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MIC2775
Micrel
MIC2775
Micro-Power Voltage Supervisor Advance Information
General Description
The MIC2775 is a power supply supervisor that provides under-voltage monitoring, manual reset capability, and poweron reset generation in a compact 5-pin SOT package. Features include an under-voltage detector, a delay generator, a manual reset input, and both active-high and active-low reset outputs. The under-voltage detector compares VDD against a fixed threshold. Ten factory-programmed thresholds are available. The reset outputs are asserted for no less than 140ms at power-on and any time the input voltage drops below the reference voltage. It remains asserted for the timeout period after the input voltage subsequently rises back above the threshold boundary. A reset can be generated at any time by asserting the manual reset input, /MR. This reset output will remain active at least 140ms after the release of /MR. The /MR input can also be used to daisy-chain the MIC2775 onto existing power monitoring circuitry or other supervisors. Hysteresis is included to prevent chattering due to noise. Typical supply current is a low 3.5A.
Features
* * * * * * * * * * * Monitors power supply for under-voltage conditions Choice of factory-programmed thresholds Generates 140ms (minimum) power-on RESET pulse Manual reset capability Both active-high and active-low RESET outputs /RST output valid down to 1.2V Ultra-low supply current, 3.5A typical Rejects brief input transients No external components Pin compatible upgrade for MAX825 IttyBittyTM 5-lead SOT-23 package
Applications
* * * * * * Monitoring processor core and input/output voltages Computer systems PDAs, hand-held PCs Embedded controllers Telecommunications systems Power supplies
Ordering Information
Part Number MIC2775-XXBM5 Marking UJXX Junction Temp. Range -40C to +85C Package SOT-23-5
Typical Application
1.8V
VDD /MR
MIC2775-17 RST /RST MICROPROCESSOR VDD /RESET GND
OTHER LOGIC
GND Manual Reset
IttyBittyTM is a trademark of Micrel, Inc. 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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MIC2775
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Standard Voltage Options*
Voltage Code 46 44 31 29 28 26 25 23 22 17 Typical Application (VDD) 5.0V 5% 5.0V 10% 3.3V 5% 3.3V 10% 3.0V 5% 2.85V 5% 2.70V 5% 2.5V 5% 2.4V 5% 1.8V 5% Nominal Threshold Voltage (VTH) 4.68 4.43 3.09 2.93 2.81 2.67 2.53 2.34 2.25 1.69
*There are ten standard versions available with an order increment of 3000 pieces. Samples of standard versions are normally available from stock. Contact factory for information on non-standard versions. Available in tape-and-reel only.
Pin Configuration
RST GND /RST
3 2 1
4
5
/MR
VDD
SOT-23-5 (M5)
Pin Description
Pin Number 1 Pin Name RST Pin Function Digital (Output): Asserted high whenever VDD falls below the reference voltage. It will remain asserted for no less than 140ms after VDD returns above the threshold limit. Ground Digital (Output): Asserted low whenever VDD falls below the reference voltage. It will remain asserted for no less than 140ms after VDD returns above the threshold limit. Digital (Input): Driving this pin low initiates an immediate and unconditional reset. Assuming VDD is above the threshold when /MR is released (returns high), the reset output will be de-asserted no less than 140ms later. /MR may be driven by a logic signal or a mechanical switch. /MR has an internal pull-up to VDD and may be left open if unused. Analog (Input): Power supply input and the voltage being monitored.
2 3
GND /RST
4
/MR
5
VDD
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Absolute Maximum Ratings (Note 1)
Supply Voltage (VDD) ..................................... -0.3V to +7V Input Voltage (V/MR) ....................................... -0.3V to +7V RST, (/RST) Current .................................................. 20mA Storage Temperature (TS) ....................... -65C to +150C ESD Rating, Note 3 ................................................... 1.5kV
Operating Ratings (Note 2)
Supply Voltage (VDD) .................................. +1.5V to +5.5V Input Voltage (V/MR) .................................... -0.3V to +6.0V Ambient Temperature Range (TA) ............. -40C to +85C Package Thermal Resistance (JA) ...................... 256C/W
Electrical Characteristics
Note 5; TA = +25C, bold values indicate -40C TA +85C; unless noted Symbol IDD Parameter Supply Current Condition VDD = VTH +1.6%, /MR, RST, /RST open, Note 5 Min Typ 3.5 Max Units A
VDD VOLTAGE THRESHOLD Under-Voltage Threshold On VDD VHYST tPROP tRST VOL Hysteresis Voltage VTH-1.5% VTH 1 VTH+1.5% V V % s 280 0.3 0.3 0.8VDD 0.8VDD ms V V V V
RST, /RST OUTPUTS Propagation Delay Reset Pulse Width RST or /RST Output Voltage Low ISINK = 1.6mA; VDD 1.6V ISINK = 100A; VDD 1.2V; Note 4 VOH RST or /RST Output Voltage High ISOURCE = 500A; VDD 1.5V ISOURCE = 10A; VDD 1.2V; Note 4 /MR INPUT VIH VIL tPROP tMIN IPU IIN
Note 1. Note 2. Note 3. Note 4. Note 5.
