Pin Selectable Input Polarity Allows Negative and OV Monitoring Buffered 1V Reference Output Adjustable Reset Timeout with Timeout Disable 70µA Quiescent Current Open Drain RST and ⎯R⎯S⎯T Outputs Guaranteed RST and ⎯R⎯S⎯T for VCC ≥ 1V Available in 16-Lead SSOP and 16-Lead (5mm × 3mm) DFN Packages Polarity selection and a buffered reference allow monitoring up to two separate negative voltages. A three state input pin allows setting the polarity of two inputs without requiring any external components. The LTC2910 provides a precise, versatile, space-conscious, micropower solution for voltage monitoring. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. APPLICATIONS ■ ■ ■ Desktop and Notebook Computers Network Servers Core, I/O Voltage Monitors TYPICAL APPLICATION Octal Supply Monitor, 10% Tolerance, 12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V Typical Transient Duration vs Comparator Overdrive 12V 700 3.3V 2.5V POWER SUPPLIES 1.8V 1.2V 5V 3.3V 54.9k 11k 88.7k 11k V8 12.7k 11k V7 24.9k 11k V6 39.2k 11k V5 54.9k 11k V4 88.7k 11k V3 TMR DIS V2 RST 600 500 RESET OCCURS ABOVE CURVE 400 300 200 VCC = 6V 100 VCC = 2.3V 0 1 10 100 0.1 COMPARATOR OVERDRIVE PAST THRESHOLD (%) V1 VCC RST SYSTEM 11k LTC2910 GND 226k TYPICAL TRANSIENT DURATION (µs) 5V 0.1µF 2910 TD01b SEL 1nF TIMEOUT = 8.5ms 2910 TA01 2910fb 1 LTC2910 ABSOLUTE MAXIMUM RATINGS (Note 1, 2) Terminal Voltages VCC (Note 3)............................................. –0.3V to 6V RST, ⎯R⎯S⎯T ............................................... –0.3V to 16V TMR ..........................................–0.3V to (VCC + 0.3V) Vn, DIS, SEL ......................................... –0.3V to 7.5V Terminal Current IVCC ....................................................................10mA Reference Load Current (IREF) ...........................±1mA IRST/⎯R⎯S⎯T..............................................................10mA Operating Temperature Range LTC2910C ................................................ 0°C to 70°C LTC2910I ............................................. –40°C to 85°C Storage Temperature Range SSOP, DFN ......................................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) SSOP ................................................................ 300°C PACKAGE/ORDER INFORMATION TOP VIEW TOP VIEW V1 1 16 VCC V2 2 15 TMR V3 3 14 SEL V4 4 13 DIS V5 5 12 RST V6 6 11 RST V7 7 10 REF V8 8 9 17 GND DHC16 PACKAGE 16-LEAD (5mm × 3mm) PLASTIC DFN TJMAX = 150°C, θJA = 43.5°C/W EXPOSED PAD (PIN 17) PCB GND CONNECTION OPTIONAL V1 1 16 VCC V2 2 15 TMR V3 3 14 SEL V4 4 13 DIS V5 5 12 RST V6 6 11 RST V7 7 10 REF V8 8 9 GND GN16 PACKAGE 16-LEAD PLASTIC SSOP TJMAX = 150°C, θJA = 110°C/W ORDER PART NUMBER DHC16 PART MARKING* LTC2910CDHC LTC2910IDHC 2910 2910 ORDER PART NUMBER GN16 PART MARKING LTC2910CGN LTC2910IGN 2910 2910I Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, Vn = 0.55V, SEL = VCC, DIS = OPEN unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS VSHUNT VCC Shunt Regulator Voltage ICC = 5mA ● ΔVSHUNT VCC Shunt Regulator Load Regulation ICC = 2mA to 10mA ● VCC Supply Voltage VCC(MIN) Minimum VCC Output Valid ● DIS = 0V ● MIN TYP MAX 6.2 6.6 6.9 V 200 300 mV VSHUNT V 2.3 1 UNITS V 2910fb 2 LTC2910 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, Vn = 0.55V, SEL = VCC, DIS = OPEN unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS VCC(UVLO) Supply