MIC2753/2754 Micrel MIC2753/2754 Power Supply Supervisors Preliminary Information General Description Features The MIC2753 and MIC2754 are ultraminiature, full-featured, power supply supervisors featuring active-high and activelow reset outputs, respectively. • • • • • Undervoltage and overvoltage monitor Separate overvoltage flag output Generates 140ms (minimum) power-on reset pulse Debounced manual reset input Choice of active-high (MIC2753) or active-low (MIC2754) reset outputs • Low 30µA typical supply current • No external components needed • IttyBitty™ SOT-23-5 package The MIC2753/4 includes an undervoltage detector with a power-on reset generator and reset output, an overvoltage detector with a separate output for activating crowbar circuits, and a debounced manual reset input. Typical supply current is a low 30µA. These devices provide a 140ms minimum reset output at power-on and assert their reset outputs any time the input voltage deviates beyond preset overvoltage or undervoltage thresholds. Reset outputs remain asserted for 140ms (minimum) after the input returns to normal or after releasing the manual reset. When an overvoltage condition is detected, the overvoltage output is immediately activated. Hysteresis on both thresholds prevents erratic operation due to noise. Applications • • • • Computer systems Embedded controllers Power supplies Telecommunications systems Typical Application VCC Fuse Microcontroller MIC2754 Manual Reset VIN RST MR HV VCC GND RST IN SCR Crowbar GND Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com June 1999 1 MIC2753/2754 MIC2753/2754 Micrel Ordering Information Part Number Mark Lower Threshold Voltage Monitored Voltage* Upper Threshold Voltage Reset Temperature Range Package MIC2753-RBM5 UDR 2.63V 2.85V±5% 3.08V Active High –40°C to +85°C SOT-23-5 MIC2753-SBM5 UDS 2.93V 3.3V±10% 3.83V Active High –40°C to +85°C SOT-23-5 MIC2753-TBM5 UDT 3.08V 3.3V±5% 3.53V Active High –40°C to +85°C SOT-23-5 MIC2753-MBM5 UDM 4.38V 5.0V±10% 5.81V Active High –40°C to +85°C SOT-23-5 MIC2753-LBM5 UDL 4.63V 5.0V±5% 5.38V Active High –40°C to +85°C SOT-23-5 MIC2754-RBM5 UER 2.63V 2.85V±5% 3.08V Active Low –40°C to +85°C SOT-23-5 MIC2754-SBM5 UES 2.93V 3.3V±10% 3.83V Active Low –40°C to +85°C SOT-23-5 MIC2754-TBM5 UET 3.08V 3.3V±5% 3.53V Active Low –40°C to +85°C SOT-23-5 MIC2754-MBM5 UEM 4.38V 5.0V±10% 5.81V Active Low –40°C to +85°C SOT-23-5 MIC2754-LBM5 UEL 4.63V 5.0V±5% 5.38V Active Low –40°C to +85°C SOT-23-5 * Contact factory for voltages not listed. Pin Configuration VIN HV RST 3 2 VIN GND HV 1 3 Part Identification UDx 2 1 UEx 4 5 4 5 GND MR RST MR MIC2753 Voltage Code MIC2754 Pin Description Pin No. MIC2753 Pin No. MIC2754 1 Pin Name Pin Function RST Reset (Digital Output): Active-high output. Asserted when VIN falls below VTHU (undervoltage threshold), or rises above VTHO (overvoltage threshold). Deasserted no less than 140ms after VIN returns within threshold limits. 2 1 /HV High-Voltage Flag (Open-Drain Output): /HV is asserted (active low) when the input voltage exceeds the VTHO (overvoltage threshold). It indicates power supply overvoltage and is intended for connection to a protection device such as a “crowbar” circuit. 3 3 VIN Analog Input: Voltage monitor input and power supply input to the IC. 4 /RST Reset (Digital Output): Active-low digital output. This output will be asserted whenever VIN falls below VTHU (undervoltage threshold), or rises above VTHO (overvoltage threshold). It will be deasserted no less than 140ms after VIN returns within the threshold limits. 4 2 GND Ground: Ground return for all IC functions. 