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MIC2753/2754
Micrel
MIC2753/2754
Power Supply Supervisors Final Information
General Description
The MIC2753 and MIC2754 are ultraminiature, full-featured, power supply supervisors featuring active-high and activelow reset outputs, respectively. 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 30A. 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.
Features
* * * * * 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 30A typical supply current * No external components needed * IttyBittyTM SOT-23-5 package
Applications
* * * * Computer systems Embedded controllers Power supplies Telecommunications systems
Typical Application
VCC Fuse MIC2754 Manual Reset VIN MR GND RST HV Microcontroller VCC GND RST IN SCR Crowbar
Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com
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Ordering Information
Part Number MIC2753-RBM5 MIC2753-SBM5 MIC2753-TBM5 MIC2753-MBM5 MIC2753-LBM5 MIC2754-RBM5 MIC2754-SBM5 MIC2754-TBM5 MIC2754-MBM5 MIC2754-LBM5 Mark UDR UDS UDT UDM UDL UER UES UET UEM UEL Lower Threshold Voltage 2.63V 2.93V 3.08V 4.38V 4.63V 2.63V 2.93V 3.08V 4.38V 4.63V Monitored Voltage* 2.85V5% 3.3V10% 3.3V5% 5.0V10% 5.0V5% 2.85V5% 3.3V10% 3.3V5% 5.0V10% 5.0V5% Upper Threshold Voltage 3.08V 3.83V 3.53V 5.81V 5.38V 3.08V 3.83V 3.53V 5.81V 5.38V Reset Active High Active High Active High Active High Active High Active Low Active Low Active Low Active Low Active Low Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5
* Contact factory for voltages not listed.
Pin Configuration
VIN HV RST
3 2 1
VIN GND HV
3 2 1
UDx
4 5
Part Identification
4
UEx
5
GND
MR Voltage Code
RST
MR
MIC2753
MIC2754
Pin Description
Pin No. MIC2753 1 Pin No. MIC2754 Pin Name RST Pin Function 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. 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. Analog Input: Voltage monitor input and power supply input to the IC. 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. Ground: Ground return for all IC functions. 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.
2
1
/HV
3
3 4
VIN /RST
4 5
2 5
GND /MR
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Absolute Maximum Ratings (Note 1)
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 = +85C) .............................................. 200mW Storage Temperature (TS) ....................... -65C to +150C ESD Rating, Note 3
Operating Ratings (Note 2)
Supply Voltage (VIN) .......................................... 1.5V to 7V Ambient Temperature (TA) ......................... -40C to +85C Junction Temperature (TJ) ........................................ 150C Manual Reset (VMR) ............................................. 0V to VIN Thermal Resistance (JA) ................................................................... 325C/W
Electrical Characteristics
VIN = 5.0V (L, M voltage code), VIN = 3.3V (T, S voltage code), VIN = 2.85 (R voltage code) TA = 25C; bold values indicate 1.5V VIN 7.0V, -40C TA +85C Note 4; unless noted Symbol VIN IDD VTHO Parameter Input Supply Voltage Operating Supply Current Overvoltage Threshold manual reset not asserted L voltage code M voltage code T voltage code S voltage code R voltage code VTHU Undervoltage Threshold L voltage code M voltage code T voltage code S voltage code R voltage code VHYST+ VHYST- Overvoltage Threshold Hysteresis Undervoltage Threshold Hysteresis VIN = VTHO (min) - 100mV to VTHO (max) + 100mV VIN = VTHU (max) + 100mV to VTHU (min) - 100mV tRST Reset Pulse Width 140 5.28 5.62 3.459 3.67 3.018 4.50 4.25 3.00 2.85 2.55 Condition Min 1.0 30 5.38 5.81 3.53 3.83 3.08 4.63 4.38 3.08 2.93 2.63 -15 +15 12 12 240 30 30 560 Typ Max 7.0 100 6.00 6.00 3.96 3.96 3.28 4.75 4.50 3.15 3.00 2.70 Units V A V V V V V V V V V V mV mV s s ms
tPROP(RST) Propagation Delay
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Symbol VOL(RST) Parameter Reset Output Voltage Low MIC2753 Condition R/S/T voltage codes, VIN = VTHU(max) + 100mV, ISINK = 50A L/M voltage codes, VIN = VTHU(max) + 100mV, ISINK = 50A VOH(RST) Reset Output Voltage High MIC2753 R/S/T voltage codes, VIN = VTHU(min) - 100mV, ISOURCE = 0.5mA L/M voltage codes, VIN = VTHU(min) - 100mV, ISOURCE = 1.0mA VOL(RST) /Reset Output Voltage Low MIC2754 R/S/T voltage codes, VIN = VTHU(min) - 100mV, ISINK = 0.5mA L/M voltage codes, VIN = VTHU(min) - 100mV, ISINK = 1.0mA VIN 1.5V, IOL = 50A VOH(RST) /Reset Output Voltage High MIC2754 R/S/T voltage codes, VIN = VTHU(max) + 100mV, ISOURCE = 35A L/M voltage codes, VIN = VTHU(max) + 100mV, ISOURCE = 35A VIH(/MR) VIL(/MR) tPROP(/MR) /MR Input Voltage, High /MR Input Voltage, Low Propagation Delay MIC2753 Propagation Delay MIC2754 t/MR(min) IPU IIH VOL(/HV) /MR Minimum Input Pulse Width Pull-Up Current, /MR Input Current, /MR /HV Output Voltage Low V/MR = 0V V/MR = VIN VIN > VTHO(max), ISINK = 0.5mA, R/S/T voltage codes VIN > VTHO(max), ISINK = 1.0mA, L/M voltage codes tPROP(/HV) I/HV
Note 1. Note 2. Note 3. Note 4.