Undervoltage Lockout VCC Rising, DIS = 0V MIN TYP MAX UNITS ● 1.9 2 2.1 V 5 25 50 mV 70 100 µA V ΔVCC(UVHYST) Supply Undervoltage Lockout Hysteresis DIS = 0V ● ICC Supply Current VCC = 2.3V to 6V ● VREF Reference Output Voltage IVREF = ±1mA ● 0.985 1 1.015 VRT Vn Input Voltage Threshold ● 492 500 508 mV tPROP Vn Input Threshold to Output Delay ● 50 125 500 µs ±15 nA ● 6 8.5 12.5 ms 1.2 Vn = VRT – 5mV ● IVN Vn Input Current tRST Reset Timeout Period VDIS(VIH) DIS Input Threshold Voltage High ● VDIS(VIL) DIS Input Threshold Voltage Low ● IDIS DIS Input Current VDIS > 0.5V ● 1 CTMR = 1nF V 0.8 V 2 3 µA ITMR(UP) TMR Pull-Up Current VTMR = 0V ● –1.3 –2.1 –2.8 µA ITMR(DOWN) TMR Pull-Down Current VTMR = 1.6V ● 1.3 2.1 2.8 µA VTMR(DIS) Timer Disable Voltage Referenced to VCC ● –180 –270 VOH Output Voltage High RST/⎯R⎯S⎯T VCC = 2.3V, I⎯R⎯S⎯T/RST = –1µA ● 1 VOL Output Voltage Low RST/⎯R⎯S⎯T VCC = 2.3V, I⎯R⎯S⎯T/RST = 2.5mA VCC = 1V, I⎯R⎯S⎯T = 100µA ● mV V 0.1 0.01 0.3 0.15 V V 0.4 V Three-State Input SEL Low Level Input Voltage ● VIH High Level Input Voltage ● 1.4 VZ Pin Voltage when Left in Hi-Z State ● 0.7 ISEL SEL High, Low Input Current ISEL(MAX) Maximum SEL Input Current VIL ISEL = ±10µA SEL tied to either VCC or GND Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All currents into pins are positive; all voltages are referenced to GND unless otherwise noted. V 0.9 1.1 V ● ±25 µA ● ±30 µA Note 3: VCC maximum pin voltage is limited by input current. Since the VCC pin has an internal 6.5V shunt regulator, a low impedance supply that exceeds 6V may exceed the rated terminal current. Operation from higher voltage supplies requires a series dropping resistor. See Applications Information. 2910fb 3 LTC2910 TIMING DIAGRAM Vn Positive Monitor Timing Vn VRT tPROP RST 1V RST 1V tRST 2285 TD01 Vn Positive Monitor Timing (TMR strapped to VCC) Vn VRT tPROP RST 1V RST 1V tPROP 2285 TD03 Vn Negative Monitor Timing Vn VRT tPROP RST 1V RST 1V tRST 2285 TD02 Vn Negative Monitor Timing (TMR strapped to VCC) Vn VRT tPROP RST 1V RST 1V tPROP 2285 TD04 2910fb 4 LTC2910 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at TA = 25°C and VCC = 3.3V unless otherwise noted. (Note 2) 0.505 105 0.504 100 0.503 95 6.8 VCC = 6V 90 0.502 VCC = 3.3V 0.500 0.499 VCC (V) 85 0.501 80 75 65 0.497 60 0.496 55 –25 0 25 50 TEMPERATURE (°C) –25 0 25 50 TEMPERATURE (°C) VCC (V) 6.55 25°C 6.45 –40°C 85°C 6.35 10 12 1.003 1.002 1.001 1.000 0.999 0.998 0.997 0.995 –50 –25 0 25 50 TEMPERATURE (°C) 300 200 VCC = 6V 100 VCC = 2.3V 0 0.1 1 10 100 COMPARATOR OVERDRIVE PAST THRESHOLD (%) 2910 G06 ⎯R⎯S⎯T Output Voltage vs VCC ⎯R⎯S⎯T Output Voltage vs VCC 5 Vn = 0.55V SEL = VCC CTMR = 1nF VCC 11 4 8 RST VOLTAGE (V) 0.6 9 100 RESET OCCURS ABOVE CURVE 400 0.8 RST VOLTAGE (V) RST/RST TIMEOUT PERIOD, tRST (ms) 500 2910 G05 Reset Time-Out Period vs Temperature 10 75 600 100 75 2910 G04 12 0 25 50 TEMPERATURE (°C) 700 0.996 6.25 –25 2910 G03 TYPICAL TRANSIENT DURATION (µs) REFERENCE VOLTAGE, VREF (V) 6.65 200µA Transient Duration vs Comparator Overdrive 1.004 8 2mA 6.2 –50 100 75 1.005 4 6 ICC (mA) 6.5 Buffered Reference Voltage vs Temperature 6.75 2 5mA 2910 G02 VCC Shunt Voltage vs ICC 0 6.6 6.4 2910 G01 –2 10mA 6.3 50 –50 100 75 6.7 1mA VCC = 2.3V 70 0.498 0.495 –50 VCC Shunt Voltage vs Temperature Supply Current vs Temperature ICC (µA) THRESHOLD VOLTAGE, VRT (V) Input Threshold Voltage vs Temperature 0.4 RST WITH 