5 5 /MR Manual Reset (Digital Input): Logic low initiates immediate, unconditional reset. If VIN is within tolerance thresholds, when /MR is released (returns high), the reset output(s) will be deasserted no less than 140ms later. /MR may be driven by a CMOS or TTL logic signal or a mechanical switch. (Switch debouncing is performed internally.) /MR has an internal pull-up to VIN and may remain open if unused. MIC2753/2754 2 June 1999 MIC2753/2754 Micrel Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Supply Voltage (VIN) ...................................... –0.3V to 10V Reset Voltage (VRST) ........................... –0.3V to VIN + 0.3V Manual Reset Voltage (VMR) ............... –0.3V to VIN + 0.3V Reset Current (IRST) ................................................... 10mA Continuous Power Dissipation (PD at TA = +85°C) .............................................. 200mW Storage Temperature (TS) ....................... –65°C to +150°C ESD Rating, Note 3 Supply Voltage (VIN) .......................................... 1.5V to 7V Ambient Temperature (TA) ......................... –40°C to +85°C Junction Temperature (TJ) ........................................ 150°C Manual Reset (VMR) ............................................. 0V to VIN Thermal Resistance (θJA) ................................................................... 325°C/W Electrical Characteristics VIN = 5.0V (L, M voltage code), VIN = 3.3V (T, S voltage code), VIN = 2.85 (R voltage code) TA = 25°C; bold values indicate 1.5V ≤ VIN ≤ 7.0V, –40°C ≤ TA ≤ +85°C Note 4; unless noted Symbol Parameter VIN Input Supply Voltage IDD Operating Supply Current manual reset not asserted VTHO Overvoltage Threshold L voltage code VTHU Undervoltage Threshold Condition Min Typ Max Units 7.0 V 30 100 µA 5.28 5.38 6.00 V M voltage code 5.62 5.81 6.00 V T voltage code 3.459 3.53 3.96 V S voltage code 3.67 3.83 3.96 V R voltage code 3.018 3.08 3.28 V L voltage code 4.50 4.63 4.75 V M voltage code 4.25 4.38 4.50 V T voltage code 3.00 3.08 3.15 V S voltage code 2.85 2.93 3.00 V R voltage code 2.55 2.63 2.70 V 1.0 VHYST+ Overvoltage Threshold Hysteresis –15 mV VHYST– Undervoltage Threshold Hysteresis +15 mV tPROP(RST) Propagation Delay tRST June 1999 VIN = VTHO (min) – 100mV to VTHO (max) + 100mV 12 30 µs VIN = VTHU (max) + 100mV to VTHU (min) – 100mV 12 30 µs 240 560 ms Reset Pulse Width 140 3 MIC2753/2754 MIC2753/2754 Micrel Symbol Parameter Condition VOL(RST) Reset Output Voltage Low MIC2753 VOH(RST) Reset Output Voltage High MIC2753 /Reset Output Voltage Low MIC2754 VOL(RST) /Reset Output Voltage High MIC2754 VOH(RST) Min Typ Max Units R/S/T voltage codes, VIN = VTHU(max) + 100mV, ISINK = 50µA 0.5 V L/M voltage codes, VIN = VTHU(max) + 100mV, ISINK = 50µA 0.5 V R/S/T voltage codes, VIN = VTHU(min) – 100mV, ISOURCE = 0.5mA VIN –0.5 V L/M voltage codes, VIN = VTHU(min) – 100mV, ISOURCE = 1.0mA VIN –0.8 V R/S/T voltage codes, VIN = VTHU(min) – 100mV, ISINK = 0.5mA 0.5 V L/M voltage codes, VIN = VTHU(min) – 100mV, ISINK = 1.0mA 0.8 V VIN ≥ 1.5V, IOL = 50µA 0.5 V R/S/T voltage codes, VIN = VTHU(max) + 100mV, ISOURCE = 35µA VIN –0.5 V L/M voltage codes, VIN = VTHU(max) + 100mV, ISOURCE = 35µA VIN –0.5 V 0.8 VIN V VIH(/MR) /MR Input Voltage, High VIL(/MR) /MR Input Voltage, Low tPROP(/MR) Propagation Delay MIC2753 V/MR ≤ VIL to VRST ≥ VOH Propagation Delay MIC2754 V/MR ≤ VIL to V/RST ≤ VOL 0.2 VIN V 1 2 µs 1 2 µs µs t/MR(min) /MR Minimum Input Pulse Width 2.5 IPU Pull-Up Current, /MR V/MR = 0V 0.2 IIH Input Current, /MR V/MR = VIN 0.01 VOL(/HV) /HV Output Voltage Low VIN > VTHO(max), ISINK = 0.5mA, R/S/T voltage codes 0.5 V V VIN > VTHO(max), ISINK = 1.0mA, L/M voltage codes 0.8 V V 30 µs +2 µA tPROP(/HV) /HV Propagation Delay VIN = VTHO (min) – 100mV to VTHO (max) + 100mV I/HV /HV Leakage Current VIN = VTHO (min) – 100mV 12 –2 µA 2 µA Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Note 4. Final test on