Micrel
Min Typ Max 0.5 0.5 VIN -0.5 VIN -0.8 0.5 0.8 0.5 VIN -0.5 VIN -0.5 0.8 VIN 0.2 VIN V/MR VIL to VRST VOH V/MR VIL to V/RST VOL 2.5 0.2 0.01 0.5 0.8 12 -2 30 +2 2 1 1 2 2 Units V V V V V V V V V V V s s s A A V V V V s A
/HV Propagation Delay /HV Leakage Current
VIN = VTHO (min) - 100mV to VTHO (max) + 100mV VIN = VTHO (min) - 100mV
Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. Final test on outgoing product is performed at TA = 25C. Device performance over -40C TA +85C is guaranteed by design.
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Typical Characteristics
Supply Current vs. Temperature
100 SUPPLY CURRENT (A) 80 60 40 20 1V 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) 2V 3V 4V 5V No Load; L, M voltage codes VIN = 6V 10
RESET PULSE WIDTH (ms)
Power-Down Reset Delay vs. Temperature
300 L, M voltage codes 9 8 7 6 5 4 3 2 1 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
Power-Up Reset Timeout vs. Temperature
RESET DELAY (s)
250
200
150 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
Normalized Reset Threshold vs. Temperature
1.010 NORMALIZED THRESHOLD 50 45
RESET DELAY (ns)
Manual Reset Delay vs. Temperature
40 L, M voltage codes
OVERVOLTAGE DELAY (s)
Overvoltage Delay vs. Temperature
10mV 30 20mV 100mV 20 Overdrive = 200mV 10 L, M voltage codes 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
1.005
40 35 30 25
1.000
0.995
0.990 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
20 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
Undervoltage Delay vs. Temperature
50 1.010
Normalized Overvoltage Threshold vs. Temperature
PULL-UP CURRENT (nA)
300 260 220 180 140 100 60
MR Pull-up Current vs. Temperature
UNDERVOLTAGE DELAY (s)
L, M voltage codes 40 THRESHOLD 30 20 10 20mV Overdrive = 10mV 1.005
5.0V
1.000
0.995
3.3V 2.85V
0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
0.990 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
20 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
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Functional Diagram
MR
Delay Line
RST (MIC2753 only) 350ms typ.
VIN
Low-Voltage Detect SQ RQ High-Voltage Detect HV RST (MIC2754 only)
1.2V Bandgap Reference
GND
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Timing Diagram
A VTHO VHYST+ VIN(nominal) VHYST- VIN VTHU 1.5V 0V tRESET VOH VRST (MIC2754) V OL tRESET VOH VRST (MIC2753) VOL B tPROP tRESET tPROP B A
VOH 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. B
Manual Reset Timing
VIH VMR VIL tRESET VRST VOH
VOL (MIC2754) VRST VOH
tPROP(MR)
VOL (MIC2753)
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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 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.
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. 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 Crowbar Circuit
Voltage Monitor and Reset Generator
Microprocessor
System Circuitry
Reset(s)
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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 100k is recommended as this is usually an acceptable compromise of leakage current and pull-down current. The resistor's value is not critical, however. 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 100k 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.
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 8.4s 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 (0.1F, for example). Ensuring Proper Operation at Low Supply 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
40
Reset Comparator Overdrive vs. Duration
8 7
Overvoltage Comparator Overdrive vs. Duration
TA = 25C
DURATION (s)
DURATION (s) TA = 25C
30
6 5 4 3 2 1
20
10
0
1
10 100 OVERDRIVE (mV)
1000
0
1
10 100 OVERDRIVE (mV)
1000
A. Reset
B. Overvoltage
Figure 1. MIC2753/2754 Transient Immunity Behavior
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VCC Fuse MIC2754 Manual Reset IN MR GND RST HV RPULL-DOWN 100k Microcontroller VCC GND RST IN 10k 2200pF MCR708A SCR
MIC94030 22 1k
Figure 2a. MIC2754 Valid Reset Below 1.5V
VCC Fuse RPULL-UP 100k MIC2753 IN MR GND RST HV Microcontroller VCC GND RST IN 10k 2200pF MCR708A SCR
Manual Reset
MIC94030 22 1k
Figure 2b. MIC2753 Valid Reset Below 1.5V
BUFFER VCC Fuse MIC2754 RSERIES 4.7k IN RST MR GND HV Microcontroller VCC GND RST IN
/RST signal to other circuits
10k 2200pF MCR708A SCR
Manual Reset
MIC94030 22 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 (<1 at VGS = 4.5V) and the 22 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 / 23 = 0.09A. The highest upper-threshold voltage is 5.38V, so available gate-drive current is about 190mA: 4.38V / 23 = 0.190A. The maximum forward gate current of the SCR is MIC2753/2754 10 200mA. The SCR trigger characteristics and the gate-drive capability provide a workable solution for the power-supply voltage range in question. The 10k 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 1k 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.
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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) 1.30 (0.051) 0.90 (0.035) 10 0 0.15 (0.006) 0.00 (0.000) 0.20 (0.008) 0.09 (0.004)
0.50 (0.020) 0.35 (0.014)
0.60 (0.024) 0.10 (0.004)
SOT-23-5 (M5)
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MICREL INC. 1849 FORTUNE DRIVE
TEL
SAN JOSE, CA 95131
WEB
USA
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
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. (c) 1999 Micrel Incorporated
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