10k PULL-UP 3 2 0.2 6 –50 1 RST WITHOUT 10k PULL-UP 7 0 –25 0 25 50 TEMPERATURE (°C) 75 100 2910 G07 0 0.2 0.4 0.6 0.8 SUPPLY VOLTAGE, VCC (V) 1.0 0 0 1 2 3 4 SUPPLY VOLTAGE, VCC (V) 5 2910 G08 2910 G09 2910fb 5 LTC2910 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at TA = 25°C and VCC = 3.3V unless otherwise noted. (Note 2) RST/⎯R⎯S⎯T Voltage Output Low vs Output Sink Current ⎯R⎯S⎯T, ISINK vs VCC 1.0 10000 RST/RST TIMEOUT PERIOD, tRST (ms) Vn = 0.45V SEL = VCC 125°C 4 0.8 25°C RST AT 150mV RST/RST, VOL (V) PULL-DOWN CURRENT, IRST (mA) 5 Reset Timeout Period vs Capacitance 3 2 RST AT 50mV 1 –40°C 0.6 0.4 0.2 0 0 1 2 3 4 SUPPLY VOLTAGE, VCC (V) 5 0 0 5 10 15 20 IRST/RST (mA) 2910 G10 25 30 2910 G11 1000 100 10 1 0.1 1 10 100 TMR PIN CAPACITANCE, CTMR (nF) 1000 2910 G12 PIN FUNCTIONS DIS (Pin 13): Output Disable Input. Disables the RST and ⎯R⎯S⎯T output pins. When DIS is pulled high, the RST and ⎯R⎯S⎯T pins are not asserted except during a UVLO condition. Pin has a weak (2µA) internal pull-down to GND. Leave pin open if unused. Exposed Pad (Pin 17, DFN Package): Exposed pad may be left open or connected to device ground. GND (Pin 9): Device Ground REF (Pin 10): Buffered Reference Output. 1V reference used for the offset of negative-monitoring applications. The buffered reference sources and sinks up to 1mA. The reference drives capacitive loads up to 1nF. Larger capacitive loads may cause instability. Leave pin open if unused. RST (Pin 11): Open-Drain Reset Logic Output. Asserts high when any positive polarity input voltage is below threshold or any negative polarity input voltage is above threshold. Held high for an adjustable delay time after all voltage inputs are valid. Pin has a weak pull-up to VCC and may be pulled above VCC using an external pull-up. Leave pin open if unused. ⎯R⎯S⎯T (Pin 12): Open-Drain Inverted Reset Logic Output. Asserts low when any positive polarity input voltage is below threshold or any negative polarity input voltage is above threshold. Held low for an adjustable delay time after all voltage inputs are valid. Pin has a weak pull-up to VCC and may be pulled above VCC using an external pull-up. Leave pin open if unused. SEL (Pin 14): Input Polarity Select Three-State Input. Connect to VCC, GND or leave unconnected in open state to select one of three possible input polarity combinations (refer to Table 1). TMR (Pin 15): Reset Delay Timer. Attach an external capacitor (CTMR) of at least 10pF to GND to set a reset delay time of 9ms/nF. A 1nF capacitor will generate an 8.5ms reset delay time. Tie pin to VCC to bypass timer. V1-V6 (Pin 1, 2, 3, 4, 5 & 6): Voltage Inputs 1 through 6. When the voltage on this pin is below 0.5V, a reset condition is triggered. Tie pin to VCC if unused. V7-V8 (Pin 7 & 8): Voltage Inputs 7 and 8. The polarity of the input is selected by the state of the SEL pin (refer 2910fb 6 LTC2910 PIN FUNCTIONS to Table 1). When the monitored input is configured as a positive voltage, a reset condition is triggered when the pin is below 0.5V. When the monitored input is configured as a negative voltage, a reset condition is triggered when the pin is above 0.5V. Tie pin to VCC if unused and configured as a positive supply. Tie pin to GND if unused and configured as a negative supply. VCC (Pin 16): Supply Voltage. Bypass this pin to GND with a 0.1µF (or greater) capacitor. Operates as a direct supply input for