outgoing product is performed at TA = 25°C. Device performance over –40°C ≤ TA ≤ +85°C is guaranteed by design. MIC2753/2754 4 June 1999 MIC2753/2754 Micrel Typical Characteristics Supply Current vs. Temperature Power-Down Reset Delay vs. Temperature 40 2V 3V 4V 5V 20 1V 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 7 6 5 4 3 2 1 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Normalized Reset Threshold vs. Temperature RESET DELAY (ns) 1.000 0.995 40 35 30 25 0.990 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 50 20mV 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Overdrive = 200mV 10 L, M voltage codes 300 PULL-UP CURRENT (nA) 20 100mV 20 MR Pull-up Current vs. Temperature 1.005 Overdrive = 10mV 20mV Normalized Overvoltage Threshold vs. Temperature 1.010 40 10mV 30 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) L, M voltage codes THRESHOLD UNDERVOLTAGE DELAY (µs) Overvoltage Delay vs. Temperature 20 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Undervoltage Delay vs. Temperature June 1999 150 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 40 45 1.005 10 200 50 L, M voltage codes 30 250 Manual Reset Delay vs. Temperature 1.010 NORMALIZED THRESHOLD L, M voltage codes RESET PULSE WIDTH (ms) VIN = 6V 60 9 8 OVERVOLTAGE DELAY (µs) 80 300 10 No Load; L, M voltage codes RESET DELAY (µs) SUPPLY CURRENT (µA) 100 Power-Up Reset Timeout vs. Temperature 1.000 0.995 0.990 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 5 260 220 5.0V 180 140 100 60 3.3V 2.85V 20 -40 -20 0 20 40 60 80 100 TEMPERATURE (˚C) MIC2753/2754 MIC2753/2754 Micrel Functional Diagram MR Delay Line VIN RST (MIC2753 only) 350ms typ. Low-Voltage Detect S Q RST (MIC2754 only) R Q High-Voltage Detect HV 1.2V Bandgap Reference GND MIC2753/2754 6 June 1999 MIC2753/2754 Micrel Timing Diagram A VTHO VHYST+ VIN(nominal) VHYST– VIN VTHU A 1.5V 0V tRESET VOH VRST B (MIC2754) V OL tRESET tPROP VOH VRST tRESET tPROP B (MIC2753) VOL VOH B HV VOL A. Very short transients will be ignored by the MIC275x. See “Applications Information.” B. Without external pull-down or pull-up resistors, the output is not guaranteed to be valid when VIN < 1.5V. Manual Reset Timing VIH VMR VIL tRESET VRST VOH VOL (MIC2754) VRST tPROP(MR) VOH VOL (MIC2753) June 1999 7 MIC2753/2754 MIC2753/2754 Micrel no less than 140ms later. /MR may be driven by a CMOS or TTL logic signal or a mechanical switch. Typically, a momentary push-button switch is connected such that /MR is shorted to ground when the contacts close. Switch debouncing is performed internally; the switch may be connected directly between /MR and GND. /MR has an internal pull-up to VIN and may be left open if unused. Overvoltage Output Functional Description The MIC275x family of devices are typically used to monitor power supplies of intelligent circuits such as microcontrollers and microprocessors. By connecting the appropriate reset output of an MIC275x to the reset input of a microcontroller or microprocessor, the processor will be properly reset at poweron, and during power-down and brownout conditions. In addition, asserting /MR (manual reset input) activates the reset function. The /HV and reset outputs are immediately and unconditionally asserted any time VIN exceeds VTHO (overvoltage threshold). /HV is an active-low, open-drain logic output. Overvoltage on a system power supply rail is generally considered to be a catastrophic condition which may cause permanent system damage. If and when an overvoltage condition occurs using a MIC275x, the system is immediately driven into reset mode and /HV (overvoltage flag), is driven active. Typically, an overvoltage signal, such as /HV, is connected to a “crowbar circuit” using a latching power device such as an SCR. See “Typical