VDD = VTH + 1.5% + 100mV to VDD = VTH - 1.5% - 100 mV 140
20
Input High Voltage Input Low Voltage Propagation Delay Minimum Input Pulse Width Internal Pull-up Current Input Current, /MR V/MR < VIL From V/MR < (VIL -100mV) Reset Occurs, V/MR < VIL
0.7VDD 0.3VDD 5 33 100 100
V V s ns nA nA
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. Human body model, 1.5k in series with 100pF. VDD operating range is 1.5V to 5.5V. Output is guaranteed to be asserted down to VDD = 1.2V. VDD equals nominal " Typical Application (VDD)" as shown in "Standard Voltage Options Table."
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Timing Diagram
VDD 0V V/MR VIH VIL VOH VOL VOH VOL tRST A A > tMIN VHYST VTH
tRST
tRST
V/RST (ACTIVE LOW) VRST
(ACTIVE HIGH)
Propagation delays not shown for clarity. Note A. The MIC2775 ignores very brief transients. See "Applications Information" for details.
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Functional Diagram
VDD
R VREF
Q
/RST
One Shot Delay Line S /Q MIC2775 RST
VDD IPU
/MR GND
Functional Description
VDD Input The VDD pin is both the power supply terminal and a monitored input voltage. The voltage at this pin is continually compared against the internal reference. The trip-point at which a reset occurs is factory programmed. A reset is triggered if and when VDD falls below the trip-point. Hysteresis is employed to prevent chattering due to noise. The comparator on the VDD input is relatively immune to very brief negative-going transients. RST, /RST Reset Outputs Typically, the MIC2775 is used to monitor the power supply of intelligent circuits such as microcontrollers and microprocessors. By connecting the appropriate reset output of a MIC2775 to the reset input of a C or P, the processor will be properly reset at power-on and during power-down and brown-out conditions. In addition, asserting /MR, the manual reset input, will activate the reset function.
The reset outputs are asserted any time /MR is asserted or if VDD drops below the threshold voltage. The reset outputs remain asserted for tRST(min) after VDD subsequently returns above the threshold boundary and/or /MR is released. A reset pulse is also generated at power-on. Hysteresis is included in the comparator to prevent chattering of the outputs due to noise. /MR, Manual Reset Input The ability to initiate a reset via external logic or a manual switch is provided in addition to the MIC2775's automatic supervisory functions. Driving the /MR input to a logic low causes an immediate and unconditional reset to occur. Assuming VDD is within tolerance when /MR is released (returns high), the reset outputs will be de-asserted no less than tRST later. /MR may be driven by a logic signal or mechanical switch. Typically, a momentary push-button switch is connected such that /MR is shorted to ground when the switch contacts close. The switch may be connected directly between /MR and GND. /MR has an internal 100nA pull-up current to VDD and may be left open if unused.
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Transient response The MIC2775 is inherently immune to very short negativegoing "glitches." Very brief transients may exceed the voltage threshold without tripping the output. As shown in Figure 3, in general the narrower the transient, the deeper the threshold overdrive that will be ignored by the MIC2775. The graph represents the typical allowable transient duration for a given amount of threshold overdrive that will not generate a reset.
Typical VDD Transient Response
Application Information
Ensuring Proper Operation at Low Supply At levels of VDD below 1.2V, the MIC2775's /RST output cannot turn on sufficiently to produce a valid logic-low on /RST. In this situation, circuits driven by /RST could be allowed to float, causing undesired operation. (In most cases, however, it is expected that the circuits driven by the MIC2775 will be similarly inoperative at VDD 1.2V.) If a given application requires that /RST be valid below VDD = 1.2V, 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 quiescent current and pull-down current. The resistor's value is not critical, however. See Figure 1.
VCC
MICROPROCESSOR VCC MIC2775-XX /RST RST /MR Manual Reset GND 100k /RESET GND
MAX. TRANSIENT DURATION (s)
100 80 60 40 20
VDD
0 0 500 1000 1500 2000 RESET COMP. OVERDRIVE, VREF-VDD(mV)
Figure 3. Typical VDD Transient Response
Figure 1. MIC2775 Valid /Reset Below 1.2V The statements above also apply to the MIC2775's RST output. That is, to ensure valid RST signal levels at VDD < 1.2V, 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.
VCC
MICROPROCESSOR VCC MIC2775-XX /RST RST /MR Manual Reset GND
VDD
/RESET GND 100k Rpull-down
Figure 2. MIC2775 Valid Reset Below 1.2V
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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)
MICREL INC.
TEL
1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
FAX
+ 1 (408) 944-0800
+ 1 (408) 944-0970
WEB
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) 2000 Micrel Incorporated
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