voltages up to 6V. Operates as a shunt regulator for supply voltages greater than 6V and must have a resistance between the pin and the supply to limit input current to no greater than 10mA. When used without a current-limiting resistance, pin voltage must not exceed 6V. BLOCK DIAGRAM 1 V1 VCC TMR 16 15 VCC – + 400k OSCILLATOR V2 2 – 3 V3 RST RESET DELAY TIMER DISABLE + 12 – + UVLO V4 4 – + 2V – VCC VCC 400k + RST V5 5 11 – + V6 6 – + V7 7 – + V8 8 DIS + – – 1V 13 2µA + 0.5V 10 REF 1V THREE-STATE POLARITY DECODER GND 9 BUFFER 14 2910 BD SEL 2910fb 7 LTC2910 APPLICATIONS INFORMATION Voltage Monitoring Table 1. Voltage Polarity Programming (VRT = 0.5V Typical) The LTC2910 is a low power octal voltage monitoring circuit with eight individual undervoltage monitor inputs. A timeout period that holds a reset after all faults have cleared is adjustable using an external capacitor and is disabled, by tying TMR to VCC. Each voltage monitor is compared to a fixed 0.5V reference for detecting undervoltage conditions. When configured to monitor a positive voltage Vm, the application is connected as shown in Figure 1. For negative inputs Vm is connected as shown in Figure 2. RA is now connected to the REF pin and RB remains connected to the monitored voltage Vm. SEL V7 INPUT V8 INPUT VCC Positive V7 < VRT → UV Positive V8 < VRT → UV Open Positive V7 < VRT → UV Negative V8 > VRT → UV GND Negative V7 > VRT → UV Negative V8 > VRT → UV 2-Step Design Procedure The following 2-step design procedure allows selecting appropriate resistances to obtain the desired UV trip point for the positive voltage monitor circuit in Figure 1 and the negative voltage monitor circuit in Figure 2. Using the configurations in Figures 1 and 2, a UV condition will result when the magnitude of the voltage at Vm is less than its designed threshold. For positive supply monitoring, Vm is the desired nominal operating voltage, Im is the desired nominal current through the resistive divider, and VUV is the desired undervoltage trip point. Polarity Selection For negative supply monitoring, to compensate for the 1V reference, 1V must be subtracted from Vm and VUV before using each in the following equations. The three-state polarity-select pin (SEL) selects one of three possible polarity combinations for the input thresholds, as described in Table 1. When an input is configured for negative supply monitoring, a reset condition occurs when the supply voltage is less negative than the configured threshold. The three-state input pin SEL is connected to GND, VCC, or left unconnected during normal operation. When the pin is left unconnected, the maximum leakage allowed from the pin is ±10µA to ensure it remains in the open state. Table 1 shows the three possible selections of polarity based on the SEL pin connection. 1. Choose RA to obtain the desired UV trip point RA is chosen to set the desired trip point for the undervoltage monitor. RA = 0.5V Vm • Im VUV (1) LTC2910 + REF + – – Vm RB Vn – + RA RA LTC2910 Vn + – 1V – UVn + RB 0.5V + – UVn 0.5V Vm 2910 F01 Figure 1. Positive UV Monitoring Configuration 2910 F02 Figure 2. Negative UV Monitoring Configuration 2910fb 8 LTC2910 APPLICATIONS INFORMATION 2. Choose RB to complete the design current in the resistive divider is 10µA. For the negative case, 1V is subtracted from Vm and VUV. Once RA is known, RB is determined by: 1. Find RA to set the UV trip point of the monitor. V RB = m − RA Im (2) If any of the variables Vm, Im, or VUV change, then both steps must be recalculated. Positive Voltage Monitor Example 1. Find RA to set the UV trip point of the monitor. 