Application”. The crowbar circuit will clamp the power rail to some low voltage by shunting power supply current to ground. This should cause some upstream power supply protection device to be activated, such as foldback current limiting, a fuse, or circuit breaker. In this way, the system is most likely to be protected against damage and spurious operation until the condition can be remedied. /HV is an open-drain output and may be wire-ORed with other open-drain logic signals. Some systems may require a pullup resistor. Reset Outputs The /RST and/or RST output is asserted any time /MR is asserted or if VIN deviates beyond the preset threshold voltages, VTHU and VTHO. Reset output(s) remain asserted for 140ms minimum after VIN returns within the threshold boundaries and/or /MR is released. A minimum 140ms reset pulse is also generated at power-on. Hysteresis is included in the overvoltage and undervoltage comparators to prevent chattering of the outputs due to noise. The MIC275x family offers a choice of two reset output options: the MIC2753 has an active-high RST output, and the MIC2754 has an active-low /RST output. Manual Reset Input The ability to initiate a reset from external logic or a manual switch is provided in addition to the MIC275x’s automatic supervisory functions. Driving the /MR input low causes an immediate and unconditional reset to occur. Assuming VIN is within the tolerance thresholds when /MR is released (internally pulled to logic high), the reset output will be deasserted System Block Diagram Reset Switch HV Voltage Monitor and Reset Generator Crowbar Circuit Microprocessor System Circuitry Reset(s) MIC2753/2754 8 June 1999 MIC2753/2754 Micrel undesired operation. (In most cases, however, it is expected that the circuits driven by the MIC2754 will be similarly inoperative at VCC ≤ 1.5V.) If a given application requires that /RST be valid below VIN = 1.5V, this can be accomplished by adding a pull-down resistor to the /RST output. A value of 100kΩ is recommended as this is usually an acceptable compromise of leakage current and pull-down current. The resistor’s value is not critical, however. Application Information Supply Transients The MIC2753/4 are inherently immune to very short “glitches” on VIN. In the case of very brief transients, VIN may drop below the reset threshold or exceed the overvoltage threshold without activating the RST, /RST or /HV output. As shown in the graphs of Figure 1, the narrower the transient, the deeper the threshold overdrive that will be ignored by the MIC2753/4. The lines on the graph represent the typical allowable transient duration for a given amount of threshold overdrive that will not generate a reset or overvoltage indication. The data from which Figure 1 is derived was taken by adding negative-going square-wave pulses to a dc VIN set at 0.5V above or below the actual measured threshold for the part being characterized. In the case of the MIC2754L/M for example (refer to Figure 1), a transient on VIN which goes below the reset threshold by 100mV and lasts no more than 8.4µs will typically not cause a reset to occur. Bypass capacitance placed as close as physically possible to the device’s VIN and GND pins will increase the transient immunity (0.1µF, for example). Ensuring Proper Operation at Low Supply The statements above also apply to the MIC2753’s RST output. That is, to ensure valid RST signal levels at VIN < 1.5V, a pull-up resistor (as opposed to a pull-down) should be added to the RST output. A value of 100kΩ is typical for this application as well. See Figure 2. Interfacing to Processors with Bidirectional Reset Pins Some microcontrollers and microprocessors utilize reset signal pins that are bidirectional in nature, rather than simply being