0.5V 5V • ≈ 56.2k 10µA 4.5V 2. Determine RB to complete the design. RB = 5V − 56.2k ≈ 499k 10µA 0.5V –5V − 1V • ≈ 54.9k 10µA –4.5V − 1V 2. Determine RB to complete the design. RB = A positive voltage monitor application is shown in Figure 3. The monitored voltage is a 5V ±10% supply. Nominal current in the resistive divider is 10µA. RA = RA = –5V − 1V − 57.6k ≈ 549k 10µA Power-Up/Down ⎯ S ⎯ T⎯ output As soon as VCC reaches 1V during power up, the R asserts low and the RST output weakly pulls to VCC. The LTC2910 is guaranteed to assert ⎯R⎯S⎯T low and RST high under conditions of low VCC, down to VCC = 1V. Above VCC = 2V (2.1V maximum) the Vn inputs take control. Once all inputs and VCC become valid, an internal timer is started. After an adjustable delay time, RST pulls low and ⎯R⎯S⎯T weakly pulls high. Threshold Accuracy Negative Voltage Monitor Example A negative voltage monitor application is shown in Figure 4. The monitored voltage is a –5V ±10% supply. Nominal Reset threshold accuracy is important in a supply sensitive system. Ideally, such a system would reset only if supply 5V 5V VCC VCC 5V ± 10% RST RST RB 449k LTC2910 RST REF RST RA 54.9k V7 LTC2910 V7 SEL RA 56.2k GND –5V ± 10% 2910 F02 Figure 3. Positive Supply Monitor SEL RB 549k GND 2910 F04 Figure 4. Negative Supply Monitor 2910fb 9 LTC2910 APPLICATIONS INFORMATION voltages fell below the exact threshold for a specified margin. All LTC2910 inputs have a relative threshold accuracy of ±1.5% over the full operating temperature range. For example, when the LTC2910 is programmed to monitor a 5V input with a 10% tolerance, the desired UV trip point is 4.5V. Because of the ±1.5% relative accuracy of the LTC2910, the UV trip point is between 4.433V and 4.567V which is 4.5V ±1.5%. The accuracy of the resistances chosen for RA and RB affect the UV trip point as well. Using the example just given, if the resistances used to set the UV trip point have 1% accuracy, the UV trip range is between 4.354V and 4.650V. This is illustrated in the following calculations. The UV trip point is given as ⎛ R ⎞ VUV = 0.5V • ⎜ 1+ B ⎟ ⎝ RA ⎠ The two extreme conditions, with a relative accuracy of 1.5% and resistance accuracy of 1%, result in ⎛ R • 0.99 ⎞ VUV(MIN) = 0.5V • 0.985 • ⎜ 1+ B ⎝ RA • 1.01⎟⎠ and ⎛ R • 1.01 ⎞ VUV(MAX ) = 0.5V • 1.015 • ⎜ 1+ B ⎝ RA • 0.99 ⎟⎠ For a desired trip po int of 4.5V, RB =8 RA Therefore, 0.99 ⎞ ⎛ = 4.354V VUV(MIN) = 0.5V • 0.985 • ⎜ 1+ 8 • ⎝ 1.01 ⎟⎠ and 1.01 ⎞ ⎛ = 4.650 V VUV(MAX ) = 0.5V • 1.015 • ⎜ 1+ 8 • ⎝ 0.99 ⎟⎠ Glitch Immunity In any supervisory application, noise riding on the monitored DC voltage causes spurious resets. To solve this problem without adding hysteresis, which causes a new error term in the trip voltage, the LTC2910 lowpass filters the output of the first stage comparator at each input. This filter integrates the output of the comparator before asserting the reset output logic. A transient at the input of the comparator of sufficient magnitude and duration triggers the output logic. The Typical Performance Characteristics section shows a graph of the Transient Duration vs. Comparator Overdrive. RST/⎯R⎯S⎯T Timing The LTC2910 has an adjustable timeout period (tRST) that holds RST and ⎯R⎯S⎯T asserted after all faults have cleared. This assures a minimum reset pulse width allowing a settling time delay for the monitored voltage after it has entered the valid region of operation. When any input drops below its designed threshold, the ⎯R⎯S⎯T pin asserts low and the RST pin asserts high. When all inputs recover above their designed thresholds, the reset delay timer starts. If all inputs remain above their designed thresholds when the timer finishes, the ⎯R⎯S⎯T pin weakly pulls high and the RST pin strongly pulls low. However, if any input falls below its designed threshold during this timeout period, the timer resets and restarts when all inputs are above the designed thresholds. Selecting the Reset Timing Capacitor The reset timeout period (tRST) for the LTC2910 is adjustable to accommodate a variety of applications. Connecting a capacitor, CTMR, between the TMR pin and ground sets the timeout period. The value of capacitor needed for a particular timeout period is: CTMR = tRST • 115 • 10–9 (F/s) The Reset Timeout Period vs. Capacitance graph found in the Typical Performance Characteristics section shows 2910fb 10 LTC2910 APPLICATIONS INFORMATION the desired delay time as a function of the value of the timer capacitor. The TMR pin must have a minimum of 10pF or be tied to VCC. For long timeout periods, the only limitation is the availability of a large value capacitor with low leakage. Capacitor leakage current must not exceed the minimum TMR charging current of 1.3µA. Tying the TMR pin to VCC bypasses the timeout period. Undervoltage Lockout When VCC falls below 2V, the LTC2910 asserts an ⎯ S ⎯ T⎯ undervoltage lockout (UVLO) condition. During UVLO, R is asserted and pulled low and RST is pulled high. When VCC rises above 2V, RST and ⎯R⎯S⎯T follow the same timing procedure as an undervoltage condition on any input. Shunt Regulator The LTC2910 has an internal shunt regulator. The VCC pin operates as a direct supply input for voltages up to 6V. In this range, the quiescent current of the device remains below a maximum of 100µA. For VCC voltages higher than 6V, the pin functions as a shunt regulator and must have a resistance RZ between the supply and the VCC pin to limit the current to no greater than 10mA. When selecting this resistance value, choose an appropriate location on the I-V curve shown in the Typical Performance Characteristics to accommodate any variations in VCC due to changes in current through RZ. At VCC = 1V, the weak pull-up current on RST is barely turned on. Therefore, an external pull-up resistor of no more than 100k is recommended on the RST pin if the state and pull-up strength of the RST pin is crucial at very low VCC. Note however, by adding an external pull-up resistor, the pull-up strength on the RST pin is increased. Therefore, if it is connected in a wired-OR connection, the pull-down strength of any single device must accommodate this additional pull-up strength. Output Rise and Fall Time Estimation The RST and ⎯R⎯S⎯T outputs have strong pull-down capability. The following formula estimates the output fall time (90% to 10%) for a particular external load capacitance (CLOAD): tFALL ≈ 2.2 • RPD • CLOAD where RPD is the on-resistance of the internal pull-down transistor, typically 50Ω at VCC > 1V, and at room temperature (25°C). CLOAD is the external load capacitance on the pin. Assuming a 150pF