input only. The Motorola 68HC11 family is one example. To use the MIC2753/4 with these processors, it is necessary to insert a resistor into the signal path between the MIC2753/4’s reset output and the microprocessor’s reset input. This prevents excessive current from flowing due to contention between the two drivers. The signal present at the processor’s reset pin will now be of limited drive capability, so it is necessary to buffer it in order to drive other circuits. This technique is shown in Figure 3. At levels of VIN below 1.5V, the MIC2754’s /RST output driver cannot turn on sufficiently to sink current and produce a valid logic-low on the /RST output. In this situation, other CMOS circuits driven by /RST could be allowed to float, causing Reset Comparator Overdrive vs. Duration 40 Overvoltage Comparator Overdrive vs. Duration 8 TA = 25°C 30 DURATION (µs) DURATION (µs) 7 20 10 1 5 4 3 2 1 TA = 25°C 0 6 10 100 OVERDRIVE (mV) 0 1000 A. Reset 1 10 100 OVERDRIVE (mV) 1000 B. Overvoltage Figure 1. MIC2753/2754 Transient Immunity Behavior June 1999 9 MIC2753/2754 MIC2753/2754 Micrel VCC Fuse Microcontroller MIC2754 Manual Reset IN RST MR HV VCC GND 10k 2200pF RST IN RPULL-DOWN 100k GND MCR708A SCR MIC94030 22Ω 1k Figure 2a. MIC2754 Valid Reset Below 1.5V VCC Fuse Manual Reset RPULL-UP 100k MIC2753 IN RST MR HV Microcontroller VCC GND 10k 2200pF RST IN MCR708A SCR MIC94030 GND 22Ω 1k Figure 2b. MIC2753 Valid Reset Below 1.5V BUFFER /RST signal to other circuits VCC Fuse Manual Reset Microcontroller MIC2754 RSERIES 4.7k IN RST MR VCC GND RST IN HV 10k 2200pF MIC94030 GND MCR708A SCR 22Ω 1k Figure 3. MIC2754 With Processors Using Bidirectional Reset Inputs. Crowbar Applications The following MIC275x applications diagrams show an SCR crowbar circuit. The function of this circuit is to protect system components from damage caused by excessive supply voltage, as might be generated by a runaway power supply. The low RDS(on) of the MIC94030 P-channel MOSFET (<1Ω at VGS = 4.5V) and the 22Ω resistor assure adequate gate current to trigger the SCR. The crowbar circuit is designed to be functional over all operating ranges of the MIC275x. Since the lowest upperthreshold voltage of the MIC275x family is only 3.08V, and since the SCR-gate forward voltage is about 1V, there is about 90mA of gate-drive current available: 2.08V ÷ 23Ω = 0.09A. The highest upper-threshold voltage is 5.38V, so available gate-drive current is about 190mA: 4.38V ÷ 23Ω = 0.190A. The maximum forward gate current of the SCR is MIC2753/2754 200mA. The SCR trigger characteristics and the gate-drive capability provide a workable solution for the power-supply voltage range in question. The 10kΩ resistor is the pull-up for the open-drain /HV output of the MIC275x, and the 2200pF capacitor avoids inadvertent premature triggering of the SCR, which might be caused by a very narrow spike on the /HV line. Similarly, the 1kΩ resistor from the SCR-gate to ground keeps the SCR-gate biased off. The fuse shown in the diagrams, which ultimately protects both the system components and the crowbar SCR, should be a fast-blow type. The SCR is rated at 4A(rms), but it can withstand a brief 25A surge. The crowbar circuit shown should, conservatively, be capable of blowing a 5A or 6A fuse. 10 June 1999 MIC2753/2754 Micrel Package Information 1.90 (0.075) REF 0.95 (0.037) REF 1.75 (0.069) 1.50 (0.059) 3.00 (0.118) 2.60 (0.102) DIMENSIONS: MM (INCH) 3.02 (0.119) 2.80 (0.110) 0.50 (0.020) 0.35 (0.014) 1.30 (0.051) 0.90 (0.035) 0.20 (0.008) 0.09 (0.004) 10° 0° 0.15 (0.006) 0.00 (0.000) 0.60 (0.024) 0.10 (0.004) SOT-23-5 (M5) June 1999 11 MIC2753/2754 MIC2753/2754 Micrel MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. © 1999 Micrel Incorporated MIC2753/2754 12 June 1999