load capacitance, the fall time is 16.5ns. The rise time on the RST and ⎯R⎯S⎯T pins is limited by a 400k internal pull-up resistance to VCC. A similar formula estimates the output rise time (10% to 90%) at the RST and ⎯R⎯S⎯T pins: tRISE ≈ 2.2 • RPU • CLOAD RST/⎯R⎯S⎯T Output Characteristics where RPU is the pull-up resistance. The DC characteristics of the RST and ⎯R⎯S⎯T pull-up and pull-down strength are shown in the Typical Performance Characteristics. Each has a weak internal pull-up to VCC and a strong pull-down to ground. This arrangement allows each pin to have open-drain behavior while possessing several other beneficial characteristics. The weak pull-up eliminates the need for an external pull-up resistor when the rise time on this pin is not critical. On the other hand, the open drain configuration allows for wired-OR connections and is useful when more than one signal needs to pull down on the RST or ⎯R⎯S⎯T lines. VCC of 1V guarantees a maximum VOL = 0.15V. Disable The LTC2910 allows disabling the RST and ⎯R⎯S⎯T outputs via the DIS pin. Pulling DIS high forces both outputs to remain unasserted, regardless of any faults that occur on the inputs. However, if a UVLO condition occurs, ⎯R⎯S⎯T asserts and pulls low, RST asserts and pulls high, but the ⎯ S ⎯ T⎯ pulls high and RST pulls timeout function is bypassed. R low as soon as the UVLO condition is cleared. DIS has a weak 2µA (typical) internal pull-down current guaranteeing normal operation with the pin left open. 2910fb 11 LTC2910 TYPICAL APPLICATIONS Eight UV Supply Monitor, 10% Tolerance, 12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V 12V 5V 3.3V 2.5V POWER SUPPLIES 1.8V 1.2V 5V 3.3V RB8 54.9k RB7 88.7k RA7 11k RA8 11k 8 V8 RB6 12.7k RA6 11k 7 V7 RB5 24.9k RA5 11k RB4 39.2k RA4 11k 6 V6 5 V5 RB3 54.9k RA3 11k 4 V4 RB2 88.7k RA2 11k 3 V3 TMR 9 2 V2 1 V1 16 VCC DIS 15 RST 13 SYSTEM RA1 11k LTC2910 GND RB1 226k RST 12 CBYP 0.1µF SEL 11 14 CTMR 1nF TIMEOUT = 8.5ms 2910 TA02 Six Positive and Two Negative UV Supply Monitor, 10% Tolerance, 12V, 5V, 3.3V, 2.5V, 1.8V, 1.2V, –5V, –3.3V 12V 5V 3.3V POWER SUPPLIES 2.5V 1.8V 1.2V RB8 54.9k RA8 107k RB7 11k RB6 12.7k RA7 11k RA6 11k RB5 24.9k RA5 11k RB4 39.2k RA4 11k RB3 54.9k RA3 11k RB2 88.7k RA2 11k RB1 226k RA1 11k SYSTEM 8 V8 7 V7 10 REF 6 V6 5 V5 4 V4 3 V3 2 V2 VCC LTC2910 GND 9 –3.3V TMR DIS 15 1 V1 13 RST 12 RST 11 SEL 16 CBYP 0.1µF 14 CTMR 22nF TIMEOUT = 200ms –5V 2910 TA03 2910fb 12 LTC2910 TYPICAL APPLICATIONS Six UV and One OV/UV Supply Monitor, 10% Tolerance, 12V, 5V, 3.3V (x2), 2.5V, 1.8V, 1.2V 12V 5V 3.3V POWER 2.5V SUPPLIES 1.8V 1.2V 3.3V RB7 27.4k RA8 4.53k RA7 1k 8 V8 RB6 12.7k RA6 11k 7 V7 RB5 24.9k RA5 11k 6 V6 RB4 39.2k RA4 11k 5 V5 RB3 54.9k RA3 11k 4 V4 RB2 88.7k RA2 11k 3 V3 RA1 11k 2 V2 9 TMR 16 VCC DIS 15 SYSTEM 1 V1 LTC2910 GND RB1 226k RST 13 RST 12 CBYP 0.1µF SEL 11 14 CTMR 1nF TIMEOUT = 8.5ms 2910 TA04 Six UV Supply Monitor Powered from 48V, 10% Tolerance, 48V, 5V, 3.3V, 2.5V, 1.8V, 1.2V 48V 5V 3.3V POWER 2.5V SUPPLIES 1.8V 1.2V RB6 12.7k RA6 11k RB5 24.9k RA5 11k RB4 39.2k RA4 11k RB3 54.9k RA3 11k RB2 88.7k RA2 11k RB1 953k RA1 11k RZ 8.25k 8 V8 7 V7 6 V6 5 V5 4 V4 3 V3 2 V2 GND 9 TMR 15 1 V1 VCC LTC2910 DIS 13 RST 12 RST 11 SYSTEM SEL 16 CBYP 0.1µF 14 VCC 2910 TA05 2910fb 13 LTC2910 TYPICAL APPLICATIONS Eight UV Supply Monitor with Manual Reset Button, 10% Tolerance, 12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V 12V 5V 3.3V 2.5V POWER 1.8V SUPPLIES 1.2V 5V 3.3V MANUAL RESET BUTTON (NORMALLY OPEN) RB8 549k RPB 10k RB7 88.7k RB6 12.7k RB5 24.9k RB4 39.2k RB3 54.9k RB2 88.7k RB1 226k SYSTEM RA8 110k RA7 11k 8 V8 RA6 11k 7 V7 RA5 11k 6 V6 RA4 11k 5 V5 RA3 11k 4 V4 RA2 11k 3 V3 RA1 11k 2 V2 VCC LTC2910 GND 9 TMR DIS 15 1 V1 13 RST 12 RST 11 16 CBYP 0.1µF SEL 14 CTMR 22nF TIMEOUT = 200ms 2910 TA06 2910fb 14 LTC2910 PACKAGE DESCRIPTION DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) R = 0.115 TYP 5.00 ±0.10 (2 SIDES) R = 0.20 TYP 0.65 ±0.05 3.50 ±0.05 9 0.40 ± 0.10 16 3.00 ±0.10 (2 SIDES) 1.65 ±0.05 (2 SIDES) 1.65 ± 0.10 (2 SIDES) PACKAGE OUTLINE 2.20 ±0.05 PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH (DHC16) DFN 1103 8 0.25 ± 0.05 0.50 BSC 1 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 0.200 REF 4.40 ±0.05 (2 SIDES) 4.40 ±0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJED-1) IN JEDEC PACKAGE OUTLINE MO-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .189 – .196* (4.801 – 4.978) .015 ± .004 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 0° – 8° TYP .0532 – .0688 (1.35 – 1.75) .008 – .012 (0.203 – 0.305) TYP .004 – .0098 (0.102 – 0.249) .0250 (0.635) BSC 16 15 14 13 12 11 10 9 .229 – .244 (5.817 – 6.198) 3. DRAWING NOT TO SCALE *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 .009 (0.229) REF .150 – .157** (3.810 – 3.988) 1 2 3 4 5 6 7 8 .045 ±.005 .254 MIN .0165 ± .0015 .150 – .165 .0250 BSC RECOMMENDED SOLDER PAD LAYOUT GN16 (SSOP) 0204 2910fb 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. 15 LTC2910 TYPICAL APPLICATION Eight UV Supply Monitor with LED Indicator, 10% Tolerance, 12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V 12V 5V 3.3V 2.5V POWER 1.8V SUPPLIES 1.2V 5V 3.3V 54.9k 88.7k 11k 11k 12.7k 11k 8 V8 7 V7 24.9k 11k 6 V6 39.2k 11k 54.9k 11k 5 V5 4 V4 88.7k 11k 3 V3 2 V2 TMR 9 DIS 15 SYSTEM 1 V1 VCC LTC2910 GND 226k 11k 13 RST 12 RST 16 0.1µF SEL 11 14 1nF TIMEOUT = 8.5ms 2910 TA07 510Ω VCC 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 LTC2900 Programmable Quad Supply Monitor LTC2901 Programmable Quad Supply Monitor Adjustable ⎯R⎯E⎯S⎯E⎯T , 10-Lead MSOP and 3mm × 3mm 10-Lead DFN Package Adjustable ⎯R⎯E⎯S⎯E⎯T and Watchdog Timer, 16-Lead SSOP Package LTC2902 Programmable Quad Supply Monitor Adjustable ⎯R⎯E⎯S⎯E⎯T and Tolerance, 16-Lead SSOP Package, Margining Functions LTC2903 Precision Qual Supply Monitor 6-Lead SOT-23 Package, Ultra Low Voltage Reset LTC2904 3-State Programmable Precision Dual Supply Monitor Adjustable Tolerance, 8-Lead SOT-23 Package LTC2905 3-State Programmable Precision Dual Supply Monitor Adjustable ⎯R⎯E⎯S⎯E⎯T and Tolerance, 8-Lead SOT-23 Package LTC2906 Precision Dual Supply Monitor One Selectable and One Adjustable Separate VCC Pin, RST/⎯R⎯S⎯T Outputs LTC2907 Precision Dual Supply Monitor One Selectable and One Adjustable Separate VCC, Adjustable Reset Timer LTC2908 Precision Six Supply Monitor (Four Fixed and Two Adjustable) 8-Lead SOT-23 and DDB Packages LTC2909 Prevision Dual Input UV, OV and Negative Voltage Monitor Separate VCC Pin, Adjustable Reset Timer, 8-Lead SOT-23 and DDB Packages LTC2914 Quad UV/OV Positive/Negative Voltage Monitor Separate VCC Pin, Four Inputs, Up to Two Negative Monitors, Adjustable Reset Timer, 16-Lead SSOP and DFN Packages 2910fb 16 Linear Technology Corporation LT 1106 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2006